NOTE TO USERS This reproduction is the best copy available. UMI ® R eproduced w ith perm ission o f the copyright owner. Further reproduction prohibited w itho ut perm ission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ta t xxrsc&ar mmm m m m potato piQ&usTxoi iw mm W Philip A* Miof®* A Thesis Subsiitted to th# graduate Faculty for th« Bogrea ©£ 906S0& OF H C & M t t Major Subject « gorbioaltuF® . m m of Graduate College Iowa gt&t® College i m R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. U M I N u m b e r: D P 1 2 1 9 3 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and im proper alignm ent can adversely affect reproduction. 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S & 6 > n .s s M & b h fa o r coxxafts m \ f&m wmwmmm* * . * * ............ 3 . 88TCBS OF IfffiltATOIUS. *.»•#,. •***,.* «►.*-♦*m, ». ».«,.»*.,»,*», ,.»»»»# **** $ .30 f!«ft *f 10 KAIm4« <al .f»e«4wp*» * • * . . * * * * *. * . * * »* . * . ♦ . * . * * * , U iiimtle €*d4%i©j*#,. ... ,, **,*, *.»».. *♦,*»* *m ........... -.*.'»... 14 [email protected] il type and O e n d i t l a n a # * 15 of lea o lta #£ fi»M t f i ai s. , . . . IB . . tapsntjsisnt 1 , . . . . . 1 8 . . M*. 18 Sxperijaent 3* »*.***.,**.,.»*, *,**»»-»*.««.*,.«»*♦**. *.,. JH 4,., •. .... .**,..... 33 fej*ri*eat 3f ®®saifcs ©f &m Sfc®irag» f a s t s , . . . . . . . . . . . .40 ^ Sssalt# @f tfe® Ft^«la3eglcM& ms/ernstm ..*........ c o m !W.it. ^ 8*. C ...am,af, KXXBUStKK .48 . . . . . . . . . . . . . . . . . . . , . . . . .46 u s f ™ i 9'™ f c ™W9 ^ ^a _* ™* . s * . , . A « » f«,gwamBPS-,. __________________ T 7 Z 7 4- R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. 55 59 42 WWB&9GWM Sweet potato production has been an important enterprise on th# sand land# of soath®a#t'«m Iowa sine# XS65* th* largest area, 1,500 acres, is located on jfetee&fcia# Island, which lie# along the Mississippi Uver to the southwest of the city of Muscatine, fh© Island includes approximately 21,OO0 acre* of coarse sandy soil# which are devoted largely 'to the pro duction of truck crops. Smaller acreage# of sweet potato## are planted near Conesville, Burlington, Icniro#® and Carlisle. Per » brief period in the early waiters of the 'crop on Muscatine Island, the natural fertility of th# soil# was sufficient to produce good yields. In time the need for fertilizers became apparent, but the use of farm manures satisfactorily solved th# fertility problem for another period* However, in recent years good manure became difficult to obtain, and as a result the growers turned to the use of commercial fertilisers* the solution of the problem was not so simple, for it was first necessary to determine the proper ingredient# and rat## of application. It was necessary also to ascertain the proper time of application and the most suitable method of placement before the satisfactory use of the fertilizers would to# possible. Further- sore, th# growers w ©m uncertain Aether the productivity of the m ils could be maintained by the use of commercial fertilizers alone. No fertilizer recommendations were available for Iowa and the information from other states was of limited value swing to differences in soil, climatic conditions and th# varieties grown. Faced with these problems, th# grower# requested aid from the Iowa Agri cultural Experiment Station, In response, the Muscatine Island Held Station R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 4 ** was establish®! near the town of Maitland, primarily concerned production, the- early investigation® were with th® use of phosphorus and potassium in sweet potato fh® use of nitrogen was not *®rloualy considered at this tin®, primarily ■because th®'growers of the district held the opinion that nitrogen m s of slight importance in sweet potato culture and might even be injurious to yields. This opinion had been derived, tmm experience In the use of £am manures# $h«R heavy applications of amurss were made, th© visa growth m s frequently svwstianlatei and th# '[email protected] of potato## was reduced. Jinee th® .assure m s used general ly without th# addition of commercial fertiliser#, it is possibl# that th# detrimental effect of th® nitrogen may have been due to m improper balase® between th# nitrogen and other mineral elements. Manure always centals® swi nitrogen than phosphorus and frequently nor® nitrogen than fsot&ssiwas,. th® muiore sd#ii have as appreciable effect m nitrification which would rosier «v#a l«a?g® qttaattii## of nitrogen .available for the growth of th® sweet potato plants. Morgan (18) conducted investigations at the luteatin© field station from 1931 to- 1937. 8® tested applications of nitrate of soda and aiamoniuiB sulfate raging in rate# fmm zero to thirty pounds of nitrogen per acre, but obtained so si^ficatab tocrmse# tmm -th® m#e of th# nitrogen fertilizer. Sine# in his aaqperiment# th® nitrogen carriers were applied approximately two weeks prior to the time of twnsplaating, the nitrates could have been leached oat of the root zone before they m m absorbed by th® plants. possibility was not studied by Morgan, This For these reasons it was deemed advisable, is 1938, to initiate a more comprehensive study of tha nitrogen factor to determine it# value in th# production of sweet potatoes on th® sandy soils of southeastern Iowa, R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 5- wartm- or u s o utb bs fm results ©£ Investigations ©onceming th© use and effect ©f nitrogen on sweet potato*® in various production areas are briefly reviewed below ■with pertinent related literature. Stuckey- (25) in Qoorgia found that nitrogen applications were beneficial in some year% but the market quality and grade ©f the potatoes was lowered when nitrate of soda was used alone, ioaplete chemical analyses showed that 'nitrogen had no effect on th* -ehemieal composition ©f the roots. Burst (8) conducted ®3f>eria»Bt« m a yellow silt loan soil in Illinois where he obtained no benefit from commercial nitrogen fertilisers but greatly increased the yields of sweet potatoes by applications of' manure. Me estimated that a 100-bushel crop removed about 12 pounds of nitrogen, 1.6 pounds of phosphorus and 18 pounds ©f potassium, and concluded that this crop is not a heavy feeder. Scott (21) in Florida reported that nitrogen fertilisers when combined with phosphorus and potassium gave »§rfe*l responses in yields* Brlet blood or ammonium sulfate were satisfactory. tteier Texas .conditions, Hotchkiss (11) found that nitrogen ,1a combina tion with phosphorus improved yields, feats conducted ty Schemerhorn (22) i» Mew Jersey revealed, that organic sources of nitrogen were more suitable than the inorganic forms. Between 30 and 45 pounds of nitrogen per acre proved to be the optimum rat# tinder lew Jersey conditions, Ihile potassium fertiliser® tended to produce short, chunky potatoes, nitrogen caused long, -narrow roots. Johnson (If) reported tat organic matter plowed into the soil did not R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 6- appear to be m Miportant la. sweat potato© production as with other truck crops, although it was somewhat beneficial ia impressing yield® when m fertilizer m s ased, Vftrioas term of fsrtill sera were tried ©a tutsan silt loan la Mss«ri toy Quian (20). .la fcis mxpmAmmtm nitrogen appllmtioas lowered yields, slightly raised tbs sugar content of the rests, bat exerted no af fect eft the starch cosj^sitioii. i®ughla®d (12) tovestotjatoed the respoase of sweet potatoes 'to© various nitrogen curlers. Me selected a Soriolk sandy loa®. soil of low fertility, this is a common soil ia IferylsndU Inorganic forms of nitrogen gave th® best yields of "primes" or first gm i® potatoes, Within this group nitrate of soda m s the most satiBf&etoiy, le I 'between 30 and 35 pounds of nitrogen per aero, Mmgklami a im obtains! food results fro® the ms# of rye or vetch as winter cover crops on sweet potato soils, ■©else (10), also working to m ry ltm d , ©btato«t some increase' to yi«M from th®' as® of nitrogen fnrtiltoear on three different soils, but the most marked response was obtained m th® very acid Sassafras gravelly type, A number of fertilises* ratios was tested on a S mmf m a sandy loam toy Stoaorley (28) to Virginia, A 2-1-5 ratio proved to be most satisfactory and increases to yield and sis# of potatoes were obtained as the rate of nitrogen application was increased to 60 pounds per acre. He warned against too heavy applimttoas of fertilisers at the ttos of planting because of the possibility of injury to the young plants. Zixaaerley found no correlation between the composition of fertilisers and the storage qualities of the crop. $dtoe«rf ftal, (24) » working on four sandy soil types to North Carolina, reported that approximately 35 to 40 pounds of nitrogen per acre were most R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - T - suitable, they discovered that there was. injury to the young plant# when nitrate of soda was applied is the tuvmw before planting, but they were able t# prevent such injury by side-dressing with sodium nitrate after the plants m m #stabli«li«d. .-or by using a ©Mbiaaiioti of organic and in- • organic sources of nitrogen. k ten-year fertiliser study m the sandy loam soils of Georgia by ■■ Woodard (-2?) revealed that a 4-8-6 analysis applied at the rate of 8GG pounds per -mm was most desirable for sweet potatoes. The most economical source of nitrogen was a combination of -nitrate of soda sad cotton seed meal in equal proportions. The effect of fertiliser treatments on the shape of the Porto Sic® variety was investigated by Carolus (4) and iiiaerley (2f). Carolus found no consistent relationship between shape.and individual nutrient elements, but eoafeinatieiaa of Smq&jmtly made mm relatively M#i «m®iust® of aitrogw and potassium chunky potatoes* 2fa««rl«y also found that increasing th® rate of nitrogen and potassium- application® decreased the ’’Length/ Diameter" ratio, and he eos&l&dsd that nitr©f«i as well as potassium was necessary for the thickening of the. root®. la California, Porter (If) reported that m the more fertile soils no fertiliser was aee®»s«y, feat on the poorer soils sweet -potatoes responded well to nitrogen applications. . Miller and Kimbrough (15) found that nitrogen m s essential, on the silt loam sweet potato soils ©f louislaas,* they recommended up to 600 pounds of a 4-12-4 fertiliser per acre. In Arkansas, Cooper and latta (5) obtained responses of sweet potatoes to nitrogen applications on both the Clarksville silt loaa and the poor Boston soils. Approximately 15 pounds of nitrogen per acre were sufficient R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. for th# Clarksville soils, whereas quantities up to 40 pounds per acre were necessary m th# tostoa soils. Andersen (1, 2} tested various levels of nitrogen ia combination with jAospborus and potassium #a three sandy loam soils ia Mississippi. Moderate applications -of idtrogea increased yield# except la the eggHMdjsents on the fertile ^sapasurf soil, Me «es34 detect a® i»fla.«we of nitrogen on the grade, shape or starch content of the mots. .Mrnmd tmA SftfHek (9) studied the effect of a deficiency of nutrients on s««H*t..jx»t*te growth ia solution cultures, Hi® pleats were placed in a complete nutrient solution tmm June 15 to July 1$ and then they were divided into equal lots, the ramala&cr of their development took place in a complete nutrient solution or in ■solutions lacking nitrogen, phosphsnu®., potassium, calcium or mgnesim, After July 11, the plants in the adans nitrogen treat ment w^iblted very slow via# growth and at th* lawdaaiioa of the experiment these plants had the smallest 400 cm. for th® minus mmufc of top growth, 225 e». as coopered with and 1,225 cm, for th# couplet# nutrient solution. the root development of the nit»g®a^#fio!