N + u/e where Y = predicted grain or protein yield (kg ha-1) N total available N (kg N ha-1)

Transcription

1 NFLUENCE OF CLMATE AND CULTVAR ON GRAN PROTEN CONCENTRATON OF WHEAT AND RYE. D.B. Fowler. J. Brydon. B.A. Darroh. M.H. Ent and A.M. Johnston. Crop Development Centre. University of Saskathewan. Saskatoon, Sask S7N OWO. NTRODUCTON The traditional winter wheat prodution area of the Canadian prairies has been southwestern Alberta. Only with the reent introdution of a pratial snow management system, whih utilied notill seeding into standing stubble immediately after harvest of the previous rop ("stubblingin"), has the risk of winterki been redued suffiiently to provide the opportunity for winter wheat prodution throughout the remainder of the prairie agriultural region (Fowler, 1983). Winter rye is also adapted to the stubblingin management system. The notill aspet of this prodution system has provided an opportunity to extend rotations and improve soil onservation methods in western Canada. Most stubble fields on the Canadian prairies are defiient in plantavailablesoil nitrogen (N). n high prodution environments, soil test results often indiate less than 3 kg available N ha 1 Therefore, N fertiliation is usually neessary to optimie yield (Fowler et al 1989a) and maintain protein onentration at aeptable levels (Fowler et al. 1989b ). Under these onditions, N fertilier also beomes the major input ost in the stubblingin managment system (Fowler and Ent, 1986). Protein is a primary quality omponent of ereals and its importane is often reognied in the marketplae. This is espeially so with wheat where most exporting ountries have some segregation of ommerial grain lots on the basis of protein onentration. n hard wheat the majority of the variation in loaf volume an be attributed diretly to differenes in protein onentration. Protein onentration of % is usually onsidered the minimum aeptable for this quality lass and premiums are often paid for higher onentrations. The pastry, and to a lesser extent the bisuit. market prefers low protein flour (<%) from soft wheat. Usually. if large quantities of ereal grains are grown for feed, high protein onentration has a market advantage. Cereal protein ontains approximately 17.5% nitrogen (N). Beause N is obtained from the soil. plantavailable soil N has a diret influene on grain protein yield (Hunter and Stanford. 1973; Olson et al., 1976; Blak and Siddoway, 1977). The entral role of N fertiliation in the suessful prodution and marketing of stubbledin winter ereal s has made it the fous of numerous researh studies in Saskathewan during the last 14 year s. This paper s ummaries the results of these geneti and agronomi studies with t he objetive of providing a detailed harateriation of the influene of genotype and environment on wheat and rye grain protein onentration and N use effiieny. 254

2 MATERALS ANU METHODS A large number of fertilier trials were onduted during the period 1974 to 1988 as a part of the winter ereal program at the Crop Development Centre, University of Saskathewan. Details on previous rop, soil type. residual N. ultivar utilied and environmental onditions for eah trial, and general experimental details on several of these studies are given in related publiations (Darroh, 1988; Ent and Fowler, 1988; 1989a; 1989b; Fowler and Brydon, 1989; Fowler et al a; 1989b). The most highly adapted wheat and rye ultivars for this region were utilied in these trials and, as a result. there were several ultivar hanges over the period of these studies. The two winter wheat ultivars utilied, 'Sundane' and 'Norstar'. have similar grain protein onentrations and grain yields (Fowler and de la Rohe. 1984). The winter rye ultivars, 'Cougar' and 'Puma', have relative grain yields of 9 and 1%, with grain protein onentration of 9.9 and 9.%, respetively. Protein yields for the rye ultivars were similar. Experimental design for the time and rate of N fertilier appliation trials was a split plot with fertilier rate and time of appliation as the main and subplots. Nitrogen treatments were repliated four times in eah trial. Nitrogen treatments were applied in the early spring (May 1) and late spring (May 3). Experimental design for the partial irrigation studies was a split plot with water regimes as the main plots and N fertilier rates as the subplots. Water treatments were irrigation to approximately 13% of the long term average applied using either trikle or flood irrigation tehniques. Treatments were repliated three or four times in eah trial. Experimental design for the 'Neepawa' spring wheat. Sundane winter wheat, and Cougar winter rye omparisons was a split plot with N fertilier rates as the main plots and ultivars as the subplots. Treatments were repliated four times i n eah trial. Experimental design for the winter wheat ultivar omparisons was a split plot with ultivars as the main plots and nitrogen fertilier rates as the subplots. Cultivars were seleted to represent low ('Yorkstar'). intermediate (Norstar and ' Ulianovkia' ). and high ('Redwin') protein onentration lasses. Treatments were repliated four times in eah trial. With exeption of the Porupine Plain trial. whih was seeded into summerfallow. all trials were diret seeded into standing stubble immediately after harvest of the previous rop (between 24 Aug. and 7 Sept. of eah year). Phosphate fertilier (51 or 48) was applied with the seed at rates reommended for eah soil type. Elements other than phosphorus and N were not onsidered to be limiting. Nitrogen fertilier was applied as ommerialgrade ammonium nitrate (34) handbroadast on the soil surfae in the early spring unless otherwise indiated. n the early spring of eah year, midrow soil samples (15, 153 and 36 em inrements) were olleted from plots that had not reeived N fertilier in eah trial for nitrate analyses by the Saskathewan nstitute of Pedology. soil testing laboratory. Only estimates of N N were utilied 3 beause field trials in both Alberta and Saskathewan have demonstrated that 255

