Influence of different treatments of organic and mineral fertilization on yield, soil organic matter and N-balance of a diluvial sandy soil – results after 45 years long-term field experiment P60 (Groß Kreutz, 1959 – 2003)

Abstract

The P60 Groß Kreutz is a long-term field experiment, established by Specht in 1958 with an root crop-cereal-cereal-rotation on a diluvial sandy soil, to investigate the effects of different treatments and intensities of organic and mineral fertilization on yield, soil organic matter and natural soil properties. This publication presents the first results of current evaluation after 45 years of different fertilization (without fertilization, mineral-N, increased mineral-N, farmyard manure, mineral-N + farmyard manure, mineral-N + straw with or without additional mineral-N, mineral-N + green manuring with or without straw, mineral-N + slurry with straw, mineral-N + increased slurry with straw). Similar total-N-fertilization (81 – 95 kg N ha−1a−1) led only by combination of mineral-N + straw with additional mineral-N and mineral-N + green manuring with straw to optimal yields, reproduced organic C- and N-supply in the topsoil and minimized N-losses. In contrast mineral-N-fertilization decreased the soil organic matter supply to the inert level and farmyard manuring showed clear negative effects on yield in spite of clearly increased soil organic matter supply. Through the application of Mineral-N + straw without additional mineral-N and Minerald-N + green manuring it was possible to reproduce the organic N-supply of the topsoil, but the organic C-supply was decreased. The cropping capacity of the sandy soil (63,1-68,1 dt DM ha−1a−1) was limited by the N-uptake with crops between 76 and 91 kg N ha−1a−1 and there were no additional increasing effects of increased total-N-input by organic and mineral fertilization on yield to be found. Furthermore, the increasing effects of farmyard manure and slurry with straw on the organic N-supply of the topsoil were limited up to 8 – 12 kg N ha−1a−1. Including the resulting N-balances these findings clearly indicated that the additional increase of fertilization N-input nearly complete turned into N-losses.