Producción de biomasa aérea, radicular y aportes de nitrógeno de distintos cultivos de servicio invernales

Uruguay has maintained, over the years, a continuous agricultural system that has contributed to the degradation of its soils, resulting in a progressive decrease in productivity, low nitrogen input by crops, decrease in biodiversity, increased use of herbicides, and erosion caused by periods of bare soil. In response to these challenges, cover crops have emerged as a partial solution to mitigate these issues, improving soil fertility, controlling erosion, and increasing biodiversity. The main objectives of this study are to evaluate the production of aerial and root biomass in cover crops in the top 20 cm of soil. Additionally, to estimate the nitrogen contribution of different winter cover crops. The following varieties were used for this purpose: Avena strigosa, Avena byzantina, Vicia villosa, Lupinus angustifolius, Trifolium resupinatum. Furthermore, mixtures formed as follows were used: Avena byzantina + Vicia villosa, Avena strigosa + Vicia villosa, arranged in a randomized complete block design with three replications. The results showed significant differences (p≤0.05) in aerial biomass production. Avena strigosa achieved the highest average production, with 10,398 kg DM ha-1. In the analysis of functional groups, grasses reached an average aerial biomass production of 9,126 kg DM ha-1. For root biomass, Avena strigosa also led with 1,921 kg DM ha-1, and the group of grasses had the highest average root biomass production, recording 1,705 kg DM ha-1. Furthermore, a direct and positive relationship between aerial and root biomass production was evidenced. The analysis of nitrogen contribution and the C/N ratio showed significant differences (p≤0.05) between functional groups. The mixture of Avena byzantina (high density) with Vicia villosa presented the highest nitrogen contribution, with 151 kg/ha and a C/N ratio of 25/1, indicating good efficiency in nitrogen fixation. Overall, the mixtures had the highest nitrogen contribution (139 kg/ha), similar to that of legumes (119 kg/ha), but significantly higher than that of grasses. Regarding the C/N ratio, legumes showed the lowest value (13/1), in contrast to grasses (40/1).