Sustainability of organic fertilization of macadamia with macadamia husk-manure compost

Macadamia husk-manure compost was evaluated as an organic fertilizer for the production of macadamia in an experiment over four years at irrigated and unirrigated sites on the MacFarms of Hawaii orchard, The treatments were (1) Fertilizer, a combination of solid and liquid chemical fertilizers applied based on leaf and soil analysis, (2) Compost, 10,000 kg ha(-1) of a macadamia husk-cattle manure compost alone applied annually between July and October, and (3) Compost+, compost plus mineral fertilizers applied based on leaf and soil analysis. In-shell nut and kernel yield and quality were higher at irrigated than unirrigated sites, but were not significantly affected by the treatments. Change in leaf nutrient composition appears minimum except for slightly lower nitrogen (N) and boron (B) at two orchard sites for the compost treatment. Compost increased soil pH, total ion exchange capacity, soil organic matter, potassium (K), calcium (Ca), magnesium (Mg) at all sites, and sodium (Na) at irrigated sites. Soil nitrate (NO3)-N was lower in the compost treatment. Fertilization with compost was not profitable because the cost of compost application exceeded conventional fertilization cost tenfold for MacFarms, the largest macadamia farm in the United States.