Location: Soil, Water & Air Resources Research2016 Annual Report
Objective 1: Evaluate the impact of temperature and soil water stress on germplasm of corn, soybean, and wheat. Objective 2: Quantify the interactions of water and temperature stresses on energy and carbon exchanges in corn and soybean fields under different management systems. Objective 3: Describe the relationships between ground-based and satellite observed water use and net primary productivity across the Upper Midwest and California. Objective 4: Evaluate agroforestry practice effects on local microclimate, and on crop and forage production, carbon sequestration, and greenhouse gas production.
Development of an enhanced understanding of the impact of temperature and moisture stress on corn, soybean, wheat, and forage phenology and productivity to provide information to incorporate into crop simulation models. Detailed analyses of the impact of different management systems (controlled drainage vs uncontrolled drainage, unsheltered vs sheltered crops) on the energy exchanges and crop productivity of cropping and agroforestry systems will be undertaken. Development of water use and net primary and gross primary productivity maps for the upper Midwest to compare to county level yield maps and evaluation of improved water management techniques. Refinement of crop growth simulation models to improve the understanding of the interactions of carbon-temperature-water under variable conditions. Improved understanding of complex interactions of variable environments on maize phenology, phenotypes, and production across North America.
Experiments were completed in the rhizotron where three corn hybrids were exposed to normal Ames, IA temperatures for a growing season and then 4°C above normal temperatures to evaluate the effect of high temperature on phenology, leaf area, and grain yield. All three hybrids exhibited an increase in the rate of leaf development with no difference in leaf size or plant height at the onset of the reproductive stage. However, there was a major effect of the high temperatures on the grain yield of the hybrids with yield losses of 75-100% under the exposure to high temperatures. This effect was in the absence of water stress because the soil was maintained at near field capacity throughout the experiment. High temperatures affect the ability of the plant to pollenate and the effect of high night temperatures during grain-filling. A further analysis conducted across the Midwest on yield gaps for corn and soybean revealed that yield gaps began to increase when the average July maximum temperature increased above 30°C and minimum temperatures increased above 25°C. The observations we found in the rhizotron transferred to field-scale analysis of yield gaps. Evaluations of the yield gaps expressed as the difference between attainable and actual county yields for corn and soybean were conducted for all of the Midwestern states. Yield gaps and the fraction of actual to attainable yields have been related to meteorological conditions during the growing season. The meteorological variables included precipitation during the summer months (May-August), July and August maximum and minimum temperatures. The relationship between yield gap and precipitation showed that above normal precipitation in July-August increased the yield gap as well as below normal precipitation. We found a similar relationship between precipitation extremes and net ecosystem productivity for both corn and soybean to show that ability to preserve yield was directly related to the ability of the crop to capture carbon and convert carbon into yield. The results of these studies quantify the interactions among the genetics, environment, and management components of agronomic systems. Experiments were established to quantify the carbon and water exchanges of corn and soybean under two different management systems and to relate these fluxes to remote sensing observations using visible and near-infrared observations. These data are being coupled with the OCO-2 (Orbiting carbon observatory-2) satellite observations over central Iowa. A recent analysis of the net primary and gross primary productivity for corn and soybean over a nine year period revealed that there was variation in net and gross primary productivity as a function of the seasonal weather variation. The magnitude of the net and gross primary productivity values were related to the crop water stress index values.
1. High temperature impacts on corn hybrids. Projections of the impact of high temperatures have rarely been evaluated with observations to quantify the response across different genetic material. ARS researchers at Ames, Iowa evaluated the effect of exposing three corn hybrids to high temperatures on the rate of growth and grain yield using a controlled environment experiment. All three hybrids showed a faster rate of growth and a large reduction in grain yield when grown under temperatures expected to occur by the end of this century. The major factor affecting grain yield was exposure to high nighttime temperatures during the grain-filling period. Development of adaptation practices for producers requires understanding what limits yield and this research helps define one of the limitations.
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Hatfield, J.L. 2016. Increased temperatures have dramatic effects on growth and grain yield on three maize hybrids. Agricultural and Environmental Letters. 1:15006.
Hatfield, J.L., Prueger, J.H. 2015. Temperature extremes: Effect on plant growth and development. Weather and Climate Extremes. 10:4-10.
Xiao, X., Sauer, T.J., Heitman, J.L., Horton, R. 2015. Soil carbon dioxide fluxes with time and depth in a bare field. Soil Science Society of America Journal. 79:1073-1083. doi: 10.2136/sssaj2015.02.0079.