Campbell, C.A.

Davidson, H.R.

Hinman, W.C.

English

eCommons@USASK

Effect of N fertility and soil moisture on yield and nitrogen accumulation in Manitou wheat

University of Saskatchewan

University of Saskatchewan Research Archive

- 102 -EFFECT OF .N FER'l'.LLl'l'l AND SOIL MOISTURE ON YIELD AND NITROGEN ACCUMULATION IN MANITOU WHEAT C. A. Campbell, H. J:i. Davidson and V.l. C. Hinman* ~NTRODUCTION The effect of N fertility and soil moisture on the growth and yield of spring wheat, and the disposition of N in the soil-plant system were investigated. In the present paper the effect of moisture and N fertility on .N accumulation in the plant tops, and grain yield will be discussed. MATERIALS AND ~THODS Manitou wheat was grown in 15-cm diameter, 120-cm deep galvanized iron lysimeters which were pushed into a Wood Mountain loam by means of the soil-coring device already described by Dyck et al. (1976). The stubble field contained 18 kg N03-N/ha in the top 60 em of soil at seeding. Two soil moisture regimes Lnatural rainfall (dry) and irrigated (wet17, seven rates of nitrogen LQ, 28, 56, 84, 112, 168 and 224 kg/ha N03-N as Ca(N03)z_l, and five sampling times (3 leaf, tillering, shot blade, late anthesis, and maturity) were combined factorially and their influence OB N accumulation and grain yield determined. There were two replicates. All lysimeters received 112 kg/ha P2o5 as superphosphate. Three seeds were planted in each lysimeter; this was the rate of seeding calculated to be equivalent to that generally used in southwestern Saskatchewan. Destructive sampling was employed. At each sampling date plant samples were taken and the number of tillers, leaves, the leaf area, dry matter and Kjeldahl N determined. Also, the soil was cut into 2.5-and 5-cm segments; odd-numbered segments were used for moisture and chemical analyses and even-numbered segments for root determinations. All pertinent meteorological data were collected. Only data pertinent to this paper will be discussed here. RESULTS Growing Season Conditions Because of abundant autumn and early spring precipitation the stubble field was moist to about 150 em at seeding time. As will be shown later, this moisture provided good growing conditions until between shot blade and anthesis when a hot dry spell during the first three weeks in July (Fig. l) caused incipient wilting on several occasions. However, timely rains fell in late July and early August thus alleviating the moisture stress problem, although this also tended to extend the period of maturation. Consequently, samples taken at maturity were harvested over a period from about day 75 to day 95 after emergence. *Research Scientists, Research Station, Research Branch, Canada Agriculture, Swift Current, Sask. ~ ~ (/) !i ..... ... z 2 I 30 ! 20 ..J ..J c( ~ 10 4 a:: 0 i! .I ;:. ~ • 12 t t :. i ~ j I ... "' • • 20 30 9 19 MAY JUNE - 103-t .!!! .. • ! ... J ·! c: " .! j 3 .. i= .II: ., ... • • ~ • 29 9 19 29 8 18 28 JULY AUG. Fig. 1. Diurnal air temperature and precipitation during experimental period Effect of N Fertility and Water on Dry Matter Accumulation • lS lj E .. ~ • 7 ~ As previously shown by Dr. Davidson (1976), dry matter of wheat increas-ed sigmoidally with time under wet conditions, and also under dry conditions at rates of N .(. 84 kg/ha /Jig. 2(a) and (b[/. Generally, dry matter also increased exponentially with applied N except under dry conditions at· rates of N). 84 kg/ha /Jig. 2(b)]. Under the latter conditions the dry matter remained relatively constant between shot blade and late anthesis. However, prior to shot·. blade, and also after late anthesis the dry, higher N treatments accumula-ted dry matter more rapidly than the dry, low N treatments. As will be shown.