Optimising Legume Integration, Nitrogen Fertilisation, and Irrigation in Semi-Arid Forage Systems

Monoculture systems depend on high nitrogen (N) fertilisation. Incorporating legumes into forage crops offers a sustainable alternative with agronomic and economic benefits. This study assesses the impact of legumes in fodder systems, evaluating yield, N use efficiency (NUE), and profitability while identifying the best cropping strategy under semi-arid conditions. The experiment, conducted at Herdade da Comenda, Elvas, Portugal, used a split–split-plot randomised block design to analyse N doses, forage species, and irrigation. Economic metrics, including costs, net revenue, return on investment, and risk analysis, were also assessed. Moderate N doses (120 kg ha−1) resulted in significantly higher NUE (15.67 kg kg−1 N) than higher doses (200 kg ha−1), which yield only 1.40 kg kg−1 N (p < 0.05), particularly in mixed fodder crops. Irrigation improved N absorption, crop nutrition, and yield, leading to higher profitability despite increased initial costs. Agronomically, irrigation and N doses influenced yield and nutrient uptake, while no significant differences were observed between different forage crops in terms of yield or NUE. Economically, the irrigated mixed crop showed the highest return on investment (ROI = 247.37 EUR ha−1), whereas ryegrass presented lower financial risk (BE = 2213.24 kg ha−1) due to lower establishment costs. Yield was the strongest predictor of net profit (R2 = 0.89). Looking ahead, optimising N management, irrigation strategies, and mixed grass–legume crops will be crucial to maximising economic returns while minimising environmental impacts.

Descrição

Funding Information: The APC was funded by national funds through the Fundação para a Ciência e a Tecnologia, I.P. (Portuguese Foundation for Science and Technology) by the project UIDB/05064/2020 (VALORIZA—Research Centre for Endogenous Resource Valorization), by national funds from Fundação para a Ciência e a Tecnologia (FCT), Portugal, through the research unit UIDP/04035/2020 (GeoBioTec), and by National Funds through the FCT—Foundation for Science and Technology under the Project UIDB/05183. Publisher Copyright: © 2025 by the authors.

Palavras-chave

Data-analysis Environment Grass–legume Management Modelling Net revenue Profitability Yield Agricultural and Biological Sciences (miscellaneous) Earth and Planetary Sciences (miscellaneous) Environmental Science (miscellaneous)