Comparison of soil chemical properties, enzyme activities, levels of biomass N and aggregate stability in the soil profile under conventional and no-tillage in Canterbury, New Zealand

Abstract

The effects of conventional tillage (CT) and no-tillage (NT), practiced at 2 sites for 7 and 9 years, respectively, on soil chemical properties, enzyme activities, levels of microbial biomass N and aggregate stability were investigated in Canterbury, New Zealand. There was no significant difference in pH, or organic-matter content in the soil profile (0–0.3 m) between tillage practices. However, a large difference in the distribution of organic matter within soil profiles of the two tillage methods was observed. There was an accumulation of organic C, total N, organic S and P and potentially available N in the surface 0.05 m of soil under NT whilst in the CT plots, organic matter was more uniformly distributed within the soil profile to a depth of 0.2 m. In comparison with CT, there was also an accumulation of microbial biomass N and extractable phosphate in the surface soil under NT. The activities of urease and protease reflected differences in the distribution of soil organic matter under the 2 systems being higher in the surface 0.05 m under NT and tending to be higher under CT at greater depths. Phosphatase and sulphatase activities were, however, higher under NT to a depth of 0.1–0.2 m. The aggregate stability of soil was also significantly greater in the surface 0.2 m under NT than at CT at both sites. Under NT, factors other than organic matter were apparently influencing these properties in the 0.1–0.2 m depth increment. It was concluded that, although a change from CT to NT had little effect on soil organic-matter content, its distribution in the soil profile was altered and in general there were corresponding changes in other properties such as levels of microbial biomass, enzyme activities and aggregate stability.