Evaluación de tres leguminosas como coberturas asociadas con maíz en el trópico subhúmedo

evaluation of three legumes as cover crops with maize under subhumid tropic. the objective of this work was to evaluate the potential of three legumes as cover crops to improve maize production systems. four treatments were evaluated: 1) control, maize in monoculture; 2) maize - short-cycle, white seed lima bean (phaseolus lunatus); 3) maize - long cycle, white seed lima bean phaseolus lunatus), and 4) maize - velvet bean (mucuna sp.), in a randomized complete blocks design with four replications during four growing cycles (1999-2002), in yucatán, méxico. we measured: crop biomass, ph, total n, potential anaerobic mineralization of n, co2 evolution, potassium (k), phosphorus (p), and soil organic matter, and biomass and frequency of weeds. legume stubble residues accumulated on maize crops were: 3436, 3425 and 4018 kg dm/ha for the first, second and third year, respectively. nitrogen contributed by stubble material was 25.8, 31.9, 52.8, and 43.4 kg/ha in treatments 1, 2, 3, and 4, respectively. maize grain yield was 841, 843, and 460 kg dm/ha in the first, second and third year, respectively, without significant differences between treatments. during the third year, velvet bean caused a reduction in weed biomass from 126 to 58 g dm/m2. cover crops had little influence on soil variables and maize grain yield.