Estimation of the potential supply of nitrogen by tropical legumes. II. Region of Itapetininga, São Paulo, Brazil

Abstract

The present experiment was carried out in the field at Posto de Ovinos e Caprinos do Instituto de Zootecnia. in itapetininga, of São Paulo, BraziI. It was evaluated the potencial supply of nitrogen through perenniaI soybean (Glycine wightii Verde.), galáxia (Galactia striata Jacq.). green leaf desmodium (Desmodium intortum cv. Green Leaf Urb.) to Setaria anceps Stapf ex Massey cv. Nandi. Theses species were fertilized with three levels of nitrogen (0, 150 and 300kg per hectare per year) and each one of the legumes was also mixed with the grass. Setaria mixed with perennial soybean, with galaxia and with desmodium showed dry matter yields equivalent to a fertilization of 124. 117 and 105kg of nitrogen/hectare/year on the grass alone. The forage production of the grass alone increased up to 300kg N per year, with increases in dry matter yield (D.M.) of 23.35kg of D.M./kg of applied N and 32% rate of nitrogen recovery. The forage legumes increased the protein contents of mixed Setaria grass compared with Setaria grass alone not fertilized with mineral N. The apparent nitrogen transfer of perennial soybean, galaxia and desmodium to the mixed setaria was 32, 38 and 32.5kg of N/hectare/year, respectively.