A STUDY OF MOISTURE STORAGE AND NITRATE ACCUMULATION IN SOIL AS RELATED TO WHEAT YIELDS ON FOUR CROPPING SEQUENCES

Abstract

On a clay soil at Winnipeg, Manitoba, at the University of Manitoba, four cropping sequences, namely: 1) fallow wheat; 2) fallow, wheat, wheat; 3) fallow, wheat, wheat, wheat; 4) wheat continuous have been under study since 1919. During the years 1956, 1957 and 1958 a detailed study of the relationship of wheat yields on these sequences to moisture consumption, nitrate accumulation, moisture storage and fertilizer use was undertaken. In general, yields were higher on fallowed than on non-fallowed plots. The higher yields on fallowed plots were, in part, related to nitrate accumulation during the fallow year. The yield differential between fallowed and non-fallowed plots was reduced by mineral fertilizer and manure treatments. Where no fertilizer was used the greatest wheat production in bushels per acre per year was on the fallow-wheat-wheat sequence. When fertilized or manured, the greatest production occurred on the wheat continuous plots.Rapid accumulation of moisture took place between harvest and the following spring. As a result, during years 1956, 1957 and 1958, there was only an average of 0.7 inches more available moisture to a 4-foot depth on fallow plots at seeding time than on plots which had been cropped the previous year.