A MASTER'S THESIS DAVID WAYNE NEWTON MASTER OF SCIENCE. Department. Manhattan, Kansas. Approved byj

Transcription

1 ' ZINC CONTENT AND YIELD OF CORN AS INFLUENCED BY METHODS AND RATES OF APPLICATION OF ZINC AND PHOSPHORUS by DAVID WAYNE NEWTON B. S. t Kansas State University, 1962 A MASTER'S THESIS submitted in partial fulfillment f the requirements fr the degree MASTER OF SCIENCE Department f Agrnmy KANSAS STATE UNIVERSITY Manhattan, Kansas 1966 Apprved byj ajr prfessr /

2 2- %(, TABLE OF CONTENTS & ', Pag< INTRODUCTION I REVIEW OF LITERATURE * EXPERIMENTAL PROCEDURES tl RESULTS AND DISCUSSION 16 Shawnee Cunty. * 17 Pttawatmie Cunty 23 Osbrne Cunty 26 SUMMARY 33 ACKNOWLEDGMENTS 35 LITERATURE CITED 36

3 INTRODUCTION Zinc deficiency as a prblem in crp prductin in Kansas has becme mre imprtant in recent years. As cultural practices are imprved, mre imprtance may be attached t this prblem. Increased use f high analysis fertilisers and the methd f placement in relatin t plants may be a cntributing factr in tine deficiencies. As use f imprved management practices increases yield ptentials, the present level f sine availability in sils may becme limiting. Leveling f land fr Irrigatin may expse sine deficient subsils. In sme areas f Kansas, enes f lime accumulatin may be expsed which culd decrease the availability f sine in sils. In these and ther tine deficient sils, phsphrus may induce tine deficiencies. Micrnutrients ther than tine may becme deficient in sme sils f Kansas. The bjectives f this investigatin were t study the effects ft (1) tine fertilizatin n crn grwn n sils knwn r suspected t be tine deficient, (2) rates and methds f applicatin f tine and phsphate fertilisers n uptake f tine by crn, (3) tine and phsphate fertilisatin n crn grwn n calcareus sils, and (U) t study the use f tine ferti liters where high yields are the gal.

4 REVIEW OF LITERATURE Zinc has been recgnised as en essentia! element fr several years. In an extensive literature review, Thrne (18) gives 191U a* the year when sine was fully cnfirmed as an essential element. Recgnitin f zinc deficiencies under field cnditins has develped extensively since. Zinc deficiencies f plants result in cmbinatins f chlrsis, rsettlng, diebeck, and abnrmal r depressed vegetative grwth (18). Barnette and Warner (2) described a physilgical disease f crn called "white bud," a frm f chlrsis, and fund a zinc deficiency as the cause. Vlets, Bawn, and Crawfrd (22) reprted deficiency symptms fr 26 crps grwn n zinc deficient sils f central Washingtn. Deficiency symptms listed fr crn Included intervelnal chlrsis and necrsis f lwer leaves plus shrtened Interndes. Plants were tentatively classified as being very sensitive, mildly sensitive, r Insensitive t zinc deficient sils. Crn, beans, and sybeans were amng the cmmn field crps listed as being very sensitive. Grain srghum was classified as mildly sensitive. Much f the early research cncerning zinc deficiencies invlved fruit crps. Chandler (9) has reviewed the histry f verifying and treating zinc deficiency symptms f fruit crps in Flrida and Califrnia. Early wrkers fund that zinc was the nly micrnutrlent, when added t the sli, effective in relieving deficiency symptms f fruit trees.

5 3 Hwever, sil treatments were fund t require large amunts f cine sulfate. It was assumed that the sine was fixed in the sil and was nt available t plants. Deficiency symptms culd be alleviated by driving a number f sine cated nails int the tree, but this methd was cnsidered impractical except fr verificatin purpses. The mst effective methd f remving sine deficiency symptms was fund t be aerial applicatins f a sine sulfate slutin. This technique has been used fr a number f years. Zinc deficiencies in field crps have been studied extensively nly recently. Deficiencies in Imprtant field crps were believed t ccur nly In islated areas and received very little attentin. Bamette, Camp, Warner, and Gall (1) fund that sine sulfate was effective in curing white bud f crn n the lighter sandy sils f central Flrida. Viets (20) reprted sine deficiencies in crn and beans grwn n newly irrigated sils f central Washingtn. Pumphrey and cwrkers (15) have recently nted sine deficiencies f irrigated crn in western Nebraska and fund that the symptms were becming mre widespread in that area. The mst effective treatment was fund t be five punds f sine as ZnSOj^ per acre bradcast and plwed under. Many attempts have been made t determine sine deficiency levels in plants. Data are nt sufficient t establish a critical level (16). The level at which respnses may ccur prbably depends n ther nutritinal r envirnmental factrs, a level f belw 15 ppm sine in leaves f

6 plants has been used. Bawn and Legget (5) fund that neither develpment f deficiencies nr eliminatin f deficiencies was well crrelated with changes in cncentratin f cine in stems and leaf tissues f ptat plants. In studies n the effect f temperature n phsphrus induced sine deficiencies f tmates, Martin, McLean, and Quick (lb) fund that bth deficient and nrmal plants had abut the same cncentratin f sine at high temperatures. Watenabe, Lindsay, and Olsen (23) suggested that the use f critical values t diagnse nutrient disrders is nt always satisfactry. The range in plant cmpsitin assciated with deficient and nrmal plants ften verlaps. Hiatt and Massey (12) als shwed that sine deficiency symptms are nt necessarily related t the cncentratin in the plant. Sil cine deficiencies ften develp where the surface hrizn has been remved by ersin r leveling fr irrigatin (11, 19, 20, 21). Vlets (20) in 1951 reprted cine deficiencies n newly Irrigated sils f central Washingtn. Crn and beans grwn n these sils were chlrtlc and stunted in grwth. Applicatin f cine sulfate slutin as fliar spray caused resumptin f grwth and cure f chlrsis. Viets et el. (21) fund the cine deficient sils f Washingtn where the tcpsll hnd been remved were generally mre alkaline In the plw layer (ph 7*6) and ften had a cne f lime accumulatin near the surface. Grunes, Bawn, Carlsn, and Viets (11) studied "cut areas" in Nrth Dakta and fund a marked cine deficiency in check plts.

