FIRST 12 YEARS OF A LONG-TERM CROP ROTATION STUDY IN SOUTHWESTERN SASKATCHEWAN — YIELDS AND QUALITY OF GRAIN

Abstract

Yield and quality of spring wheat in particular, and of flax, fall rye, and oat hay, in general, in 12 rotations deemed feasible for southwestern Saskatchewan, were summarized and discussed after the first 12 yr of a long-term rotation study. The study was conducted on a Brown Chernozemic loam. The factors examined were the effect of rotation length, fallow-substitute crops, and N and P fertilizer. On a crop-year basis, continuous wheat yields averaged 75% of fallow yields when recommended rates of N and P fertilizers were applied. Yield variability was lower for rotations that included high proportions of fallow than for continuous-type rotations. Fertilizer N applied at recommended rates increased yields of wheat grown on fallow by an average 5% (from 1780 to 1860 kg∙ha−1) and wheat grown on stubble by an average 7% (from 1350 to 1455 kg∙ha−1). Application of P fertilizer at recommended rates increased yields of wheat grown on fallow and stubble by an average 12%. Total wheat production (kg∙ha−1∙yr−1) was inversely related to the frequency of fallow in the rotation. Thus, continuous wheat (N and P applied) outproduced wheat grown on fallow in the 2-yr rotation by 53% over the 12-yr period. Wheat yields were directly related to growing season rainfall. Flax yields were generally poor because of their low drought tolerance and poor ability to compete with weeds. Fall rye yields were generally higher than provincial averages because the soil used in this study was more fertile than those in which rye is normally grown. Protein concentrations of wheat grown on fallow were high (average 15.9%) and generally greater than that of wheat grown on stubble (except for wheat grown on flax stubble). Failure to apply N fertilizer to continuous wheat resulted in the lowest grain protein (average 13.5%). P concentrations of wheat grown on stubble were greater than that for wheat grown on fallow due to P dilution by yield. The P concentration in wheat was directly related to rainfall. The volume weight of wheat was not greatly influenced by treatment and was above the base criterion of 74.5 kg∙hL−1 in all years.Key words: Crop rotations, grain yields, protein, yield-rainfall interaction, grain quality, fertilizer effects