Water Use by No‐Till Winter Wheat Influence of Seed Rate and Row Spacing

Abstract

AbstractManagement practices are required in rainfed agriculture of western Canada to reduce early season water evaporation from soil relative to loss by transpiraition. The objective of this study was to measure the effect of two seed rates and two row spacings on the pattern of water use and writer use efficiency (WUE) of no‐till winter wheat (Triticum aestivum L.). Nine field trials were conducted on Udic Haploboroll and Molllic Cryoboralf soils in Saskatchewan from 1987 to 1989. Higher dry matter production and more rapid early season plant ground cover associated with the 9 cm row spacing and 140 kg ha−1 seeding rate, compared to other row spacing‐seeding rate combinations reduced water loss from evaporation and increased the partitioning of evapotranspiration to transpiration during the pre‐anthesis growth period. Pre‐anthesis water use was 11% higher, post‐anthesis wateir use 6% lower, and growing season water use 4% higher for the 140 compared to the 35 kg ha−1 seeding rate, The 140 kg ha−1 seeding rate produced 40% more preanthesis dry matter than the 35 kg ha−1 rate, thus establishing a higher yield potential for the crop. A row spacing of 9 compared to the 36 cm resulted in water use that was 6% higher during the pre‐anthesis, growth period and 3% higher during the entire growing season. The combination of 140 kg ha−1 seeding rate and 9 cm row spacing ultimately produced a 21% higher grain yield and a 9 kg cm‐−1 higher WUE than the combination of 35 kg ha−1 seeding rate and 36 cm row spacing. Grain protein concentration increased from 13.1% with the 35 kg ha−1 seeding rate to 13.9% with the 140 kg ha−1 seeding rate. Grain protein yield increased from 198 to 227 kg ha−1 for the 35 compared to the 140 kg ha−1 seeding rate. The increase in grain protein concentration and yield associated with 140 kg ha−1 seeding rate was related to the pattern of water use by the crop. Even under conditions of high dronght stress, a larger number of more uniformly distributed plants associated with seeding rates higher than 35 kg ha−1 and row spacings narrower than 36 cm resulted in a higher WUE and a water use pattern that produced larger yields and higher grain protein concentration.