USDA study: Temperature linked to plant water usage

From AgResearch Magazine:

When crops get thirsty, they get hot. Scientists can use canopy temperatures to determine if crops are water stressed. An Agricultural Research Service engineer in Colorado has found a way to simplify this process for farmers. The goal is to manage irrigation water more effectively in an area where saving water has become a top priority.

A key to Kendall DeJonge’s research in Fort Collins is the use of infrared radiometric thermometers (IRT), affordable sensors that can determine the crop canopy temperature, and subsequently whether a crop is water-stressed. IRTs can be placed on field posts or center pivot irrigation systems to gather hourly or daily temperature readings on crops. Scientists interpret the IRT data by using one of several indices, including the commonly used Crop Water Stress Index (CWSI). Developed by ARS scientists in the early 1980s, the CWSI requires knowing air temperatures and humidity levels to calculate a “vapor pressure deficit,” in addition to knowing the canopy temperature. The process is fairly technical and requires additional measurements, so many farmers in Colorado instead just “guesstimate” when irrigation is needed. In some cases, farmers will either overirrigate and waste water or underirrigate and reduce yields. Providing farmers with a simple yet effective method of monitoring crop water needs is key.

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