· later, these interactions were related to the rate of soil moisture use as - 104 -influenced by fertility, as well as to the relative amount of available N still present in the soil just after late anthesis. 16 _!14 .. e ·;; -' 12 .... 01 -~10 {! ~ 0 .. 8 :! .. 0 2 ... s .. 0 4 2 0 0 10 N Applied ( k9 I ho) • 0 0 28 6 56 " 84 I 112 0 168 • 224 .. 01 f .. ~ 0 .. 40 :! 0 50 60 I 70 .. 01 ~ .. ,.. 0 85 ~ 16/6 23/7 ~ Days otter EmerCiJence (DAE) Fig. 2(a). Dry matter production of above-ground parts -wet treatment Effect on N Concentration in Above-Ground Parts Nitrogen concentration in the above-ground vegetative parts decreased with time (Fig. 3). This was at least partly due to the gradual decrease in available soil N with time (data not shown). The average % N in plant tissue for all N treatments was 5.3 at the 3-leaf stage, 4.6 at tillering, 2.2 at shot blade, 1.5 at late anthesis and 0.5 at maturity (only straw). Thus, the greatest decrease in N concentra~ tion occurred between the tillering and shot blade growth stages; this corresponds to the period of maximum dry matter accumulation (Fig. 2). Although the differences were small, % N tended to be greater in the drier treatments; this was especially true during the later stages of development. Nitrogen concentration tended to increase with N application - 105 -r: ------··-- --- ···~ N Applied ( kg I ha) ... 0 Cll • -Cll 0 28 E ·u; 10 .. 56 >- Cll _J A 84 "' ...... I 112 ~Dl .Q 8 a 168 -0 Cll >< 224 .s::. a. Cll 0 ,_ ..... 6 >o 0 -·;: ... ::J Cll --0 -Cll E 0 4 'iii :E Dl Cll tV tV c .s::. Dl Dl ... -0 >o 0 tV c ... ... -Cl tV 0 Cll > tV Cl 2 - -Cl Cl Cll 0~----r-.-m~~--,-----T-----n---~~--~----~ 0 10 30 40 50 60 I 16/6 23/7 Days after Emergence ( DAE) 70 85 ~ Fig. 2(b). Dry matter production of above-ground parts -dry treatment up to 84 kg/ha but above this there was no further increase. The relationship between N concentr•tion and dry matter accumulation was inversely and curvilinearly (concave upwards) related (data not shown). Willcox (1954) has suggested that yield was inversely and linearly related to % N, while Steenbjerg (1954) reported that these parameters were related by U- or S-shaped curves. However, Viets (1965) reported that the latter types of curves were rarely obtained when semiarid soils were irrigated. We attempted to quantify the relationship between N concentration and dry matter accumulation. First we checked Willcox 1s•increase yield-nitrogen law" (1954) by plotting the reciprocal of % N versus dry matter at various stages of development. The results (not shown) indicated that during vegetative growth the law held but not thereafter. Furthermore, the rate of change in N concentration with dry matter accumulation was a function of 6 5 ~ 4 01 0 ... -z3 2 - 106 -- 3 Leaf Stage - Tillering -Shot Blade ··~ - Late Anthesis """"- Maturity - Dry Treatment -- Wet Treatment ---·--- -,... _______ ,... ..,, ---A----~::-:::-:;; ..... - __ ..,._-------~----6 ... ---- --- -----------~ 0+----r----r---~--~---------r------~ 0 28 56 84 112 168 224 N Applied ( kg/ho) Fig. 3. Effect of N and water on vegetative N concentration fertility level and soil moisture. In another attempt at quantifica-tion we tested the hypothesis that dry matter was related to N concen-tration by a negative power function of the type: Dry matter (DM) • (%N)-k. Except for the values at the 3-leaf stage of growth this relationship fitted the data much more precisely than did the "inverse yield-nitrogen law11 (Fig. 4); k was