Agronomic Responses of Winter Wheat Cultivars to Management Systems

Management of winter wheat (Triticum aestivum L.) should include N fertilization, crop protection, and seeding rates that allow efficient production based on cultivar and environmental yield potential. These studies were conducted to evaluate regionally grown cultivar responses to crop management systems in northern Idaho. In three environments, four cultivars were grown using management treatments (MT) similar to current recommended practices (MT3); a treatment with conservative N fertilization (MT2); a low input treatment with lower N, lower seeding rate, and minimal herbicide (MT1); and a high input treatment with higher N with split applications, plus a fungicide and growth regulator application (MT4). Data on grain yield, protein, test weight, plant height, and lodging were collected in all studies. In the two studies in 1992, leaf tissue N and soil N were analyzed and yield components were determined. Environment × MT and enviroment × cultivar interactions were found for grain yield, test weight, and protein. In 1991 at Moscow, the hard red wheat ‘Weston’ produced the highest grain yields across MTs and was the only cultivar to produce highest yields with MT4. Also in that environment, the three soft white cultivars produced higher yield and test weight and lower protein in MT2 than in MT3. In 1992 at Potlatch, limited soil water restricted yield, and MT1 had lower yields than other MTs, but protein content increased with higher N fertility. At Moscow in 1992, agronomic performance appears better in MT1 than in other treatments due to abundant early vegetative growth in the higher N fertility treatments that was followed by a soil water deficit throughout reproductive stages. Weston produced the lowest yield, heads per acre, and kernels per head at Moscow in 1992, but was highest in test weight, grain protein, and plant height. At both sites in 1992, yield components were positively correlated to yield, indicating treatment differences were influencing yield throughout several plant growth stages. High inputs (MT4) can be beneficial under some circumstances, but conservative N fertilization with conventional practices (MT2) gave the best overall agronomic performance across the tested environments and cultivars. Research QuestionGrowers want to optimize management of winter wheat for the greatest economic returns. Recommended management practices could be replaced by reduced inputs to control costs and minimize environmental impacts, or replaced by intensive cereal management (ICM) systems with increased inputs and management costs. Management system effectiveness may depend upon cultivar response to input level and environmental influence on production potential. This study evaluated the effects of four management systems, two with lower inputs than recommended, one with the recommended input level, and an ICM system, on agronomic performance of commonly grown winter wheat cultivars, three soft white and one hard red, in three northern Idaho environments. Literature SummaryManagement practices for winter wheat production have been studied extensively in the Midwest to determine agronomic and economic feasibility. Many practices evaluated are components of ICM systems including high N fertilization, increased seeding rates, foliar fungicides, and plant growth regulators (PGR) that have been integrated into ICM systems in Europe. Foliar fungicides were often identified as beneficial under highly productive conditions. Many studies have shown that cultivar productivity and susceptibility to lodging or diseases contribute to variable response to management inputs. As costs of chemical inputs increase, use may become more limited. Little research has defined the loss of productivity with limited inputs, and ICM has not been evaluated extensively in the Pacific Northwest. Study Description Location: Moscow, ID, in 1991 and at Potlatch and Moscow, ID, in 1992. Soil: Palouse silt loam (fine-silty, mixed, mesic Pachic Ultic Haploxeroll) Main plots (management treatments (MTl-MT4): MT1. Low input—20 seeds/sq ft, 50% of projected N needed, minimum herbicide MT2. Current recommended but with low N—30 seeds/sq ft, 75% of proejcted N needed, standard herbicide MT3. Current recommended—30 seeds/sq ft, 100% of projected N needed, standard herbicide MT4. ICM—30 seeds/sq ft, 125% of projected N needed split-applied (50:50), standard herbicide, fungicide, and PGR. N management: N rate was based on 100 to 110 bu/acre yield goal, N as urea was broadcast after spring green-up and for MT4 as a 5050 split application with the second application at flag-leaf emergence. Moscow,Moscow,Potlatch,N application rate, lb/acre199119921992N need projected for 100% level270297270Soil available N (from soil test)157180116Applied MT1 (50% N)0020Applied MT2 (75% N)464387Applied MT3 (100% N)113117154Applied MT4 (125% N)90 + 9095 + 95111 + 111Fungicide: Tilt, 4 oz/acre (Zadoks' growth stage 37). PGR: Cerone, 1 pt/acre (Zadoks' growth stage 37) Subplots: ‘Weston’ (hard red); ‘Malcolm’, ‘Lewjain’, and ‘Kmor’ (soft white) winter wheat cultivars. Growing season precipitation departure from average (24 in.): + 4.7 in., Moscow, 1991; −2.2 in., Moscow, 1992; −3.7 in., Potlatch, 1992. Applied QuestionAre different management systems viable for some currently grown cultivars in the Pacific Northwest?. Management treatments and cultivars produced different winter wheat responses in different growing environments. In the 1991 trial that had adequate soil water, Weston had the highest yield and protein in MT4 while the soft white cultivars yielded most in MT2 (Table 1). Weston is taller, lodges more, and has more foliar diseases than the soft white cultivars and thus, responded to PGR and fungicide application in MT4. In 1992, available soil water was deficient at both locations. At Potlatch in 1992, wheat that received MT1 yielded less than MT2, MT3, and MT4 (Table 2). At Moscow in 1992, wheat under MT1 produced more grain and a higher test weight than under MT3 and had the lowest protein. MT1 appears desirable at Moscow in 1992, but results were influenced by abundant early vegetative growth and limited soil water during grain formation. High input management systems may work for specific cultivars and environments, but most environment-cultivar combinations in these studies produced the best grain yield and quality with conservative N input (75 or 50% of the projected N needs) and other currently recommended management practices. Table 1Effects of management and cultivar on winter wheat agro nomic performance at Moscow, ID, in 1991. GrainGrainTestLodgingFoliarTreatmentyieldproteinweightindex†diseasebu/acre%Ib/bu% flagleafSoft white cultivars MT180.28.356.40.22.5 MT291.38.458.10.25.0 MT381.510.155.20.35.9 MT486.011.054.10.51.2 LSD (0.05)4.80.62.10.22.5Weston (hard red) MT185.210.464.70.65.0 MT293.110.961.72.910.0 MT389.912.663.95.817.5 MT4101.313.163.73.12.3 LSD (0.05)7.20.9NS1.04.7†Lodging index = S × I × 0.2, S = area lodged (1 = none to 9 = total), I = lodging intensity (1 = upright to 5 = flat) giving a 0.2-9.0 range. Table 2Agronomic performance of winter wheat as influenced by management treatments at Potlatch and Moscow, ID, in 1992. GrainGrainTestLodgingTreatmentyieldproteinweightindex†bu/acre%lb/buPotlatch MT159.89.659.70.2 MT268.411.258.40.7 MT369.512.357.60.7 MT468.012.959.70.3 LSD (0.05)3.90.60.90.3Moscow MT189.311.958.33.6 MT282.713.656.54.5 MT372.414.855.65.6 MT478.715.457.05.1 LSD (0.05)10.90.71.5NS†Lodging index = S × I × 0.2, S = area lodged (1 = none to 9 = total). I = lodging intensity (1 = upright to 5 = flat) giving a 0.2–9.0 range.