Resource utilisation and economy of soil tillage in crop production systems

Resource use in crop production is analysed with reference to the concept of potential yield, based on the relationships between the balances of energy and mass in plant growth. Three models of the production process are proposed: a bio-physical model which looks at the conversion of energy and mass into a potential yield of biomass, a business model which assesses the economics of the conversion process and a feed-back model which points the way towards on-line optimisation. The impacts of environmental, nutritional and physiological constraints on potential yield are discussed. The business model emphasises the importance of scale of operation in reducing the costs of crop production by spreading the fixed costs of machinery. The contributions of additional energy inputs in the form of fertilisers, agrichemicals and machinery in improving the overall efficiency with which solar energy is converted into biomass, together with the pivotal role of nitrogenous fertiliser in increasing yields, are examined. Nitrogenous fertilisers underpin high yields and account for about half the energy supplied by the farmer to a cereal crop. Tillage helps in ameliorating the environmental constraints on crop growth. The implications of sustainability, and climate change, for resource use in crop production are discussed briefly.