SOIL-PLANT NITROGEN DYNAMICS - WHAT CONCEPTS ARE REQUIRED

Soil-plant N dynamics lie at the heart of some of the questions being asked of researchers by farmers, environmentalists and policy makers. Our aim in this paper is to highlight areas in which research is neede d to address these questions. Although we have a general understanding of many processes, fundamental understanding of the processes of the soil-plant system is not complete. Improved understanding of crop and soil processes should lead to the continuous improvement of simulation models, which are able to integrate the complex effects of management and environmental factors. However, farmers cannot wait for the achie vement of perfect models, but need researchers to put their current kn owledge to use. We suggest that for both crops and soils, diagnostic m easurements be used in conjunction with the best of, or a combination of, current models. Development work should be carried out with all po ssible speed to draw suitable models and diagnostics together. We stre ss the importance of conducting research to understand and improve N e fficiency at a range of scales and indicate the need for the involveme nt of related disciplines, such as statistics, to allow the developmen t of robust guidelines and methodologies for up-and down-scaling measu rements and models. Above all, it is essential that our understanding of the processes of soil-plant dynamics continues to underpin the deve lopment of strategies for dynamic optimisation and improve simulation models that are used in fertiliser recommendation systems. (C) 1997 El sevier Science B.V.