Beyond Conservation Agriculture - Principles, Pragmatism and Productivity in Wheat Farming Systems.

Australian broad-acre wheat farms have evolved in the last 30 years from the traditional mixed farming system based on cereals and grazed pasture leys to more intensified crop production. In the two decades from the mid-1980’s crop area doubled and sheep numbers halved, and many farms or parts of farms are continuously cropped (i.e. pastures are not part of the rotation). Conservation agriculture (CA) principles (no-till, stubble retention, diverse crop sequences) underpinned the evolution, and recent research initiatives have demonstrated significant potential to close the “yield gaps” of cropping systems by capturing the synergy possible from the combination of improvements (e.g. crop sequences, improved summer fallow management, more timely sowing with improved varietal choice). However a pragmatic rather than a rigid approach to CA has been needed to realise the benefits and avoid the problems that can emerge in continuously cropped, no-till cropping systems. Strategic tillage, managed crop residue reduction, integration of livestock on cropped land, and diverse end-uses for crop legumes in the system (grain, graze, hay, brown-manure) are all approaches that can assist to improve the productivity and sustainability of intensive cropping systems. Maintaining soil fertility and managing weeds and disease remain challenges in these intensive systems. The recently reported climate-induced reduction in wheat yield potential of 27% in Australia since 1990 was not reflected in actual farm yields suggesting significant uptake of new technology to offset climatic constraints. However this highlights the need to develop integrated agronomic solutions that also manage the economic risk and resilience challenge faced by wheat growers in the driest continent on earth.