Yield Gap and Production Gap of Rainfed Winter Wheat in the Southern Great Plains

Abstract

Since 1980, average wheat (Triticum aestivum L.) yields have remained nearly stagnant in the southern Great Plains (SGP) and stagnant in the state of Oklahoma. Yield stagnation can sometimes be attributed to a relatively small gap between current and potential yields, but the magnitude of the yield gap for this region has not been well quantified. The objective of this study was to determine the wheat yield and production gaps in Oklahoma at state and county levels. This involved estimation of attainable yield (Y a ) using a frontier yield function and water-limited potential yield (Y p ) using estimated transpiration and transpiration efficiency. Yield gap and production gap relative to Y a and Y p were calculated using grain yields and harvested area for 19 counties. Current average yield (Y c ) was 2.06 Mg ha -1 at the state level, well below the maximum recorded yield at the plot level of 6.59 Mg ha -1 . The Y p of current wheat varieties is far above Y c in Oklahoma, and Y c represents 74% of Y a but only 30% of Y p at state level. For growing season rainfall (GSRF) amount <250 mm wheat yields were often water-limited. However, average GSRF was 471 mm, and yield was typically limited by factors other than GSRF amount. Production exhibited greater temporal variability than yield, and production gap may be a better indicator than yield gap for regions with highest potential to increase production. Low yields and yield stagnation in Oklahoma cannot be attributed to a small remaining yield gap, nor to inadequate GSRF amount.

Agronomic Practices for Reducing Wheat Yield Gaps: A Quantitative Appraisal of Progressive Producers

“…Mean wheat Y a in our database was very similar to these long-term estimates and was considerably greater than state-or county-level yields (Patrignani et al, 2014). Mean wheat Y a in our database was very similar to these long-term estimates and was considerably greater than state-or county-level yields (Patrignani et al, 2014).…”

“…RESEARCH I mproved agronomic management and crop genetics resulted in high rates of yearly yield gain for wheat (Triticum aestivum L.) between 1960 and 1980 (Bell et al, 1995;Brancourt-Hulmel et al, 2003). After approximately 1980, yield gains decreased and yield stagnation has been reported for several important regions such as the US Southern Great Plains (Patrignani et al, 2014), the North China Plain (Wu et al, 2006), France (Brisson et al, 2010), the Netherlands, the United Kingdom, and India . In high-yielding wheat regions, yield stagnation might result from regional yield approaching 70 to 80% of the yield potential , resulting in a small yield gap (Y G ), which is the difference between average regional yield and the yield limited only by moisture regime in rainfed regions (i.e., water-limited yield [Y w ]; Lobell et al, 2009).…”

Nitrogen management impact on winter wheat grain yield and estimated plant nitrogen loss

“…Similar results in Oklahoma were noted by Patrignani et al. (2014), where they noted that winter wheat yield has been stagnant since the 1980s, with a current state yield of 2.0 Mg ha –1 compared to experimental state yields of 6.59 Mg ha –1 . Similar yield stagnation issues have also been noticed in other wheat‐growing regions of the world, such as the Netherlands, the United Kingdom, India, France, Germany, and Denmark (Grassini, Eskridge, & Cassman, 2013).…”

“…It covers approximately 3 million hectares of Central Rolling Red Plains of the United States, including parts of Kansas, Oklahoma, and Texas (Bushong, Arnall, & Raun, 2014). In the state of Oklahoma, winter wheat encompasses 75% of the cropland (Patrignani, Lollato, Ochsner, Godsey, & Edwards, 2014) and is produced under rain‐fed conditions (Baath, Northup, Rocateli, Gowda, & Neel, 2018; Vitale, Godsey, Edwards, & Taylor, 2011).…”

Soybean yield gaps and water productivity in the western U.S. Corn Belt

“…Based on this framework, French and Schultz (1984) demonstrated that the boundary function of the relationship between producer wheat yields and seasonal water supply (WS) in Australia could be used to determine the Y P across the range of WS values, with the slope of the boundary function representing the highest attainable water productivity (WP A ; kg grain per unit transpiration) over that range, with the x-intercept providing a rough estimate of the seasonal amount of soil evaporation (mm). The WP boundaryfunction approach was subsequently validated for wheat (Angus and van Herwaarden, 2001;Sadras and Angus, 2006;Passioura and Angus, 2010;Zhang et al, 2013;Patrignani et al, 2014) and applied to other crop species, such as sunflower (Grassini et al, 2009a) and maize (Grassini et al, 2011a;Zhang et al, 2014). To date, however, a WP boundary function that can be used to estimate Y P in producer soybean fields across the U.S. Corn Belt has not yet been determined.…”