calculated to be 0.63, 0.52, 0.37 and 0.43 under unfertilized-wet and -dry, and fertilized-wet and-dry conditions, respectively. Effect on N Content in Above-Ground Parts Under wet conditions N content was as great in the early stages of development and much greater in later growth stages than for the corresponding dry treatments (Fig. 5). The latter was primarily - 107 ------·-·-·-·--···-· Treatments Fertilit~ Moisture !. - Unfertilized Dry 0.52 o---o Unfertilized Wet 0.63 -k -1'Fertilized Dry 0.43 DM•(%N) 1.8 •---• Fertilized Wet 0.37 ( 1'AvQ. of all Fertilized Treatments) 1.5 I t 1.2 z ~ • ..... 0.9 • ~ 0.6 0.3 .0~--~----~---r----r---~--~~--~--~~~~---~ -2.0 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 2.0 lov, Dry Motter Fig. 4. Quantitative relationship between dry matter and N concentration 2.5 because of the substantially greater dry matter produced under the wetter conditions. N content increased more or less exponentially with time under wet conditions. Under dry conditions the e.ame was true up to shot blade but between shot blade and late anthesis there was no increase in N content at rates of N .( 84 kg/ha, while at the three highest rates there was actually a loss of N from the tops of abou-t 0.03 g N/ lysimeter (i.e., 2($ of the N in the tops a.t shot blade). The roots of these dry, high N treatments aleo lost N du.ring this period of drought (data not shown). This loss of N was due to a lower N concentration (Fig. 3/because d~ matter had remained constant during the period in question ffig 2(blf. The total N of all treatments increased significantly between late anthesis and maturity, with the treatments which had received >84 kg/ha increasing more rapidly than those which had received smaller rates. These increases were, no doubt, facilitated by the timel;r rainfall rece.ived in late July to early August after late anthesis (Fig. 1). The relative increase was likely related to the amount of mnused fertilizer N which of the~ fo:rn1 tl-:.~;ae the soil; TILL~~!NG conditicn_s ~ 108 ~ ;~~.tl'Y i11:Ltia]_ l,e'!~re.l n~r (:d.; r; ~ £\ c::;f.J:c~~:~ta.nt; aJKl - 109 -are proportionality constants which are dependent on tne conditions of growth. The response under dry condn,J.ons was different from that normally obtained. For example, the response to low increments of N was small, while response to increments >84 kg N/ha was large (Fig. 7). -6 c .. E -0 e s ... -.. J: ,......,4 -""' I <( -.,3 gt 0 I <( 2 .. gt 0 .....=... I y=A(I-e-kN)(wet soil) •--- y = ae kN (dry soil) A = max. yield y = yield ot ony Initial level of N in soil k1, k • rote constants )( • 7.9 7.8 7.7-c .. e -0 7.6~ ""' .. Q 7.5 • 0 o· 7.4 o~--~~---r----~--~~---r----~--~~--------------~~3 0 40 eo 120 160 200 240 280 Available N03 - N in 90 em. Profile at seeding plus N mineralized to 3 leaf stage (kg /ha) Fig. 6. Quantitative relationship between grain yields and N concentration in soil ~trapolating the lysimeter yields to a kg/ha basis snowed tnat without added water or N stubble-wheat yielded 1600 kg/ha. (Incidentally, this was exactly the same yield obtained when square meter samples of the inter-lysimeter guard crop was sampled). Irrigation alone increased yield by 72% (2740 k~/ha); addition of 224 kg N/ha increased yield by about 45% (2352 kg/ha) under dry conditions and by 75% (4795 kg/ha) under wet conditions. Under dry conditions grain crude protein concentration increased from 15.4% in the zero-N treatment to 17% at rates of N application ~ 84 kg/ha (Fig. 7). Under wet conditions protein increased from 14.1% to just over 15% with increasing N fertility. The protein yield was ,--8.5 -~ 7.5 --Q) E -et: 5.5-UJ .... .... <t ~ >-et: 0 4.5-~ 3.5-: (!) 