Effect of cultivation on physico—chemical, humus—chemical and biotic properties and fertility of two forest soils

Abstract

A loamy Orthic Luvisol (Typic Hapludalf) and a sandy Haplic Podzol (Typic Haplorthod) under forest and agricultural cultivation were compared to assess the effects of cultivation on chemical and biotic properties and soil fertility. In the field, water, oxygen,thermal and nitrogen supply, soil respiration and cellulose degradation were determined during a 2 year period. In the laboratory soil organic matter (SOM) compounds, using a wet-chemical procedure, microbial biomass, enzyme activities and CO 2-release were determined in samples taken in autumn. In the arable Luvisol SOM turnover is limited by the lack of oxygen. A large mineral N-input enhances microbial activity in comparison with forest soil. This affects soil fertility and productivity. However, good environmental conditions for microorganisms are unecessary to obtain high yields. In spite of the high N-fertilization in the loamy soils derived from boulder clay there is little risk of groundwater pollution by nitrates. The Iron-Humus Podzol has been improved by agricultural management, which has increased pH, base saturation, SOM turnover and microbial activity. However, only 50% of the fertilizer is taken up by the crops and the remainder is leached or probably incororated into the SOM. In the sandur region characterized by sandy Podzols (1) large fertilizer nitrogen inputs nitrogen pollute the groundwater and (2) slurry fertilization of the arable soils also enhances the NH 4 + input into the forest soils. At present the nitrogen is fixed in solid organic matter and nitrate leaching in the forest soils is not important.