Morfologia, produtividade e valor nutritivo de Jureminha em resposta à densidade de plantio e altura de colheita

Abstract

The use of forage legumes represents an important alternative to improve the supply of N in the soil and the diet of ruminants. The aim of this study was to evaluate the effect of different planting densities (40,000; 15,625 and 10,000 plants ha-1) and harvest heights (20 and 40 cm) on the morphological, productive and nutritive characteristics, in addition to the survival of Jureminha (Desmanthus pernambucanus (L.) Thellung) cultivated in the Zona da Mata Norte of Pernambuco, as well as to estimate the repeatability coefficient of the evaluated traits. The experiment was designed in randomized blocks with subdivided plots and four repetitions. Planting densities were evaluated in the plots, and the harvest heights in the subplot. Seeds from the 7G accession of Jureminha were used. The plants were subjected to uniform cutting 127 days after transplanting, and eight more harvests were carried out with an interval of 84 days. The following variables were evaluated: plant height; stem (SD), branch (BD) and canopy (CD) diameters; branch length (BL); number of branches per plant (NBP); number of leaves per branch (NLB); number of leaflets per leaf (NLL); leaf length and width (LL and LW); leaf area index (LAI); light interception (LI); survival; productions of leaves, branches, pods, forage and total; and leaf/branch ratio (LBR). The chemical composition, and in vitro dry matter digestibility (IVDMD) of the forage were determined, and the fractionation of carbohydrates and protein was carried out. Harvest heights did not affect yield or survival of plants. Cultivation under a density of 40,000 plants ha-1 allowed to obtain taller plants, with higher LAI (0.98), LI (49%), and individual yields (18.8 g DM.plant-1) and by area (576.5 kg DM.ha-1.harvest-1), even providing a smaller CD (87.9 cm) and a final stand (66%) more reduced. The LBR was higher in December/2018 (1.44) and February/2020 (1.34). Dry matter (DM: 356.3 g.kg-1), mineral matter (38.2 g.kg-1), lignin (145.6 g.kg-1), digestibility (433.1 g.kg-1), fraction C of carbohydrates (20.5% DM), fractions B3 (8% crude protein: CP) and C (17% CP) of protein were not altered (p≥0.05) by any factor studied. Higher CP contents (181.6 g.kg-1) and lower neutral (NDF: 568.4 g.kg-1) and acid detergent fiber (ADF: 426.5 g.kg-1), hemicellulose (143.6 g.kg-1) and cellulose (281.3 g.kg-1) were observed in forage harvested in the dry season. Denser cultivation allows greater yield however reduces survival. Only harvest seasons promote changes in the chemical composition of the forage, but do not affect the digestibility of DM. Jureminha has potential for use in protein banks, being harvested, conserved and supplied in addition to animals, but producers must expect fluctuations in yield. The persistence of the nutritive value of forage indicates your potential as a protein supplement in the diet of ruminants fed with tropical grasses, especially in the dry season. It is possible to reduce the number of measurements for SD, NLL (R2=95%), plant height, CD, LAI, LI, LL, LW, NLB, BD, LBR, NDF, ADF, hemicellulose, lignin, total carbohydrates and your fraction C, and fractions A and B1+B2 of the protein (R2=90%), optimizing resources in future research with Jureminha.