1a.Objectives (from AD-416):
1) Evaluate interactions among nitrogen, carbon, soil water, and crop growth response across a range of soil types in a production field; and. 2)Evaluate field scale decision support system for nitrogen and crop management.
1b.Approach (from AD-416):
Field scale studies will be developed to evaluate nitrogen response to varying soil water regimes across a production field and the carbon dynamics in response to nitrogen management. Corn-soybean rotations will be evaluated over three growing seasons. Water, CO2, nitrogen, and light exchanges will be measured at several field locations within the field.
This agreement has focused on the implementation and evaluation of farming systems which govern production efficiency in corn and soybean production systems. Measurements of energy balance, crop growth and yield, and production inputs across a production field have been made for 15 growing seasons. The detailed flux measurements of carbon dioxide and water vapor have been coupled with the meteorological conditions and plant growth response and have revealed that exposure to high night temperatures decreases the photosynthetic rate and hastens senescence of the plant leading to a decrease in water use efficiency. The effects of the weather conditions during the growing season outweigh the effects of management systems.