SUSTAINABILITY OF ORGANIC FERTILIZATION OF MACADAMIA WITH MACADAMIA HUSK-MANURE COMPOST

Macadamia husk-manure compost was evaluated as an organic fertilizer f or the production of macadamia in an experiment over four years at irr igated and unirrigated sites on the MacFarms of Hawaii orchard, The tr eatments were (1) Fertilizer, a combination of solid and liquid chemic al fertilizers applied based on leaf and soil analysis, (2) Compost, 1 0,000 kg ha(-1) of a macadamia husk-cattle manure compost alone applie d annually between July and October, and (3) Compost+, compost plus mi neral fertilizers applied based on leaf and soil analysis. In-shell nu t and kernel yield and quality were higher at irrigated than unirrigat ed sites, but were not significantly affected by the treatments. Chang e in leaf nutrient composition appears minimum except for slightly low er nitrogen (N) and boron (B) at two orchard sites for the compost tre atment. Compost increased soil pH, total ion exchange capacity, soil o rganic matter, potassium (K), calcium (Ca), magnesium (Mg) at all site s, and sodium (Na) at irrigated sites. Soil nitrate (NO3)-N was lower in the compost treatment. Fertilization with compost was not profitabl e because the cost of compost application exceeded conventional fertil ization cost tenfold for MacFarms, the largest macadamia farm in the U nited States.