Texas and Israeli Irrigators Give Plants the Last Word

Irrigated cotton fields in arid Israel and Texas may one day be watered automatically based on plant temperature.

Steven R. Evett, an Agricultural Research Service soil scientist based at the ARS Conservation and Production Research Laboratory in Bushland, Texas, and colleagues are working with the Israelis on infrared field thermometer sensors to take leaf temperatures from a short distance. They are designing computer programs that can automatically translate temperature readings into on/off irrigation decisions to get the most "crop per drop" of water.

This is the second year of a 3-year project, part of the Binational Agricultural Research and Development (BARD) program, a joint research program between Israel and the United States. The Texas work is funded by the state's Texas-Israel Exchange Fund.

ARS and Israeli scientists are comparing two different methods, both of which rely on the plant to signal water needs through leaf temperature: the newer time-temperature threshold, and the older crop water stress index. Both were developed by ARS.

For cotton, the time-temperature threshold method involves turning on irrigation when leaf temperature exceeds, for example, 82 degrees F for more than 4.5 hours. It is based on a discovery by ARS colleagues in Lubbock, Texas, that each crop has its own preferred temperature range for optimal growth. For cotton, that range is 73 to 90 degrees F.

The Israelis are using leaf temperatures and the crop water stress index to predict the water pressure in leaves, a measure of plant water deficit or stress.

Next year the Israeli and ARS researchers will each test both automated methods, along with a manual system based on soil moisture. Israel uses drip line irrigation and Texas uses center pivot irrigation.

In addition to the data exchange, the exchange of different irrigation concepts helps both Israel and the United States get the most out of each precious drop of water. The ultimate goal is to develop farmer-friendly wireless irrigation systems.

ARS is the U.S. Department of Agriculture's chief scientific research agency.