Comparing the 2023 and 2019 hard red winter wheat crops.
The effects of drought on both wheat production, quality, milling performance, and markets are significant. Millers across the world are impacted by wheat crop production issues, carryover, and market price impacts at both time of harvest, as well as futures pricing.
Whether or not a mill is in a wheat production area (wheat milled near wheat origin) or destination mill (flour produced near flour market served), the effects of drought elsewhere can impact wheat availability, selection, and cost. Undoubtedly, many of the issues presented are also applicable to other wheat classes as discussed in later sections of this article.
This article is based on observations made on experience with hard red winter (HRW) wheat samples from the Gulf and Northwest tributaries of the United States as shown in Figure 1 above.
Critical Moisture Requirements for Wheat Production
Both the timing and amount of moisture are critical factors in wheat production and quality. Of course, adequate moisture is essential for plant establishment and vegetative growth. The critical stages for both agronomic yield and quality occurs after flowering a stage also referred to as anthesis. Figure 2 identifies the general growing stages for both winter and spring wheat classes or varieties. A more detailed explanation of wheat growth and development stages (Feekes Scale) can be found at bookstore.ksre.ksu.edu/pubs/MF3300.pdf.
Research Evaluating the Impact of Drought on Wheat Production and Quality
Jang et al. (2023) studied the effect of drought stress on soft white, hard red, and hard white spring wheat in the United States and found significant differences between the three wheat varieties in most end-use quality parameters. The impact of drought stress at three different stages – including tillering to stem elongation (T-SE), booting to heading (B-H), and anthesis to soft dough (A-SD) – were evaluated and reported.
Data suggests pre-anthesis drought stress did not affect grain yield or most end-use quality parameters; however, yield and more end-use qualities were impacted by post-anthesis drought stress. Post-anthesis drought stress impacted flour protein, lactic acid, and sucrose solvent retention capacities, mixograph peak time, and ultimately baking performance of spring wheat.
Rao et al. (2021) compared a drought-tolerant and drought-sensitive wheat in India. Relative to grain appearance score, the drought-sensitive wheat was unchanged under irrigated and drought conditions, while the drought-tolerant wheat scored slightly lower under drought stress conditions.
Hectoliter weight decreased under drought stress with a greater decrease observed for the drought-tolerant wheat than drought-sensitive wheat. Grain hardness decreased under drought conditions with a greater decrease observed for the drought-sensitive wheat than the drought tolerant wheat. Crude protein and gluten content increased for both wheat types under drought stress with a greater increase for drought-sensitive wheat.
Yu et al. (2018) studied correlations between the drought severity index (DSI) in China and winter wheat yield. Winter wheat yield is negatively correlated with drought intensity. Lower drought intensities roughly link with higher winter wheat yield.
Droughts with different intensities occurring at different growth stages have distinctly different impacts on wheat crop yield. Mild drought during the wintering, greening, and jointing stages of winter wheat growth may have a promoting effect on yield. Monitoring of droughts and irrigation has important food security implications during these critical periods to ensure normal yield of winter wheat.
Olckers et al. (2022) reported specific protein composition changes because of drought stress. While these changes have significant impact on wheat production and end-use properties, milling practices that could alter performance were no identified. Olckers et al. reported that both heat and drought stress caused significant changes in most gluten protein fractions and baking quality parameters. However, the general conclusion that drought and heat have either negative and/or positive effects on the wheat end-use quality could not be drawn. The response of cultivars to stresses varied in their study.
These four articles suggest the impact of drought on wheat production is generally more well-known and immediate than the impact on wheat quality. Wheat production yield can be observed and measured at the point of harvest, while quality attributes can only be assessed with grain laboratory analysis and laboratory milling, reflecting commercial practices to facilitate flour, dough, and baking assessment.
HRW Production Years Selected for Drought Analysis Impact
For purposes of evaluation the U.S. Drought Monitor for Kansas, the leading HRW wheat producer was examined. Figure 3 and Table 1 indicate the 2023 crop year was an intense drought year, while 2019 was a considerably less severe drought year.
Comparing 2023 to 2019
Table 2 presents data extracted from the U.S. Wheat Associates Crop Reports for 2023 and 2019, including measures overall and exportable wheat from the Gulf and Pacific Northwest tributaries.
Composite HRW samples from the HRW growing region or grain shed were collected and analyzed individually for grade and non-grade characteristics. Individual samples were formed into composites based on protein level within each grain shed, analyzed, tempered, and milled using a Bühler Tandem Mill at the U.S. Department of Agriculture facility in Manhattan, KS. The resulting flour was analyzed, followed by physical dough and baking tests.
