Efecto residual de la cobertura invernal sobre el suministro de nitrógeno y el rendimiento de cebada sembrada después de maíz y soja

This study addresses the impact of winter cover crops (CCs) on nitrogen (N) supply and the yield of barley sown after corn and soybeans. Recognizing the issues of soil degradation caused by production systems characterized by limited crop diversity and long fallow periods, the study proposes alternative CCs: grasses, legumes, and their mixtures, to protect the soil during winter fallows. These CCs aim not only to prevent erosion but also to improve agricultural sustainability by fixing or recycling nutrients. The main objectives of this study are: quantify the residual effect of annual crops sown to cover the soil during winter on the "nutrient supply" service and the barley yield sown after two summer crops predecessors and to determine if there is a possible interaction with nitrogen fertilization when the summer crop predecessor is corn. Different CC varieties and mixtures were used: Avena byzantina, Vicia villosa, and their mixture (Avena byzantina + Vicia villosa). The experiment was conducted at the Mario A. Cassinoni Experimental Station (Paysandú), using a randomized complete block design for soybean and a split-plot randomized complete block design for corn. Parameters evaluated included soil nitrate concentration, biomass production, and nitrogen uptake. Results indicate that legume CCs, such as vetch, excel in nitrogen fixation and availability in the soil, while grass CCs, such as oat, are more effective at providing soil cover. The mixture of both types combined these benefits, maximizing biomass production and improving N use efficiency. Regarding subsequent crops, barley showed better yields following legume CCs or mixtures, especially after corn as the previous crop. However, these differences were not always statistically significant. Climatic conditions, such as drought, affected nutrient dynamics and yields. The thesis concludes that the inclusion of winter cover crops generates a residual effect on nitrogen supply, which extends at least to the second crop in the sequence. The implementation of legumes and mixtures is essential for agricultural sustainability, as it reduces dependence on fertilizers and improves soil conservation. Although they involve initial costs, their implementation provides long-term benefits for the productivity and health of the agricultural ecosystem. While they involve initial costs, their implementation provides long-term benefits for productivity and agricultural ecosystem health.