DRY-MATTER PRODUCTION AND NUTRIENT CYCLING IN AGROFORESTRY SYSTEMS OF MANDARINE GROWN IN ASSOCIATION WITH ALBIZIA AND MIXED TREE SPECIES

A study on dry matter production and nutrient cycling in agroforestry systems of mandarin grown in association with N-2-fixing Albizia and mixed tree species (non-N-2-fixing) was carried out in the Sikkim Himalaya. A site with Albizia was referred as Albizia-mandarin stand and the other site with mixed tree species as mandarin stand. The stand total biomass, net primary productivity and mandarin fruit production was higher under the influence of Albizia. Agronomic yield of crops remained nearly the same in both the stands. Nitrogen and phosphorus concentrations of different components of Albizia were higher than those of mixed tree species, whereas their back translocation from leaf to branch before abscission was lower in Albizia. The mandarin-based agroforestry is a highly nutrient-exhaustive system evaluated in terms of nutrient exit through the removal of agronomic yield. This system, under the influence of Albizia, was more productive with faster rates of nutrient cycling. Nutrient use efficiency increased under the influence of Albizia, in contrary to the hypothesis that efficiency should decrease with increasing rate of uptake. The poor nutrient conservation of Albizia, and malleability of nutrient cycling under its influence make it an excellent association which promotes higher availability and faster cycling of nutrients. Albizia should be utilised more extensively in the management of mandarin-based agroforestry systems.