How external inputs can maintain Pacific island soil fertility

Agriculture is the main base of the economy of the South Pacific islands, and a subsistence system of mixed cropping, starchy root crops mixed with banana, breadfruit and coconut, is the mainstay. Farmers use a variety of local resources to maintain soil fertility, but external inputs can increase fertility, says Stanley Weeraratna of the University of the South Pacific. Crop yields on newly-cleared land are high, but decline sharply after the first couple of year's cropping. Constraints on available space mean that the same land is cropped over and over again without fallowing. Mulches of dadap leaves, grass, weeds, dried coconut fronds, banana and breadfruit leaves at 30 tonnes per hectare can increase yields by up to 65%. In atolls where organic materials are limited farmers use shredded coconut logs, wood chips and coconut husks. Poultry and pig manure is used where available. Organic fertilizer in the form of mulch has to be applied in large quantities, and it is sometimes necessary to replenish the soil nutrients that are removed with the biomass in the form of inorganic and/or organic fertilizers as an external input. Results of studies indicate that a mixture of local and external inputs obtain the maximum benefits from local resources. Stanley Weeraratna, School of Agriculture, University of South Pacific Alafua, WESTERN SAMOAAgriculture is the main base of the economy of the South Pacific islands, and a subsistence system of mixed cropping, starchy root crops mixed with banana, breadfruit and coconut, is the mainstay. Farmers use a variety of local resources to..