Nitrogen Fertilizer Efficiency Determined by the 15N Dilution Technique in Maize Followed or Not by a Cover Crop in Mediterranean Chile

Abstract

Nitrogen (N) in a maize crop is a determining yield factor, but its negative impact on the environment is also known. Therefore, it is necessary to propose mitigation strategies that allow an improvement in the N fertilizer efficiency (NFE), such as the use of cover crops (CC) and the adjustment of the fertilizer dose. The objective of the study was to determine NFE using N-15 isotopic techniques and nitrate (NO3-) leaching in a maize-fallow versus a maize-CC rotation with optimal and excessive doses of N in the Mediterranean area of Chile. The treatments were a combination of crop rotation (maize-fallow versus maize-CC of Lolium multiflorum) with the optimal dose of N (250 kg ha(-1)) or excessive dose (400 kg ha(-1)). We found that the optimal dose of maize-CC rotation contributed to reducing the losses of N by leaching and improving the NFE. Using the optimal dose decreased the dissolved inorganic N (DIN) emission intensity by 50% compared to the excessive doses. Even if grain yield was higher (19 t ha(-1)) when applying the excessive N dose, the NFE (28%) was lower than when applying the optimal dose (40%). In the maize-CC rotation with optimal dose, yield was 17 Mg ha(-1). The excessive N dose generated higher DIN content at the end of the maize season (177 kg N ha(-1)). In conclusion, replacing the traditional autumn-winter fallow in the maize monoculture with a CC with optimal N dose contributed to improving NFE and reducing N leaching in a Mediterranean agricultural system. Consequently, it is a strategy to consider as it has positive advantages in soil and N management, helping to reduce diffuse pollution of surface and groundwater bodies.