7 5 Ferti 11 eat in with tine and additin f manure were bth effective in relieving zinc deficiency symptms and increeaing yieida f crn. Travis (19) determined zinc availability in the prfiles f several knwn r auspected zinc deficient Kansas sils. Sils frm areas recently leveled fr irrigatin cntained lw cncentratins f available zinc. The available zinc cntent f the sil Is nrmally assciated with the surface rganic cntaining hrien and decreases in cncentratin In the lwer hrizns. Where the surface hrien f calcareus sils had been remved by erain r land leveling, a zne f free carbnates was ften fund. This might be imprtant in decreasing availability f zinc in calcareus sils. Zinc deficiencies frequently ccur in sils cntaining abnrmally high cntents f sluble r ttal phsphates (18). Zinc deficiencies induced by phsphate fertilizer applicatins have been reprted by several wrkers (5» 7» 8, 10, 11, 13, 1U, 16, 23). Other wrkers (6, 8, 21) have fund that such treatments d nt Induce zinc deficiencies. Mst f the early evidence f phsphrus Induced zinc deficiency was bservatinal (6). The appearance r accentuatin f zinc deficiency symptms as a result f phsphate applicatin prvided qualitative evidence that the symptms were phsphrus induced. Rgers and Wu (16) were amng the first t present quantitative data which shwed a decrease in ttal zinc cntent f plant tps as a result f applying

8 I phsphate fertilizers. Wrking with varying treatments f lime, phsphate, and sine n ats in Flrida, it was fund that cine cntent f plants decreased t an almst cnstant value with Increasing rates f phsphate, while phsphrus cntent increased regularly in direct rati t that applied. Subsequent wrk in Washingtn (6, 21) and Tennessee (17) failed t shw tine deficiencies induced by phsphrus. Viets et a]_. (21) fund that applicatins f phsphate did nt induce zinc deficiency symptms r restrict zinc uptake in crn as shwn by leaf analysis. Hwever, ptassium and phsphate accumulated in tine deficient plants. The cnclusin was that accumulatins f sluble phsphate in the sil culd nt accunt fr tine deficiency f crn n thse sils. Bawn (6) cnsidered the effect f phsphate applicatins t the very sensitive field bean in the same area f Waahingtn. Phsphate applicatin had n effect n the uptake f either applied r native sil ainc. Seats, Stergea, and Kramer (1?) atudled the respnse f flax and srghum t f erti li eat 1 n in Tennessee. Yields were significantly affected by liming and phsphrus end ainc fertilizatin. Plants receiving ainc cntained less phsphrus then thse nt receiving zinc. Hwever, phsphrus fertilizatin up t 1000 punds phsphate per 2,000,000 punds f sil had n influence n zinc respnse, but did significantly increase yields. In mre recent wrk, there is better agreement that phsphrus can induce ainc deficiencies. C-runes and

9 7 cwrkers (11) nted that in crn grwing in cut areas in Nrth Dakta, cncentrated superphsphate appeared t increase sine deficiency symptms. Fr tw cnsecutive years, Burlesn, Dacus, and Gerard (8) bserved phsphrus induced tine deficiencies In crn grwn in the Lwer Ri Grande Valley f Texas. Mst f the recent wrk has been cnducted in greenhuses using sils that prduced phsphrus induced sine deficiencies in the field (7, 6, 10, 13, lit, 23). Burlesn et al. (8) nted severe phsphrus induced sine deficiency in kidney beans with phsphrus fertilisatin. Zinc absrptin was increased by sine fertilisatin and decreased by phsphrus fertilisatin. Phsphrus uptake was increaaed by phsphrus fertilisatin and decreased by sine fertilisatin. When bth sine and phsphrus were applied, the uptake f bth sine and phsphrus were reduced, it was cncluded that phsphrus fertilisatin may induce sine deficiencies in sme crps under certain sil and climatic cnditins. Langin, Ward, Olsn, and Rhades (13) shwed that phsphrus applicatins markedly reduced sine cncentratin in crn. The mre effectively phsphrus was utilised, the mre severe the curtailment f sine uptake. It was believed that the prblem was greatest in calcareus sils which are initially high in available phsphrus and where sine slubility is restricted by high ph. Ellis, Davis, and Thurlw (10) studied sine availability in a calcareus Michigan sil. High phsphrus applicatins

10 decreased zinc cncentratin end ten punds f sine edded increased sine cncentratin in crn tps. Yields f field beans were reduced mainly due t phsphrus induced sine deficiency* Bawn and Legget ($) grew Russet Bur bank ptates n field plts f the Clumbia River Basin in Washingtn and in nutrient slutins. Levels f phsphrus and sine nutritin were varied s that bth nrmal and sine deficient plants were prduced. Increasing the supply f phsphrus induced a grwth disrder that culd be eliminated by an increased supply f sine. Brwn and Tiffin (7) and wetanabe et ak (23) studied nutrient balances invlving phsphrus, irn* and sine. Brwn and Tiffin (7) fund that In the absence f Irn and sine, Increasing additins f phsphate accentuated r caused sme plants t develp sine deficiencies when grwn In Tulare clay (a sine deficient sil). It was als reprted that t much sine caused Irn chlrsis t develp in crn and millet. Watanebe (23) encuntered varius nutrient interactins frm additin f mdest levels f sine, Irn, and phsphrus t s calcareus sil shwing respnse t these nutrients. Further investigatins f nutritinal effects f varius levels f phsphrus, irn, and sine in nutrient slutin cultures buffered by means f slid phase C8CO3 were made n crn and pint beans. Results with crn shwed that sine cncentratins were depressed at all zinc levels with additin f phsphrus. Additins f phsphrus

11 did nt Interfere with the utilisatin f tine in pint beans. The effect* f temperature n phsphrus Induced sine deficiencies have been reprted by several wrkers (8, 10, III). Burlesn (8) nted tine deficiencies in crn grwn in cld wet sils during the early part f the grwing seasn and suggested that this was prbably phsphrus induced. It wss thught that phsphrus induced tine deficiency is caused by restricting rt develpment near the tne f ferti liter placement. Ellis and cwrkers (10) fund that yield, tine cncentratin in the plant, and tine uptake by crn decreased when the sil temperature f a calcareus Michigan sil wms decreased frm 75 t 55 F. Martin, McLean, and Quick (lu) grew tmates ss indicatr plants in cine and phsphrus deficient sils. On e sil mderately lw In tine, phsphrus Induced tine deficiency symptms ccurred at 50 and 60 F. On an acutely tine deficient sli, phsphrus Induced tine deficiencies were nted at all temperatures. The mechanisms end cnditins invlved in the develpment f phsphrus induced tine deficiencies are nt fully understd. Frequently ffered as en explanatin is that Insluble tine phsphates and hydrxides ere frmed (3, k, 16). Bingham and Martin (k) cncluded that cpper end sine were adversely affected by Large applicatins f CafHgPOjj^'^O and presumeably by ther phsphate carriers. Bingham and Garber (3) later studied availability f tine

