Nutritional imbalances and reduced forage production under intra-seasonal drought are alleviated by irrigation in tropical forage grasses

Forage production is affected by water deficit, but it is not known how grasses cope with dry periods during the rainy season and how irrigation can be used during dry periods in pastures. This field study analyzed the effects of water deficit during the spring-summer season on the nutritional, productive and morphological composition aspects of Mavuno and Zuri grasses, as well as the potential of irrigation to mitigate the damages caused by drought, using a randomized complete block design in a 2 × 2 factorial scheme, with two water conditions (rainfed and irrigated) and two forage grasses (Zuri and Mavuno). Water restriction impaired nutrient uptake and accumulation, and altered the C:N:P balance in Zuri and Mavuno grasses. Zuri grass was more tolerant to water deficit due to amino acid accumulation (62%), modifications in C:N:P: Si homeostasis, and maintenance of C and mineral nutrient use efficiency. Irrigation in Mavuno grass improved nutrient use efficiency, tillering, and forage production (41%), showing a positive response to irrigation. The morphological composition of forage improved under irrigated conditions for both forage species. Therefore, drought periods impair the production of sensitive grasses, and irrigation mitigates forage production losses during these water restriction periods in the spring-summer season.