Review: Environmental biology and crop improvement.

The average yield of Australia's major grain crop, wheat, rose at its fastest rate ever during the last decade. The environmental biology behind this advance was predominantly ecological and nutritional - endemic root diseases were controlled through better management of inoculum levels, and the consequently healthier crops were more responsive to fertiliser, especially nitrogen. Applying nitrogen fertilisers became less risky; farmers used much more and thereby achieved much higher yields. Despite Australia's reputation for being drought prone, its crop yields have not hitherto been typically limited by water - poor health and poor nutrition have been more influential. Improvements in the management of health and nutrition have resulted in many crops now being limited by water, so the effectiveness with which that water is used in producing grain has become more important - capturing more of it, using it effectively in producing photosynthate, and ensuring that a large fraction of that photosynthate is converted into grain. Further improvement will come from the steady 1% per year achieved by breeders, overlain by agronomic advances based on deeper ecophysiological understanding of the interaction between roots and soil biota, how roots access resources in the subsoil, and the basis of spatial variation in yield across a paddock.