Good Stubble, Bad Stubble – More Profit, Less Profit

John Small, Central West Farming Systems

Take home Messages
• CWFS regional site trials during 2013 and 2014 suggest stubble loads greater than 3 t/ha can limit yield.
• “No till with no stubble is no good” on hard setting red brown soil types. The delimma is that the annual incorporation of stubble just prior to sowing by cultivation or removal by burning would result in the loss of signifigant long term benefits to soil health.
• “If you do not measure it you cannot manage it!” Field measurements of stubble are the starting point for deciding what to do.
• Options to manage stubble loads above 3t/ha need to be made seasonally. Good planning may allow other agronomic and farm efficiency outcomes to be achieved at the same time.

Background
Stubble retention research is not new. The publication Scott et al “Stubble Retention in Cropping Systems in Southern Australia: Benefits and Challenges” (2010) cites research back to 1978. The focus of recent research is concentrating on maintaining profitable retained stubble systems rather than investigating agronomic and economic benefits of stubble retention.

The herbicide “glyphosate” was patented by Monsanto in the early 1970s as the active ingredient in the herbicide Roundup®. Roundup® was introduced to the consumer market in 1974 as a broad-spectrum herbicide and since 1980 has quickly become one of the best selling herbicides in Australia and worldwide. When its patent expired in 2000 the number of glyphosate based products grew dramatically and the cost of the product fell dramatically. The development and adopation of stubble retained farming systems has been and continues to be reliant on the development of glyphosate and different formulations of glyphosate based chemistery.

Major agronomic drivers for the adoption of stubble retained farming systems has been minimising soil erosion risk and within season benefits of soil moisture, particularly at sowing. Economic drivers for stubble retention have been lower input costs for machinery (less horsepower per hectare), improved efficiencies and timeliness of operations. Most research cited by Scott reports that the presence of stubble in-crop has a negative impact on yield as opposed to stubble removed farming systems. Cameron et al reports similar findings.

Looking to the future and based on a quick review of papers delivered at GRDC updates in recent years, it is reasonable to suggest that the decision to retain stubbles in a cropping business will continue to be driven by limiting soil erosion and degradation, maximising sowing soil moisture and improved machinery efficiencies and timeliness of operations. These overarching benefits may be tempered, however, as seasonally tactical stubble management approaches are required for managing herbicide resistance, lowering input costs or production risk and reliably improving yield under certain conditions.