©nt plants was also drastically retarded, but not ipib® ia proportion to the top growth, the test showed that nitrogen was eseaniisl for th® proper development of both th®' vines and roots and indicated that nitrates should be available to the pleat during most of the p w i a g period. 1» tests conducted by Surrey (?) ia the Mississippi Delta district, nitrogen proved to be the most beusHcial nutrient for increasing yields and Improving grads, satisfactory. fro® 26 to 40 pwaads of nitrogen per acre appeared to be Oarrey found that varying the kind mi fertilizer had.little R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. influence on th® shrinkage of th® root® during curing and storage. Morgan (li) ran a series of fertilizer tests on sweet potato®® at Muscatine during th® period of 1931-1937, inclusive. Me obtained responses in yield to phosphorus and potassium, bat was able to show only a slight benefit tmm nitrogen fertilisers, 1® concluded that if legumes were used in a rotation with sweet potato#®, nitrogen could be omitted fro® the com mercial fertiliser applications. Jiergaa reported that nitrogen had no in fluence on the sugar content or the storage qualities of the roots. the work of Crowther, «t &l, (6) and Mirehandani (16) In iSngland casts suspicion on the value of legwas ia supplying nitrates on sandy soils, they fowl that When two heavy crop®' ©f vetch m m plowed under during one season the decomposition of the organic matter art. leaching of nitrates was .so rapid that practically no benefit from the nitrogen .added was obtained fey crop# in the following spring, Taylor and fldmore (26) found that as high m 36 percent of the nitrogen ia a green manure crop of eowpeas m s lost .during th® winter. Uei general, the literature relative to the problem indicates that nitrogen applications have proven beneficial m most sandy soils devoted to sweet potato culture art ©a some of the heavier textured soils of the .South where leaching la an important problem, from 23 to S§ pounds of nitrogen per acre have usually been recommended, the inorganic sources of nitrogen have proven more satisfactory than commercial organic fertiliser or manure. Th® effect ©f nitrogen on the shape ©f sweet potato roots appears to 'have been quite variable, the differences in the results reported are un doubtedly due t© variations in soil and environment, nitrogen fertilizers apjarently have slight if any effect ©a the chemical composition of the roots. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. 10 - SffMIMlNTM. Plan of Investigation Three possible effect® of nitrogen fertilizers were explored j pro duction, keeping <|aality sad certain phases of the chemical composition. The effect of nitrogen on production was studied by means of field ex periments, the keeping quality by storage of potatoes from, designated treatments and the chemical composition fey laboratory analyses. fertilizer field trials included the following experimental 1. A' factorial experiment with three levels each of nitrogen, phosphorus and potassium set up far the purpose of establishing the proper rate and balance of nitrogen is ©«abiiiait«i with other fertilisers. 2. A delayed nitrogen application experiment designed to test the possibility of the lose of nitrates fey leaching and also to determine the proper time ®f application. 3* A nitrogen carrier test outlined to ascertain the most suitable source of nitrogen for the conditions involved. 4. A combination manure and commercial fertiliser test which was undertaken to determine the value of manure as an organic source for nitrogen. 5. A miscellaneous experiment desired to check the rates of nitrogen in various fertiliser analyses .and to test the value ©f nitrogen ia starter solutions. The. sweet potatoes taken from the plots In Experiment 2 were placed in storage for the purpose of checking the effects of the heavy and the late applications of nitrogen on the storage qualities of the roots. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. -12 The potatoes taken from th# plot# ia i&periaent 2 were used ia th# laboratory f©** determinations of th# sugar, starch and nitregen content of sweet potatoes produced under different conditions of nitrogen fertili sation. Ia addition,.a farttUafaaxgr m m g r of the nitrates, total nitrogen, organic matter oo»t«at and ns&stwr# constants of the a o U was made ia order to gain a more thorough' lotei&odgo of the nature of the soil used ia the ex periment#* Methods and procedure Because of tfc# n«l«r of eacpiziaeisis involved., only general methods of procedure ar# gIw®R lore. letail# are included with the discussion of each experiment. H I of th# field eaqperlaea&s were conducted at the Musca- tiae Island field. Station. Ia all cases th# taste were laid, out la designs approved by Snedecor (23) or fata# (30) and th# data taken during tit# season were subjected to appropriate statistical analyst#, a # sis# and shape of th# plots were varied according to the design awt available space. In Bxperiiaent 1, owing to the large nsnbor of treatssmte, a relatively small siae of plot m s used. Seven .rows spaced 3*5 feet apart and 50 feet in length were fertilised and planted. At harvest the two outside rows were discarded, leaving a plot 50 feet by 17.5 feet in size and equal to 1/50 of an acre. Th# plots for ex periments 2 to 5, inclusive, were laid out with six rows 103.7 feet in length. At harvest th# two omtsM® rows were discarded, leaving a four-row plot 103.? feat by 14 feet in area and ®«pal t© 1/30 of an acre, in addition to th# area harvested at least ten f##b were left on th# end of s&eh plot to prevent R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. -oa th« occurrence of end effects. ffc# fertilizers w®r® applied in the bottom of th© furrow about tm days before planting tmOows othorwiso indicated. fh® side-dressings of n£tr©g#n were broadcast by hand along the. side of the ridges and then worked into the soil fey cultivation, Varieties of the <fara#y /roup of sweet potatoes were used for these experiments, Th# plants were grow i» hotbeds and were transplanted between lay 15 and May tf. 4 22-i»ii spacing ia the row was used, the plot® were irrigated whenever necessary by means of portable overhead irrigation equipmeat. tigging ©f the -potatoes w started about September 15 and was completed by October 15. la 1938 and 1939, growth contiamed until the latter date, but ia lf40# the vines were killed by a frost- on September 26, Baring the season careful observations were kept on the relative foliage color and rate of vine growth., grading of the potatoes m s dsn® in the field arid, after grading, the weight of the Be. 1, lo, %. and cull grades were recorded. At this time any possible effects of th# fertilisers- on shape, color and degree of maturity were noted. Because ©f the variability in grading by different workers both th# data -on total yield and yield of the He, 1. grad® of potatoes were treated statistically in the analysis of the results of' th# experiments. une bushel, 50 pounds by weight, was taken from each replication of each treatment -for the storage or keeping $utllty test#. The potato-®# were stored in & separate room in a local »i»«reial storage house. The potatoes were held until lai® nareh, at which time they were eaatwsd for shrinkage and rots, first the filled baskets were weighed to determine the total loss in weight after which th® rots were sorted out ant the sound root# reweighed. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 13 Thus a record ' wm obtained of.the shrinkage due to water loss mi physiolog ic a l changes mi also losses in# to storage diseases. . The material for ths'f^fsiologle^.. 'testa was taken fm m the treatmenta la S^riaeni S., thirty potatoes were sleeted at random from each set of tre&tmB&ts. cent alcohol* ft*©* ttiase, 100-gMit saaples m m killed and stored ia 80 per Hie swsples for the Xf3§ crop «*r® taken ia larch frwa the storage lot# after th® eoapietion of the .storage tests, Th* 1939 samples were esleeted in the field m & eared for three weeks before killing ia hot 80 percent alcohol. The methods outline by lenais and SialX (141 for sugars, starch m i nitrogen iotora&mM.©as were followed. the soil saiaplee mm collect«& from the 1937 and again ia the spring of 1939. H«M late ia the fall of M&mo no nitrates were, preseat, the IJ«Xd®Jsl method for total nitrogen was used as outlined ia Methods of Analysis of th* Association of 'Official Agricultural Chemist* (3)-. The organic carbon content was det*r»!a«4 by the dry esmlmshie® method (3). the moisture constants were determined by the methods of Loomis and Shull (34)* filtrate of .soda (14 percent, nitrogen) and calcium cyanamid (22 percent nitrogen) were wjpioyed -m the m v m m ©f nitrogen, except in &[email protected]«»nt 3 in. which other ®©«re«® were tested, 4 basal rate of 45 pounds of nitrogen per acre was used except where minor variations were desirable. ■ On all ex periments except-the factorial, all plots received an application of 36 pounds of phosphorus and ?2 pounds of potmsim per acre. H i m complete com mercial fertiliser mixture® were used half of the nitrogen m m supplied as. nitrate of soda and half as. »xm»eaki«« sulfate. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. Cliraatic Conditions The possibility that leaching- b* m important factor ia til# in vestigation necessitates a careful study of the rainfall as it occurred during th® growing periods, fh# rainfall for th# Fmiitland district during tli# period of th® Investigation is gives in table 1. f«*1® 1. Rainfall in inches'as registered at Fruitland, lews, for'the growing' seasons of lf3§, lf|f and 1 W , fears.. 1940 ..... S S I .....i p i Period april May June July August Sqpteaher October total '* f.f. Mormal* . 1.48 3.18 1.26 3.17 1.36 5.67 .6? 1.79 .3m 3.8f 4.22 3.46 4.04 3.93 2.5© .....27,85.. 27-35 17.1© .25*131..... 3.93 5.8$ 8.28 2.6b 2.68 2.35 2.10 3.75 2.73 5.43 6*09 6.97 .90 Weather Bureau Both th# 1938 and lf3? seasons ted' periods of coaparatively heavy rainfall whereas 1940 was relatively dry throughout th# frewing * m m n, except for * rainy we* which occurred about th# aiddle ©f August, la 1938, the wet period #asfc#iii«i throughout # 1# spring with the last heavy rain ©a June 22. Soring 1939, the heaviest precipitation occurred in late dune ami early July and again in ' late August. The suimer ta^perature# averaged about nonaal for all three seasons, although th# month of August, 1939, was comparatively cool. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. -3.5 Soil Tfc® soil im th# Muae&tlne district i« classed as a Buckner scarce . ft# top » i l la very p m w , gritty, dark col©r«t and has a small sand, content of silt wMLcii causes th® soil to puddle easily. The profile is only poorly developed for the apgmraao* of tbs -soil rera&ins unchanged to a depth of &ppr«iaat^y si* feet where it bcsottes a little lighter 1m color the next two to three feet, the soil is wad«rlaitt with gravel with the water table at about 12 feet, The result® of the analysis of locations ia the «a$>aria®ataX field® fable 2. the soil saa^ples taken £rmi various are given ia table 2. Total nitrogen and organic content of a composite saapleof Buckner soars© saai taken from thesurface si* laches of soil -m which the experisents were conducted. Time mi Ifibregpa sampling ^ percent faH 193? ©.