Nitrate-N in the Soil Profiles of Long-term Field Experiments

Abstract

Long-term N fertilization experiments were established with identical treatments at two different growing areas in Hungary: one on a calcareous sandy soil (Őrbottyán) and the other on a calcareous chernozem soil (Nagyhörcsök). The aim was to create differences in mineral-N content in the soil profiles in order to determine their N supplying capacity and to establish whether the accumulated nitrate may be regarded as a supply index for crop production. The results showed that under certain environmental conditions N may accumulate in the soil profile in the form of nitrate, resulting from N fertilization in previous years, to such an extent that it must be taken into consideration when determining the fertilizer rates to be applied. This is important not only from the point of view of economical management and environment protection, but also for reaching better yield quality. The calculations can be reliably performed if they are based on the measurement and calibration of the soil's mineral-N content. The environmental importance of such calibration experiments is that by estimating the utilization of N from the mineral-N pool, the additional costs incurred due to over-fertilization can be eliminated, and at the same time the potential danger of NO 3 leaching to the groundwater can be reduced. Extrapolation of the experimental results to farm scale can lead to both economical and environmental achievements.