Nitrogen balance and soil nitrogen dynamics in two areas with different soil, climatic and cropping conditions.

摘要

Field trials were carried out in 1990-93 in the Krummbach and Eisenbach catchments, N. Germany, to assess the effects of reduced N fertilizer application on yield, N balances and N leaching. The Krummbach catchment had a loam soil and was used for sugarbeet/winter wheat rotation. The Eisenbach catchment had sandy soils and was used for a winter wheat/winter rape/winter barley rotation at 1 site and a sugarbeet/spring barley/spring barley rotation at a second site. The usual N fertilizer regime in both watersheds was characterized by a N input excess of 50-80 kg N ha-1 year-1. On fields which regularly received organic manure, N input surpluses of 210 kg N ha-1 year-1 were found. Reducing the usual mineral N fertilizer by 45-55 kg N ha-1 year-1 inthe sugarbeet/winter wheat rotation on the loam soil had a negligible effect on the yields (2-4% reduction) while NO3 concentrations in the soil solution and NO3 leaching were reduced. In contrast, on the sandy soils, yield decreases of sugarbeet, winterrape and spring barley were more severe (5-17% reduction) when the mineral N fertilizer was reduced, but omitting organic manure application had little effect. On these soils, the NO3- content of the soil solution and N leaching was less affected or even increased by a reduction of fertilizer input.