©36 Spring 1 W ©,©32 Mtrogen pound® per acre* .. ©rf&aic aattcr C© * l.?2) percent C/S ratio mi ©.» S2.9il ■ 64© 0,67 12.2il * Per surface acre of 2 million pawls of soli - The data' show that the soils are very low in total nitrogen and in organic carbon, which strongly suggests that th® natural supply of available fora® of nitrogen is Insufficient to. satisfy th® growth requirements of most plants, A study of the nitrogen and organic.matter content was made of soil asaples taken from plots receiving different tpeatwnts for the three year® R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. «, X6 — prior to th® time ®f .awarding, On® series of plots had received applications ©f 2-14-14 f«rfcili*«r at a rat# of 75® pcrnods pm- acre ia 1935 and 193&* hat w left latfsrtilissci ia 193?. A ©[email protected] of sweet potato*® wa® grown on these plots each season, J» a rnmmtA mt&mm of plot® a eowpea crop had fee® plowed t*ai«r is- If3f aad 1936* la 193?-# this aeries iN*#«iv«d an application of 2-14-14 fertiliser at th# rat® of ?5G pounds per acre and. a. crop of sweet potato®® was grows ©a th# plots* fh# third m w I m of plot® remained idle and uncultivated over th# three-year peri©#* th# results of the®# analyses in table 3. are fable % total nitrogen and organic content in soils fmm differently treated Samples taken in the fall of 1937, plots. Plot iriatsert prior i© sasfliitg 1935 1936 . . Iff? Btrogaa percent ©vguto latter £©' x 1*92) percent Fertilised and cropped with sweet potato## Fertilised and cropped'with sweet potatoes Hot fertilised and- cropped with sweet potato## #,#36 0,85 Golems Oowpe&s plowed under Fertilised and 0»©9* 0,92 plowed under Idle ZdU Idle ©,#36 ©*74 ; cropped with sweet potatoes It Is evident from the data"In tsM® 3 that th® plowing under ©f green manure.©.raps d M not smfcerially iswitmm the nitrogen content of th# soil, although a® algjht be expected th® organic matter ©oatant was raised to a slight extent fey the mwpms, fh# results of q$iek tests indicated that the supply ©f available ,phosphorus s M potassium in this soil w m low* 'Si# soil is fairly acid with a soil reaction varying from pH 4*6' to pH 5*5 in samples taken frora various R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 17 locations on th# far®. However, the list© requirement is low, having been found to he between 3/2 and f/4 of a ton of limestone per acre, as# in dicating that the base erohsag* capacity of this soil is correspondingly low. Hie total. sat#r-4i©Miag capacity of the soil was found to be 22.0 percent, the field j»er©«nt&i® 5.7 sal th* peraaneat wilting percentage 1.8 percent. ©a the basis of these flgwres, appro*Sj®t©ly .75 inches of rain would raise the solstura ©sntsai of It inches of top so-.il from the persianent wilting point to the field psmmtmg® after which any additional precipita tion would cause m rtm m t of water to the lower soil layers, therefore,.it sight be anticipated that when precipitations, of over .75 inch, occurred there would be leeching of nitrate* fmm the upper foot of soil. If the soil moisture contest was above the permanent w ittin g capacity at th® tine of the rainfall still less precipitation would be raqnired to start the downward aoYosent of nitrates. ferfaa and Street (If) showed by their lysinister studies that in the mmfy m il a of -ioaneeticut 50 percent of the nitrate nitrogen was leached from the soil by .ff of aa inch of drainage water and that a .4-inch rain would reaoro 85 be fO percent of th# nitrates in the soil. Since rains of mt im h or acre, are eataaaii in the iuscatiae district, particular ity. daring th® spring Heaths, it ia «[email protected] that the loss ©f nitrates by leashing eeuld be- an ifipreeiafet® faster. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - it - ftresmtatisa of tesnltii ®£ Sfrpweimmb* B M M M s. * t e & » & I Th# factorial msfimrimmb which m s designed to detemiin© the proper rate m i 'Imlmm-e o f nitrogen with ©thisr nutrient® ms conducted for three levels mmh of nitrogen, phosphorus and years* 1938, 1?3? and 1940. pstassim w e ssad In m m f poswifel# soatelaailoa.* a total of 27 different treatments, With th# two replication* of #«©!* treatment, the layout gave a total of 54 plots' in th®. expeidiiesb, Hi# jwwis of mmh element per acre for th# various levels were as follows* Year % 1938 1939, m m © s* • . IIT^ 3?*5 ?f,0 % 0 1 *6.4 !i 52,i 4 0■ i 72.0 10® 0 »,5 0 20.0 4©*© 0 54.0 10S mm Th® rates of application o f the phosphorus and potassium in this ex periment war® eh&ngwt for th® 193? eeaeen hee&as# th® results of th® 1938 test indicated that th® a«di«» rates worn to© high to predm## an intermediate effect, Th# nitrogen rates were changed because ©f the switch fro* .nitrate of soda to calcium cyanaaid. The nitrogen fro® the latter source should not leach as badly, A m high applications of calcium ©yaaasid have been known to cans® injury to crops if planting was done m a r th# time ©f th# application of the eysBsssid., The fertiliser ingredients were mixed sad then applied by hand in th# bottom of the farrow® .after which the ridges w«r# threw and allowed t© settle for a week before planting, 'In lf38, th# nitrogen mm applied as nitrate of soda* kit in th® other year# ealcim cyawssiit m s used. The varieties planted R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. in this experiment were? Muscatine Ho, % X$3t» .Prolific} 1939? Muscatine Ho. 1} 1940? In 1938 and If39, ■the crop was grown following a green aanur# crop of cowpeas* Identical lee&tloas -were used for the same treat ments ia the If3f and 1940:experiments, th® harvested area in- each plot was 1/50 m m in else. 'The average yield# of each trsataent for the three years are shown in table 4. The plants m the plots receiving .nitrogen applications showed a. marked stim & jxttm of vine p*«sbh in all years and the foliage developed a m c h deeper green color than ia the untreated plots. The only axesyption occurred in the medium nitrogen plots in. 1938 where early stimulation of growth m 9 evident? 'but there was little difference is vine growth betwea these plots a M the cheeks later in the .season? 4m probably to leaching of the nitrogen by heavy rains, ft® .extra vine growth on the nitrogen plots was advantageooe in 193® and 1939, but la the dry season of lf4© the vine development stlmsl&tad by the nitrogen applications m m apparently a dis advantage. In addition? m®m burning of th® foliage was evident on all plots, receiving cyanasdd in 1940. fable 4 gives the yield data m which the rnm&yma presented in tables 5 to. 8, inclusive, are based* Srea without these analyses it is evident in table 4 that sows fertiliser eosMnatiosa used have given considerable increases in yield over the i»-f«*tili»«i (©-©*<4) plots, yet It is izsfjosslbl© to show conclusively the effects of the Individual WBpMWsts fro® these data % t i l the various effects of the t*mt«ests are segregated. k mmmvf ®f the main effects will present m m responses produced by each nutrient. clearly the individual A raain effect is derlved by taking the differ*®# between the average of th® no-nitrogen, plots, for instance, and R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. fable 4* fields of sweet potatoes in bush®!# |®r aer® on the plots of a factorial .«qpwrlaaja& with three l « d i saeh of nitrogen, 'phespheru# sad petassiw, 'Average# of two replications. fertilizer i level s fetui 'H-P-K* s yield' [email protected] U.S. t ' 'fetal Ho. 1*8 1 yield 81.0 90.0 93.5 83.5 109.0 87.5 93.5 92.5 103.0 60.0 61.5 63.0 47.0 82.5 52.5 56.5 66.5 75.0 77.5 95.0 111.5 93.0 106.0 115.0 129.5 126.0 97.0 1—G—1 1-0—2 1-1-0 1-1-1 1-1-2 1-2-0 1—2—1 1-2-2 65.0 92.0 86.0 79.0 79.5 116.5 83.0 120.5 87.5 37.5 52.5 55.5 51.5 53.5 78.0 56.0 89.0 55.5 81.5 100.0 114.0 80.0 2-0-0 2-0-1 a-o-t a-i-o 2-1-1 2—1—2 2—2—0 2-2-1 a-s-a 75.0 110.0 90.0 102.0 114.0 313.5 94.0 110.5 97.5 32.2 0-0-0 0-0-1 '0-0-2 0-1-0 0-1-1 0—1—2 0—2—0 0-2-1 ■0-2-2 . 1-0-0 U S JW field 0.3. i fatal Wo. 1*» 1 42.0 51.5 64.0 59.0 65.5 73.0 85.5 71.0 55.0 71.5 104.0 130.0 79.5 123.0 112.0 77.0 131.0 91.0 field U., He. l*s ■ 43.0 68.0 100.0 41.0 85.® 84.0 43.0 85.5 61.5 26.0 147-5 112.5 123.5 160.0 76.5 47.0 73.0 89.0 81.0 73.0 107.0 55.0 86.5 80.0 80.0 107.0 118.5 90.5 97.0 137.0 64.0 61.0 48.0 78.5 88.5 47.5 69*5 96.0 42.0 74.5 57.0 74.0 88.0 84.5 67.5 79.5 66.5 79.5 121.0 123.0 102.0 113.5 125.0 89.0 136.0 120.5 48.0 84.0 81.5 62.0 75.0 86.0 56.0 85.0 81.0 41.0 72.0 93.5 55.5 76.5 122.0 60.0 114.0 83.5 23.0 48.0 70.5 31,0 53.5 93.0 38.5 81.0 61.0 ■ 27.3 29.7 26.0' 23.7 25.8 109.0 47.5 64.O ♦ Throughout this thesis seogiiza&tcms of fertiliser nutrients will always be stated ia tii# usually [email protected]©#[email protected] n w , th# first, fifur# la th# group of three representing .aitrog«B| th# second, phosphorus; th# third, potassium. «l#a»t wlpdficanh iiffsreac# R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. th* average of the plots receiving th® sedium level of nitrogen.* The «®i» affect, therefore, present# the actual rmptmm in plant growth attributed to- th® mXtm-gm whether used alone or ia combination with other fertiliser ingredient#. th# average total yields and sain effects for nitrogen, phosphor®# and pota#M.» for the three-year period are presented in. table the main effects for .nitrogen are not significant in If38, although the high level of nitrogen ahowwd a i«[email protected] to increase the yield of sweet potatoes* Since nitrate of soda was used to supply the .nitrogen in this test, it' is conceivable that leaeltiii# of the nitrates ©ouM .have taken place with the result that insufficient nitrates were present throughout the paring s*nson for proper development of the plants. This possibility was supported by bits result# of another experiment conducted daring th# same season. the results' for 1939 ahow that the. effects attributed to nitrogen «re si^ificast'-for the fa, 1 yield but not for th# total yield* This shows that the nitrogen applications were beneficial in increasing size as well as yield since the grade -1® aainly determined by th® sia# of the potatoes* Is this tost th® nitrogen was ftt-roishad in th® fora of Swiftian cyaaaaid, which should provide a for® of nitrogen that is mam resistant to leaching than the nitrate of soda* This fact say account for the response in yield from nitrogen in this season. The data show that 22.5 pound# of nitrogen were sufficient .in thi* season. The yield# in 1940 showed a deaided decrease when 45 pounds of nitrogen ware applied as calcium cyanaraid. Sine* this was a relatively dry year, very little leaching probably ©ecurytd, with- the result that R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. t f\-Sf ■a • m 01 t t rjl *#a\ * ii ««s * • ■ty*»* 15 O'© ad r~ 0 -<r 0 O'© ♦ !>!>■© p! p O *n 4 «s F' VTv•£>sO « >% 0* Z *"?v -S'® Ms OS • © tH ia H -O 'OOON «5 HI ^ ® Sft8 1*4 O -H 1*1 OSHI ■©*«• ■ dd nn OSCJ 0 O© « iii 4«e^ 00 Q O' r4 © H 'O <0 V\r-I O' ■* Jgs* §O •*. St 3£•#*4 • C^ H 1 $ ss « as r4#'« ' o•» « 0 0 v\r- m ft ft • • • m WNO O t*tft SS <»%t» m %4 vs© R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w ith o u t perm ission. - * o © «\ •&** •* m i 5i»JS ||lp' fwet Jp^s ^ S if aaa n. *« O'® ¥1 .si s© V\ ■SSI: • . I to m »<\ 1 *i O T» 31 ... a - * o. O' ssgg JWI 1 SSS h I N 0} ■ * «**» C K H I * sii *0• **•# 0 * r*f f4 O'® Md ws« • ♦ O- i I • m•rt# «£CB * sis HJ3 g ® c- -sfc*\vs vst-vO • IA-O as e~ • • a« n P 5~ Tabl# 5. hi r tf yislAs and sain ©fleets ia twshsls p®r mm abtajLaad by tbs varXoms iiXiir©g«a» phosphorus and potassium levels in the factorial «&i»ris®»t for th* years If|S to 1940, inclusive, ffa® data give both total m& ». S, I®. 