When it's hot, crops get thirsty. Scientists at the U.S. Department of Agriculture's Agricultural Research Service (ARS) devised a method that uses canopy temperature to assess the water-stress levels of crops.
It was Kendall DeJonge's work that led to the temperature-taking method. An engineer with the Agricultural Research Service, he carried out research using affordable sensors capable of taking crop canopy temperature called infrared radiometric thermometers (IRT). Depending on the temperature result, it can then be determined if a crop is water-stressed or not.
IRTs can be installed on center pivot irrigation systems or field posts to take daily or hourly measurements of crop temperature. These measurements will then be interpreted by scientists using indices, such as the Crop Water Stress Index (CWSI).
The CWSI was developed by scientists from the ARS back in the early 1980s. To use it, humidity level and air temperature measurements are gathered, calculating for vapor pressure deficit aside from canopy temperature. The process is generally technical, requiring additional measurements so many farmers are forced to just guess when they have to irrigate crops. This leads farmers to either underirrigate which reduces yield or overirrigate which wastes water. By coming up with a simple but accurate method of keeping track of crop temperature, scientists are providing farmers with the key to acting according to their crops' water needs.
No thanks to droughts and population growth, water has become a major concern.
"With water becoming more precious, we need to exploit the potential of every tool available," said DeJonge.
The ARS engineer worked with colleagues to compare the CWSI with other indices to better interpret data from IRTs, assessing how well they can detect water stress levels in corn and sunflower crops. Two indices, the Degrees Above Critical Temperature(DACT) index and the Degrees Above Non-Stressed index(DANS), developed for use in the study were simpler compared to the CWSI, the gold standard in quantifying levels of water stress.
The results of DeJonge's work showed that the DACT and DANS indices produced results just as effective as what the CWSI can offer in determining levels of water stress, even when the two required simpler once-a-day temperature readings.
In the future, DeJonge is planning to develop "crop water coefficients" that will define water needs for certain crops in different scenarios. With that kind of information, he is confident that IRTs will become more popular with farmers as a tool for caring for their crops.