3 the relationship between grain yield or protein onentration and NO N plus NH N is no better than for NON alone (Nuttall et al., 1971; Malhi et al 19A5). Available N 3 N onenirations were determined olorimetrially by autoanalyer using admium redution (Tehnion ndustrial Method #1 7W, Tehnion nstrument Corp., Tarrytown, N.Y.). Beause soil and fertilier N were onsidered to be equally plantavailable total available N was alulated for eah treatment as the sum of soil N 3 N to 6 em depth and added fertilier N (Heapy et al. 1976; Zentner and Read. 1977; Frane and Thornley, 1984; Bole and Dubet, 1986). Grain protein onentration and protein yield (grain yield x protein onentration) were determined for eah plot in eah trial. Protein onentrations were determined from Kjeldahl N (N x 5.7) or by the Udy dye method (Udy, 1971). Kjeldahl analyses were utilied to standardie protein onentrations in eah trial analyed by the Udy dye method. Analyses of variane were onduted to determine the signifiane of treatment differenes within eah fertilier trial An inverse polynomial equation with a modifiation for yield depression at high N levels (Frane and Thornley, 1984 ) was used to desribe the relationship between available N and both grain and grain protei yield. Use of this funtion to desribe the N response urves of grain and grain protein yield has been elaborated on in earlier publiations (Fowler et al 1989a; b). The inverse polynomial equation takes the form: y = un (1N/). N + u/e where Y = predited grain or protein yield (kg ha1) N total available N (kg N ha1) = a measure of yield sensitivity to high N levels (larger indiates less sensitivity) u upper limit of yield aeved in the absene of sensitivity to high levels of N (kg ha ) maximum N use effiieny at low levels of N (kg yield kg N1) Nonlinear regression proedures outlined by the SAS nstitute (1985) were used to provide leastsquares estimates of the regression oeffiients. and n most ases, limited data prevented the statistial program from onverging on reasonable estimates of all three oeffiients. n these instanes, was held onstant at the value (93 for grain and 949 for grain protein yield) determined in earlier studies (Fowler et al., 1989a ) and and were suessfully estimated. The Gompert equation was employed to desribe the relationship between protein onentration and available N. Use of this funtion to desribe the protein onentrationn response urve has been detailed in an earlier publiation (Fowler et al., 1989b). [1] 256

4 The Gompert equation takes the form: P M + A exp [ exp (KNl] [2] where P predited protein onentration (14% water) M minimum protein onentration (%) M A asymptoti protein onentration ahieved at high N levels = determines N level at whih protein onentration reahes M +.5A = oeffiient that determines the rate P inreases to M + A. N "' total available N (kg ha 1). The oefffiient K was held onstant at.23 and the oeffiient M was held onstant at 8.4% for wheat and 8. 2% for rye (Fowler et al 1989b). Nonlinear regression proedures outlined by the SAS nstitute (1985) were used to provide leastsquares estimates of the oeffiients A and The level of total available N at whih maximum protein yield is obtained was alulated from the following equation. N MAX= u <J 1 + _;!? 1) Maximum yield was estimated by inserting NMAX into Eq. [1]. [3] Nitrogen use effiieny (NUE) for grain protein yield was determined as kg N ha1 reovered as grain N for eah 1 kg inrement of fertilier N applied ha1. RESULTS AND DSCUSSON Grain Protein Conentration N Response Pattern Problems are often enountered in desribing the grain protein onentrationn response urve. Lak of preision in estimates of residual plantavailable soil N, the influene of environment in modifying the N yle, and the fat that most experiments only sample part of the N response urve make it diffiult to ompare results from different studies. These problems were onsidered in a 12 year investigation that inluded forty field trials onduted over a wide range of soil types and environmental onditions in Saskathewan (Fowler et al 1989b). n this study, the Gompert equation (Eq. [2]) provided the most omplete desription of the relationship between protein onentration and total plant available N. The protein onentration N response urves for wheat and rye were similar. After an initial lag (lag phase). protein onentration inreased rapidly (inrease phase). and then tailed off at high N levels (Fig. 1). The length of the initial lag phase of the urve was refleted by the sie of the value in Eq. f2l (Table 1). n several trials the lag phase extended beyond the 5 kg ha level with the indiation that there was an initial derease in protein onentration (Bole and Dubet. 1986; Partridge and Shaykewih. 1972). The presene of the initial lag phase indiated that there was a minimum grain protein onentration that was approximately 8.4 and 8.2% for wheat and rye, respetively (Fowler et al 1989b). 257

