Respostas morfogênicas e estruturais de leguminosas forrageiras à frequência de corte e balanço hídrico negativo

Abstract

Legumes are an important family of high-protein forages cultivated in Brazil. In order to adopt the appropriate cutting frequency for each forage species, it is important to know their morphogenic and structural responses, since they are related to growth and, therefore, to forage production. Also, considering that, under natural conditions, forage plants are subject to annual water deficit, which tends to worsen due to current climate changes, with more frequent and longer droughts, it is necessary to understand how legumes grow during the dry season. The objective was to study morphogenic and structural responses of forage legumes [Stylosanthes spp. cv. Large field; Desmanthus pernambucanus (L.) Thellung and Clitoria ternatea L.] at cut-off frequency (60 and 90 days) and negative water balance in the municipality of Carpina-PE, Brazil, in 2019 and 2020. The experimental design was randomized complete blocks, with subdivided plots and four replications, where the main plots were composed by legumes and the subplots composed by the cut frequencies. Legumes differed in structure due to their morphogenic characteristics, according to cutting frequency and intensity of annual water stress. Cutting frequency of 90 days favored a greater quantity of Campo Grande leaves due to the higher leaf appearance rate and lower phyllochron. D. pernambucanus showed greater height and branch length due to the higher growth rate and branch elongation rate. C. ternatea stood out in the elongation of the leaves, which presented larger dimensions. There are indications that plants under the same cutting frequency made adjustments in the allocation of resources for the development of organs according to the intensity of the annual water stress. Even under negative soil water balance, legumes maintained their growth, thus demonstrating an adaptation to the water deficit. The differences in the structural and morphogenic characteristics of the legume plants can allow the multiple use of these plants according to the cultivation system and the adopted management.