1 yields of surest potatoes ~ m - • m - this rate of application plus the available nitrates released from the soil produced, m uafetlaaeed ©onditien for sweet potatoes between the nitrogen ant the other fertiliser eleaeats. The media* rat.® of 22,5 pounds of nitrogen per acre showed neither a significant increase nor redaction in yield. The 'yields and main effects.given in table 5 show, that a response in yield# from phosphorus was obtained in all three years. In 1938 and 1940* the a«din» rate of phosphorus application gave »« good yields as the high rate, M 1959* the high rats gmm significantly higher yields than the medium rate of W pounds per acre. These date 'show that a rate of approxi- aately a© t© 25 .pounds of phosphors® per acre will be insistently beneficial t© .yields. Although the'hlj$» ate of 4© pounds of phosphorus proved m-rm beneficial to yields in the one year* it is doubtful if it would be economical to apply this quwatity each year in orft«r to gain the fainter yields in the few yea n that this a t e might prove beneficial, potassium applications also increased yields in all three seasons (table 5), In 1936* the rate of 72 pounds per acre gave a greater yield than the higher level- of 306 pounds. In 1939 and 1940, when the mediae level was lowered to % pounds of potass!®* per acre, the 106 pound level gave the better average, bmt the results m m not significantly- greater than those for the medium, level. Therefore* the op-tiara* rat® of potassium application appear® to b# app*m!j®t«iy 75 peeads per acre, 1». view of the variability of the nitrogen effects .shoe®, in table 5, an attempt was aade to segregate the single effect of nitrogen by a method outlined fcgr Tates (30), . fbr the 1939 and 1940 results the medics and high levels of nitrogen were grouped for ©caparison with the no-nitrogen level, R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. a s ■indicated by the formula (S^ ^ I11 193®j awing to the low [email protected] of the medium level, the grouping was m i # of the medium level and the no-nitrogen level and' c«ap&r#fii with the high nitrogen as follows; fee single effeets of aitrog®* based, on sin#® 'degrees of freedom are shown la table 6. fable 6. The vari«i«s« ani average main effects (in bushels per aero) of nitrogen based on single degrees of freedom. Data taken from the factorial eo^erimmt, S&periment .1i (lith the lf3S yields the grouping m s the high nitrogen level compared with th® medium and the no-nitrogen level, 2f’£~(Mj_ / Ko)» Sith the 1939 awl 1940 yields the comparison was ( % f %}-%), Kean sauares .lain effect tr«ata«t Sff«©t fercr 1.1.1.* _ ..- .....i'bushels per aiire) Year Grade 1938 Total »«. i 1083** 990** 1939 fatal fc. 1 1940 Total ffe. 1 248.3 227.8 9,4 9.1 9*26 ®,87 747 1247** 212.6 172.9 7.9 10.2 8.56 7.73 2670** 759 267.6 212.4 -14.9 - 7,9 9.56 8.53 • * least significant difference at M i s of 19;1 ** Mean square# are significant at odd# ©f 19*1 When the singls effect ©f the high nitrogen level is compared with the mediut end &©HRlt3*©g«a. level, there is a significant increase to yield due to nitrogen in 193$. the significances shown in this table for 1939 and 1940 are in agr®*®#iit with th# results of table 5. 'la a factorial esqjertoeat mm is able to test the possibility, that a owMaaiioit of factors any work together to exert a greater effect on plant growth than can foe attributed to the additive effect of the independent R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 25 factors, . This possible eoiifaiimtion effect is israed an interaction. The . first order interactions for &peris#»t 1 are g l w ia table 7 Table 7. tbs first order interaction values ef the factorial ea^oriasnt, ixpcriaetit 1. Data given is yield in bushels of U.S. Ho. 1 potatoes per acre Interaction nitrogen - pho^hcrua Iltrogsn - potassium 1938 .19.M... 1940 -3.25 -3.2 10.3 11.6 - 1.0 .0 0 5 ■phosphorus - potassium 1.86 least significant difference 8.7 - 5.85 .... JL3L. .7 8*1 The data she* a significant .interaction for nitro gen-potasaium in 1939 aad for nitro^n-^o^owES. in 1940# feat these offset# are not suf ficiently consistent- to mggoat any definite trends. The average percentages of 8. S, Ho. I grad* potatoes fro® the plots of the different nitrogen level# of aporiment 1 are shown in table ®. Table 8. The percentage of U. 3. Mo. 1 sweet potatoes frora plots with different nitrogen levels in Experiment 1. Iitroa» levelsNon# 11# ®iag# of In pounds per acre u. S. Mo. 1 potato#® X9H . *a35L_*J6S___ .......M » ..._ x a » _ . 1940 Ave. <%> 0 c%) 37.3 Ob) 75.M 67.7 59.6 66.5 64.6 22.5 66.6 63.8 68.0 .66.1 45.0 69.9 65.1 69,6 68.2 © R eproduced with perm ission o f the copyright owner. Further reproduction prohibited w ith o u t perm ission. the data indicate that the grad® of potato®* i® improved slightly by th® addition# of nitrogen. fee increase is the grade, however, is not suf ficient t® warrant th# as# of nitrogen for this purpose alone. fee result# of issperisent 1 have stew that nitrogen can be of value under certain conditions. It appears that a rat# of 25 pound® of nitrogen per acre applied as eyaaaisM is sufficient, If nitrate of s M # is to be used either larger implications will fee necessary if applied at the tla© of planting ©r scant other procedure ©f application should bs used, ft# time of application #f nitrogen fertili#«r# will be discussed under another «&» periseat* in general, th# interactions of the nutrients Involved in this test do not appear to be significant. Phosphorus and potassium, applications were valuable in increasing yields, Approxlmteiy 20 pound* of phosphorus and. 75 pounds of pctasslw should be applied per,acre* fiHBBSggflBft i fee delayed nitrogen application test was outlined t© determine th® proper its® of application of nitrogen and to gs&a some information on th® possibility of preventing nitrogen losses from leaching by two or more smaller .applications during the season,. the «p#ri®eijt was conducted for three years, bit sine© the If40 design mm radically changed the 193$ and 1939 results will b® presented first, A randoutiued block arrangement of plots was used with four replications in I f * and five in 1939. All of the plots reeelved an application of 0-42-12 eoiamercial fertilizer at the rat® of 756 pounds per acre, litrogen was ap plied to all'feat the check plot# which received only the 0-12-12 application. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - m - *h«a the nitrogen was applied at planting the.nitrate of soda was placed is the farvm , th# d«lay®4 applications of nitrogen. were applied as a aid©- dressing and worked into the soil by cultivation. The e©apl#te nitrogsa application ■insisted of 45 pounds ©f nitrogen per acre in the fora of 280 pounds of nitrate of soda, with the delayed Mounts consisting of fractions thereof* Th® e^perlasttt m s comimcisi-both.years m fields that had had a crop of oompm® plowed under daring the previous season. The plants wars set oat on lay 22, th# first delayed application was sade on Juno 22 mA th® second application on July 22. the variety Prolific was grown both years, the yields for the two years are i e « in table 9. fable 9. Jteperlitent 2. Yields of sweet potatoes from plots receiving 280 pwisds ©f nitrate of soda at different dates during the growing season. (Data are given in total bushels per acre, bushels of S* 8. I©,. 1*# and percentage of I®. 1*®. H I plots received an application of 0-12-12 fertiliser at the rat® of 95© pounds per acre* kmmgrn of four replications in lf$f and five in 1940.) If3f yield# * s . : f. .3. • fereeai 4 iTotal 1®. 1 1®. 1 t Total i A I© nitpogm (cheek) 96.3 * Hi.® 122.® 78.9 i B All nitrogen before i planting 87.6 153.® 103.5 t 131.4 % G 1/2 before planting s (May 22) * 1/2 after 1 month t (Swm M ) 156.® 120.9 • 128.7 77.5 i D I/2 alter 1 month t (June 22) i 1/2 after 2 aaa&hs i (July 22) 143.0 106.8 74.5 t 142.4 # E 3 application# t 1/3 before planting J 1/3 after 1 month J 1/3 after 2 months : 75.5 149.® 112.5 * least significant i ***& £ 4 m£««££ difference a 12.8 1?.® fists of applying nitrate of soda 1939 yisMs Percent » . 'S. So. 1 Ms. 1 78.5 81*3 85.5 65.® 80.8 63.7 93.5 65*8 14.8 R eproduced with perm ission o f the copyright owner. Further reproduction prohibited w ith o u t perm ission. Itt both years th© Tin® growth was heavier and greener on th© plots receiving late applications of nitrogen than It was on the plots with the other two treatments. -fcaotieslly no difference eoaM he seen between the plot® receiving all of the nitrogen at plating and the cheeks. Selsyed applicable t, gmm ai^stfio&at increase® over the check plot® in both years. freais».nt £ gave the highest yteM is lf3fi, whereas ireatawmi B m ® th# most satisfactory in 1939. the difference® in the response to these treatments mm bast be plained .-by taking th® rainfall. Into considera tion, In ifM* weafc of the heavy r&i»» were over before the dune 22 applica tion m& na&e with the result that th# first delated application was not lost by leaching, while in 1939, the precipitation was heavy until after the middle of July and St i® probable- that the nitrogen application a&de ©a June 22 was lost. I very heavy tain of 2,f5 inches fell during the night of. duly 4* Ttm late application in 1939 could have been therefor© beneficial, ■whereas is lf3# it apparently m s superfluous. treatment B with all of th® nitrogen applied at tiiae of planting showed a ®[email protected]**fc increase is total yield only to 193#. the data show a high yield of tfo. 2 grad* potato®# which suggests that the set of potatoes was good, but that the poor vine growth resulting from a lack of nitrogen in th® later stages of the p ^ m a g season was not capable of producing large stood potatoes with the heavy set. lb# data of this w^rjsjest show that inereae.ee of 2$ bushels ef So. 1 .potatoes per acre were obtained by the use of nitrogen fertiliser® when the nitrogen m s supplied at the proper periods* the selection of the time for application is dependent in part mn the m om t and time of rainfall. One application of nitrate of soda at th# beginning of the season does not appear R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - to b® satisfactory. 2 f - Th® results suggest that an initial application of approximately 25 pounds of nitrogen per acre should be made either before planting or aoon thereafter* The use of later application® of the same ■quantity should then depend on the time and severity of th® rainy periods that may occur during th# growing season. The 1940 experiment m s designed to test placement and time of ap plication of a complete commercial fertiliser* Th© following treatments were included: A. in furrow before planting. 8. Baud in bottom of furrow before planting. C. One-half spread in furrow before planting and one-half as a side-dressing. 0. 411 aide-dressed. S. Phosphorus and potassium spread' in furrow 'before planting with the nitrogen side-dressed on® month after planting. 