2.5-,... ,.... ,_,.... ..... ,... ..... ~ ~~ ~ ~~ ~ ~ ~~ 7:; ? ~ ~~ 'JI" % ~~ ~ '/: % ~ t% ~:/1 1 234567 N APPLIED (kg /ho) - 110 -0 0"' 17--z Q ~ ~ 16-.... z UJ u z 0 15-u -z UJ .... 14-0 et: a.. 0 WET ~ DRY 13- .................. ..L..,ju.. 1234567 N APPLIED (kg/ho) I • 0 2. 28 3• 56 4• 84 5• I 12 6•168 7•224 .... .... 1.4-~ 1.2-Q) .§ en ::0... ...l -....1.0-CI .... 0 ...l !:!:!0.8->-z UJ .,_o.s-o et: a.. 0. 4- WM"""IU.""-dt4. 1234!567 N APPLIED~ Fig. 7. Effect of N and water on grain yield and protein approximately twice as much under wet as under dry cond~t~ons even though protein concentration was higher under the dry conditions. Available Water in the Profile as Influenced b N Time and Irri ation Up to the )-leaf stage of growth, applied N had no obvious effect on the amount of available water in the soil profile (Fig. 8). By ~~~l 1,::Jl'-5lfl'~ tli!!"~rt w:;.~ ~ t.JNM t,o~s a. decrease in available water with increasi·ng, ra.it.:es of nit!f'(!)~ ~~ ~ rcomi.lt.ions. The i..nvef'se rel-ation-ship between available water and nitrogen !ertil.it:r was evident in b~h moisture treatments at the shot blade stage. By late anthesis th€ same trend was evident in the wet treatment, but in the dry treatment all available water had already been depleted at all levels of nitro~en and soil moisture was actually below the 15 atm level (zero line). -:.-, . 151 12 daJs before = 10 ·c; .. e .. In !5 0 ..... emerfJence 3 leaf stage (14 O.A.E. - 111-(a) DRY Tillering (25 O.A£.) WATER ADDEO • DURING PERIOD INCLUDING RAIN Shat blade (39 O.A.E.) 0 xN °t-~~12~3~4~!5~6~7t-~~--~~izt,i4~5~6~7~~----~~~2~!~4~!5hs~7f-~~--~~~~--~----rrrrrr~-----e .. -w ..I Ill ct ..I ~ 15 ct ..I :! . 0 10 ~ I • 0 2 • 28 3 • !56 4 • 84 5 • 112 6 • 168 7 • 224 12 daya before emer..,.ce 3 Leaf atave (14 O.A.E.) NITROGEN APPLIED (kQ/ho) {b) WET Tlllering (2!5 D.A.E.) WATER ADDEO • DURING PERIOD INCLUDING RAIN Silo! blade (39 D.A.E.) 1234567 Anlhetls (51 D.A.E.) !5 O·t-~.~2~3~4~!5~6~7f---~--~12t3t4tt!56~7--~~--~~~2~3~4~!5~6~7~--Jll __ ~l2~:t~~5~6~7--_JIL __ L,~Jnrt~,L41~[6t7L-__ __ NITROGEN APPLIED ( k9 I ho l Fig. 8. Effect of fertilizer N on total available water in soil profile at 4 growth stages DISCUSSION Under wet conditions growth and yield responded to N in the classical manner, conforming to Misterlich 1s law of diminishing returns principle (Itussell 1973). Under dry conditions growth started out in a similar manner to that under wet conditions because soil moisture conditions were good up to near shot blade. However, because of the direct relationship between rate of water use and rate of N applied (where available water was not limiting), plants grown under the dry conditions at rates of N.;>84 kg/ha depleted their available water more rapidly than those grown at lower rates of N. Consequently, between shot blade and late anthesis when we received .C::.·l em of rain and very hot conditions the 11dry11 plants at low N continued to increase slowly in dry weight, but the plants grown at the highest rates of N levelled off abruptly in dry matter production. Shot blade to anthesis is the most critical stage of growth with respect - 112 -to the effect of moisture stress on grain yield. For example, Bauer (1971) reports that serious moisture stress at the heading to anthesis stage of growth will reduce the grain yield by 30 to 40%. In our study, if the wet treatment is considered to have represented optimum moisture, then the reduction in grain yield was 42, 57, 59, 57, 55, 52 and 50% in the dry treatment grown at 0, 28, 56, 84, 112, 168 and 224 kg