Effects of soil management regimes on biochemical properties of a loess soil

Abstract

A long-term field experiment was conducted over a twenty year period to examine the effects of three different soil management regimes (Abandonment, Fallow and Cropping) and eight nutrient management regimes under Cropping on soil organic carbon (SOC), N and P levels, microbial biomass, and enzymatic activities related to C, N, and P cycling in a loess soil. The nutrient management regimes examined involved treatment with various combinations of inorganic nitrogen, phosphorus, and potassium fertilizers (N, NP, PK, and NPK), as well as combinations of NPK fertilizers with either residual plant material (SNPK) or manure (MN1PK and MN2PK). Abandonment resulted in greater levels of soil microbial biomass than did Cropping but similar levels of enzyme activity were observed under both regimes. The Fallow regime gave significantly lower soil organic carbon levels and enzyme activities than did Cropping. Within the Cropping system, the treatments containning nitrogen and phophorus significantly improved SOC, N and P levels and also increased microbial biomass and enzyme activity relative to the control. In general, the highest values of the tested soil parameters were observed under the M2NPK treatment. With the exception of invertase, the activity of all soil enzymes tested correlated significantly with SOC and microbial biomass. It was concluded that the use of fertilization regimes involving applying organic material in conjunction with NPK fertilizers should be encouraged in order to maintain or improve the chemical and biological properties of the tested loess soil and to thereby increase its productivity.