4 baas rate of 750 pound# per acre of 3-12*42 fertiliser was applied for treatment® 4 to D, inclusive, 'for treatment £ a 0-12-12 analysis was applied in the- furrow at the rat# of 750 pounds per acre and nitrate of soda was side-dressed later at th® rate of 140 pounds per-acre. 4 Latin Square design with five replications was used. the field had cowpeas which w«r« plowed- under in 1938 and sweet potatoes in 1939. the farm. The soil in thia location was lighter than the rest of The experiment was planted to the variety Prolific, on May 23 and the side-dressing was applied m Jm® 28. The results of this experiment . are shown in table 10 R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. “ Table 10, 3© I&!j»erii»@st 2, fields in 194© of plots with different placement (Average of five replication*• Fertiliser of a >£$•42 analysis applied at the 'rate of 750 pounds per acre. treatment*. Bata are expressed ia total, tmisbels per acre, bushels of W. S. So. l*s and percentage of If, S, So, 1*8.) lethod of application of fertilise? Total yield. A - Spread in furrow before ridging 1 - Band in farrow before ridging 0 » 1/2 spread 1» farro* and 1/2 #tie**are8s«t B » A H #tt«-dr©##©4 136.3 107.9 79.1 l|t.4 107.9 m. 3 149.© 122.4 82.2 142.4 239,2 82.9 ,154.1 12S.3 i-3.2 U.S.* X*3.* 1 - Phosphorus and pot&ssiua spread in furrow and nitrogen ®M«dressed Least significant difference 0. 9. -»0, 1 yield Percent Mo. 1 * The *f*'vftl®e from the analysis of variance is not significant at odd® of Iftl. Baring the growing season m difference* could be detected ia the affiount of via© growth on the various plots. The difference* between the yields of the individual treatment* shown in table 10 are not statistically significant, the large e^periaeiital error in this cm& mm undoubtedly due to a greater variation in the soil where the es^erineot was eondnetei than was evident at the time the expmrim,m% was laid out. Bowever, by a special statistical procedure it Is possible to compare the two groups of treatments, namely, side-dressings all or in part .as a.§atsst applying all of the fertiliser in the furrow before planting. This aethsi of ©caparison reveal® a significant response in yields at odds of If to 1 ia favor of the side-dress method of application, the sMe-dresaing method of application appeared -to increase R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. mm $1 the effectiveness a t the nitrogen aor® than it diet that of phosphorus awl potassim* la tr*at«#at 1# where the phosphorus m& potassium were spread ■ia the furrow before- planting awl nitrogen was side-dressed after the planting of the erop, the yield-* were imermstmA awr® than ia the treatments where all or -part of the eeaplefc* fertiliser * Ixtare was side-dressed. Sjmeriaent % the test-of mriow® aitrogea earriew was eondaeted 4# determine Aieh aowreas wwld prove most satisfactory la this type of soil, Pitrate of soda (16 percent attrogi®), ma m k m selfat# (?0 percent aitrogaa), ealeta® nitrate (15.$ percent mrmm (42 percent nitrogen) and ealoiw cyanaaid (22 percent nitrogen) mm® ia the test, Its# latter two fertilisers were of iaterest hmmm® of their rspwbsd resistance to leaching. k hlaafewt sppli-eatioa of ?$0 powds per «sro of ©-12-12 m s applied' in the furrow before planting. ft*# mttragm fertilisers were added ia sueh quantities that 45 pounds of nitrogen wwiM hm supplied per sow. 1m 1939* two extra eyiaiwid treat®«t« were isolwlwt, ©as tr«A-sw«t sapplyiag '22.5 po*®i« and the other 6f,$ ptwfls of nitrogen per aors. the fields used had he«s cropped with sweet potatoes th# year prior to the test in -fjaeation. A a M o w i a M Moc k srrsBgemmt m s used in If3f awl a Jjttin Square i««ipi in Xf40* XI tie 3&«a Jersey mm th© variety planted in both year** The result® of IssperiaMfe 3 are given ia table 11. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - -yt %* fields of sweet potatoes froa plcta treated with . vnriaaa nitrogen fertilisers. (Average of sis replication® ia If39 aad fir# replications in 1940. fee data are sires 1» total bushel® per acre, bushels of u. 3. So. 1*.* and percentage of P. s, lo. 1*«.) table XL* fre»ta«t Check (m nitrogen) Sitrate of soda (4$ lbs. nitrogen) Ammonium sulfate (45 lbs. nitrogen) Sresma (45'lbs* sltregea) Calcium cyanauid (45 lbs, nitrogen) Calcium cyanaiaid (22| lb®, nitrogen) Calcium cyanasid (6?| lbs. nitrogen) Calcium nitrate (45 lbs. nitrogen) least sigftifiCMii difference * * s If39. yield® t S., S, 'ihswwtf. i fetal in* 1 I®. 1 s fatal 1 52,« 5«.t t 151*3 fO.f # • H5.® .144 m *s 1 141*4 « 115,5 4§,7 59*5 * 134,3 s m 4 ■58*3 57.7 ,t 124,0 t 54.7 » 109.® m*4 i»M 1 104,1 17.4 54.3 * s loi.t 57*4 52*7 * t 11.3*3 45.4 57*7 s * 17*« 12,1 1 25.3 * m m yi w d ® 0. S. ' So. 1 lo* 1 125.0 82*5 107.6 75.7 507.3 77.7 m.7 74,1 81.2 73.8 21.7 the. foliage showed a rest difference ia favor sf the nitrogen treated, plots ia 1939. the foliage ©f the check plot®: definitely shewed spptogw #f stir##®, deficiency, Of the treats* plots the ur&xaon and cysnamid. plots had the best -vine growth and the deipesfe sole?. 8©«w*r,. the ey®a«si*t plot® receiving the heavy rate of application, shewed miAmm® of leaf injury which was more intense during dry periods, the injury consisted of an ashy gray discoloration along th# margins of the leaf', The aaomt of vine growth and the general color of the foliage m s net affected. the foliage differ®##® were less instead ia 1940. A lighter shade of green ea the .cheek plots than m those receiving nitrogen « s tee chief R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 33 - recognisable variation* teat injury m s again observed on. th© calciu® c^aaasdd plots although th# foliag® ms a good grew©.* Significant differ*#®# ware obtained in each tost. Is 1939, responses la yields were obtained from th© ass of nitrogen fertilisers with nitrate of soda, ureaon, a*»alaa aaUtete and the nedlm level C4I poemla per acre) of eyasoaM giving significantly higher yieM* than the ehecfe* The high eyaiaaM. rats (67.5 pound* aitregaj per aero) m s definitely injurious to yields, ?lte results in 1940* a d*y m m m t. show that nitrogen fertilisers at th# rate of 45 pound# per acre applied before planting were not helpful to yields wrier the eonrtltloas of this season, reger&ess of the soar©# of nitrogaa* % a « ® i d In partiealar seeoed detiinental to tooth yield and grade* attMaBBgl 4 The test eoapating meagre# with' eosBKrcial fertilisers was conducted for the purpose of dstoraljiiitg the value of aaoure as a source of nitrogen* Barnyard or etcH&yard m » and turkey a*n«r« were ©erapared 'with e©»wreial. fertilisers alone awl In eoafcdtaation. the IwMfiayard sanur# was applied at the rat# of ten tons par eere «fe«» alone mA five ton® when. ia ©©atoiaati&a with the ferfciiis#!'#, The fertilizer* tewr# applied at the rate of ffO pounds per acre stiea »8®i alone or at W f powAs when used ia conjunction with the asm re. turkey asnare wee .applied at th® fate of four ton# per acre, 4 2-14-14 analysis m s used on the fertiliser plots ia. lf|§, tout ia 1939 and lf4§, &-3J-42 sikI 3~li~12 analyse* were utilised, The eot»@«ial fertiliser treatment ia lf3f consisted of 750 ootmg# of 0-ia**t2 plus 213 pounds of cyanaaid per acre, la lf4t, this treatawnt and a 3**i»»12 R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - ,34 eom&ercial sdxture M r s both tested.(see table 13)» ■ h raaiaadaed block design with fear replications m s used ia 1938, while tatin Sqastr® designs wore set up in the other two years, a 4 x 4 in 1339 and a $ x 5 in lfi©» the mama"# and jf«rtiliss«r» were applied, ia the ferrows before plaiting, 'The v&riettes used were little Stew Jersey ia 1936 and 1939, and felt# ia 1940* The «qj#ri.»afc followed eowpeas i» 1938 and 1939, and mtevmlmm. with itenure,in 1940, the yield data for lf|i are given .ia table It, and for 1939 and 1940 ia table 1%. Table 12, ®*j}#*4*wi 4. Yields of sweet potatoes froa plots treated with ■anw# and eoioaercial fertilizer, (The data are for the 193® season and are expressed in. total bushels per acre, bushels of 8-*'3* lb, l*d and percentage of U. S. JJo. I1®, Average of four replications.) Treatments Check (no fertiliser) Itali# 0.S.Wo. IT 'S3,* * lereiwt lo, I •9*1 41.1 0.# 4§,2 Barnyard manure (10 ton# per acre) 151,$ 92,1 18.0 60.8 1/2 Bauer* (5 tons per acre) and 1/2 2-14-14 (375 lbs. .per acre) iaM 78,9 U.3 §2,2 2-14-14 (750 lb»..per acre) 225*7 •0.4 5.7 §3.8 Turkey sense*# (4 tons per acre) 107.4 §3,0 H.1 58,7 3®. 5 33*§ least significant difference The vim growth on th® treated plots in. the 1938 teat wm far superior to th# growth on th# check (no fertiliser) plots. The manure plots stewed somenshat better growth than the straight coaaercial fertilizer plats, R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. In Table 13. Bgperlaegit 4. TleM® of ®w®»t potatoes fro® th® plots treated nith aanitre and ewwereial fertiliser. (Bata are given im total bushels per aere, bushels of a, S. !©, I's and pereesfcage of f, i. I®-, l*s, The results ar« for the 1939 and 1940 seasons, four replication# «em aad® in 1939 and five ia 1940.) - #n Ps* Pi •H a ♦o . 08M« & » Stt o I® ti H$> *f4to P* £»*i S H I rl 0 §? I 3 1|r4f -4- <n *• • OS -4 »rs o* rm. to *# ♦ t § 1 m 1 e\ #n 3 3 H * © ■Sr $ I m» © 3 5 li * *' t? 1 35 - « •A 0 * i £ -©* ■ s H CA «V « ■H H « ♦ O' fc r.* *Hs > II S.S- 1 ! | la if w\nr\ R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. -36 1939# the cyanaatd plots produced the heaviest and most normal amount of vine growth, iM'le, in If40, all of th# t?©ai»®nia showed sufficient vine growth* Oy&aasM caused very little leaf tejwy in this teat is lf4®, the X93S data show all of th® treatments, with the exception of turlcey maure, t© be significantly better'than the plots without fertiliser. Although mmmm had the highest average jd e M of the three top treatments, the variability of the plots was too great to attribute the difference to the effect of «asur# alone, the large suafeer of culls on the nanar# treated plots indicates m unsatisfactory, effect of »»«re on the appearance of sweet potatoes, These culls were da® to wire -mm and grub injury and to surface rots, the data ia table 13 reveal that ©oowreiitl fertilisers were superior to mmwm la 1939 and 1940, Manure d M m% pmvo to be as good a source of nitrogen m th© commercial soar®#®, Aliheu# th® culls were not recorded, the plots receiving manure produced mrm cull potatoes in both 1939 ami 1940 tits® did the plots with fertilizer® alone* The data for 1939 indicate a small difference ia the percentage of S* S. lo* 1 grade in favor of th® m m m m ial fertiliser treatseats, bat sine# a© effect is evident in the lf3# or 1940 data th® difference s»®t be considered wt&gpertast. Ia contrast t© result® from ©the? experiment* far 1940, the high rate of 43 pounds of nitrogen sopited as cyaaaaii did not prove injurious to either th® foliage or yields ia this experiatat. this may have been due to the location of the plots which were oa & light soil that is considered the poorest section of th© expeilse&taX faro, It is possible that the nitrates were not supplied fey the soil in as large qaaatities as fey soils ia ©the? locations ©a the f&ran Therefore, the nitrogen supplied by the cyanamid did R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. 