Efecto de los cultivos de servicio leguminosa y gramínea en la productividad del maíz a largo plazo

The agricultural intensification in Uruguay has caused erosion and nutrient loss problems due to the replacement of the agricultural-pastoral system with continuous cropping. Cover crops (CC), sown to provide ecosystem services, are a key strategy to mitigate these problems and improve agricultural sustainability. This study analyzes the long-term effect of CC and nitrogen fertilization on maize yield in a 13-year trial. The aim of this study is to evaluate the effect of cover crops and different levels of nitrogen fertilization (0 and 50 kg N ha⁻¹) on maize yield in a long-term no-till system. Functional groups of CC (legumes and grasses) and bare fallow are considered. The trial was conducted at the Dr. Mario A. Cassinoni Experimental Station (Paysandú) using a randomized complete block design with split plots. Nine treatments were evaluated (eight CC and one fallow control) along with two levels of nitrogen fertilization (0 and 50 kg N ha⁻¹). Maize yield was measured from 2007 to 2019. Analysis of variance (ANOVA) and mixed models were used to determine the effects of CC, N rates, and their interaction, classifying years as "good" or "poor" based on historical average yield. The results indicate that CC significantly affected maize yield, especially legumes, which increased yield compared to fallow and grasses. Nitrogen fertilization had a greater effect from the fifth year of the trial, reflecting the loss of the soil's N-supplying capacity. Grasses, due to their high C/N ratio, caused N immobilization, negatively affecting maize yield. The agronomic efficiency of N was higher in grasses during favorable years and in legumes during poor years. The relative yield decreased over time in fallow, while legumes showed a positive trend with N addition. Legume CC managed to increase maize yield thanks to their N contribution, even in years with lower maize yield potential. On the other hand, grasses showed greater agronomic efficiency of N in favorable years, although they limited long-term yield due to their high C/N ratio. The response to nitrogen fertilization increases as continuous agricultural use intensifies.