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Closing wheat yield gaps

Dr. Sheri Strydhorst, Agronomy Research Specialist and Jeremy Boychyn, Agronomy Extension Specialist | Alberta Wheat and Barley Commissions

You can’t manage what you don’t measure. Many growers do an excellent job of tracking their yields and quality relative to their inputs, but that is only part of the story.

The concept of “yield gap analysis” provides insight on how farmers can measure what they manage. Yield gaps are the difference between theoretical yield potential and actual on-farm yields. The theoretical yield potential is the yield that can be achieved when there is no abiotic or biotic stress. In simpler terms, it is the yield that can be achieved at a specific time and place when growing conditions are perfect. However, all farmers know that actual yields are reduced by things like: nutrient deficiencies, poor quality seed, suboptimal plant stands, weed pressure, insect damage, disease, and the list goes on.

There are many methods to calculate theoretical yield potential including: crop model simulations, maximum farmer yields, or research plot experiments. Theoretical yield potential is also calculated for both irrigated and rainfed systems and accounts for the length of growing season. For example, the theoretical yield potential of Canadian Western Red Spring (CWRS) wheat at Bow Island, Alberta under irrigation, may be 160 bushels per acre (bu/ac) while the theoretical yield potential of CWRS wheat at Oyen, Alberta under rainfed conditions, on an average year, may be 70 bu/ac (Table 1). However, according to crop insurance data, average farmer yields for CWRS wheat at Bow Island, Alberta under irrigation are closer to 100 bu/ac and at Oyen, Alberta under rainfed conditions it is not quite 40 bu/ac.

While complete yield gap closure is not economically or environmentally sustainable,1 it is suggested that wheat yields can be economically increased up to 70 to 85 per cent of their potential.2 In North America, Dr. Brian Beres with

Agriculture and Agri-Food Canada suggests that farmers can increase their yields by 10 to 40 per cent with improved management.

Yield gap analysis looks to identify what management practices are missing or could be improved to overcome yield drag. Focus can then be put on implementing management that takes the least cost or effort but results in the largest returns. For example, if it is found that low plant populations (i.e., 15 plants per square foot) are consistently reducing yields, then increasing plant populations (i.e., 35 plants per square foot) would be a relatively easy, low-cost solution that could result in substantial yield increases, along with other agronomic improvements. Although only farms with lower seeding rates would benefit from this management change, this solution is fairly simple and easy to implement.

It is also important to recognize that the closer a grower is to the theoretical yield potential, the more difficult it will be to close the remaining yield gap. If a grower achieves high plant populations, uses balanced fertility, carefully controls weeds and disease, then making further yield improvements will be more challenging and may have reduced return on investment.

Yield gap analysis in various growing environments also helps to fine tune agronomic management based on things like soil type and local weather conditions. This will help growers, agronomists and extension staff to improve yields by putting management efforts towards those practices that will give the biggest bang for the buck in specific growing environments.

The Alberta Wheat and Barley Commissions, Alberta Innovates BioSolutions, the Saskatchewan Wheat Development Commission, and Manitoba Crop Alliance are

co-funding research led by Dr. Brian Beres from Agriculture and Agri-Food Canada and his colleagues at Kansas State University. This research team is using the Global Yield Gap Atlas methodology to establish yield gaps in CWRS wheat fields across the Prairies.

With farmer participation, researchers can continue to find and pin-point management practices through yield gap analysis to offer agronomic solutions resulting in the greatest yield for farmers. Researchers require producer data to compile actual on-farm yields and the management practices that produced those yields. Any western Canadian producers interested in participating in this wheat yield gap study should contact Jamie Puchinger at jamie@farmingsmarter.com or call 403-317-0022. Producers will be asked to provide yield and agronomic data from at least two 2019 and two 2020 CWRS fields. All levels of management are welcome to participate and results from individual growers will be kept strictly confidential.

Table 1. Theoretical and actual yield potential of CWRS wheat grown at Bow Island, Alberta under irrigation and at Oyen, Alberta under rainfed conditions. Note: these examples are for demonstration purposes only and do not necessarily represent actual yield values.

1 Van Ittersum, M.K., Cassman, K.G., Grassini, P., Wolf, J., Tittonell, P., and Hochman, Z. 2013. Yield gap analysis with local to global relevance – A review. Field Crops Res. 143, 4-17.

2 Lobell, D.B., Cassman, M.K., Field, C.B. 2009. Crop yield gaps: their importance, magnitudes, and causes. Ann. Rev. Environ. Resour. 34, 179-204.