Perennial pastures and winter cover crops in agricultural rotations

Effects on N and P dynamics in the system: Doctoral thesis abstract

Abstract

The Uruguayan agricultural sector faces critical environmental sustainability challenges, including erosion and soil organic matter (SOM) losses, nutrient imbalances, and water contamination. Intensification and simplification of production systems exacerbate these issues. This study investigates the impact of agricultural diversification strategies, such as the integration of perennial pastures and cover crops (CCs), on nitrogen (N) and phosphorus (P) dynamics, crop productivity, and the environmental sustainability of agricultural systems. The research outlines three main objectives: (1) evaluating the effect of crop-pasture rotations compared to continuous cropping on N dynamics and wheat yield; (2) assessing the residual effects of two winter legumes (berseem clover and blue lupine) and one grass (black oat) on the subsequent maize crop; and (3) analyzing the ability of legumes from the Lupinus genus to solubilize P in soils with contrasting textures, acidity, and natural fertility. The methodology integrates long-term experiments, on-farm trials, and greenhouse assays, combining conventional and isotopic techniques. Measurements during the study included plant parameters (grain yield, nutrient uptake, above-ground biomass in different plant components) and soil properties. Results show how these strategies enhance agricultural productivity and system sustainability, fostering practices promoting nutrient cycling and resource conservation in Uruguay. Future research directions prioritize understanding the mechanisms behind differences in plant responses to N inputs and P availability. A deeper exploration of processes such as mineralization and immobilization, alongside the influence of microbial communities on nutrient cycling and SOM dynamics, remains essential.