5 CLAR 71n CLAR n KPLNG 42 5 :i Earty Sprtng ;::_ '/ Earty Sprtng Late Sprtng : !arty Sprtng Late Sprtng # 14 e 12 # 14 e i.5.4 >.,.3.2 e.1 Q...,. _. Q >.,.3.2 e.1 Q. a.1.5 l.4,.3 :.2 e.1. ""'. '', 1..1.! Q..1 Q..4.2, ::>. ' Q a.2,._._. o.2, 1..1.! Q..1 i:., ::>. Q L._. L_L_.,_ a 1..1,.! i "' ::> Total available N (kg/ha) Figure 1. Norstar winter wheat grain yield, grain protein yield, and grain protein onentration response to total available N and nitrogen use effiieny (NUE) for grain protein prodution for early and late spring N fertiliation. Total available N level at whih axiaua grain () and grain protein (o) yields were ahieved. 258

6 Table 1. Estimated regression oeffiients (Eq. [2]) and redutions in sums of squares due to model (r2) for grain protein onentration in a) date of N fertiliation, b) partial irrigation. ) wheat and rye omparison, and d) winter wheat ultivar omparison trials. Regression Coeffiient Trial Treatment A B a) Date of N fertiliation (Fig. 1) Clair 1976/77 Early spring Late spring Clair 1977/78 Early spring Late spring Kipling 1981/82 Early spring Late spring b) Partial irrigation Clair 1985/86 Outlook 1985/86 Saskatoon 1987/ 88 (Fig. 2) rrigation Dry land rrigation Dry land rrigation Dry land ) Wheat and rye Clair 1976/77 Clair 1977/78 Saskatoon 1977/78 omparisons Fig. 3) Winter wheat Spring wheat Winter rye Winter wheat Spring wheat Winter rye Winter wheat Spring wheat Winter rye d) Winter wheat ultivar ompa risons (Fig. 4). Paddokwood 1985/ 86 Norstar 2.9 Ulianovkia 3.1 Redwin Porupine Plain 1985/86 Norstar Ulianovkia Redwin Yorks tar <17 <17 <17 <

7 Table 2. Estimated regression oeffiients (Eq. [1]) and redution in sums of squares due to model (r 2) for grain yield in a) date of N fertiliation. bl partial irrigation. ) wheat and rye ompar ison. and d) winter wheat ultivar omparison trials. Trial Treatment Regression Coeffiient.!! a) Date of N fertiliation (Fig. 1) Clair 1976/77 Early spring Late spring Clair 1977/ 78 Early spring Late spring Kipling 1981/82 Early spring Late spring b) Partial irrigation Clair 1985/86 Outlook 1985/86 Saskatoon 1987/88 (Fig. 2) rrigation Dry land rrigation Dry land rrigation Dry land ) Wheat and rye omparisons (Fig. 3) Clair 1976/77 Winter wheat Spring wheat Winter rye Clair 1977/78 Winter wheat Spring wheat Winter rye Saskatoon 1977/ 78 Winter wheat Spring wheat Winter rye d) Winter wheat ultivar omparisons (Fig. 4) Paddokwood 1985/86 Norstar 8139 Ulianovkia 4219 Porupine Plain 1985/86 Redwin 288 Norstar Ulianovkia Redwin 566 Yorkstar

