Utilisation of wastes as fertilisers with particular emphasis on the Bay of Plenty region

Abstract

Estimates of the wastes produced in the Bay of Plenty region indicate that 22 million m' (tonnes) is produced annually. The main contributors to waste production are the dairy industry (shed, factory),municipal sewage, pig, poultry, meatworks, kiwifruit, fishing and pulp and paper industries. In fertiliser terms these wastes are valued at $7.7 million. In addition the timber industry produces > 1 million tonnes of timber residues (sawdust, bark, woodchips) approximately 20% of which is currently dumped. Wastes, when recycled back on to the land, offer a potential source of nutrients to enhance pasture and crop production. In addition organic wastes provide a source of organic matter which may have beneficial effects on the physical properties of soils. Research results indicate that pumice soils are well suited to the application of wastes. Some general recommendations are given for the use of wastes in dairying, orcharding and cropping situations. Three factors are considered important for the successful utilisation of wastes (a) application rates need to be balanced to the nutrient needs of the soil-plant system (b) safeguards in the form of regular chemical monitoring of the effluent, soil, plant and animal need to be implemented, and(c) the economics of using the waste materials must be favourable to the farmer and orchardist. The principle of the producer of the waste paying for its safe disposal or utilisation needs to be adopted in New Zealand as it has in many overseas countries. Keywords nutrients, organic matter, waste recycling, pumice soils, fertiliser value