Crop management must improve if the quantity and quality of food is to continue to meet the needs of a growing world population. At the same time, crop management must minimize soil erosion, acidification, salinisation, the leakage of nutrients and pesticides to ground water and steams, and the impact of biodiversity. These improvements must be made against a likely background of increased cost of energy and a changing and more variable climate. During the 20th century, the increase in crop productivity generally stayed ahead of the demand for food, due in equal part to improved crop management and plant breeding. Progress in crop management during the 21st century must be based not so much on the increased inputs that have characterized the last century, but more on increased efficiency with which these inputs are used, and increased reliance on the ways they are brought together. We need inexpensive inputs such as precise timing, novel rotations and reduced tillage systems. The first paper in this theme explores the balance between the food and fibre produced, and all the economic and environmental costs incurred in that production. The second plenary paper deals with the growing worldwide problem of nutrient pollution of water bodies. This paper deals particularly with nitrogen and the temporal and spacial aspects in obtaining on-farm solutions to regional environmental problems.

Symposia focus on specific farming systems, in terms of crop sequences and methods of managing nutrients, agrochemicals and tillage that increase productivity and reduce environmental harm.