David Roget, Bill Davoren and Gupta Vadakattu (CSIRO)
• Pre-season rainfall (Nov –Apr) was slightly below average at 83 mm (Avg 112) with 37mm falling in Mar/Apr providing a valuable early break.
• Growing season rainfall (95 mm) was well belowaverage (173mm).
• At sowing all treatments had between 29mm (after canola) and 50mm (after fallow) of available soil moisture stored to 1.2m.
• Soil nitrogen levels after either pulses or fallows were high at sowing while after wheat N levels were only slightly lower and still more than adequate.
• Yield potential at sowing was 2.9 t/ha of wheat (after fallow) based on the available water (stored soil moisture and an expectation of average rainfall from sowing).
• The below average rainfall, for the remainder of the growing season, reduced yields below the estimated potential, with RT Wheat / Fallow providing the best yield (1.8 t/ha)
• Gross margins in 2006 varied markedly and were highe st in the RT Wheat / Fallow treatment ($211/ha) and lowest for peas ($-79/ha). After5 years of the trials there is now little difference in cumulative gross margins between the better intensive cereal treatments and the district practice wheat /fallow. Three severe droughts in 5 seasons has been very favorable for the wheat /fallow treatment.