BENEFICIAL IMPACT OF PRECISION NUTRIENT MANAGEMENT ON THE ENVIRONMENTAND FUTURE-NEEDS

The necessity for precision nutrient management has arisen from a decl ine in agricultural commodity prices, the advent of new technology, an d demographic changes resulting in increased urbanization. Community p erceptions and attitudes to agriculture, food quality and the environm ent are often negative: thus management of essential and beneficial nu trients as well as agriculturally undesirable ions is progressing at a more rapid pace than would be dictated by economic and technological factors alone. Some of the main agronomic reasons for developing preci sion nutrient management are: the potential for ground water pollution particularly nitrate; heavy metal pollution; salinity including risin g water tables; nutrient run-off into streams and rivers from cropping , pastoral, intensive livestock and horticultural enterprises; suitabl e crop, pasture or other ground cover to minimize soil erosion; and th e introduction of new cultivars of plants. Opportunities for developin g more precise nutrient management abound but they need to be targeted to a particular industry or enterprise. These opportunities include s oil-less agriculture, inert matrix agriculture, timing of fertilizer a pplications, nutrient supply in relation to demand and nutrient availa bility, nutrient cycling, foliar fertilizers, development of compounds to promote translocation, exploiting nutrient interactions, location of agricultural enterprises, water management, decision support system s and selection of genotypes of a crop which are nutrient efficient an d effective. Precise nutrient management in most situations can only b e achieved with sound, regular soil and plant analyses. Theory can pla y a substantial role in improving nutrient management. Basic ion uptak e studies can provide information on the genetic potential of a crop's nutrient quality and on nutrient limitations. They can also provide a n means of calculating the nutrient requirements of a crop or pasture. Estimates of nutrient requirements can also be made from desired yiel ds particularly, if growth rates are known for that environment. Nutri ent balance (ratios) and interactions between nutrients also provide a basis for improved management procedures. Further developments are ne eded for translocation, demand functions for nutrients at particular t imes, and root/shoot ratios during crop growth. At a field level, deve lopment must occur on equipment to deliver and place nutrients precise ly; rapid, effective scanning of soils to monitor the local nutrient s tatus rather than relying on extensive sampling; plant responses in th e field to single nutrient and multiple nutrient fertilizers to assess the interactive components of nutrition; and training of personnel wh o have excellent interpretative skills in plant and soil analyses.