Jörn Breuer

The effect of bio-compost application on crop yield and nitrogen dynamic in the soil

Since 1997 bio-compost with and without optimised mineral N fertilisation is applied to maize, winter wheat and summer barley (crop rotation) in a randomised field experiment on a Luvisol in south-west Germany. The aim of this experiment is to evaluate the effect of bio-compost application on crop yield and N-net mineralisation in soil. In the bio-compost application treatment (100 kg total N ha−1 a−1, that is about 7.5 t DM) with optimised mineral N fertilisation yield of summer barley (1999) and maize (2000) was higher than in the optimised mineral N treatment without bio-compost application. Similar results were obtained with the higher bio-compost application rate (400 kg total N ha−1 a−1, that is about 30 t DM) without additional mineral N fertilisation. The yield increase can be attributed to an improvement of soil structure in the Luvisol. During the vegetation period of summer barley net-N-mineralisation on the field plots of the bio-compost treatments with additional mineral N fertilisation was lower than in plots without additional mineral N application. The higher Nmin values after harvest (Sept. 1999) in bio-compost treatments with additional mineral N-fertilisation can be partially attributed to the remineralisation of immobilised N at the end of the growth period.

Sequential extraction of Cu and Zn from soil amended with bio-compost for 12 years: risk of leaching

A long-term field experiment was set up on a Luvisol with various fertiliser treatments including bio-compost. The effect of compost application on total (aqua regia extractable) Cu and Zn contents in soil layers were investigated. After 12 years compost application, organic fractions considered as bioavailable and less accessible inorganic Cu and Zn fractions had altered compared to the treatments without compost application. In comparison to the topsoil, the subsoil aqua regia extractable Cu and Zn were higher in the mineral fertilisation treatment (topsoil: 18.46 mg Cu kg−1, 62.89 mg Zn kg−1; sub-soil: 19.89 mg Cu kg−1, 66.88 mg Zn kg−1), but lower in the compost treatment (topsoil: 22.58 mg Cu kg−1, 70.80 mg Zn kg−1; subsoil: 21.03 mg Cu kg−1, 68.68 mg Zn kg−1). In compost, Cu was mainly found in less accessible inorganic fractions and a smaller proportion in the organic fraction. In contrast, the organic fraction was most dominant for Zn followed by the less accessible inorganic fractions. Only a non-drastic accumulation of Cu and Zn in soil was detected. Cu and Zn fractionations in composts had the same trend of the corresponding fractions in the soil.