Prediction of Nitrogen Inputs for Sugar Beet.An Evaluation of Soil Tests and Soil

Abstract

Currently, advice on nitrogen (N) use for tillage crops employs an index system based on crop management. However, there has not been a systematic evaluation of several of its components or of the relevance of soil tests, alone or in conjunction. The objective of the current study, therefore, was to evaluate relevant soil management data, various biological and chemical soil tests, and measurements of Nmin (NH4 + NO3) in the root profile, for prediction of fertiliser N requirements. The data used in the study were derived from a data bank of results of field and laboratory experiments for sugar beet. The following topics were addressed: selection of regression models based on soil management criteria; sustainability of contribution of soil N reserves; limitations of soil tests for N; long-term trends in Nmin and biomass C; relationship of mineral-N flush with biomass C; relevance of Nmin with growing-season rainfall; implications of winter rainfall for residual effects and their justification within the current soil N index.