Nutritional factors limiting growth of tropical forage species in two soils from Zona da Mata, MG. II. Red-yellow podzolic

Abstract

Two pot experiments were carried out in a glasshouse to identify the nutritional factors which limit the growth of forage species in a Red-yellow podzolic. Molasses grass (Melinis minutiflora Beauv.) and Centrosema pubescens Benth were used as test plants. The omission of P, N, S, Zn, Cu, B, Mo or Co and the addition of Mn, Fe or K to a complete nutrient control were used to assess the effect of these nutrients on forage growth, and nodulation and N₂ fixation of the legume. Molasses grass was harvested twice. The most serious limitation to the grass growth and to nodulation and growth of the legume was determined by P deficiency. In the absence of P, nodule dry weight was considerably more reduced than root dry weight. After the first harvest the grass growth was limited by N and S deficiencies. Sulphur deficiency also reduced the dry weight of tops and total N yield of the legume. In the absence of Mo, there was a tendency for the N Concentration in the tops of the legume to decrease. Other nutrients tested had no significant effect on forage growth or nodulation and N₂ fixation of the legume.