Soil water use, biomass accumulation and grain yield of no-till winter wheat on the Canadian prairies

Higher water use efficiency provides no-till-seeded winter wheat with an advantage over spring-sown crops in western Canada. However, like all crops, winter wheat (Triticum aestivum L) is subject to large yield losses due to drought. This study was undertaken to identify the effect of weather and crop soil water status on water use, aboveground biomass production and grain yield of no-till winter wheat gown on the Canadian prairies. Five winter wheat cultivars were grown over a 3-yr period at a total of 17 sites scattered across the different climatic zones of Saskatchewan. Both the establishment and expression of gain yield potential were limited by drought in these dryland environments. Early-season moisture was required to set up a high grain yield potential while low ET and high precipitation during grain filling were necessary to secure yield. Rapid growth under cool temperatures during April and early May consumed much of the available water in the top 50-cm of the soil profile and large ET deficits, as a consequence of a continuous decline in available water, characterized drought stress in most trials. While stored soil water at greenup was not sufficient to support a crop, there was growing season rainfall at all trial sites and improvements in water availability led to higher grain yields and an increased range in mean environmental grain yield. Rainfall had its greatest influence on grain yield during tillering, while atmospheric conditions and soil water content were more important from heading to anthesis. Because environmental differences in drought stress were related to the volume and distribution of growing season precipitation, some dryland environments were exposed to intermittent stress while stress was terminal in others. Therefore, to be successful, winter wheat cultivars and management systems for the Canadian prairies must be able to accommodate variable patterns of growing season water availability.