Influence of Soil and Climatic Factors on Fertilizer Response of Wheat Grown on Stubble Land in Southwestern Saskatchewan1

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AbstractIn southwestern Saskatchewan moisture and nutrients are frequently limited for wheat (Triticum aestivum L.) grown on stubble land which had produced a crop the previous year. Variations in the severity of limitations between years resulted in wide variations in yield, quality, and response obtained from fertilizer application. Field fertilizer tests were conducted for 4 years to determine the effect of measurable soil and climatic factors on the response of wheat on stubble land to applied N and P fertilizer.A stepwise multiple regression computer program was used to measure the effect of independent variables on dependent variables when different rates of N and P fertilizers were used. The independent variables were soil moisture and nutrient content at seeding, rainfall during the growing season, and rainfall deficits for half‐month periods during the growing season. The dependent variables were yield, protein and P content of the grain, and net returns.Each of the independent variables assumed a different degree of importance when compared with different dependent variables. However, certain generalizations are possible.The NH4‐N form of soil N was responsible for more of the variations than the NO3‐N form. Rainfall during the growing season had a greater influence than stored soil moisture on the yield and protein content of grain grown on unfertilized plots, but the amount of stored soil moisture had greater influence on the effect of fertilizer on the variation in yield and protein content than did summer rainfall. Climatic factors during the growing season were important in causing yearly variations in the unfertilized plots, but the factors that could be measured before seeding had a greater influence on the response to fertilizer.A knowledge of these variables and of the effect that they have on variations in the response to fertilizer is necessary when planning a fertilizer program.