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 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.

Isotopic Signatures of Nitrogen in Selected Soils from Croatia

“…Recently, many studies have focused on δ 15 N abundance in the optimization of nitrogen fertilizer use [31][32][33]. Using fertilizers labelled with 15 N isotope made it possible to determine crop use efficiency and the optimal application of fertilizer, which will greatly enhance the sustainability of the agroecosystem.…”

Cover crops affects soil nitrogen fractions and maize responsiveness to nitrogen in the Cerrado region

“…However, similar to our findings, other studies have shown neutral effects on N uptake by maize in cover crop rotation systems. Salazar et al (2021) did not observed effect of cover crops on N content in maize compartments when compared to fallow. These results can be explained by the possible lack of synchrony of cover crops residue N release and maize N demand .…”

“…However, the N fertilizer use efficiency can decrease if the N rate was excessive, contributing to losses of N and environmental issues (Salazar et al, 2021), and must be avoided in agricultural systems.…”

“…The establishment of cover crops can enhance N recycling, with reduce of N losses , and can increase N availability to subsequent crop through N mineralization of the residues (Salazar et al, 2021). On the other hand, cover crops like ruzigrass (Urochloa ruziziensis), can decrease the yield and N uptake by the main crop, and consequently, reduce N fertilizer use efficiency due to N immobilization in organic N forms (Gabriel et al, 2016;Rocha et al, 2019).…”

“…On regard to the N transformations, studies have reported the positive effect of introducing cover crop in rotation systems, especially leguminous cover crops, that provide N by the biological nitrogen fixation (BNF). Salazar et al (2021) in an experiment with maize-leguminous rotation system, have shown that the introduction of cover crops contributed to increase the NUE, but without yield gains. Hu et al (2023) have found in a long-term experiment that leguminous and non-leguminous cover crops increased the NUE by maize and also promoted better yields of the main crop.…”