Leading farmers in South East Australia have closed the exploitable wheat yield gap: Prospects for further improvement

Harm van Rees, Tim McClelland, Zvi Hochman , Peter Carberry , James Hunt , Neil Huth , Dean Holzworth - Field Crops Research Volume 164, 1 August 2014, Pages 1-11

Farm Table says:

This paper has an interesting approach since Access to 16–20 years of individual farm field data, together with site-specific climate and soil data, is a rare resource against which farm performance can be assessed.

Australia’s Further Improvement:

To keep pace with global population growth and food consumption patterns, future global food security will require agricultural production in 2050 to be 60% more than it was in 2010. Australian dry-land crop producers farm in regions with highly variable climate and soils. Farmers have responded to the pressures of rising costs by pioneering and adapting new technologies to narrow the gap between actual and water-limited yield. With yields reaching a plateau in many of the developed world’s cropping areas, it is possible that Australia’s leading farmers have similarly closed the exploitable yield gap and require technological breakthroughs to sustainably push the production frontier to new and higher levels.

The objective of the paper is to demonstrate how simulation modeling can assist farmers and their advisers to identify:

  • how close crops, grown under current management, are to their water-limited yield.
  • new practices with potential to increase yield and/or reduce risk.
  • innovative agronomic management opportunities to increase yield above the current achievable water-limited yield.

To assess the potential for Australian farmers to continue closing the yield gap, and possibly increase water-limited yield, the long-term farm production records of individual wheat fields of three leading farmers in South East Australia were used to ascertain the applicability of modeling to develop new and innovative practices. The cropping systems simulator APSIM was used to establish the attainable simulated yield based on the farmers’ chosen management inputs for wheat crops over a period of 16–20 years. A strong relationship (r2 = 0.89, RMSD = 508 kg ha−1) was found between actual and simulated yields. This relationship indicates that yield-reducing factors not simulated by APSIM (weeds, disease etc.) were largely controlled on these farms and confirms APSIM’s suitability for this analysis.

Over the 16–20 year study period, the average yield gaps on the three farms ranged from 480 to 770 kg ha−1; representing between 74 and 82% of their water-limited yield potential. For these leading farmers, the yield gap is only small and unlikely to be economically exploitable under current management practices.

Consequently, three tactical management innovations with the potential to improve farm wheat yield and reduce risk were evaluated.

• One innovation investigated whether farmers practicing no-till crop establishment, who were able to control weeds prior to sowing, could benefit from sowing current cultivars earlier than present-day practice. It was found that leading farmers are already sowing at the optimum time and sowing earlier would not increase yield because of greater risk of frost damage.

• The first used Yield Prophet® to assist farmers to decide when to apply in-crop nitrogen fertilizer based on a complete understanding of nitrogen and water requirements of crops in variable growing seasons.

• The next involved sowing slows maturing wheat cultivars earlier than current practice but only in years with adequate stored soil water and early season rainfall.

• All innovations were found to increase grain yield and reduce the risk of over- or under-application of nitrogen fertilizer.

The analyses were undertaken here demonstrate that APSIM can simulate wheat yields in a water and nitrogen-limited environment with a high degree of accuracy. This ability supports simulation analyses of farm management options to assess yield gaps and opportunities for their closure.

A critical conclusion for leading farmers is that the prospects for increasing production by closing the gap between actual and water limited yields are relatively small but an opportunity does exist with tactical applications of N fertilizer during the cropping season aided by Yield Prophet. This adaptation can significantly reduce costs (not applying N fertilizer when the risk is high) and increase production by using more N fertilizer when the conditions point towards a low-risk return. The innovation of using slow maturing cultivars in seasons when conditions are favorable and the risk of failure is small requires further evaluation in the field. If confirmed, it has the potential to help farmers improve their productivity by increasing the yield frontier at no additional cost.

Investigation of strategic and tactical management options to increase yield using simulation modeling for subsequent evaluation in the field has the potential to keep Australian farmers at the forefront of innovations in crop production.

2014 - Australia - Harm van Rees, Tim McClelland, Zvi Hochman , Peter Carberry , James Hunt , Neil Huth , Dean Holzworth - Field Crops Research Volume 164, 1 August 2014, Pages 1-11
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