3? not eause mi over-abundance of nitrates in th© soil, such as has probably occurred in •m e of the orher bxpsrimeatc. Sine# the 3-12*12 fertiliser which sullied -22*5 pounds of nitrogen gave- yields as great as the eyaasaM, th®'-extra nlfcro^a supplied-by the eyansaid m # apparently act necessary* this result substantiates th© conclusions drawn. fro» the other that ajspro-xliistely 25 pound# of nitrogen per acre ire sufficient for th# initial application ®f nitrogen* MBBSS&ggS&l A- test was sads is l$ 3 f e-ospariisi eoHSwroial fertiliser aixiurss cosssnnly used by the- growers with sdxtares containing ey««a»M. fee soil in this test block was very light-, but a crop of eospees had bees plowed aider' the previous fall, fee fertiliser m s applied in the- furrow be fore- planting, and at the rat® -of 750 peaode per acre for all the mixture# except the ©-2G-30 which was applied at a rate of 450 pounds per acre* a ® eyaawaM rate w&® 45 pounds of nitrogen per acre which was equal to six. percent in the tenas of fertiliser analysis at rates used* wore need in a r#M<»iJ.iseA block design* Five replications Kbit® was the variety planted* fee yields of this tost are shewn ia table 14* luring the summer, the vine growth. was much more favorable oa the plots f«rktH*«d with cyaaaaii* So difference® in Ibliage response [email protected] be detected between the 0-3.2*42 plot# end the plots receiving the eewwreia! fixtures o f 2-14-44 sad [email protected]* file yield# ahsnr & Marked eaperlorlty of th® 0-12-12 or 0-20-20 plots receiving the «yan«id. Since these plot# received about 30 pounds mere nitrogen per acre than the plot ® ®n stitch the 2-§46 ©r 2-1444 was applied, R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - Table 14. 31- Esq?eriraent 5, fields of sweet potatoes from plot# treated with miscellaneous cosiaercisl fertilisers with and withmgt cyanassid. (Test conducted in 1939. Data are expressed in total bushels per acr®, bushel® of U* S. lo. l*s and percentage of U. $. I©* l*a. Fertilisers applied in furrow before planting at th# rat® of 750 pounds per acre, except for the 0-20-20 analysis which mm applied at the rate of 450 pounds per acre. 1km cyanasdd me applied at the rate of 213 pounds per acre.) Treatsmts Total 8* ■§. So. 1 Fereent la, 1 ©-12-lt / efanwdd 144 m 61.3 6—26—80 •f ©yanauM 147 n 63*0 0-9-27 ^ mftm&A us w 54*7 2—8—16 124 ft 51.4 2-14-14 133 75 56*3 6-12-12 (ebeek) Ilf m 55.4 least sifBifleant difference li.O 12*1 R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. applied, it appeared that th* hi^er application of nitrogen m s of value. m the other hand, the nsall mmmt. of sitragea (15 per acre) applied ia the 2»14-14 tod 2*-S*»l& fertilisers showed practically no hsnefiel&X effect m yields. Rie low fields «» th* 0-9-27 plus cyajRaatd trestmasEt suggest an IspFeper M o » saumg the nutrient# of thi«.*iacfcnr#* Starter solutions were, tried is order to test the pessihl* effect m. plant® of ^sickly «*sllabX# .nttrsgen at th® %Jj» of t««ispli®tiaf* 1 ©eatpariaaii « * fssie befcweer plants set with water and 'with water to whieh had been added nitrate #f soda at the rate of two pounds per 50 gslXen* of water* A regular application of" >-13-12 fertiliser m ® applied in the S m r m before planting* the test wag. ©asiittcied in 1939 with th* Maryload ®®M«n variety sad ia lf4& with th# lasnatiae Ho. 1, ffae fields f m a the starter eolation test are given in table 15. fable If. Experiment 5. fields of sweet potatoes obtained by including nitrate, of soda in the water used in transplanting. (Data are expressed in bushels of 13. b* Ho. 1 potatoes per acre, average of five replications.} fr«ftt«®ots Iff! 1940 . So nitrate of soda 55 m 3 51 125 jwbiwIs per 5® ga&Um# water least signifieaaife difference 10.5 3.4 the only differs®©# in feMag® response was noted -daring th® second and third week after t»a^liwM.ng whets & slightly darker green color m s evident ia th# plant* which had received two pound# of nitrate of *st& in the tmmpHmttmg » l « . R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. -40Th* yield® far the two season® indicate that th® plants did not r*~ ■ e®lvs any lengiij*® benefit from the nitrate treatment. In If39, the yields from th# treated plot® were not significantly lower than from the entreated (check) pints, hut. In 1940, a definite dafcsimantal effect of'the treatment was observed. Imwftta at t|® storage tests the potatoes used for the storage tests were taken fro® the delayed nitrogen application plots of 3^p«rii»ni 2* One 50-pound bushel of lo. 1 grade roots were selected from each replication of th® different treatments. the records ®a the peroeatage of shrinkage and of rots were taken in the spring and were analysed fey statistical i»etbod8. The result®: of the storage test® with sweet potatoes grown in 193® ■and in. 1939 are tabulated ia table 16. the 193® data shoe soa® 'difference® ia favor of th# treatment *fe«r* all of the nitrogen, was applied at planting, feat there was too natch variability between the individual wits for the differences to fee significant, the 193f data disclose a 'significant decrease in the nsaiber of rotted, potatoes from the delayed nitrogen treatments, feat the treatments had no effect oa th® asaouni of ®t»iikii.ge. It can fee concluded safely that th* late nitrogen applications were not detrimental to th* keeping quality of sweet potatoes. In addition, there is evidence that in son# years at least, aitrogw applications may fee of vain* in reducing the «ou»t of rot occurring .ia storage. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. 41 .s i 0 +> s y js ” j’dHr4I ** & » 0 u ■« H « 3 3 a 3 g <B c» .*»+» *H fa Q.H o ® e ® sf »< ,c ifa«h M © :Vt c ■H >,~l*3 &> t* i * t m .■« j * & Hr «*\ ft 5 C M * * ^ s .5 8 3 3 ofi-1 *rs a o fe «r c O§ S*rtL* a sl«3i * s' s s £ spi:? O* « 15 •g-ss s i c ;h :*3 “-S^S |f a s a&.*«€S.'SS v\+» «*3 K s* © w s' $ * ♦ o.« * m ♦ 4» r-i IS tf\ W* ** C M <50 a' a 6^* <© *#*• - nr *A ® s «s * IB ' a %« a IS t „ 1 *>5 -*i w *a » «S0M > §S C rf «d $*« .. Inv p *8 O Q> > C Xi M I* «ff i £ 4*1 •a i w * %Q 1 # $ >m !, i jI P Sh i 1« m ii I h m *3 "Si 8 uSS *rSH -i <r%<r\« ■$ ■$£ a«i. 6 > » h JS» * «* * a a * | m o ^ d | m u * R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. — 42 — Basalts gf th# physiological analyses fh« snaples selected for.the cat^hfdr&t# sad. aiirofeii analyses, like these used for fee storage observations, were taken from the delayed nitrogen treatments of IS^erlasesi 2. fhe results of fees# analytes are given in tables If and IS. the redwing sugars were cUtu^ied as gltisow, Ail# the non-reducing sugar® were ©alettlated m smemm# fetal sugar® represent fee aa* of fee redwing and tt^-redaoing sugars. Starch was determined a# glucose times th® factor O.g. The soluble nitrogen fraction consists of that portion of nitrogen aolnbl® In hot (60 percent alcohol and would include mainly nitrate# and «#to® acids, ft© colloidal aitf»g«a fraction. iwl«l«S' all nitrogen in fo-rsi# not aetobla to hot 60 pmemat alcohol* Hi® data establish no telatioasbip b i t n m nitrogaa explications and th# starch or sugar content ©f swoet potato##. gaeis variability occurred between plots, but the differences between treatments were not consistent for the two year®, It is of interest to note, however, that to both years the ir«ati*®»h giving the hipest yield showed the lowest total sugar content. The hi# starch content of the Xf3S *»-eitrog«i treatment is out of line and should be disiNsgaried. The most sipiificaat trend to the soluble nitrogen traction is a de crease of th® soluble nitrogen content m the plots treated with a tot# (July) application of nitrogen fertiliser. The hi# nitrate content of the root#' firm th* no-nitrogen plots to If38 is out of line with the 1939 results and cannot b® chained. The .data reveal a definite increase in the colloidal nitrogen content R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 43 - 1 I . t?g 1*4 *». 'O B 1 8 8& S8 33 45 IA «-t H • *■ ♦• • - # H S <*\ «3 H rt • ■A • ■ * *a1 *o p *H 5*0 f- 52 <31 I 1 •a JS © ^ H H • * # *• H * • • . i A I I §* I 111 13 3 3 ■|i § .8 t fii- S' A M #4 & t is A •* * ♦ ■ * ■ # • • • s' wt © ** o +* tic © +» I .SS-6 SS ^ 21 ® *, ¥ 'gV* *3 J3 o fr* t*\r4 re <n •© o 8 «© S4 8 s '. 8 —3' -st ■4 ♦ A an UN UN UN s <* B g *r4 fs. « s * *♦ - w* ■# ♦ #, l 4#*t fHI- g ,m " g a ® 1 gf ii * © i i I f i f v «■«■! H et 6H *sfM s#» 4* «?I» g8 ^ €»! *!-0 * -. * ®*sf*U® « “*I C M & W ^ *' ■ © H -Q « H*W K « r-s ia > " > 0% • 1§ * ■ «5f« o d #*■*! 1§ «0SIsail I Jllfl ** _, I «| H 1 « “ tt-Ss^S I l 2 | 1 s 1 ^ - S % j « * « » r i i « r f m **f § d * > * «*« > * * O' a R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. Jirp&*p in f»rjrp«wa @-f«#»e# « •i U . - 2 « ** ■3rt•© © a * E~ 8 U N UN mm f | | | g £n a « 4. UN . 44 ** table IS. Percentago of total sugars, starch and total nitoogoit la sweat potato roots taken froia plots receiving nitrogen at different dates during the growing season, (all plots received am applica tion of 0-12-12 fertiliser at the rate of 750 pounds per acre. All plots except the checks received nitrogen at the rate of 45 pounds per acre. The data are recorded * a dry weight basis.) Trea&ent from which mmple warn taken total sugars -Percent Stareh total aitregen percent 1938 crop - Mapled April 6, 1939. A* Check (no nitrogen) 13. A H nitrogen before planting 0* 1/2 at planting 1/2 after 1 aonlh 9. 1/2 after 1 month 1/2 after 2 raontha S. 3 applications 1/3 at planting 1/3 after 1 jsonth 1/3 after 2 months 1939 drop - eaag&edi ftoveaber 1939. A. B. Check (no nitrogen) All nitrogen before planting C. 1/2 before planting 1/2 after 1 noatfe D. 1/2 after 1 month 1/2 after 2 aen&ha 20.59 20.85 57.16 .54 49.62 .52 30,65 5©.|i .53 a.oi 50.66 .77 lf.,42 si.es .66 18.38 17.7? 49.37 51.36 .43 .53 19.76 50.22 .61 If.67■ 52.96 .59 % R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. of the roots when nitrogen applications were made. the largest amounts of colloidal nitrogen were found in potatoes grown m the delayed nitrogen applieatiott plots, the potatoes from the plots receiving delayed applica tions of nitrogen also contained the highest content of total nitrogen* R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - *6- ■ DI3CU33KW The results &t this iisvestig&tioii have shown that all: three ©f the major plant nutrients give j i e M releases wbra applied to 'the Muscatine Island soils. Phosphatic and potash fertilisers gave good responses ia, all three years, thus substratiatiiig th# findings of Morgan (18) and indicating that It is necessary to add these nutrients to, these soils before any benefit cm be expected from fertilisers. Although sea* variability occurred during 'the three- seasons in the yield response to different rates of phosphorus end potassium, the wist economical rate® of application appear to be approximate ly 20 pounds of phosphorus and ff pounds of potassium .per aera. thmm aiaoants are- equal to 56 pound® of P2G5 m 250 pounds of M percent mpe*pl»»|feat* and 92.5 pounds of KgQ or 165 pounds ©f muriate of potash, It apparently makes little difference whether these lmgradirat® are applied under the ridge before planting or as- a side-dressing after planting. One result of interest Is th® fast that potash gave the greatest yield response in the dry season of 1940. Further, in. this season potash fertilisers showed a decided tendency to erase the development of chunky sweet potatoes, m effect previously reported by Schmerhorn (22) in Sew Jersey. However, sine® this effect was observed in only one year, it cannot be considered a consistent potassium response, but rather a response of potassium in conjunction with seasonal factors as well. The .