Kelly Angel1 and Sébastien Sester2
1 Birchip Cropping Group, 73 Cumming Ave., Birchip, VIC, 3483, www.bcg.org.au, firstname.lastname@example.org
2 Birchip Cropping Group (internship)/Wageningen University and Research, email@example.com
Weeds are responsible for large yield losses and increasingly there is a need for sustainable alternatives for weed management since herbicide-resistant weeds appeared. This experiment aimed to determine if sowing direction and row spacing can be used to influence grass weed populations and growth, and to measure their impact on crop performance in the Mallee. Wheat was sown in a paddock containing brome grass (Bromus diandrus Roth.). Crop and weed populations and growth were monitored, and data on ground cover and light interception was gathered. After harvest, samples were processed for standard yield and grain quality assessments. Results showed that east-west rows intercepted more light than north-south rows and narrow rows intercepted more light than wide rows. A grain yield penalty was found for wide row spacing, but grain protein content was higher. Sowing direction had no influence on grain yield. The presence of weeds reduced yield, lowered grain protein content and test weight. In narrow rows, a possible reduction in weed biomass was found, which can be linked to the measured increase in light interception by the crop in narrow rows. There was no effect of row spacing or sowing direction on weed seed set after one year. However, farmers should reduce row spacing as far as practical due to demonstrated benefits on crop yields. Weed populations should be monitored over a longer timeframe to examine whether cumulative effects are significant.