EFFECT OF CROP ROTATION AND FERTILIZATION ON THE QUANTITATIVE RELATIONSHIP BETWEEN SPRING WHEAT YIELD AND MOISTURE USE IN SOUTHWESTERN SASKATCHEWAN

The effects of crop rotation and fertilization on the quantitative relationship between spring wheat (Triticum aestivum L.) yields (y), available spring soil moisture (AvSpSM), and growing season precipitation (GSP) were determined from an experiment conducted on a loam soil in the Brown soil zone of southwestern Saskatchewan for the period 1967–1984. Moisture used (MU) was defined asand AvSpSM as volumetric moisture content at time of planting minus the lowest soil moisture measured at harvest. For discussion of moisture use characteristics GSP was defined as precipitation received from 1 May to 31 Aug.; for predictive equations GSP was more effective if GSP was taken as 1 May–31 July. When the 18-yr data were analyzed, the relation of y to MU was curvilinear. If data for 1 or 2 yr (1970 and 1983) with skewed distribution of GSP were omitted, the relationship between y (kg ha−1) and MU (mm) for well-fertilized fallow- and stubble-seeded wheat combined was(where GSP = 1 May to 31 July). This equation perf...