-data obtained from tit®, nitrogen fertiliser tests appear acre conflicting than til# phosphorus and potassium data, but a careful survey R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 47- Ql th# factors Involved will clarify th© situation. X» two years yields wwr© markedly increased fey eertaln applications of nitrogen, ©toil© ia th® third year (1940) the use of nitrogen appeared to hav© little value and m m proved detMaastal to yields in sob® of th© tests where eyanamid was used, •the years in which nitrogen fertilisers proved of value were seasons of atoorately heavy rainfall' with the precipitation above normal in th© spring and early summer months. In these years- there were sufficiently heavy rains to cause leashing of the-nitrates, a fact which Is substantiated by th® weak and yellow vine growth oa the plots when® soluble nitrogen was applied before planting* Th© effect of leaching is particularly demonstrated by th# results of the delayed application.- tests in j£Kperi»mt 2. 'The relationship of min periods and th® time of fertiliser application for this sxperiisent is shown graphically in fig. 1. Ia 1938» th® heavy rainfall occurred in May and th® early part of with the result that th© treatment receiving the last nitrogen application on June 22 gave th# best yield. Th® cheek plots and th© plots receiving all of th# fertiliser at th® time of planting stowed weak vine growth with a consequent l-ewering ©f yields. The plots r®c®iviijg both th® June 22 applica tion and a later application m July 22 likewise showed lowered yields, probably due to m crrsovptinaX&tioo of via® growth lata in th® season which th«n'twenlted in a deficiency of carbohydrates for storage ".in the roots. Boring th# 1939 season th# period of heavy rains occurred during June mid «arly July. 1». this year the plots receiving the late nitrogen applica tion gave the high##! average yields, fit® other treatments in which the nitrate of soda was applied before or daring th® rainy period showed no totter R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 48 ~ 1938 B 1939 I Fig. 1. April | May | June | July | August j Chart showing the periods of heavy rainfall and time of application of nitrate of soda on delayed application plots of Experiment 2. The bars show the period of heavy pre cipitation and the lettered vertical lines the dates of fertilizer applications A - May 10, before planting B - June 22, first delayed application C - July 22, second delayed application R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - m - via® growth or yields than the check plots thus indicating that the heavy rains leached th© nitrate# from the- root m m awl that unless sore nitrates were added, the crop suffered fro® a deficiency of nitrogen. This conclusion with the result® of Wsr§m and Street (If). is In The resets obtained from l^eriasita .1 and 3 in 1940 indicated that in seasons of limited rainfall leaching ices not become a serious factor and, therefore, the nitrate# produced naturally in the soils may satisfactorily support the crop. At most ©ally light rates of nitrogen need be applied, the data showed that nitrogen applied at the rate of 45 pounds per acre could be Injurious to' yields particularly if the nitrogen was applied as cyan&said. Applic uiouii of .22.5 pounds of nitrogen did not prove injurious even when cyanaaid was the carrier and there Is son® Indication that this quantity ai#t be beneficial to yield# in dry years if nitrate of soda or ewoniua sulfate were applied m a side-dressing after the plants are established. low that it has be* shorn that nitrogen application# will be beneficial in years of abundant rainfall, but any be umeeeaeary in dry years, the question# arises as to a sound ©c«i«ical approach to the problem of nitrogen fertilisation, first, it will be best to evaluate the various factors con cerned, after which a logical solution may be developed, The proper rate of application 1# not easy to determine because of the coarse tester® of th® soils* The. results of the tests have shown that rates i$> to 75 pound# of nitrogen per acre were not too great in rainy seasons, while sa the other hand 45 pounds could be distinctly injurious in other year#* The data suggest that 25 pounds ©f nitrogen will satisfactorily support a crop of sweet potatoes if sever® leaching dees not occur- after it is applied. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. •- ** However, if' heavy rains do occur after the initial application, additional, quantities of nitrogen fertiliser should be applied as soon as the rainy period ha# passed. The time sad the rat® of the application will depend oa the tine of transplanting, m the amount of preeipitaties in a given period and oa the visible plant responses. It 1® the general practice in the Muscatine locality to apply eoa^iete fertilisers ia the furrow before ridging, this operation usually Is perfoiaed two to three weeks prior to planting in order that the ridges any settle properly. Sine# it is probably three weeks •after transplanting before the plant# are able to absorb nutrient a to any great extent, there is thus a period of about six weeks daring which the nltratee added'in the ©ossplste fertiliser are subject to possible leaching. Moreover, in view of the conditions stated above there should be m need for nitrates to be present during this period. Therefore, it should be generally more seoaosical to forego the ms® of n ltm g m fertilizers until after the rsiddle of June regardBess of the nature of the season. If fairly heavy - rains have occurred during the spring, It should, be best to sake the initial application of about 25 pounds of nitrogen-per m m after mid-June, however, If it 1#' cpestioasfale whether aaeh leashing has occurred, it night be wise' to wait until the via® ge&w&h is well under way ia order to employ the ap pearance of the plants as an aid la- diagnosing1possible nitrogen deficiency. *h©» the foliage shows a dLatlnct yellow color or should the amount of vine growth be below normal, an application of nitrogen should be made regardless of the. seasonal condition*. After this Initial application, the condition of the plants should be watched, very carefully end if -Mr® rainy periods occur with concomitant serious leaching, further additions of nitrogen should be R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. made, [email protected] is a limitation, however, to this recoivaendation inasmuch as ajfilieatloiis of Mtregaa made late ia the season say prove to be harmful. Cultivation is usually discontinued about August 1, and the suggestion is made that fertiliser applications &m»m at about that date, Calcium cyaaaaid is less snst^tible to leaching than nitrate of soda or atsffionium sulfate, ^therefore,, it m s tested with the 'hop® that, applied before plaiting, it mmM prowl4# a steady supply ©f nitrogen to the plants during the mtire swamv regardless of seasonal ©os^ltloRs. In lf3f* the study with three rate* of oyaaaaid fertilisation indicated that the mm of a quantity of this ch<»ioal which would supply between &2.J and 45 pounds ©£ nitrogen per acre gave satisfactory yields, A heavier application than this tended to lower the yield, la all but M e experiment in 1940 the 45 pound rate m s definitely Injurious, causing excessive vine growth and burning of the foliage with a consequent reduction in yield. Although the 22*5 pound rate m less injurious than the 45 pound rat® ever this smaller ap plication appear*! to be without value to the crop because the yields from its us# sere no better than those on the plots reeeiviag no nitrogen. %anaaid cannot be safely used in aide-dress trmtwsiiis because of the danger of toxic substances formed during gdtrlficatiou. Because of certain chemical ■properties it cannot be used m the principal source of nitrogen in & mixed fertilizer to b® applied ahead of ^planting, la view of these limitations is its us® and the conclusion that ©a the Husc&tlise sweet potato soils the nitrogen should toe- applied as a side-dressing, the miiMmtioa of eyaaamid as a source of nitrogen for sweet, potatoes ia m t advised. the other nitrogen carriers used ia the investigations, nitrate of soda, aiwoniu® sulfate, calcium, nitrate and uramon, were satisfactory 'Aen proper R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 52 ■amounts m m applied, la 1939, rates supplying up to 45 pound® of nitrogen per acre were beneficial, but, la 1940, when the rate of application m s above 22.5 pound® ofnitropo -per acre, the yields were lowered although no harmful effects were observed * tbe foliags* Therefore, it appears safe to recoMtesd the use of ammonium sulfate, nitrate of. soda, calcium nitrate sod possibly mmmm for side-dress treatments at such'quantities that nob m m than if pounds m i Mtrogs® per mwm will be supplied in any one application-. Sancre -can b© used to supply Mir©#® and if a good grade le used this material serves- the purpose fairly well, however,'a better yield of clean potatoes mm generally be obtained from the- use of eoaraercial fertilisers alone anti,therefore, it appears advisable to mm the manure m other truck crops or to so rotate the- cropping of the lead that manure can be applied in other years when sweet potatoes a w not g m m . Oonpeas new plowed water as green manures ia August m some of the esqseriaent plots. The remits showed that the potatoes respond^ to the application of inorganic .nitrogen f-m ebiU sm s on the plots where this legume m s plowed nadar, indicating that the legume crop did' not supply sufficient nitrogen, for the growth of the sweet petat© crop. analyses also substantiate this conclusion. The results -of tbs soil The nitrates could have been release, from the green Manure crop taring the fall and spring and then have been leashed out of the soil during the- apriag rains. There was ample opportunity for aibraies to fee lost between the plowing ©f the cowpeas Jji August and the planting of sweet j»[email protected]«B the following May. Moreover the growth of eowpeaa is meager under the o©isd4ti®*i® of the Muscatine district and the lasoasi of nitrogen fixed 1®, therefor®, probably very limited. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. . . - S3 - Therefore, cowpeaa as a legum® green manure crop cannot fe® considered as a substitute for inorganic nitrogen fertilizer. However, it■should not be assumed that the green manure crop used ia thee# e^eriments m s of' no the soil analyses showed that the organic content of the soil m s value, intrmsed slightly by-tfcft'lttgsne crop and it is not unlikely that the use of such a green isanure crop ia ■a rotation would be very beneficial to the sweet potato orop* The storage trials showed that the use of the higher nitrogen levels or late applications of nitrogen-bad no deleterious effect on the storage quality of sweet potatoes wader the conditions of this experiment. Since no potatoes., w e stored ttm the 1940 crop It is impossible to state what effect excessive nitrates would -have m the storage quality of sweet potatoes -grown in. a dry year. The resalts fro* the 1938-storage trials ■■showed that excess nitrates were not hawtsfial under the conditions of that season. .In the 1939 trials the potatoes stored from plots receiving late applications of nitrogen were sore resistant to storage- rots than the potatoes which received m nitrogen or all of their nitrogen at planting ties, the iartimtioaa are that under certain conditions the potatoes re ceiving sufficient nitrates fro® the soil are in better condition to for® periderm layers over wounds and are, 'therefore, sore resistant to the in vasion of storage rot or^aiwi. ■ Tbs' physiological analyses revealed that nitrogen fertilisers had no consistent effect on the sugar content and only a slight influence on the starch and soluble nitrogen content af sweet potatoes, the most pronounced effect of nitrogen fertilizers ms that of Increasing the colloidal nitrogen content of the root® when late applications of nitrsgsn were -made, This R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 5* increase m a consistent ia both years hh# anlyaes were made and on all of the delayed treatments, the.value of this increased nitrogen content is not'known, 'but it is' reasonable to assists that- the. patois, content mm fetter and, therefore, the food value #f these potatoes mas greater than that of potato#® from the cheek plots. fh« r#s»lt» of the chemical analyse# demonstrated that, no- serious re duction In food value for human consumption is likely to occur from heavy or- late appMe®ii«»»: of nitrogen to sweet potatoes and there is the possibility that the. protein content of the potato#* tuty be materially enhanced. Con sequently, the grower mm practice any method- of nitrogen fertilization that will improve lis yield# without the danger of lowering the quality &£ hi# potatoes for us# as food. