Effect of zero-till continuous wheat on soil quality after four and six years

Abstract

After four and six years of continuous spring wheat cropping using zero-tillage on the N × P × Snow-trap test site, soil samples were taken from the test area and from the adjacent area which has been in a wheat-fallow rotation for over 70 years. Biological characterization of these soil samples have shown that zero-tillage has already improved the potential productivity of the test site. For example, the amount of organic matter C and N have been increased in the 0-7.5 cm depth, as have CO2 respiration, the potentially mineralizable N (and thus N mineralization), amino acids, and the neutral phosphatase activity. However, no significant changes in microbial biomass C or N, alkaline phosphatase or urease in the 0-7.5 cm depth were found. There was little change in N or C mineralization or soil enzyme activity noted in the 7. 5 to 15 cm depth. Evidence in support of the improvement in soil productivity is the fact that in 1986, a year of above average precipitation, yield response to N and P was insignificant on test plots where yields ranged between 2550 and 2750 kg/ha for N fertilizer ranging from 25 to 100 kg/ha. In contrast, on adjacent stubble-cropped land, response to N applied was substantial.