8 Table 3. Estimated regression oeffiients (Rq. [1]) and redution in sums of squares due to model (r2) for grain protein yield in a) date of N fertiliation, b) partial irrigation, ) wheat and rye omparison. and d) winter wheat ultivar omparison trials. Trial Treatment Regress"ion Coeffii_ent s a) Date of N fertiliation (Fig. 1) Clair 1976/77 Early spring 29 Late spring 13 Clair 1977/78 Early spring 1953 Late spring 61 Kipling 1981/ 82 Early spring 477 Late spring b) Partial irrigation Clair 1985/86 Outlook 1985/86 Saskatoon 1987/88 (Fig. 2) rrigation Dry land rrigation Dry land rrigation Dry land ) Wheat and rye omparisons (Fig. 3) Clair 1976/77 Clair 1977/78 Winter wheat Saskatoon 1977/ 78 Spring wheat Winter rye Winter wheat Spring wheat Winter rye Winter wheat Spring wheat Winter rye d) Winter wheat ultivar omparisons (Fig. 4) Paddokwood 1985/ 86 Norstar 61 Ulianovkia 497 Redwin 398 Porupine Plain 1985/ 86 Norstar 1989 Ul ianovkia 1813 Redwin Yorks tar

9 Limited variation in the sie of the oeffiients that determined minimum grain protein onentration (Ml and the rate at whi h protein onentration inreased to its asymptote () in Eq. [2) indiated these two variables were under strong genotypi ontrol in both wheat and rye (Fowler et al., 1989b). n ontrast, large ex.periment effets indiated that the relative length of the initial lag phase () and the asymptoti protein onentration (A) were both under greater environmental influene (Fowler et al., 1989b). Critial Growth Stages and t he Effet of Environment Studies on the influene of rate and time of N fertiliation have identified the general grain yield, grain protein yield. and grain protein onentrationn response patterns for stubbledin Norstar winter wheat grown in Saskathewan (Fowler and Brydon, 1989). As indiated in the previous setion, there is a minium N level required for plant growth that yields grain with a protein onentration of approximately 8.4 and 8.2% for wheat and rye, respetively. When onditions are favorable for growth, the orretion of severe N stress through N fertiliation results in proportional inreases in grain and gr ain protein yield. Consequently, inimum protein onentration is maintained for the first inrements of added N giving rise to the lag phase in. the protein onentrationn response urve. One other environmental or genotypi fators beome limiting to growth and subsequent inreases in grain yield, exess N is utilied aainly for grain protein prodution and the protein onentrationn response urve enters an inrease phase. Delays in the. availability of N to the plant as a result of late spring appliations (Clair trials Fig. 1) or prolonged dry periods following spring fertjliation have the effet of limiting grain yield potential. f aessed later, the fertilier N beomes surplus to the plants minimum N requirements for growth at lower total N levels. This results in a ore rapid inrease in grain protein yield than total grain yield, lower values and a shift of the protein onentrationn response urve to the left (Clair trials Fig. 1, Table 1). The importane of ritial growth stages in determining grain yield, grain protein yield, and grain protein onentration was investigated further in detailed studies onduted on stubbledin winter wheat in Saskathewan (Ent and Fowler, 1988). Root one and profile extratable soil water. preipitation, pan evaporation. and growing degree days were monitored throughout the growing season. Variation in pan evaporation during the 2 week period i mmediately prior to anthesis (Zadok stage 46 to 65) aounted for 72 and 71% of the variability in grain and grain protein yield, respetively. When measurements of root one extratable soil water at anthesis (Zadok stage 65) and pan evaporation two weeks prior to maturity (Zadok stage 83 to 91) were inluded in the equation, the amount of variability in grain yield aounted for rose to 91%. Pan evaporation for the 2 week period immediately prior to anthesis and temperature in the 2 week period immediately after anthesis (Zadok stage 65 to 74) together explained 82% of the variability observed in grain protein yield in these trials. Protein onentration was negatively orrelated with soil water at all development stages onsidered, but was most dependent on root one water at elongation (Zadok stage 31). Measures of root one water at elongation and pan evaporation during the 2 weeks prior to maturity explained 73% of the variability observed in grain protein onentration. Stepwise addition of other environmental variables onsidered in this study did not provide additional information on grain yield, grain protein yield. or grain protein onentration. 262

