Nitrate Leaching in Maize (Zea mays L.) and Wheat (Triticum aestivum L.) Irrigated Cropping Systems under Nitrification Inhibitor and/or Intercropping Effects

The use of nitrogen fertilizers in agriculture is currently under high pressure to reduce its environmental impact and improve its currently low efficiency. Nitrification inhibitors and/or intercrops emerged in recent decades as useful tools to combat these problems. The objective of the experiment is to study the effect of these techniques on the yield, the nitrogen use efficiency (NUE) and N leaching in a maize-wheat rotation. Six treatments were studied, combining the use of ammonium nitrate sulfate (ASN) alone or with a nitrification inhibitor (DMPSA or 3,4-dimethylpyrazole succinic acid) and the use or absence of vetch (Vicia sativa L.) as an intercrop. The results showed that fertilized treatments did not show significant differences in crop development, but the use of DMPSA delayed the nitrate (NO3-) availability and reduced N leaching losses (average N leaching reductions around 25% after maize harvest). On the other hand, the use of vetch as an intercrop helped to reduce the negative effects of N deficiency and, at the same time, increased the concentration of N in the soil during the following crop harvest (4.5 kg N ha(-1) on average after wheat harvest) and reduced losses due to leaching (average N leaching reductions around 14% after the maize-wheat season). The combination of both techniques (DMPSA and vetch intercrop) at the same time presented a synergic effect and greatly improved the environmental impact of the irrigated maize-wheat system.