100
and competition. While there is a diversity of soil types across the dryland crop
production areas, characteristically soils are low in natural fertility, organic matter
and water-holding capacity. Across large areas, these issues are combined with high
salinity and soil pH extremes (alkalinity or acidity) creating hostile soil environ-
ments for crop production. Consequently, the average wheat yields across the grain
belt are only 2 t ha-1. Erosion-prone soils have been a further barrier to cropping,
however, the adoption of reduced tillage crop establishment systems and stubble
retention have combined to minimise the soil erosion problem. Fertilizer inputs are
an annual necessity and soil physical and chemical amelioration are frequently
required to allow the growth of productive and weed competitive crops.
Increasing global population growth is driving demand for greater food produc-
tion. However, for crop producers in dryland cropping regions particularly in devel-
oped and developing countries, low yield potentials, decreasing produce prices and
increasing input costs are severely impacting the viability of crop production.
Consequently, these enterprises are increasing in size as financial pressures force
growers to rely on the economies of scale to remain viable. These production sys-
tems are now highly mechanised to address the need for timeliness of seeding, weed
control and harvest operations in typically short growing seasons.
Current and future cropping practices will more frequently lie within the conser-
vation production approach, based on reduced tillage and crop residue retention.
Fig. 1 Variable long-term average monthly rainfall distributions for nine centres across the
Australian dryland cropping region (Adapted from Cramb 2000 )
M. Wa lsh