Response of four tropical legumes to phosphorus, potassium and lime when grown in red-yellow latosol of the campo cerrado

Abstract

The response of Stylosanthes gracilis, Centrosema pubescens, Glycine javanica and Phaseolus atropurpureus to P, K and lime were compared. A very acid, P deficient red-yellow latosol soil was used for the study. A composite design with respect to the three factors plus some additional treatments of lime and P were used. All of the legumes responded to P reaching near maximum yields between 100 and 200 kg p/ha. The response of S. gracilis was much less than the other three species. The concentration of P in the plants ranged from about 0.10 to 0.25%. Applied in small increments, lime gave marked increases in yield. Maximum yield for S. gracilis was obtained with only 250 kg Ca/ha. Maximum yields for the other three species occurred at the 1000 kg Ca/ha level. The response pattern of each legume differed from the others. The depression in yield occuring with heavy applications of lime apparently was not due to induced nutrient imbalances caused by a surplus of Ca ions. Analysis of the plant material for Mn, Fe Cu, Zn and B as well as for the macronutrients indicated that all were within normal limits. The mechanism causing yield depression by lime needs further study. The response of the tropical legumes to applications of K was not statistically significant. C. pubescens was lower in protein than the other three species. Percent protein increased with increasing level of lime.