Produção biológica de nitrogênio e proteína bruta de acessões de Leucaena spp. cultivadas para emprego na suplementação protéica de ruminantes

Leucaena spp, can be a valuable legume component of tropical forage systems since they have the capacity to produce up to 3 to 4 of protein/ha/year. Thus, we have been testing various Leucaena lines at Campo Grande, MS for potential in providing supplemental protein in beef-cattle production systems in Central Brazil. L. cunningham , L. pulverulenta , L. divenifolia , L. campina grande and L. Ieucocephala Peru type were evaluated in 12 x 22 m plots arranged in a randomized block design; plant spacing was 3 m between rows and 1 m between plants in the row. Cuttings to a 30 cm hight were made in September, 1982 and January, 1983. Subsequently, green matter (including the edible fraction, e.i. leaflets, pods and stems less than 1 cm in diameter and the stem fraction not useful as forage),dry matter (DM) and nitrogen (N) were measured. We had difficulty in establishing L. diversifolia , hence it was eliminated from the trial. Moreover, L. pulverulenta had to be replanted and thus yielded insufficiently to be cut. L. campina grande , L. cunningham and L. leucocephala produced 6.8; 9.9; and 10.1 t DM/ha in the edible fraction accumulated from the two cuttings. Nitrogen accumulated in the aerial biomase was 267, 370 and 376 kg/ha/year respectively, for the three acessions. Considering that a Brachiaria decumbens pasture, our major grass forage, maintains a yearly nitrogen offer, in the available forage of 100 to 250 kg CP/ha, the addition of 2,000 kg of CP obtained in the Leucaena protein-bank represents a valuable tool for supplementing cattle diets in Central Brazil.