Effect of alley cropping with Calliandra calothyrsus (Meissm) on sequentially grown maize and cowpeas
A series of trials were conducted at the International Institute of Tropical Agriculture, Ibadan, Nigeria, between January and December 1988 to evaluate the potential of calljandra for alley cropping. In a field experiment, the growth, biomass production and nutrient yield of calljandra and the growth and yield performance of sequentially grown maize and cowpea were assessed. Six treatments were used comprising three nitrogen rates (0, 45 and 90 kg N ha-1) factorially combined with and without prunings in a randomized complete block design. Concurrently, a comparison of the decomposition rates and nitrogen release of calliandra and maize stover, and that of green and dry wood of calliandra, leucaena, calliandra, cassia and acioa was made using the same experimental field and design. In a greenhouse study, the N-manuring value and residual effects of dry and green leaves of calliandra and calliandra maize production were also investigated and compared with inorganic N-source in a randomized complete block design. Nitrogen from legume leaves and calcium ammonium nitrate (CAN) was supplied at 0, 50 ppm and 100 ppm N rates and the plant height, dry matter production and N-content in tops determined. Calljandra recorded an impressive one year's growth of 306.7 em, a maximum of 35 coppices per tree and a biomass production of 5.0 tons Dm ha-1 from four prunings contributing an estimated nutrient yield of 185 kg N, 13.3 kg P, 64.2 kg K, 55.2 kg Ca and 16 kg Mg ha". Maize plant height and leaf area index were increased (xv) by pruning and inorganic N application, but not significantly. Levels of N, P and Mg in maize earleaves increased with increasing nitrogen and with pruning application, but only N was significant while K and Ca remained largely unaffected. Without prunings, the application of 45 and 90 kg N ha-1 increased total grain yield by 108 and 176% respectively. With pruning application, however, the respective yield increases were only 6 and 12%. Prunings alone double maize yield while the addition of 45 kg N increased yields by 12% and that of 90 kg N depressed yields by 8%. The effect of pruning applicaiton was approximately equivalent to the application of 45 kg N ha-1. Hedgerows significantly reduced per plant grain yield of plants grown adjacent to them, but the latter accumulated more N in grain than the former. Pruning application, residual Nand calliandra hedgerows did not significantly influence cowpea plant height or leaf area index. Plants near hedgerows' showed higher nutrient status than those in middle of alleys. Application of prunings significantly affected weed growth and flora in cowpea crop. Prunings slightly increased total seed yields and the proximity of cowpea to hedgerows had a significant positive effect on both number of pods and yield, with a significant interaction with residual N. Calliandra prunings decomposed four times faster than maize stover and green wood faster than dry wood, rates which were proportional to their respective C:N ratios. The order of decomposition was leucaena > gliricidia > calliandra > cassia> (xv i) acioa. The decomposition rates of cassia and acioa were significantly different from the rest. Under greenhouse conditions, inorganic N was a better Nsource than dry leaves of calliandra at same N-rates while calliandra was inhibitory at increasing application rate. Incubation of green and dry leaves for periods of 9, 6 and 3 weeks did not improve performance significantly, but green leaves were better than both inorganic N and dry leaves and gave a greater residual effect on subsequent maize crop.