Influence of pruning frequency of Albizia lebbeck, Gliricidia sepium and Leucaena leucocephala on nodulation and potential nitrogen fixation

The influence of four pruning frequencies on biomass, nodulation and N2 fixation was investigated on Albizia lebbeck, Gliricidia sepium and Leucaena leucocephala grown in the screenhouse for 16 months, using acetylene reduction and 15N dilution methods. Frequent prunings at 4-month intervals had no deleterious effect on symbiotic N2 fixation, which increased in Gliricidia and Leucaena in particular. Nodulation and nitrogenase activity varied inconsistently within species, and were not influenced by pruning frequency. Cumulative assessment of pruning effect showed higher biomass, N yield and N2-fixing capacity of the woody species than at last harvest, and appeared to have more practical relevance. Across species, cumulative total dry matter, N yields, and both percentage and absolute amount of N2 derived from atmosphere increased with pruning frequency, except when trees were pruned 3 times. Of the three species, G. sepium had the lowest biomass production, N2 fixation and N accumulation

Screening woody and shrub legumes for growth, nodulation and nitrogen-fixation potential in two contrasting soils

In order to identify for alley cropping new candidate species with high biomass and nitrogen-fixing potential, a screening study was conducted on ten woody and shrub legumes (Acacia auriculiJormis, Albizia lebbeck, Gliricidia sepium, Leucaena diversifolia, L. leucocephala cv. K28 and cv. K636, Lonchocarpus sericeus, Cajanus cajan, Crotalaria juncea and Tephrosia candida) for 6 months using an acid Ultisol and a non-acid Alfisol. A wide interspecific variability of legumes appeared within soil types, and there were significant species by-soil interactions for many parameters in this study. In the acid Ultisol, plant growth in height and grith, nodule numbers, nitrogen yield and Nrfixing potential were significantly (P = 0.05) lower than those in the Alfisol. While Albizia lebbeck was outstanding in both acid and nonacid soil conditions for most performance criteria, L. leucocephala cv. K28 was most sensitive to soil acidity with 41.7% of total nitrogen yield in the Ultisol relative to that accumulated in the Alfisol. In addition to L. leucocephala cv. K28 and G. sepium, the most common hedgerow species, A. lebbeck, L. leucocephala cv. K636, L. diversifolia on Alfisol, and A. lebbeck, L. leucocephala cv. K636, L. diversifolia, Tephrosia candida and Cajanus cajan on acid Ultisol, could be considered promising and thus, worthy of further site adaptability trials