12 10 in the presence f en excess f Ca(H2PC^)2 in 19 zinc deficient Califrnia sils. It was cncluded that phsphrus fertilisatin may prduce imprtant interactins with tine in sils lw in available sine* Data f Ellis (10) supprt the pssibility that the zinc-phsphrus interactin ia either at the rt surface r within the plant. Langin et il. (13) cncluded that damaging effects f phsphrus n zinc utilizatin is physilgically within the plant, perhaps in plant rt cells, and is nt a simple chemical precipitatin f zinc phsphate external t the rts. Since applied zinc cunteracts the harmful phsphrus effects, it wuld appear t be an absrptin phenmna in rt cells where increasing levels f phsphrus wuld blck absrptin f zinc, and vice versa. Watanabe et ak (23) suggested that phsphrus may interfere with nrmal utilizatin f zinc In the plant. Data cllected by Bawn and Legget (5) shwed that abnrmal grwth Is nt assciated with decline in zinc cncentratin r ttal zinc In the plant, but suggests that abnrmal grwth results frm an imbalance between phsphrus and zinc. Results shwed that high cncentratins f phsphrus in tissues resulting in a high phsphrus/zinc rati appear t ffer a better explanatin fr metablic upset. Healthy ptat plants had a phsphrus/zinc rati f less than 1*00, while deficient plants had a rati f greater than hoo, Watanabe (23) reprted that slightly depressed yields f crn appeared t be assciated with an extremely high

13 11 phsphrus/ainc rati. Further evidence f the imprtance f prper nutrient element balance was given by Brwn and Tiffin (7). Burlesn, Dacus, and Gerard (8) suggested the pssibility f a phsphrus-einc antagnism within the rt, Bawn and Legget (5) stated that a mutual antagnism might exist, but that a full understanding f the mechanism will prbably invlve mre than a simple relatinship invlving nly phsphrus and sine* Further prgress in understanding the phsphrus-ainc relatinship depends t a large extent upn understanding the factrs invlving plant and sil relatinships. The research that has been dne demnstrates the imprtance f nutrient element balance in plant nutritin and sil management (7). EXPERIMENTAL PROCEDURE Field experiments were cnducted with irrigated crn at three lcatins in Kansas in 1965* One lcatin was n the farm f U.r. Je Campbell in the Kansas River valley in Shawnee Cunty. This experiment was cnducted during the secnd crp seasn after leveling fr irrigatin. A secnd lcatin was in the Kansas River valley in Pttawatmie Cunty n the farm f Dr. Ernest Mader. The sil at this lcatin had nt been leveled fr irrigatin. A third lcatin was In the Slmn River valley In nrth central Kansas.

14 12 This experiment was n a newly leveled* calcareus sil n the farm f Mr. Gerge Oiisn in Osbrne Cunty. A randmised cmplete blck design with fur blcks and twelve treatments was used. The blcks were 50 feet in length at the Pttawatmie and Osbrne Cunty lcatins and 25 feet in length at the Shawnee Cunty lcatin. Fur rws (rw width was 1 0 inches) were used fr each treatment. All lcatins received a blanket applicatin f nitrgen befre the crn was planted. Applicatins f 150 punds per acre f actual nitrgen were made in Shawnee and Pttswatmie Cunties. Experimental fertiliser treatments were made immediately after the crn was planted. Rates f fertiliser used, n a per acre basis, were 10 punds f sine as sine sulfate, starter ( ) withut sine and starter (10-UO-20) with 5, 10, and 20 punds f sine as sine sulfate mixed with the starter. These rates were applied by tw methds, bradcasting and banding. Fertilisers fr the bradcast treatments were distributed by hand. The banded treatments cnsisted f placing the fertiliser in a lcalised area at the side f the rw with a tillage implement. One additinal treatment was made using starter (10-1*0-20) plus 10 punds f sine as sine sulfate as a split applicatin, i.e., half was bradcast and the ther half banded, a check plt was the twelfth treatment. Tw absrptin spectrscpy techniques were used fr the labratry analyses. Phsphrus was determined using a clrimetric prcedure. Clrlmetry cncerns the absrptin

15 13 f visible light by a clred slutin. Radiatin absrptin is measured as a functin f wavelength and sample cncentratin. The wavelength f incident light chsen is the wavelength mst absrbed by the test slutin. The amunt f light absrbed is related t the intensity f incident light I and the intensity I after passing thrugh the slutin. The sample cncentratin c can be fund by using the Beer 's- law expressin: InO/i) m <=< c i t where 1 is the length f the sample cell and is the absrptin cefficient. The amunt f light transmitted thrugh the sample, %1, can be used t determine sample cncentratin since #T» l/l x 100. Atmic absrptin spectrscpy was used fr zinc, irn, and manganese analyses. Certain atms in their grund state will 8bsrb radiatin f a resnance wavelength. In atmic absrptin spectrscpy, a slutin cntaining the test element is vaprized by using a high temperature flame. The absrbance f the flame fr light f a resnance wavelength is a measure f the cncentratin f absrbing atms in the flame. Therefre it Is als a measurement f tha cncentratin f atms in the test slutin. Sil samples frm each lcatin were analyzed fr available zinc. The extracting agent used was 0.2N HC1. The staples were prcessed using a wden rller and a I4O mesh stainless steel sieve t avid cntaminatin. Five grams f sil were placed in 100 ml plyethylene centrifuge tubes and 50 ml f 0.2N HCi were added. After stirring, the tubas

