Crop Water Use Predictions Available On-Line for Sprinkler Irrigated Rice in the United States and South Africa.

Rice is an important food source for people in most of the world.  Traditional rice culture requires flood irrigation which commonly uses 60 to 150 cm of water per growing season.  Rice production is limited to fields with enough clay in the soils to retain 5 to 10 cm surface floodwater and places with high rainfall and/or an adequate irrigation water supply.  In 2008, rice trials were begun with center pivot irrigation in Missouri fields which do not hold floodwater.  The objective was to develop a crop water use coefficient curve for predicting daily evapotranspiration (ET) for sprinkler irrigated rice.  Soil moisture sensors were installed and linked to a web page.  Also, research was conducted to develop optimum nitrogen fertilizer and weed control programs.  In 2010-12, further sprinkler rice irrigation research was conducted in Limpopo Province, South Africa; and, in 2012, a third study was started at Willcox, Arizona.   For each location, websites were created which displays data from nearby electronic weather stations and predicted evapotranspiration for the rice fields.  Daily reference short grass evapotranpiration (ET_o) was calculated with the ASCE Standardized Penman Monteith equation and multiplied by an experimental coefficient to provide daily rice crop water use predictions.  The web pages have two functions:  (1) help us apply irrigation rate and frequency treatments in experiments, and (2) develop an extension delivery system for farmers to improve irrigation efficiencies for crops on their farms.  In 2011, an on-line beta version was released to the public for maize, soybean, cotton, and rice for farms located near electronic weather stations in South Africa and Missouri.  Farmers input crop and planting dates with computers or smart phones to view predicted crop water use in their fields.  In 2012, we began developing phone apps to help farmers track of soil water deficits in fields.