Variable Temperature and Soil Water On Energy and Carbon Fluxes in Corn and Soybean in Iowa.

Throughout the growing season, corn and soybean plants are subjected to a range of weather conditions which affect the exchange of energy and carbon dioxide between the plant and the atmosphere. The impact of extreme conditions of temperature or soil water has been well-documented on plant growth and development; however, the information of these effects on energy and carbon exchanges is less well-defined. We have a continuous record of energy and carbon dioxide fluxes over corn and soybean fields in central Iowa since 2004 using eddy covariance methods coupled with remote sensing and plant growth observations. These data sets allow for the assessment of the impact of deviations of temperature and soil water content on the short-term photosynthesis and transpiration rates and the long-term impact on growth rates, plant development, and grain yield. During these nine growing seasons there has been a large range of meteorological conditions within and among growing seasons which has added to the richness of the data sets. Exposure of plants to high temperatures does increase the transpiration rate and decreases the short-term water use efficiency because of the water stress induced in the plant. High night temperatures effects the photosynthetic rate the next day and continued exposure to high night temperatures leads to increased respiration, increased rate of senescence, and reduced grain yield. The variable meteorological conditions among growing seasons have both short- and long-term impacts on growth response and ultimately the yield response. These data sets provide a method of being able to quantify the effect of variable weather on corn and soybean physiological and growth response in a way to be able to provide insights on how these responses can be incorporated into crop simulation models.