Effect of fallow frequency on soil water conservation in the semi-arid region of Saskatchewan

Abstract

The effects of fallow frequency on soil water conservation were quantified for a 40 yr (1967-2006) field experiment conducted on a medium textured Orthic Brown Chernozem (Aridic Haploboroll) in semiarid southwestern Saskatchewan, in which soil water contents were measured each year in early spring, shortly after harvest, and again just prior to freeze-up in the fall. The three treatments examined were continuous wheat (Triticum aestivum L.) (Cont W) and fallow-wheat (F-W), each receiving N and P fertilizer and Cont W receiving only P. On average, 36 % of the precipitation received during the fall and winter months for Cont W (N+P) was conserved in the soil. In the summer fallow system (F-W (N+P)) a greater proportion (42 %) of the precipitation was conserved during the first fall and winter. During the second overwinter period, only 6 % of the precipitation received was conserved in the F-W system compared to 44 % in the first overwinter period. Compared to the 36% of fall and wither precipitation conserved in Cont W (N+P), inadequate N fertility (Cont W (+P)) resulted in only 27 % of the precipitation being conserved during this period. We developed equations that will allow estimation of water conserved as a function of precipitation received between harvest and seeding for F-W and Cont W (N+P. Trends in grain yield were fairly closely correlated with growing season precipitation and potential evapotranspiration.