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. 51 o»iem<*s Iwwst potato®* y*qpire » supply m£ m&ilafel* nitrogen from tfa® time they twfe*©.esfcafeUshad 4a tit* field until epUjmim via® growth ha* fe*«a reached.. Wm&hm the soil is capable of supplying the necessary staowih of .nitrogen will depend in part m tfee'anoniih of leaching occurring during the isffiring and early-Bummer* ttaier *®a&£&£*&* of limited rainfall and,, therefore* hut -slight cfportimity for leaching*, the natural soil nitrates may fee available in sufficient quantities for optimum plant growth. How ever, if the plant symptoms indicate a nitrate deficiency. at any time* mm *i#BMlre»*l»i a^licatloo ©f 2$ pussi* of mftmsgeti- per acre should prove profit*!!#.. Ob the ether hand* ia ease of severe leaching* due to excessive rain fall, s^5li©ati«B* of nitrogen will definitely fe« accessary far maximum yields, ?h® time of application and tiw Mount respired for the season will depend on. the mmfcer and extent of the rainy periods, there appear# m need t© apply nitrate* until the plant® have heeome established in the field, fhi# preclude® the danger of loss of nitrates at a time tften the crop would not fee them. Therefore*, after heavy or frequent spring precipita tion* an initial application of 25 pound* of alfcrogmi should fee made approx imately three weeks after transplanting in the flfeM* additional appMea- tions of a like amount should tee mad* after rainy periods that- follow the initial dosage, Steder most conditions one extra application will be suf ficient, except in the m m of prolonged heavy ndLsui. Unless tls® crop show* very drastic symptoms of nitrogen starvation, no fertiliser need be spiled R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. after the first of August under Iowa conditions. Ammonium sulfate or nitrate of soda are considered the test fertilizers for side-dressing sweet potatoes, These materials hare shown no evidences of fearful effects when used 'with discretion} they a?* quicky available and are easy to apply with side-dressing equipment. Since the soils of the i«#©atiii* district are extremely «eid, l$m$Ag saty bare to to® practiced in conjunction with the us# of ammonium sulfate. .gale&ia cyanamid proved' satisfactory ia rainy -seasons, bat since it is not suitable in dry seasons, its as® Is to to# questioned. & & e l m nitrate and urasmn 'are more expensive fertilizers, but they can to# used if deaired. Manure ©as serve as a source of nitrogen, tout the metours used in these experiments apparently did not supply nitrates ia sufficient amounts for laaxiiaua yields, sad, furthermore, th# appearance of th# harvested crop is frequently lowered ©wing to insect injuries to the 'roots and surface- root ret* which seem to to# associated with th# u»@ of s w r a , the application of phosphorus -«ad potassium fertilizer* i« essential for the satisfactory production of sweet potatoes on the Muscatine Island soil*. These materials must to® present before yield responses can toe ob tained from th# use of nitrogen fertilizers »jpnfflb©#» of th# climatic ■ conditions of a season. Appp®^aat^y 20 pounds of phosphorus and 75 pound* of potassium should toe applied each year* These fertilizers can to# applied in th# furrow before- ridging or as a -side-dressing at- th# time of to® initial nitrate application. fh#n toe furrow method of irrigation is practiced toe f«n»r- placement will probably be preferable, whereas either placement will be suitable under the- overhead method of irrigation. large or delayed applications of nitrogen did not have any harmful R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 57 effects on th# aterag* quality of sweet potato®* and ia on# year the potatoes freerdelayed trwriSM&t*. showed good resistance to. storage rots, .the use of nitrogen fertilisers protest a© consistent or pronounced variation in the sugar, starch or soli&lo nitrogen fractions of sweet potato roots* the w e of delayed applications A M lolAal Mtrdfwi .In the: root®* the content of col* this iaAlwi**. that a continuous supply of nitrogen throughout the season is beneficial .in, improving the nitrogen content of swat potato roo*s. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - 58 ^ flMSf Th# general aspects of th# of Mtvogae fertilisation on the yield, storage ipality uni «h«aieftl e^oaitiea of sweet potatoes have been covered .in this throe-year is»«#bii&tien at Muscatine Island. Sweet potatoes responded to nitrogen fertilisers whenever ImMh&ng of the .s&iwral soil nitrates occurred. Tb« «s# of delayed application# of nitrogen appears to fee the feast approach to tfee solution of th# problem. ffo nitrogen should be applied to ito# soil until the plants have be come «tafeli»h#i. Then, providing that a loss of soil nitrata# is probable bm m m of Isschiag due to heavy rainfall,, an initial application of nitrogen ahoaia fee sad# st this tin#. farther plications should, be made if tli# .plants csbsMm# to star #ppt mm of nitrogen deficiency or if other rijity periods feUow. art « # & & & • .8otwwCL fertiliser# urason -nitm gm im si#«-dr#ssissg. i%o#pfeeim# and potassim m m dtfinitsay limited in Hi# sell® used in th© iwestijatioj* and tees# »rtrt«sfc# mart be supplied before beneficial effects can fee MKmred from the- ms# of x&tvogm* fertiliser i^ppliartfesas. showed no c«asist«t os* pronounced effect on tee storage qualities art tee sugar, stttreh or soluble nitrate oofitetife of sweet .potato##, fh* nee of delayed sjfAIeatioes of nitrogen increased tli# coHoi&l aitm g m contest of th© root# ana an one year materially reduced the .loss £mm «borage rota* R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. \1, Anderson, W. S. The influence of fertilisers u p * the yield: end starch content of the Triumph sweetpot&to. Proe* Amer. See* Sort. 3d. 34*449-450. 1936. а. _________ . The""iSiu«nce of nitrogen ea'tfe* grade and shape of Triuiaph sweetpotaioes In Mississippi. Proc. kmmr. Sec. Sort.. Sci. 36*605-608. 1938. 3. Association of Official Agricultural Chemists.'‘ ' Official and teatetire netlwis of analysis. 4th ed. Miingtcn, 0. C. 1935. '4. P. 4-5. Barelas, 1. 1* Effect of fertiliser the shape of Perto Bieo sweet potato. Proc. A m t, fee. fcrt, »£. 29*425-428. 1932. 5. Cooper, J. t, .said Watts, f. K. Fertilisers for Irish potatoes, sweet potatoes, tomatoes, muskBSdons and watermelons. Arts. Agr. Sia. Bui. 333* 1936. б. Crowther, E. M. and Mirchandani, T« J. Winter leaching and the manurial mSm ®£ green aiaaures and crop r e d d ^ s for wider wheat. .fear* Agr. -id. 21*493-52$. 1931. 7. ©urrey, I. 4. Growing ismfe'potatoes ia the Taaoo-Sississippi Delta. Agr. Sep. its. id. J2?* 1939* t. 9. IB. fiurst, C. B. Methods of fertilising sweet potato*** 188. 1916. Miss. 111. Agr. Ittjs. Sia. Bui. Sdiaond, «i*. 1. and Scfielfc, 1. j. A description of certain m«tri«t gsfletsaey eysptoms of the fort© M m sweetpotato, free. Amor. fee. lost. Set* 36*544-549. 1938. Gsise, f. «• fertiliser studies and the production of sweet potatoes. mqp. Sta. Bui. 3S1. lf»f* R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. Md. Agr. • Si ll. iofcehkfs»y ft. s. Sweet potato fertiliser experiments at substation so. 2, fr©«#. t«hk* lif. 2xp. Sta. Bui. 2??. 1921. 12. Soaghlacsi, #.?.€». ' fertiliser studies wltls sweat pointmm* ifsm . Sell' Soi. 26?291-304. If. Johnson, f. C. Bffects of organic setter to aaiataiBiag soil fertility for truck crop production, ft©®., isser, fee* Start. Sci. 21*277-281. 1924. 14. Loomis, 9 S. wid Shull, C. A. Methods in plant physiology. [email protected]*«»-ilIl look -Omapssgr, Inc. Sew York. 1937. 15. Uller, J. S. and Eiabrough, 1 , 1 . Sweet potato production la jtetdwiasa. 'la, 4gr. Ssp, Sts, Bui. 281. in*. . . 16 f. J. fhe effects of smmar greea Mature# on the aamonia and nitrate contents of soils crowed for winter wheat, I w * Age, Sci, 21*458-468. 1931. 17. lorp®, M*. F* and Street, f * 1* Seasonal mat®* .uni nitrate lewrtiitif# in f^tl&tlon.i© sell and sown# of fertiliser nitrogen. Conn. flew Sw«tt| Jtgr, Ssp. Sta, Bui. 42$. li. Oargaa* M. S» Elation ©f f#ftiM»tioa t© the yield and keeping quality of sweet potatoes, 9mm. laer. 3oc. Hurt, Sci. 37*849-854. 1939. If. Porter, i. 1. Srowiag and hanCULng sweet potatoes in Califomia. JSstt. Cire. 55. 1931. Calif. Agr. 30* ClttSmi, J. f» Sane effects of .fertilisers ©a sweet .potatoes, free* Aaer. Soc. Hort. Sci. ■.12*3^-363, 1909. a, Scott, J. M, Sweet potato fertiliser eKperiaent. . H a , Agr, &p. Sts. Bui* 156. 1920 22. &a!i«*am&«*% 1. -ft. Sweat potato stadia# ia lew Jersey. 1904. ». J. Agr. fiqa. Sts. Bui, 39®. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. - a * 23* ■24* 25, Saedeeor, 0. I. Statistical, methods. lews. If4§* ji «4. fte# Iowa State College Press. Ames, J, 3 ., lilli&as, C. B. and Mann, i. B. for sweetpotatoe# baaed on investigations in Sorth ©mali m * i* 3. Dept. Agr. Tech. lal, 335. 1932. Stuckey, It, P. Sweet potatoes, culture, storing and studies in fertilising, Qa. Agr. Exp. Sta. Bui. 10?. 1914* 26. Taylor, J. B., Jr. and Tidatore, J* S. Hitrogen economy in different systems of soil and crop aanagesaent. Ala, Agr. JSsep. Sta, Ann. Ipt. 48:12-13. Iff?* 27* Ibedard, Otis. Sweet potato eulittre la "the coastal plain of .Seorgia. Plain Exp, Sta* Bui. 1?, 1332. SB, Ga. Coasts Bisuaerley, I, 1, Sweet point® fertilisers, .fa. 'track Crop Sxp. Sta. 'ML, 66. 1929* .... -j..— — . ft» eTfeei of 'IMME fertiliser ratio on tie shape of the Bart© lie® sweet pitat#. Pros. Aaer. A m u Jtori* Set, 32:498-501, 1934* 30* Tates, f. .......... Th® design and analysis of' factorial e^erijstsAe, Imp. Bar, Soil Bci. feelt* Ommu 35. 193?. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission. The writer wishes to m ^rnm M e sincere ;s^pr*^#iati« to the following; Professor B. I. Pickett for M b gaMam* during the progress of the isreeti-* fatten and the preparation of the timgiiej Professor i* f. Sreia for M s .assistaas# ia. outlining the profelea smA £or M s tsa«y *»gg©«hii»* ia. connection Mill, the ©^periiaental detail*$ Pr. A* ft* i««sa sad Or, 1 , H* Pierre for ItMStr 'Mi la the soils phase mi the iarsstifstiasi Sr. ¥, 'I* laeais for his advice m the storage end physiol©0m M phases of the workj Br, S* S, Haber for aany helpful suggestions* lh»f«s©r S. ¥* .InMooor and Mss Gertrude fos for th*tr eo^eratioa mad help with the. statistical assays#* and experi mental designs. R eproduced with perm ission o f the copyright owner. F urther reproduction prohibited w itho ut perm ission.