16 Ik were stppered with plyethylene stppers and placed n a wrist actin shaker fr ne hur. After shaking, the ph f a small prtin f the suspensin was measured. The pk must be less than 5 in rder t insure cmplete extractin f available sine. The samples were then centrifuged until the supernatant liquid was clear. A 40 ml aliqut f the supernatant liquid was taken t dryness. The residue was brught int slutin* filtered, and made t a final vlume f 25 ml with 0. In HC1. A Perkin Elmer Mdel 303 atmic absrptin spectrphtmeter was used t determine tine cncentratins. The wavelength used was 2136a. A standard curve was made using cine cncentratins f 1, 2, and 3 ppm. The third leaf frm the tp f the crn plant was used fr tissue analyses f phsphrus and cine. Ten leaves were taken frm the tw center rws, excluding ten feet at each end {2\ feet at each end in Shawnee Cunty) fr each treatment. The samples were dried at 65 C fr three days and then grund. The grund samples were stred in cardbard bxes. Phsphrus cncentratin in leaf tissues were determined in duplicate using 0.4 gm samples. Samples were placed in $0 ml pyrex beakers and 5 ml f alchl slutin cntaining MgfCgJ^O^g'UHgC were added t each sample. The beakers were placed n a ht plate and the samples were ignited by applying a flame t the beakers. After the burning had stpped, the samples were placed in a muffle furnace and ashed at 550 C fr tw hurs. After cling,

17 10 ml f 2N KC1 were added t the residue. The residue was filtered and the filtrate taken t the desired vlume with distilled water. The ph f the filtrate was adjusted t a phenlphthalein end pint with 0.2n NaOH. A blue clr was develped in the filtrate by adding 2 ml f ammnium mlybdate slutin and 2 ml f rganic reducing agent (aminnaphthi-sulf nic acid) and mixing. The cncentratin f phsphrus in slutin is related t the amunt f light that can be transmitted thrugh the clred slutin. After 15 minutes, the transmittancy was measured with a Cleman Junir spectrphtmeter at a wavelength setting f 660 mfl. A standard curve was made using knwn phsphrus cncentratins. Fr the determinatin f sine cncentratin in plant tissues, 2.0 gm samples were used. Duplicate samples were placed in 50 ml pyrex beakers and dry ashed at 550 C in a muffle furnace fr tw hurs. Abut 10 mi f 0.1N HC1 were added t the residue and stirred. The residue was filtered and the filtrate waa made t a final vlume f 25 ml with O.iN HC1. Zinc cncentratin was determined using the atmic absrptin spectrphtmeter. Irn and manganese cncentratins were determined fr the plant tissue samples frm Osbrne Cunty after pr grwth was bserved at that lcatin. The atmic absrptin spectrphtmeter was used fr these analyses using the extract prepared fr the ainc determinatin. Wavelengths used were 2U80A fr irn analysis and 2800A fr

18 16 manganese analysis. Yields were determined fr etch treatment by hand harvesting the middle 30 feet f the tw center rws (the middle 20 feet f the tw center rws in Shawnee Cunty) and weighing. The misture cntent was determined by weighing a three ear sample immediately after harvesting, then drying at 65 C t a cnstant weight. The weights f the harvested crn were then crrected t misture. The weight f crn per plt was cnverted t bushels per acre (ne bushel ear crn?0 punds). RESULTS AND DISCUSSION The effects f phsphate and sine fertilisatin n the cncentratin f sine and phsphrus in crn leaves, and yields f crn were studied at three lcatins. Varius fertiliser rates and methds f fertiliser applicatin were used. Data btained at each lcatin are discussed separately with n attempt being made t crrelate the results btained at different lcatins. The significance f differences are based n the $% level. Available sine levels In the sil at each lcatin are given In Table 1. Available sine levels at a sil depth f three feet are given fr the Shawnee and Osbrne Cunty lcatins.

19 17 Table 1. Levels f available sine In the sil prfiles at three experimental lcatins. Lcatin f experiment Cncentratin f available zinc LeeeJ Sampling depth 0-6 Inches j feet Shawnee Cunty Pttawatmie Cunty 2.7 Osbrne Cunty Shawnee Cunty The sil at the Shawnee Cunty lcatin cntained 1.6 ppm f extractable sine in the surface hrizn and 0.9 ppra at a depth f three feet. This level f extractable sine was cnsidered t be t lw fr nrmal grwth f crn. Visible sine deficiency symptms were nted in crn plants that had nt received sine. Deficiency symptms were prnunced during the early stages f grwth, but tended t disappear during the latter part f the grwing seasn. Sil cnditins were clder and wetter than nrmal during the early stages f grwth, which may partially accunt fr the prnunced deficiency symptms. Mre extensive rt grwth after the sil had warmed may have decreased the severity f sine deficiencies. A mre extensive rt system may increase zinc uptake by the plant because f Increased rt cntact with the sil, r pssibly by rts

20 18 grwing int & sil layer with a higher cncentratin f available zinc. Hwever, in this sil, the level f available zinc appeared t decrease with sil depth. The cncentratins f zinc and phsphrus in crn leaves and yields f crn are given in Table 2. Zinc cncentratins In crn leaves were higher, when cmpared t the check plt, fr all fertiliser treatments cntaining zinc, except where ten punds f sine per acre was banded. Banding zinc increased tine cncentratin in the plant, but the difference was nt significant. Zinc cncentratin was nt significantly effected by applying 10-U0-20 fertilizer withut zinc. The methd f fertilizer applicatin appeared t be a factr in leaf einc cncentratin when 10-U0-20 fertilizer was used. Fr the bradcast applicatins f 10-1*0-20 fertilizer there was little difference in leaf zinc cncentratin, except the treatment f 10-JjO-20+20Zn did have a higher cncentratin than the 10-1; 0-20 withut zinc treatment. Hwever, differences were bserved when 10*^0-20 fertilizers with varius rbtes f zinc were banded. Treatments f 10 -I[ OZn and 10-l Zn had higher leaf zinc cncentratins than the ther banded treatments. Fr the 10-^0-20+OZn treatments, leaf zinc cntent was lwer when the fertilizer was banded. Leaf zinc cncentratin was nt affected by the methd f applicatin fr the 10-l*0-20+5Zn treatment. Banded treatments f 10-l Zn and 10-lj Zn had higher leaf zinc cncentratin than

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22 20 did the crrespnding bradcast treatments. The split applicatin f lo-l* zn gave the same effects as the bradcast treatment. Bth the methd f applicatin and the rate f zinc in the 10-1*0-20 fertilizers affected phsphrus cncentratin in crn leaves. The treatments where 10-1*0-20 was banded, regardless f the sine rate, had higher leaf phsphrus cncentratins than the check plts. Bradcast treatments f 10-1*0-20 fertilizers als increased leaf phsphrus cncentratin, but nt t the degree that the banded treatments increased phsphrus cncentratin. Hwever, increases fr the bradcast treatments f 10-1*0-20 with 5 and 20 punds f tine were nt significant at the 5% level. Zinc alne did nt influence phsphrus cncentratin in leaves. The rate f zinc did nt affect phsphrus cncentratin in the crn plants when the 10-1*0-20 fertilizers were bradcast. Hwever, leaf phsphrus was affected by banding the 10-1*0-20 fertilizers with different rates f zinc. Leaf phsphrus cncentratin was very high fr the 10-1*0-20 withut zinc treatment and decreased with increasing rates f zinc. Banding the 10-1*0-20 fertilizer withut zinc and with 5 punds f zinc resulted in much higher leaf phsphrus levels then when these rates were bradcast. The methd f applicatin did nt significantly affect leaf phsphrus cncentratin at the higher rates f zinc In the 10-1*0-20 ferti llzers.

