ARS | Publication request: Wheat growth response to increased temperature from varied planting dates and supplemental infrared heating

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 15, 2011
Publication Date: October 1, 2011
Citation: Ottman, M.J., Kimball, B.A., White, J.W., Wall, G.W. 2011, Wheat growth response to increased temperature from varied planting dates and supplemental infrared heating. Agronomy Journal, 104(1):7-16.

Interpretive Summary: Projected future increases in temperature due to global warming may threaten wheat production and food security around the world. To help devise strategies to overcome the potential negative impacts of global warming, research was undertaken to characterize how wheat crops grown in the field respond to elevated temperatures. Two systems were used to expose plants to elevated temperatures under agriculturally realistic conditions: supplemental heating and planting crops over an unusually wide range of dates. The field study was conducted at Maricopa, AZ, USA, where wheat was planted from September to May over two years, allowing a total of 12 planting dates. Supplemental heating was provided for six of the 12 planting dates using infrared heaters placed above the crop, which increased canopy temperature by 2.3°F (1.3°C) during the day and 4.9°F (2.7°C) during the night. Grain yield declined 42 g m-2 (6.9%) per 1.8°F (1.0°C) increase in seasonal temperature above 61.3°F (16.3°C). Supplemental heating had no effect on grain yield for plantings in winter (Dec./Jan.) since temperatures were near the optimum 59°F (14.9°C). However, in spring (Mar.) plantings where temperature (22.2°C) was above optimum, supplemental heating decreased grain yield from 510 to 368 g m-2. Supplemental heating had the greatest effect in the early fall plantings (Sep./Oct.) when temperature was slightly below optimum 57°F (13.8°C) and a mid-season frost limited the yield of the Unheated plots to only 3 g m-2 whereas yield of Heated plots was 435 g m-2. Thus, future increases in temperature may decrease wheat yield for late plantings and shift the best time to plant to earlier dates in areas of the world that are similar to the desert southwest of the US. This includes large irrigated wheat producing regions in Mexico, China, India, Pakistan and Egypt, which are typically among the most productive wheat regions globally.

Technical Abstract: Future increases in atmospheric temperature may threaten wheat (Triticum aestivum L.) production and food security. The purpose of this research is to determine the response of wheat growth to supplemental heating and to seasonal air temperature from an unusually wide range of planting dates. A field study was conducted at Maricopa, AZ, USA, where wheat was planted from September to May over a 2-year period for a total of 12 planting dates. Supplemental heating was provided for six of the 12 planting dates using infrared heaters placed above the crop which increased canopy temperature by 1.3°C during the day and 2.7°C during the night. Grain yield declined 42 g m-2 (6.9%) per 1°C increase in seasonal temperature above 16.3°C. Supplemental heating had no effect on grain yield for plantings in winter (Dec./Jan.) since temperatures were near optimum (14.9°C). However, in spring (Mar.) plantings where temperature (22.2°C) was above optimum, supplemental heating decreased grain yield from 510 to 368 g m-2. Supplemental heating had the greatest effect in the early fall plantings (Sep./Oct.) when temperature was slightly below optimum (13.8°C) and mid-season frost limited the yield of Unheated plots to only 3 g m-2 whereas yield of Heated plots was 435 g m-2. Thus, future increases in temperature may decrease wheat yield for late plantings and shift optimum planting windows to earlier dates in areas of the world similar to the desert southwest of the US.