New Insights into Fertilisation with Animal Manures for Annual Double-Cropping Systems in Nitrate Vulnerable Zones of Northeastern Spain

Abstract

Compared with maize monocropping systems, maize double-cropping production systems have a much greater nitrogen extraction capacity. This study aims to assess if in these farming systems, animal manures could be applied, using adequate management practices, exceeding the maximum annual amount of livestock manure established in the European Nitrate Directive for vulnerable zones (170 kg N ha-1) without increasing the risk of water nitrate contamination. We compare the risk of nitrate leaching under two fertilisation strategies, one with synthetic fertilisers (M) and the second with maximized application of pig slurry (P). The study was conducted in two contrasting soil types, a deep and heavy-textured soil and a shallow and stony soil. Crop yields and N extractions were not affected by the fertilisation strategies. The nitrate concentrations in the soil below the crop root zone were lower in the deep soil than in the shallow soil, where values exceeded 1000 mg L-1. The soil nitrate concentration was not affected by fertilisation strategies at each site. The results show that pig slurry can be applied above the limit of 170 kg N ha-1, in the conditions of the study up to 360 kg N ha-1, without increasing the risk for nitrate leaching.