23 21 Yields f crn were higher with all treatments f 10- l40-20*zn, regardless f the methd f applicatin and rate f zinc, when cmpared t the check plts. Treatnents f sine alne and bradcast applicatin f IO-I4O-20 withut tine Increased yields, but the Increases were nt significant at the $% level. Banding IO-I4O-20 fertiliser withut sine decreased the yield 15 bushels per acre, but the difference was nt significant at the accepted level f significance. Fr bradcast applicatins, there were n significant differences In yield fr the varius lo-uo-20+zn r rettnents. Fwever, yields were lwer when zinc alne and IO-I4O-20 withut zinc were applied. When the fertilizers were banded, yields did nt differ fr the varius 10-l 0-20+Zn treatments. Where 10-J 0-20 withut zinc was banded, the yield was much lwer than fr all ther banded treatments. Applicatins f with the higher rates f zinc were mre effective in increasing yields than banding zinc alne. In general, the methd f applicatin did nt significantly affect yields fr the varius fertilizer treatments. Hwever, the withut zinc treatment was an imprtant exceptin. Banding C+0Zn resulted in a decreased yield f 28 bushels per acre. The yields were relatively high thrughut the experiment with nly tw treatments giving yields f less than 115 bushels per acre. Hwever, yields were affected by the phsphrus-zinc relatinship, especially when the treatments

24 22 were banded. Fr the banded i0-l*0-20+0zn treatment, sine cncentratin In the leaf was very lw (3.9 ppm), phsphrus cncentratin in the leaf was very high (0.39%), and yields ware much lwer than the ther treatments (93 bushels per acre). It appeared that a phsphrus induced sine deficiency was prduced by this treatment. Increasing rates f tine up t ten punds with the banded 10-1*0-20 treatments increased sine cncentratin in the leaf, decreased phsphrus cncentratin in the leaf, increased yield f crn snd apparently was effective in relieving deficiency symptms f the plants. It appeared that a level f 9 ppm tine in the crn leaf, at the time f sampling, was sufficient fr yields f abut 11*0 bushels per acre except where leas than ten punds f sine was banded with the 10-1*0-20 fertiliser. Applicatin f five punds sine with the banded 10-1*0-20 fertiliser gave a yield f 131 bushels per acre while the leaf sine cncentratin was 9.3 ppm. The phsphrus level in the leaf fr this treatment was , which was greater than when higher rates f sine were banded with the 10-1*0-20 fertiliser. The Increased cntent f phsphrus might have caused the slight decrease in yield. Results btained In thia experiment indicate that the phsphrus-sine relatinship was imprtant under the existing experimental cnditins. Results shwed that applicatin f sine with 10-1*0-20 starter fertiliser was effective

25 23 in alleviating cine deficiency symptms and increasing yields f crn. Pttawatmie Cunty The experiment in Pttawatmie Cunty was n a sil that had nt been leveled fr irrigatin. The cncentratin f available sine in the surface hrizn was 2.7 ppm. Available tine was nt determined in the lwer hrizns. This level f available cine was nt very high, but there was n reasn t expect the sil t be zinc deficient befre the experiment was started. All ther sil factrs were cnsidered t be sufficient fr the prductin f high yields* This was supprted by 8 check plt yield f 126 bushels per acre (Table 3). The main bjective f this experiment was t determine If the additin f sine fertilizer wuld Increase crp yields where ther cnditins were nt limiting. Grwth was unifrmly gd fr all fertilizer treatments thrughut the grwing seasn. There were n visible signs f zinc deficiencies nted at any time. Cncentratins f zinc and phsphrus in leaf tissues and yields fr the varius fertilizer treatments are shwn in Table 3. Statistical analysis f variance shwed that differences in yield and leaf phsphrus cncentratins were nt significant at the $% level. There were significant differencea in levels f zinc cncentratin in crn leaves with varius fertilizer

26 2k is 6 9 O U w av V) *> C 15 a«*!> a w I".1 c 0)0 >- ja.. \0 **\ j$ «-f CM OJ f*v 7^ c.sr cm cm cm cm 3 CVJ cm w s ft) O U ~«C V ft) t«c V* v. t O c n a *f w u a > i C 1 4 ItO M O V ««d >» I a *-> 6 - c -4 O a C 1 V«*I X) 9 t jc «*J ft} *> a» *j c > ffi c 9 O c U to M 6 O +>.«* O U *» *» V. c «-» V» ft) UUD. C V. I CO O V c I u c en 11 a t 1 a. *J g c c i.1 c a ««<5 O a c fa cvj <n a. «VA vo O O O VN 3 CN " O (\ ^ 1A CM CO r\ O I I I i CM & in CM CM CM CM CM 1 t 1 1 O -3-1 O f Jt 1 vo ft) 6 J s ft) c v. x ft) u c Q> s Vi V» V) +* c in CM 5. Vi c c O) ft) u «a 0) J g: s U U ft) a c t? U 4-> 1 I a UN O U a M C -U <-4 O U *J U «J *J CD t «M 6X -< jc <C a*-> *j a C <M U C x Vi Oft) Vi O) J= c u 9 «J ft> < c 6 A

