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 15N 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.
Highlights
It is common to apply excessive N doses based on maize production guidelines, where it is indicated that for a monoculture of maize with yields between 10 and 20 t ha−1, doses around 400 kg N ha−1 are recommended [6,7]
The present study was carried out between October 2018 and April 2019 in an experimental site whose soil was subject to the same agricultural management since 2016
The highest precipitation event occurred in winter and was 26.3 mm
Summary
Maize (Zea mays L.) is a leading staple crop worldwide, whose production has been controversial in most producing countries, as its high demand for inputs is frequently linked to a high environmental impact [3]. In Chile, maize is of great importance in agricultural cropping, covering an approximate area of 74,000 ha, with a production of 955,000 t, and an average yield of 13.3 t ha−1 during the 2018–2019 season [5]. It is the most important crop for small producers, who associate maximum performance with the nitrogen (N) fertilizer application. It is common to apply excessive N doses based on maize production guidelines, where it is indicated that for a monoculture of maize with yields between 10 and 20 t ha−1 , doses around 400 kg N ha−1 are recommended [6,7]
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