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Reduce Chemicals – Increase profit

Jamie Thornberry – Central West Farming Systems Extension Agronomist, Condobolin

Significant yield advances have been made in the low rainfall southern region as a result of gains in water use efficiency. However cropping remains risky within these environments. The Low Rainfall Regional Cropping Solutions Network identified the need to develop farming systems with lower input costs. It has been found that herbicides and fertilisers account for 50% of the input costs for wheat growers. Therefore reducing the dependence on agrochemicals would assist growers with reducing risk on farm.

What are agrochemicals?

Agrochemicals are quite simply the chemicals used for agricultural production. These chemicals include fertilisers, pesticides, herbicides and fungicides. The adoption of minimum till systems over the last thirty years has increased the reliance on these chemicals within agricultural production systems.

In Central Western NSW herbicide resistance and the dependence on agrochemicals is on the rise. A key example of this is the ever increasing number of glyphosate resistant weeds which includes fleabane, annual ryegrass, barnyard grass, windmill grass and brome grass just to name a few. Within Australian farming systems, weeds are having the largest impact on yield in comparison to pests and diseases. In Australia alone weeds, cost the agricultural industry about $4 billion dollars per annum in lost productivity and decreased grain quality.

This significant cost to the system has resulted in the development of wheat cultivars with an inherent competitiveness against herbicide resistant weeds. Competitive crop genotypes have the enhanced capability to access light, moisture and soil nutrients in a limited space. With genotype competitiveness and weed suppression in mind, a trial was conducted in Condobolin and Wagga Wagga by the NSW DPI and CSU.

The core aims of the project were:

  1. To assess the competitive nature of Australian wheat genotypes within the southern grains region of NSW.
  2. To assess the impacts of environmental factors such as moisture and temperature on the weed suppressive nature of wheat.
  3. To assess and measure wheat metabolites involved in weed suppression.
  4. To measure the suppression of weeds by wheat stubble post-harvest.

In the first year of the experiment, it was demonstrated that the genetically diverse wheat cultivars performed differently in the two separate trial locations at Condobolin and Wagga Wagga. The varying rainfall patterns allowed for significant differences in crop biomass and weed counts as well as biomass between cultivars.

The results proved that even though the suppressive nature of wheat is driven by genotype, the environment will also have a significant impact on the suppressions success. The cultivars Espada, Condo and to a lesser extent Janz performed well in both regions. At Condobolin, Janz CI produced the highest level of biomass while Wedgetail produced the lowest, followed by Condo, Whistler and Gregory. In regards to weed suppression within the Condobolin area, Condo proved to be the most effective genotype for reducing weed biomass.

Additional field experiments will be conducted over the next three years to determine the impacts of seasonal conditions and location on wheat cultivar performance and weed suppression.

Mwendwa.J, Weston.L.A., and Brown.W.B Mechanisms of weed suppression in early vigour and weed suppressive wheat genotypes. 1 Graham Centre Of Innovation (NSW Department of Primary Industries and Charles Sturt University), Wagga Wagga, NSW Australia 2015