10 The effets of N and water on grain protein onentration were further larified in field studies onduted in Saskathewan between 1984 and Partial irrigation of stubbledin winter wheat signifiantly inreased grajn and grain protein yield over omparable dryland treatments in these trials (Fig. 2). The addition of water also inreased the length of the lag phase ( in Eq. [2]) of the protein onentrationn response urve (Fig. 2, Table 1). n ontrast to the differenes observed in the length of the lag phase, the asymptoti maximums (!) of the protein onentrationn response urves for dryland and irrigation treatments were often simi lar. Consequently, removal of the fator most limiting grain yield, i.e., water limitations in this instane, resulted in a delay of the protein onentration inrease phase of the N response urve. One limits on the expression of yield potential were reimposed, the protein onentrationn response proeeded in a manner similar to that observed for dryland treatments. nvestigations into the interation between N and water in determining the agronomi performane of stubbledin winter wheat have also assisted in the identifiation of growth stages and environmental fators that have a major influene on protein onentration. Grain yield is onsidered a good measure of the umulative influene of environment upon plant growth. i.e., the more favorable the environment the greater the yield. Environmentally indued hanges in grain protein yield have been shown to be losely related to hanges in grain yield (r=.93**: Fowler et al 1989b). However, maximum grain protein yield was not signifiantly orrelated with either the asymptoti protein onentration (!) or the relative length of the lag phase () in Eq. [2] (Fowler et al; 1989b). Length of the initial lag phase() of the protein onentrationn response urve was orrelated with dry matter at anthesis (r=.97**) and root one extratable water at stem elongation (r=.85**) indiating that, as preanthesis growing onditions improve, more N is required to produe an inrease in grain protein onentration above the minimum 8.4% (Ent and Fowler, 1989b). n ontrast to the lag phase (). identifiation of the ritial growth stages and important environmental fators determining the asymptoti maximum protein onentration (!) has proven more diffiult. Asymptoti protein onentration (!) has been shown to be negatively orrelated (r=.67**) with water availability from May 1 to anthesis (Ent and Fowler, 1989b). However, explanation of the positive influene that evaporation during the 2 weeks prior to maturity has in determining protein onentration (Ent and Fowler, 1988), and the sie of. requires an understanding of the fators determining grain yield and grain protein yield. Reports in the literature suggest that from 5 to 8% of the grain protein N is derived from vegetative tissue produed during the preanthesis period (Spiert and Vos, 1985) with the remaining N being supplied by uptake after anthesis. Under moist soil onditions, wheat may ontinue to take up N until near maturity but, under dry onditions, very little N is taken up after anthesis (Gregory et al 1979). Field trials onduted with stubbledin winter wheat have shown that, under average Saskathewan onditions, 7% of the total dry matter and 9% of the total plant N is aumulated by anthesis (Darroh, 1988). Maximum grain yield is determined primarily by kernels m2 (Fowler et al., 1989a; Ent and Fowler, 1989a) and high dry matter rrodution in the preanthesis period is required to establish high kernels m (Ent and Fowler, 1989a). The only adjustments in yield potential to take plae after 263

11 CLAR 15H OUTLOOK 15 SASKATOON 17 2, ;:. '! 5 lrrtgatjon Dryland 4 1 o.... s: l, ;:. '! " lrrtgauon Orytand s: 4, 'i ;:.! " rrigation Oryland,.. # 14 'i tf'..!;.,.. _ 14 'i 12 1 =_. _.1 :E.5.3 a 2.4! ;:..2 e : o.e.4.2,....2.""" 1 2 a a a ;:..2 'i.1 g.4 e, o.ol!; : o.e.4,.2. \ a a s:, 'i ;: ,.8 Q. Q..8 at.4 l.2.._,. 4.2 C Total available N (kg/ha) Figure 2. Norstar winter wheat grain yield. grain protein yield, and grain protein onentration response to total available N and nitrogen use effiieny (NUE) for grain protein prodution in irrigation and dryland trials. Total available N level at whih aximua grain () and grain protein (o) yields were ahieved. 264

