Nitrogen recycling in mango orchards from litterfall and pruning biomass

Mango production systems in the NT require low nitrogen (N) inputs, with excess applied N having negative impacts on fruit quality. Crops remove ~0.85 kg N t-1 of fruit harvested, or 13-20 kg N ha-1 . Potential in-orchard N cycling from litterfall and pruning biomass is not accounted for when calculating orchard N needs. To increase precision in N application, we monitored litterfall and pruning biomass from Calypso® and Kensington Pride mango cultivars. Mean annual litterfall was 1.3 t ha-1 and pruning biomass 1. 2 t ha-1 . The litterfall provided 12 kg N ha-1 , predominantly from flowers (4.4 kg) and leaves (5.15 kg) while pruning biomass provided 8.4 kg N ha-1 . Results indicate that biomass recycled in mango orchards is a significant source of N for the trees, similar in quantity to fertiliser applied N.

In the mango production system, falling leaves and other plant parts (dried branches, flowers, fruits) as well as end of season pruning biomass constitute the litterfall. Growers prune trees after harvest to maintain canopy shape, control vigour and promote new growth. However, the amount and nutrient content of mango plant material abscised and pruned from mango trees over time has not been documented, nor is it considered when applying N seasonally. As part of a project on enhancing nitrogen use efficiency in horticultural systems and how various factors impact on the nitrogen required, this study examined the seasonal quantity of litterfall from two mango orchards in the Northern Territory (NT), Australia.