Using Cornwater, an Online Real-Time Tool to Help Determine When to Irrigate a Corn Field.

CornWater (http://hprcc3.unl.edu/cornsoywater/cornwater/) is an online, real-time decision support tool that helps irrigators determine when to irrigate a corn field. CornWater aims to optimize irrigation scheduling by predicting crop development, water uptake and water balance and possible crop water stress using the Hybrid-Maize crop simulation model. Unlike traditional irrigation triggering using 50% water depletion of total available soil water, CornWater applies a combination of crop water stress and available soil water depletion as the trigger for irrigation. Crop water stress is assessed by crop transpiration deficit. Comparison was made on timing and irrigation amount between CornWater method and the traditional method for three locations in Nebraska, including Lincoln, Mead, and North Platte. The CornWater method recommended the first irrigation around silking time when top 2 feet of soil had 1.8 inches of available water, while the traditional method recommended an earlier irrigation when the top 2 feet of soil had 2.6 inches of available water. Over the entire season, the CornWater method led to a saving of 1.25 inches of water compared to the traditional method. Using real-time weather data and robust crop simulation modeling, the CornWater provides irrigators comprehensive information about crop phenology, soil water input, usage and balance, and issues calls for irrigation when crop stress is predicted.