12 anthesis are ompensation for adverse environmental onditions through tiller loss, floret abortion (blasting) and/ or as a last resort redued seed sie. Consequently, under Saskathewan growing onditions, most of the protein N is in position for remob i liation in the plant by an thesis. n ontrast, dry matter yield at anthesis only determines the maximum yield potential of the rop. The period after anthesis determines the level of expression of this yield potential. Observations from timing of N fertiliation trials further demonstrate the important influene on protein onentration that arises beause the period of maximum N assimilation ours prior to anthesis and grain arbohydrate synthesis ours after anthesis. As desribed earlier, delayed N appliation normally shifts the protein onentrationn response urve to the left (Fig. 1). However, the reverse situation was observed in a field trial at Kipling in that experiened low early and high later season drought stress (Fowler and Brydon, 1989). n this trial, inreased N rate dereased grain yield exept for late spring appliations where the hek yield was maintained even at high N rates (Kipling Fig. 1). These observations indiate that, as normally ours, the late spring applied fertilier N was not available before N beame severely limiting to plant growth. Consequently, in the absene of Nstimulated luxuriant spring growth, plants in late spring applied N plots did not sustain the same level of damage from the subsequent extended drought as plants in plots with high levels of available N from earlier fertilier appliations. Redutions in grain protein yield were also assoiated with early N appliations. This suggests that, while N uptake most ertainly ourred early in the season, the resulting droughtindued sensitivity to high levels of N also interfered with N transloation to the developing seed. However, ontrary to the normal inrease in the length of the lag phase () assoiated with early spring N fertiliation (Clair trials Fig. 1), early spring N fertiliation produed a shorter lag phase () than late spring N appliations in the Kipling trial (Fig. 1, Table 1). Moisture availability during the growing season is one of the major fators limiting rop produtivity on the Canadian prairies. On average, only 2% of the moisture used by stubbledin winter wheat omes from soil moisture reserves and most of this reserve will have been depleted by anthesis (Ent and Fowler. 1989b). Consequently, water utilied after anthesis is mostly derived from intermittent rainfall events. Average growing season pan evaporation is approximately three times preipitation resulting in a very large water demand and onsiderable drought stress in most seasons. These observations underline the importane of growing season rainfall distribution relative to plant growth stage in this region. Tenfold differenes in maximum grain yield of Norstar have been attributed to environmental differenes experiened by stubbledin winter wheat trials in Saskathewan (Fowler et al 1989a). This grain yield inrease required a 3.2fold inrease in N emphasiing the unpreditable nature of rop N demands in Saskathewan. Maximum protein onentration at high levels of N have been observed to vary from.4 to 2.3% for Norstar winter wheat and 9.5 to 15.5% for Puma winter rye (Fowler et al., 1989b). Under average to good environmental onditions, the maximum N requirements of the Norstar winter wheat plant an be expeted to have been met when the grain protein onentration reahes approximately 13.% (Fowler and Brydon, 1989). The protein onentrationn response urve reahes a maximum near this level 265

13 unless spring environmental onditions favorable for plant growth an N uptake are followed by extreme drought that severely limits grain yield. Under these onditions, maximum protein onentrations will range from 15. to 2.3% for Norstar winter wheat. Genotypi Erfets Signifiant (PO.Ol) differenes in grain yield, grain protein yield, and grain protein onentration were observed among Neepawa spring wheat. Cougar winter rye, and Sundane winter wheat in the three trials reported on in this study (Fig. 3). However, a signifiant (P.5) ultivar by N fertilier rate interation for all three haraters indiated that the response to inreased N levels was not always the same for these ultivars. The grain yield advantage was in the order Cougar. Sundane, and Neepawa over most of then response urve onsidered (Fig. 3). Differenes among ultivars were not as lear for grain protein yield, espeially at lower total N levels. n all instanes, Cougar had the highest grain yield and the longest lag phase () in the protein onentrationn response urve (Table 1). Neepawa had the lowest grain yield and the shortest lag phase. Cultivar rankings for protein onentration did not hange over the entire range of N rates onsidered (Fig. 3). These observations learly established a geneti advantage for protein onentration that was in the dereasing order Neepawa, Sundane, and Cougar. Nitrogen fertilier trials that inluded only winter wheat ultivars demonstrated why the expression of geneti differenes in grain protein onentration is not always as lear as indiated in the previous study (Table 1). Differenes among winter wheat ultivars were signifiant (P.5) for grain yield, grain protein yield, and grain protein onentration in both the Paddokwood and Porupine Plain trials. The lose relationship between grain yield and grain protein yield was evident in both trials. however. differenes among ultivars were more obvious for grain protein yield in the Porupine Plain trial than the Paddokwood trial (Fig. 4). While the magnitude of the differenes hanged onsiderably between trials, grain and grain protein yield rankings were similar for ultivars ommon to these two trials (Fig. 4). Norstar had the largest grain and grain protein yield advantage in the Paddokwood trial. As expeted, the higher yield potential of Norstar was refleted in a larger lag phase () of the protein onentrationn response urve (Fig. 4. Table 1). A high residual soiln level did not allow for a reliable estimate of the lag phase in the Porupine Plain trial. While ultivar rankings were similar in the two trials. the differene in protein onentration between Norstar and Ulianovkia was muh smaller with the high N rates experiened at Porupine Plain (Fig. 4). The lower yield potential, high protein onentration of Redwin when produed in Saskathewan was evident in both trials. n ontrast. the soft white winter wheat ultivar Yorkstnr produed both low grain yield and low protein onentration in the Porupine Plain trial (Fig. 4). The following general onlusions an be drawn from the observations that have been made on the effets of environmental and ultivar variability on the protein onentrationn response urve (Eq.(2]). Only when total plant available soil N levels are extremely low, or environmental onditions are very favorable, is it possible to obtain an aurate estimate of the minimum protein onentration () for a ultivar. The transition from the lag Cg) to the inrease CK> phase of the protein onentrationn response urve of a ultivar ours when N is no longer the fator most limiting grain yield. 266