27 25 treatments, but a general relatinship culd nt be established. It appeared that additinal fertiliser applicatins might have depressed leaf sine cncentratin except where fairly high rates f sine were placed clse t the plants. All f the bradcast treatments f 10-1^0-20+Zn had lwer leaf sine cncentratins than the check plts. Banding treatments f ten punds f sine and lo-uo-20 withut sine als gave lwer leaf sine cntents than the check plts. There was sme difference nted amng the bradcast treatments, but n definite trend culd be established. Bradcasting the 10-ljO-20+Zn treatments gave lwer leaf sine cncentratins than the ten punds f sine per acre treatment, but nly the 10-U0-20+5Zn treatment was significantly lwer. Fr the banded treatments, a higher sine cncentratin ccurred fr the 10-i* Zn treatment than fr sine alne. When 10-IjQ-20 treatments were banded, increasing the rate f sine appeared t Increase leaf sine cncentratin. Higher leaf sine cncentratins ccurred when the 10- ijq-20+5zn and 10-J n treatments were banded rather than bradcast, using a split applicatin f fertiliser did nt influence the level f sine cncentratin in leavea. Althugh differences in phsphrus cncentratins in leaves were nt fund, the cncentratins fr all treatments were high, ranging frm 0.33 t 0.37* phsphrus. Banding fertilisers cntaining sine increased yields frm 5 t 10

28 26 bushels per acre, but these Increases were nt significant at the level. Data btained in this experiment were nt sufficient t establish a critical level f plant sine cncentratin. The suggested value f 1$ ppm was nt valid fr the cnditins at this lcatin since gd yields were btained fr all treatments. Levels f sine cncentratin, at the time f sampling, were less than 15 ppm except fr ne treatment. The high phsphrus cncentratins may have depressed the sine cncentratins t a degree, althugh yields btained were nt affected. The slight increase in yields btained fr the treatments where 10 and 20 punds f sine per acre ware banded suggests that slightly higher rates f sine might be mre effective. Hwever, Increasing sine rates might develp cmplicatins with regerds t ther essential nutrient elements. Osbrne Cunty The experiment in Osbrne Cunty was cnducted n a recently leveled calcareus sil. The surface hrizn f the sil cntained 2.3 ppm extracteble sine. The sil had a slightly higher level f extrsctable tine, 2.6 ppm, at a depth f three feet. Befre the experiment was started, it was suspected that this sil was sine deficient. The main bjective f this experiment was t study the effects f tine and phsphrus fertilisatin n irrigated crn grwn n a calcareus sil.

29 27 Grwth f crn was stunted thrughut the experimental area fr the duratin f the grwing seasn. Severe deficiency symptms similar t thse fr sine deficiencies were nted fr all treatments. The bradcast treatments f 10-1*0-20 fertiliser were nt as severely deficient as the ther treatments. Applicatins f tine were nt effective in relieving the deficiency symptms. The failure f tine treatments t alleviate deficiency symptms suggested that sme ther minr element might be deficient r adversely affected by the calcareus nature f the sil. Fr this reasn, leaf tissues were analysed fr irn and manganese as well as fr tine and phsphrus. The cncentratins f tine and phsphrus In leaf tissue samples and yields f crn are shwn in Table k* Irn and manganese cncentratins in leaf tissues are given in Table 5* The banded applicatin f ten punds f tine per acre was the nly treatment that had significantly higher leaf tine cncentratin than the check plts. Sme differences were nted fr the ther treatments when cmpared t the check plts, but nne were significant at the S% level. Fr the bradcast treatments, applicatin f tine increased leaf tine cncentratin. Bradcasting 10-U Zn and tine alne were the mst effective treatments. When the fertilisers were banded, the withut tine and the ten punds f tine per acre treatments had the highest leaf tine cncentratins.

30 t*- -«V\ Ch U\ 1 >*3 vo O O \0 \0 C\i c\ a 2 CD u *J, C Vi f CO in u &v> a. _3" IA V\ IA U\ 4»C vo *H XA w» O ft * c >> *-> *J s. c *-> r c ut, 6) *J O w8 M i i u ~* *j c c I t5 u ci. 1 a In 5 (Mm 0, (0 I -«c I I CO -si «JVT\ c (8 C) w M ~< c c D) «J u V) V» ce -«CO T> 6 3

31 1 29 Table 5. Cncentratins f irn end manganese In leaf tissues f crn grwn n Irrigated sil in Osbrne Cunty. Treatment 8! l rn cncentratin : Manganese cncentratin N_P 2 CV-H 2 0*Zn t (pp* in leaf) : (ppm in leaf) (as 2nSCf ) j Bradcast t Banded t Bradcast I Banded U CC * w 71 I * $ 20.U ; l0-l b 19.1 iu Check Least significant h.2 15 difference (.05) A unifrm applicatin f nitrgen in additin t the nitrgen In the starter was applied. One half f the fertiliser was bradcast and the ther half was banded.

32 30 The methd f applicatin did nt affect leaf cine cncentratin when sine was included in the fertilizer treatment. Hwever, higher leaf line cncentratin did ccur when 10-i*0-20 withut nine was banded rather than bradcast. Under the existing experimental cnditins, banding phsphrus fertiliser withut sine did nt decrease leaf zinc cncentratin as might be expected. Instead, banding 10- UO-20+OZn increased zinc cncentratin by U.2 ppm. Phsphrus cncentratins in leaf tissues were lw fr all treatments, but significant differences were nted. Applicatin f zinc alne had slightly lwer leaf phsphrus cncentratins than the ther treatments. Higher phsphrus cncentratins ccurred when 10-1*0-20 fertilizers, bth with and withut zinc, were bradcast. Yields fr all treatments were much lwer then nrmally expected fr Irrigated crn. Yields shuld have apprached, r even exceeded, 100 bushels per acre with a prper nutrient balance under the existing envirnmental cnditins. Yields fr all treatments ranged frm 6 t nly 36 bushels per acre. An extremely lw yield f 12 bushels per acre fr the check plts suggested a severe sil deficiency f sme nutrient r nutrients. The highest yield f 36 bushels per acre indicates that the fertilizer treatments used were partially effective, but that ther elements might be lacking. Applicatin f zinc alne decreased yields when cmpared t the check plts, but decreases were nt significant

