Influence of organic and mineral fertilisers on soil biological and physical properties

The aim of this research was to study in a held experiment the influence of different fertiliser applications on soil biological and physical properties. Vermicompost (VC) from biological sludge, stabilised dairy manure or mineral nitrogen fertiliser (NH4NO3) were applied to a corn crop (Zea mays L.) at 200 kg N ha(-1). Soil enzyme activity (acid phosphatase, dehydrogenase and protease BAA) and CO2 production were measured as indices of soil biological activity. These measures of metabolic activity were correlated to soil physical properties such as soil porosity. The soluble fractions of C and N were taken as indicators of fertiliser effects on soil fertility. There were positive correlations between soil porosity, enzymatic activity and CO2 production in organic and mineral treatments. The addition of organic fertilisers improved soil physical and biological properties. The increase in macropores, ranging from 50-500 mu m, in soil treated with organic fertilisers was mainly due to an increase in elongated pores, which are considered very important both in soil-water-plant relationships and in maintaining a good soil structure. Organic treatments stimulated soil biological activity probably due to an enrichment of soil organic matter. Mineral fertiliser enhanced soil porosity by increasing regular and irregular pores and caused a priming effect of native soil organic matter. (C) 1999 Elsevier Science Ltd. All rights reserved.