14 ! CLAR CLAR 7771 / SASKATOON 7771 Winter Wheel Spring WhHt Winter Rye, e CL 12 1 Wlnw Wheat Spring WMet Winter Rye,., A. 1 / /,..o l 14 e 12 A. 1 / " /,; / / _ L l.4 'V.3 >..2 e.1 A. 'V.4.3 >..2 e. A 'V.3 >..2 e CL.1.1 / o. _ / G. L''1 1. o.a 'V.! Q &L :;) o.o o.a 'V.! Q..1.4 at.2 &L ;:). Winter Wheel Spring Wheel Winter Rye o.2 L_.L. L._.J_..L 'V 1. o.a.! Q..1 l.4.2 &L :;) Totl vllble N (kglh) Figure 3. Grain yield, grain protein yield, and grain protein onentration response to total available N and nitroen use effiieny (NUE) for grain protein prodution of Sundane winter wheat, Neepawa spring wheat, and Cougar winter rye. Total available N level at whih axiau grain (e) and grain protein (o) yields were ahieved. 267

15 .. Q).s ' 'ii >. 2 '! CJ 1 Redwln Ullanovkla Porupine Plain Norstar Yorkatar. Paddok wood :::::::..6.5 l.4 s ".3 >..2! A..1 Redwln Ullanovkla Noratar Yorkatar Paddok wood uplne Plain. o''', ,J! Redwln Ullanovkla Norstar Yorkstar Paddok wood Porupine Plain " ;;; a. a. at. w :l Redwln Nontar Olhen Paddokwood \ upfne Plain :: Total available N (kg/ ha) 1 2 Total available Figure 4. Grain yield, grain protein yield, and grain protein onenl >n response to total available N and nitrogen use effiieny (NUE) for g1 DrOteJn Drodut(On of SP.VP.r.A wfnt"" r wh"at.ultfuao,,,.,.,,

16 Therefore. ultivar differenes in protein onentration at low N levels are largely a funtion of differenes in grain yield potential and ultivars with low yield potential will start into the inrease phase of the protein onentrationn response urve at lower total available N levels. The negative relationship between grain yield and protein onentration will mask the expression of genotypi differenes in protein onentration until the N requirements for grain yield have been met. Consequently, the most reliable estimates of genotypi differenes in protein onentration should be arrived at one the inrease phase of the N response urve has been ompleted. The end of the inrease phase of the N response urve ours at total plant available N levels that approximate those required for maximum grain yield (Fig and 3). These observations emphasie the importane of ensuring that N fertiliation is in exess of normal grain yield requirements when the identifiation of genotypi differenes in protein onentration is an objetive. Values of asymptoti maximum protein onentration () a1 e determined from data that meet these requirements. Consequently, differenes in values should provide a reliable estimate of differenes due to geneti variability for protein onentration among ultivars. However, it must be emphasied that preise estimates of will only be obtained from ultivarn fertilier trials that inlude several N levels in exess of those required for maximum grain protein yield. NUse Effiieny for Protein Prodution Grain and grain protein yieldn response urves are very similar in shape (Fig. 1,2,3, and 4). Observations made in the present studies have demonstrated that hanges in grain yield are also usually aompanied by hanges in grain protein yield. For example, any environmental or genotypi fator that inreased grain yield also inreased grain protein yield (Fig. 1, and 4 ). The first inrements of N fertilier stimulated the greatest inreases in grain protein N (Fig. 1,2,3, and 4). At low levels of residual soil N. the N use effiieny (NUE) for grain protein prodution has been shown to be as high as 8%. The NUE for grain protein prodution drops off rapidly for subsequent i nrements of N fertilier. approahing ero for maximum grain yield and reahing ero when maximum grain protein yield is ahieved (Fig. 1,2, and 3). Maximum grain yield oinides with the end of the inrease phase of the protein onentrationn response urve. Consequently, it an be onluded that high grain protein onentration an only be ahieved at the expense of nitrogen use effiieny for grain and grain protein yield. Therefore, management systems designed for the prodution of ereals with high grain protein onentration will have very low NUE's for grain and grain protein yield and high levels of N will be left unharvested. n high moisture environments, espeially where water leahing and surfae runoff are problems. management of this residual N ould have extremely important environmental impliations, i.e., nitrate pollution. Consequently, while high protein onentration an be ahieved under intensive management systems in high moisture environments, semiarid limates like that of western Canada provide eologially safer environments for the prodution of ereal grains with high protein onentration. ACKNOWLEDGEMENTS The authors would like to aknowledge the finanial support of the CanadaSaskathewan Eonomi Regional Development Agreement (ERDA). 269