The general effects of drought stress often expressed by millers are clearly identified in the data. Moreover, were the data disaggregated by location and drought stress severity, the differences may be more pronounced.
One of the differences is the shift in distribution of low-, medium-, and high-protein wheat samples. There is a slight shift in the test weight between 2023 and 2019; however, it may not be significant.
The overall protein is higher in 2023. Wheat kernel ash appears to be only slightly higher in 2023. Wheat kernel size appears to be lower in 2023. Sedimentation test in 2023 is higher, perhaps due to increased protein.
Flour test results reflected the increase in wheat protein between 2019 and 2023 impacting wet gluten and – to a lesser extent – SRC results. Dough properties and baking results were impacted by the difference in protein between the two harvest years. The importance of these observed shifts may or may not be critical to your customers.
Milling Results
Milling results for composite samples as well as control samples are provided in Figures 3 and 4 for the years 2023 (drought stressed) and 2019 (not drought stressed). Mill settings and practices were intended to be identical in both years; however, the narrower standard deviation experienced reflects somewhat greater control and uniformity of the milling process in 2023 compared to 2019. The control wheat was not the same for both years, with both samples having aged one to two years post-harvest.
There appear to be subtle shifts in location of flour production overall. The shift may be due to kernel and endosperm hardness. Flour yields appear to be lower for composite samples than freshly harvested samples. The time between harvest and milling was not controlled and could be expected to influence composite milling results from the beginning of harvest to the end of harvest. The time between harvest and milling for samples milled at the end of harvest experience less idle time than those milled earlier in the harvest period. Feed production appears to be greater under less drought stress.
While these samples are milled, observable differences in bran flattening or shattering in the early breaks are easily discernible. The thought of the potential impact of these changes in a commercial milling operation are well known and are of concern. Changes in mill stock physical characteristics represent a challenge to millers in both material transfer and handling in the milling process. These observed differences are not often a significant factor in laboratory milling given excess of roll and sifter surface and operating near or over design capacity.
More work is needed to evaluate milling performance beyond simply yield, as changes in stock characteristics impact mill balance and processing efficiency. These observed differences are not often a significant factor in laboratory milling given excess of roll and sifter surface and flexibility in material handling, and in most cases, they do not impact flour, dough, and baking specifications.
There appear to be subtle shifts in location of flour production overall. The shift may be due to kernel and endosperm hardness. Flour yields appear to be lower for composite samples than freshly harvested samples. The time between harvest and milling was not controlled and could be expected to influence composite milling results from the beginning of harvest to the end of harvest. The time between harvest and milling for samples milled at the end of harvest experienced less idle time than those milled earlier in the harvest period. Feed production appears to be greater under less drought stress.
Conclusion
Analysis of the data make clear the wheat crop is different between the two tributaries and between the assumed drought conditions. Considering those differences observed with limited variable definition concerning drought (severity and timing) further exploration of individual wheat data combined with appropriately refined location, weather, planting, and timing information like that collected and analyzed by Yu et al. (2018) is warranted.
Improved environmental monitoring is needed to properly understand drought stress impacts beyond production alone. The next article is focused on Kansas HRW wheat in which varieties, agronomic conditions, and practices are more similar than observed across the entire U.S. HRW wheat production area.
References
Olckers, L., Osthoff, G., Guzmán, C., Wentzel, B., van Biljon, S., Labuschagne, M., (2022). Drought and heat stress effects on gluten protein composition and its relation to bread-making quality in wheat, Journal of Cereal Science V. 108(11)
Rao, D.S., Raghavendra, M., Gill, P., Madan, S. and Munjal, R. (2021). Effect of Drought Stress on Grain Quality Attributes in Wheat (Triticum aestivum L.) varieties. Biological Forum – An International Journal, 13(3): 58-63.
Yang, J., Yang, R., Liang, Xi., Marshall, J. M., & Neibling, W. (2023). Impact of drought stress on spring wheat grain yield and quality. Agrosystems, Geosciences & Environment, 6, e20351. doi.org/10.1002/agg2.20351.
Yu, H., Zhang, Q., Sun P., Song, C., (2018). Impact of Droughts on Winter Wheat Yield in Different Growth Stages during 2001–2016 in Eastern China. Int J Disaster Risk Sci 9:376–391.
Dr. Jeff Gwirtz is CEO of JAG Services, Inc., an international consulting company in Lawrence, KS; 785-341-2371; jeff@jagsi.com. He also is adjunct professor in the Department of Grain Science and Industry at Kansas State University, Manhattan.