Farm Table says:
Influence of annual ryegrass seed retention height on harvest weed seed control (HWSC)and harvest efficiency
What is the problem?
Seed retention at maturity has been identified as a weed control target for the problematic annual weed species of Australian crop production systems.
This study aimed was to establish the distribution through the canopy of mature wheat crops of retained annual ryegrass seed at widely dispersed WA Wheatbelt location.
HWSC is an Australian innovation where systems have been invented to specifically target the weed seed bearing chaff fraction during crop harvest.
This approach to weed control is a response to escalating frequencies of herbicide resistant crop weeds that was developed because there is the opportunity to target the high seed retention levels of these weeds at crop maturity
What did the research involve?
At the start of the 2013 harvest, wheat crops at 25 locations across the WA Wheatbelt were sampled to establish the height of annual ryegrass seed retention at crop maturity.
Annual ryegrass samples were weighed to determine dry matter production, threshed and then the seed produced was counted to determine seed production at each sampling height.
What were the key findings?
Wheat crop sampling at 10 cm intervals from 40 cm downwards identified a uniform distribution of retained annual ryegrass seed through the wheat crop canopy at harvest.
With the major proportion of total wheat biomass (61%) located above the 40 cm sampling height, there were only reduced amounts of biomass collected at lower 10 cm sampling increments.
Incremental sampling identified an average harvest height of 30 cm that would likely have been used to harvest the sampled wheat crops in 2013.
High average seed retention levels were recorded for annual ryegrass present in wheat crops across the WA wheat belt during the initial stages of the 2013 harvest.
Annual ryegrass seed production levels clearly highlighted the seed bank replenishment/establishment potential for annual ryegrass plants surviving to maturity.
Across the 25 wheat crops sampled in this study, 66% of total biomass was located above 30 cm wheat only harvest height. Reducing this height to 10 cm resulted in just 14% additional biomass being collected.