17 REFERENCES Blak. A.L. and F.H. Siddoway Winter wheat reropping on dryland as affeted by stubble height and nitrogen fertiliation. Soil Si. So. Am. J. 41: Bole, J.B. and s. Dubet Effet of irrigation and nitrogen fertilier on the yield and protein ontent of soft white spring wheat. Can. J. Plant Si. 66: Darroh, B.A The effets of genotype and environment on grain protein of winter wheat in Saskathewan. Ph.D. diss. Univ. of Sask Saskatoon, Sask. Ent. M.H and D.B. Fowler Critial stress periods affeting produtivity of notill winter wheat in western Canada. Agron. J. 8: Ent, M.H. and D. B. Fowler. 1989a. nfluene of rop water environment and dry matter aumulation on grain yield of notill winter wheat. Aepted. Can. J. Plant Si. Ent. M.H. and D.B. Fowler. 1989b. Response of winter wheat to N and water : Growth, water use, yield and grain protein. Submitted. Can. J. Plant Si. Fowler, D.B The effet of management praties on winter survival and yield of winter.wheat produed in regions with harsh winter limates. pp n D.B. Fowler, L.V. Gusta, A.E. Slinkard and B.A. Hobin (eds.). New Frontiers in Winter Wheat Prodution. Div. Co mm. Rei Univ. of Saskathewan, Saskatoon, Sask., Can. Fowler, D.B. and J. Brydon Notill winter wheat prodution on the Canadian prairies: Timing of nitrogen fertiliation. Submitted Agron. J. Fowler,.8., J. Brydon. and R.J. Baker. 1989a. Nitrogen fertiliation of notill winter wheat and rye. 1. Yield and agronomi responses. Agron. J. 81: Fowler, D.B J. Brydon, and R.J. Baker. 1989b. Nitrogen fertiliation of notill winter wheat and rye. 2. nfluene on grain protein. Agron. J. 81:7277. Fowler. D.B. and.a. de la Rohe Winter wheat prodution on the NorthCentral Canadian Prairies: potential quality lasses. Crop Si. 24: Fowler, D.B. and M.H. Ent Role of winter wheat in tillage systems. p n Pro. Tillage and Soil Conserv. Symp ndian Head Exp. Farm. ndian Head, Sask. Frane, J. and J.H.M. Thornley Mathematial models in agriulture. pp Butterworths, London, England. Gregory, P.J Crawford, D.V. and MGowan, M Nutrient relations of winter wheat. 1. Aumulation and distribution of Na. Ca, Mg, P. s and N. J. Agri. Si., Camb. 93: Heapy, L., J.A. Robertson, O.K. MBeath, V.M. von Maydell, H.C. Love, and G.R. Webster Development of a barley yield equation for entral Alberta.. Effets of soil and fertilier Nand P. 56: Can. J. Soil Si. Hunter, A.S. and G. Stanford Protein ontent of winter wheat in relation to rate and time of nitrogen fertilier appliation. Agron. J. 65: Malhi, S.S., M. Nyborg, D.R. Walker. and D.H. Laverty Fall and spring soil sampling for mineral N in northental Alberta. Can. J. Soil Si. 65:

18 Nuttall. W.F., li.g. Zandstra. and K.E. Bowren Exhangeable ammonium and nitrate nitrogen related to yields of Conquest barley grown as seond or third orp after fallow in northeastern Saskathewan. Can. J. Soil Si. 51: Olson, R.A., K.D. Frank, E.J. Derbert, A.F. Dreier, D.H. Sander, and V.A. Johnson mpat of residual mineral N in soil on grain protein yields of winter wheat and orn. Agron. J. 68: Partridge, V.R. and C.F. Shaykewih Effets of nitrogen, temperature, and moisture regime the yield and protein ontent of Neepawa wheat. Can. J. Soil Si. 52: Spiert, J.H.J. and J. Vos Grain growth and its limitation by arbohydrate and nitrogen supply. n W. Day and R.K. Atkins (eds.). Wheat Growth and Modelling. Plenum Press. pp Statistial Analysis Systems (SAS) nstitute The ANOVA, GLM, and NLN proedures. n: SAS User's Guide: Statistis, Version 5 Edition. Statistial Analysis Systems nstitute n., Cary, N.C. 956 pp. Udy, D.C mproved dye method for estimating protein. J. Am. Oil Chem. So. 48: Zentner, R.P. and D.W.L. Read moisture in the brown soi l one. Fertilier deisions and soil Can. Farm Eon. 12: