Caracterização morfogênica e estrutural de Desmanthus pernambucanus (L.) thellung sob diferentes densidades de plantio e altura de colheita

Abstract

The native forages use has expressive relevance for the animal husbandry sustainability, however, environmental and management factors affect the morphogenic and structural characteristics of forage plants over a development period. We assessed the forage potential of Desmanthus pernambucanus (L.) Thellung submitted to different plant densities and cutting height through morphogenic and structural characteristics in a Sub-humid tropical region. The trial was performed in the city of Carpina, Pernambuco, Brazil, over 2018 and 2019. The experimental design was randomized complete blocks with split-plot scheme. The main plots consisted of plant densities (40,000, 15,625 and 10,000 plants ha-1), subplots consisted of cutting heights (20 and 40 cm), and harvests were considered repeated measures in time. Increase rates were estimated for plant height, crown expansion, leaf appearance, leaf expansion, leaf and branch elongation, as well as number of branches, number of leaves per branch and leaf size. There was interaction (P<0.05) between planting density and harvests for the increase rate of plant height, with greater response observed for the first harvest during rainy season (1.35 cm day-1) and 40,000 plants ha-1. Only the crown expansion rate developed an isolated effect from the factors plant density, cutting height and harvest, with 0.92 cm dia-1 crown expansion observed when grown under 10,000 plants ha-1 density. For morphogenic rates, a significant effect was observed only for the harvest factor, which rainy season results were greater than dry season for rates of branch elongation (1.14 vs 0.20 cm day-1), leaf appearance (0.19 vs 0.017 leaves day-1), leaf elongation (0.041 vs 0.0031 cm day-1) and leaf expansion (0.020 vs -0.008 cm day-1) regarded 2018 and 2019. Stem and branch diameter had influenced of the harvests, and only the stem diameter was influenced by plant density, which developed lower results when grown at 40,000 plants ha-1 density. There was interaction (P<0.05) between cutting height and harvest for number of remaining branches. For number of secondary branches, there was effect of 10,000 plants ha-1 density that reached 6.57 secondary branches. There was no effect of plant density or cutting height on number of primary branches (20.67 branches), number of leaves expanded (16.54 leaves) and in expanding (3.01 leaves) and leaf size (5.42 cm). Plant densities and cutting height modify the increase rate of plant height, crown expansion, stem diameter, number of remaining and secondary branches, although no changes occurs on morphogenic and structural characteristics of Desmanthus pernambucanus (L.) Thellung.