N/ha, respectively. Immediately after late anthesis, and up to maturity, the soil moisture and temperature were again good for grain production. As can be seen from the yield curves (Fig. 7), in the dry treatment the good weather conditions benefited the plants grown at 112, 168 and 224 kg N/ha considerably more than it affected those grown at lower rates of N. Why? The reason for this interaction was apparently due to the following: By the late anthesis stage the treatments receiving up to 84 kg N/ha had absorbed almost all of the readily available N in the lysimeters, they had incorporated the N into plant tissue, some of which died off during the mini-drought period between shot blade and late anthesis. The plants grown at ;>112 kg N/ha had also absorbed a good portion but not all of the available N in the lysimeters (data not shown). Consequently, when the rains came just after late anthesis all plants recovered sufficJ.ent~y to produce a better-than-average crop but the ones receiving the highest rates of N were still able to translocate more residual N from the soil to the tops to be combined with stored starch in the flag leaves and produce substantial grain yields and protein. On the other hand, the rate of mineralization was too slow to provide the plants grown at the lower nitrogen rates with sufficient available N to replace that which was lost in the tillers and leaves which died during the mini-drought. This then explains how weather-fertility interactions can result in apparent anomalies in plant response to fertilizer. It should be noted that if the recommended rate of fertilizer had been applied (28 kg/ha) tnere would have been little response under natural rainrall, and even 56 kg N/ha would have given little response. The top growth (and roots) of dry, high N fertilized plants apparently lost N during the droughty shot blade to late anthesis period; however, the treatments which were experiencing less moisture stress during this period did not lose N. The soil tension in the dry treatment at ~ate anthesis was well above 15 atm (Fig. 8). We postulate that the moisture tension in the plants was lower than that in the soil, and this created a gradient that induced liquid excretion from roots to soil during this period. This exudate might have carried with it soluble N compounds. Marshall (1972) has reported that plants fertilized heavily with N have been found to excrete materials from the roots. l:iEFER.ENCES Bauer, A. 1972. ~ffect of water supply and seasonal distribution on spring wheat yields. Agr. Exp. Station, N. Dakota State Univ., Fargo, N. Dakota, Tech. Bull. No. 490. Davidson, H.R. and Campbell, C.A. 1976. The effect of N fertility on the rate of growth of spring wheat. Soil Fertility Workshop. 1976. Univ. of Saskatchewan, Saskatoon, Sask. (This issue). - 113-Uyck, F .B., Campbell, C.A. and McLavghlin, N .B •. ;~' 1976. A device for taking undisturbed soil cores.' Soil Fertility Workshop. 1976. Univ. of Saskatchewan, Saskatoon, Sask. tThis issue). Russell, ~.W. 1973. Soil Gonctitions and Plant arowth. lOth Edition. Longman Group Ltd., London. Steenbjerg, F. 1954. Manuring, plant production and the chemical. composi-tion of the plant. Plant and Soil ): 226-242. Viets, F.G. (Jr.). 1965. The plants need for and use of nitrogen. pp. 503-549. In Soil Nitrogen. Willcox, O.W. 1954. Quantitative Agrobiology: I. The inverse yield-nitrogen law. Agron. J. 46: 315-320. 

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Effect of N fertility and soil moisture on yield and nitrogen accumulation in Manitou wheat

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