33 31 at the 5% level. All bradcast treatments f 10-1*0-20 fertilisers had higher yields than the check plts. Banded and spilt applicatin f IO-JjO-SO* lozn als resulted In slightly higher yields. Fr bradcast applicatins f 10-1*0-20 fertilisers, Increasing rates f sine up t ten punds Increased yields. The bradcast treatment f sine alne resulted In a much lwer yield. Ten punds f sine applied with 10-1*0-20 fertiliser was the mst effective treatment when the fertilisers were banded. Bradcasting 10-lj0-20 fertilisers, at all sine rates, was mre effective than banded treatments f crrespnding rates. A general relatinship between yields and sine cncentratin in the leaves culd nt be established. Treatments where the higher yields were btained did nt necessarily have higher cncentratins f sine In leaves at the time f sampling, a pssible explanatin may be that dilutin f the leaf sine cncentratin ccurred where plant grwth was Increased. Yields did appear t be related t phsphrus cncentratin in the leaves. Althugh leaf phsphrus cncentratins were thught t be t lw fr gd yields, the higher yields were btained fr treatments where phsphrus cncentratins were als higher. It was expected that crn plants wuld have higher leaf phsphrus cncentratins when lo-ljo-20 fertilizers were banded, but this was nt the case under the existing cnditins. Data btained were nt

34 32 sufficient t explain this unexpected result. Since the applicatin f bth sine and 10-1*0-20 fertilizer failed t relieve deficiency symptms and increase yields t the expected levels, it was cncluded that sme ther nutrient was limiting. Levels f irn and manganese in the leaf tissues were determined t see If these elements might have affected yields and plent grwth. Leaf cncentratins f manganese were relatively high fr all treatments, rsnglng frm 71 t 105 ppm. Generally, where yields were highest, leaf manganese cncentratins were lwest, and vice versa. Where manganese cncentratins were lwest, It was nted that plant grwth was generally the best. The lwer cncentrstlns may have been due t a dilutin effect caused by increased grwth. The pssibility that manganese might have been a factr in plant grwth and yields f crn was discarded. Irn cncentratins in the leaf tissues ranged frm 10.8 t 23.3 Ppm. There appeared t be n general relatinship between leaf irn cncentratins and yields f crn, but the levels f Irn present were prbably t lw fr gd plant grwth. There are n data available that wuld indicate the critical level f irn needed fr the existing experimental cnditins. The availability f Irn t the crn plant may have been decreased due t the celcareusness f the sil, a decrease in availability was prbably mre likely than an actual deficiency f irn in the sil, rganic matter may

35 33 increase availability f irn, but the rganic cntaining ail hrien had been remved prir t the experiment. The lack f rganic matter and the excess f calcium carbnates in the sil prbably were bth effective in reducing irn availability t the plant. The reaults btained indicate that bth sine and irn were deficient in the sil used fr this experiment. Breadcase applicatins f fertilisers with sine increased yields t a degree. Levels f irn in leaf tissues indicate that this element might be lacking. Increasing the rganic matter cntent f the sil, either by natural accumulatin r applicatin f manure, might Increase the availability f bth sine and irn. Further wrk needs t be dne at this experimental site t determine the sine and Irn relatinships t plant grwth. It may be fund that slnc-lrn Interactins are Imprtant and that phsphrus may be Invlved at higher cncentratins f all elements cncerned. SUMMARY Data btained shw that zinc-plant relatinships were Imprtant when crn was grwn n sine deficient sils. Sme evidence was fund that sine may be limiting when ther factrs are sufficient fr high yields f irrigated crn. Visible sine deficiency symptms were nted in crn grwn n the zinc deficient sli In Shawnee Cunty. Applicatin f sine was effective In relieving deficiency symptms.

36 3k Bth sine and phsphrus cncentratins in leaves were affected by rates and methds f applicatin f 10-1*0-20 fertilisers cntaining sine. Treatments cntaining sine increaaed yields, hut the increases where sine alne was applied were nt significant at the $% level. The sincphsphrus relatinahip was imprtant at this lcatin. There were indicatins that sme f the severe deficiencies were phsphrus induced. Banding rates f sine up t 20 punds per acre increased yields f crn in Pttawatmie Cunty, but the increases were nt significant. Phsphrus cncentratins in leaves were extremely high fr all treatments. 21nc cncentratins in the leaves were affected by the varius fertiliser treatments, but the levels appeared nt t be related t yields. In Osbrne Cunty, grwth f crn was stunted and deficiency symptms were apparent fr all treatments. Yields were lw in all cases indicating that sme nutrient besides sine was deficient. Zinc cncentratins in leaves were affected by varius fertiliser treatments, but levels culd nt be related t yields. Leaf phsphrus cncentratins were very lw, regardless f the fertiliser treatment. Manganese cncentratins in leaves apparently were sufficient fr gd grwth. Lw cncentratins f irn were fund in the leaves. Irn deficiency may have been the mst imprtant factr limiting prductin f high yields f crn at this lcatin.

37 35 ACKNOWLEDGMENTS The authr withe* t extend grateful appreciatin t Dr. Rsce Ellis, Jr., majr prfessr, fr his guidance and assistance during this study and in the preparatin f this thesis. Appreciatin is expressed t members f the supervisry cmmittee fr their helpful criticisms and suggestins in the preparatin f this thesis. Special thanks are due t Dr. Ernest Wader, Mr. Je Campbell, and Mr. Gerge Gllan, n whse farms the field experiments were cnducted. Appreciatin is given t the Eagle-Picher and Bennett Chemical Cmpanies fr financial assistance in supprt f this investigatin.

38 36 LITERATURE CITED 1. Barnette, R. M., Camp, J. p., Warner, J. D., and Gall, 0. E. The uae f sine sulphate under crn and ther field crps, Fla. Agrl. Exp. Sta. Bui Barnette, R. M., and Warner, J. D. A respnse f chlrtlc crn plants t the applicatin f cine sulfate t the sil. Sil Sci. 39:11*5-160, «Bingham, F. T. and Garber, M. J. Slubility and availability f micrnutrients in relatin t phsphrus fertilisatin. Sil Sci. Sc. Am. Prc. 24: I960. i. Bingham, F. T. and Martin, J. P. Effects f sil phsphrus n grwth and minr element nutritin f citrus. Sil Sci. Sc. Am. Prc. 20: » Bawn, L. C. and Legget, G. E. Phsphrus and fine cncentratins in Russet Burbank ptat tissues In relatin t develpment f sine deficiency symptms. Sil Sci. Sc. Am. Prc. 28: Bawn, L. C., Viets, F. G., Jr., and Crawfrd, c. L. Effects f phsphate fertilisers n sine nutritin f field beans. Sil Sci. 78: Brwn, J. C end Tiffin, L. 0. Zinc deficiency and irn chlrsis dependent n the plant species and nutrientelement balance in Tulare clay. Agrn. J. 54: Burlesn, C. A., Dacus, A. D., and Gerard, C. J. The effect f phsphrus fertilisatin n the sine nutritin f several irrigated crps. Sil Sci. Sc. Am. Prc. 25: Chandler, W. H. Plant physilgy and hrticulture. Ann. Rev. Plant Physil. 10: Ellis, R., Jr., Davis, J. F., and Thurlw, D. L. Zinc availability in calcareus Michigan sils as influenced by phsphrus level and temperature. Sil Sci. Sc. Am. Prc. 28: j. 11. Grunes, D. L., Bawn, L. C., Carlsn, C. and Vlets, F. G., Jr. Zinc deficiency f crn and ptates as related t sil and plant analysis. Agrn J. 53: Hiatt, A. J. and Massey, H. F. Zinc levels in relatin t sine cntent 8nd grwth f crn. Agrn. J. 50:

39 37 13* Langln, E. J., Ward, R. C., Olsn, R. A*, and Rhedes, H. F. Factrs respnsible fr pr respnse f crn and grain srghum t phsphrus fertilisatin: II. Lime and p placement effects n p-zn relatins. Sil Sci. Sc. Am. prc. 26:57li *. Martin, W. E., McLean, J. G., and Quick, J. Effect f temperature n the ccurrence f phsphrus-induced sine deficiency. Sil Sci. Sc. Am. Prc. 29tUll-l Pumphrey, F. V., Kehler, F. E., Allmaras, R. R., and Rberts, S. Methd and rate f applying sine sulfate fr crn n slnc-def icient sil in western Nebraska. Agrn. J. 55: Rgers, L. H. and Wu, C. Zinc uptake by ats as influenced by applicatin f lime and phsphate. Agrn. J. 1*0: U Seatz, L. F., Sterges, A. J., and Kramer, J. C. Crp respnse t sine fertilisatin as influenced by lime and phsphrus applicatins. Agrn. J. 51:1*57-1* Thme, W. Zinc deficiency and its cntrl. Adv. In Agrn. IX: Travis, D. 0. Zinc availability in prfiles f selected Kansas sils. Unpub. r 'asters Thesis. Kansas State University Vlets, F. G., Jr. Zinc deficiency f crn and beans n newly irrigated sils in central Washingtn. Agrn. J. 143: Vlets, F. G., Jr., Bawn, I. C., Crawfrd, C. I., and Nelsn, C. E. Zinc deficiency in crn in central Washingtn. Agrn. J. 1*5: Vlets, F. G., Jr., Bawn, L. C., and Crawfrd, C. I. Zinc cntents and deficiency symptms f 26 crps grwn n a sine deficient sil. Sil Sci. 78: Watanabe, F. S., Lindsay, W. L., and 01 sen, S. R. Nutrient balance invlving phsphrus, irn, and sine. Sil Sci. Sc. Am. prc. 29:

40 ZINC CONTENT AND YIELD OF CORN AS INFLUENCED BY METHODS AND RATES OF APPLICATION OF ZINC AND PHOSPHORUS DAVID WAYNE NEWTON B. S., Kansas State University, 1962 AN ABSTRACT OF A MASTER'S THESIS submitted in partial fulfillment f the requirements fr the degree MASTER OF SCIENCE Department f Agrnmy KANSAS STATE UNIVERSITY Manhattan, Kansas 1966

41 / BS TRACT An investigatin was cnducted t study the effects f sine and phsphrus fertilisatin n irrigated crn under varius field cnditins. Three lcatins were used fr the experiment. Lcatins were in Shawnee and Pttawatmie Cunties in the Kansas River valley and in Osbrne Cunty in the Slmn River valley. Fertiliser treatments were ten punds f sine per acre and lo-ijo-20 starter with 0, 5, 10, and 20 punds f sine per acre. The methds f applicatin were bradcast and banded. The experiment In Shawnee Cunty was cnducted n a recently leveled, sine deficient sil. Visible sine deficiency symptms were bserved in crn plants that had nt received sine. Deficiency symptms tended t disappear during the latter part f the grwing seasn Indicating that temperature may play a rle In the uptake f sine by crn. The rates and methds f fertiliser applicatin affected bth sine and phsphrus cncentratins In crn leaves. Yields f crn were increased with treatments f 10-1*0-20 fertiliser cntaining sine. Applicatin f sine alne Increased yields, but the Increases were nt significant at the $% level. The slnc-phsphrus relatinship in crn plants was Imprtant at the Shawnee Cunty lcatin. Banded applicatin f 10-^0-20 fertiliser withut sine decreased yields

42 2 end zinc cncentratin in the leaves* but increased phsphrus cncentratin In the leaves* Increasing rates f sine in the bended fertiliser treatments increased yields, increased leaf sine cncentratins, and decreased leaf phsphrus cncentratin t a nrmal level. There were indicatins that sme f the severe sine deficiencies were phsphrus induced. The experiment in Pttawatmie Cunty was cnducted n a sil that was nt cnsidered t be zinc deficient. High yields f crn were expected at this lcatin. A yield f 126 bushels per acre wa3 btained fr the check plts indicstlng that cnditins fr grwth were gd. Zinc cncentratins in the leaves were affected by the varius fertiliser treatments cntaining zinc. Levels f phsphrus cncentratins in the leaves were high fr all treatments, but differences between treatments were nt significant. Yields ware increased 5 t 10 bushels per acre by increasing banded rates f zinc up t 20 punds per acre, but these increases were nt significant at the 5% level. The experiment In Osbrne Cunty was cnducted n a recently leveled, calcareus sil. The sil was expected t be zinc deficient due t the remval f the rganic cntaining sil hrizn and the calcareus nature f the sil. Grwth f crn was stunted and deficiency symptms similar t thse fr zinc deficiencies were nted fr all treatments. Zinc cncentratins in the leaves were affected by the varius fertilizer treatments, but n general relatinships

43 culd be established. Phsphrus cncentratins In the leaves were higher where 10-1*0-20 fertl liners were bradcast, but the levels were lw in all cases. Yields were Increased by the bradcast treatments f 10-1*0-20 fertilizers, but were still nt as high as expect«d. The levels f manganese cncentratins in the leaves indicated that manganese was nt a Uniting factr. Irn cncentratins in crn leaves were lw and culd have been the mst imprtant limiting factr. A relatinship Invlving phsphrus, zinc, and irn might have been respnsible fr the pr grwth and lw yields f crn at this lcatin.