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Auburn U. research goes deep into irrigation sensors


Water is the most limiting factor in the world, especially when it comes to growing crops. And unfortunately, farmers cannot depend on Mother Nature to provide them with this nourishment. Because of this, much of the crop land in America is irrigated. This is a great solution to not relying on Mother Nature, which we all know can be moody. But irrigation is not without its problems: The most common questions from farmers when it comes to this process is when to apply the water and how often.

Dr. Brenda Ortiz, extension specialist and associate professor at Auburn University, has worked the past few years to address these exact questions through her research. Usually farmers wait until the plants are beginning to wilt before they apply irrigation, but Ortiz explains that is too late. Once the plants start curling, there is too much stress on the plant to mitigate the damage. She argues that farmers should apply water before this point to see the best results in plant health and yield.

But how does one know the perfect time to apply water? Ortiz says it is simple: by using sensors attached to probes. Her and her team take probes that have three sensors attached and place them throughout a field.

The soil sensors technically measure the tension, which is the force the roots have to impose in order to take up the water. “The more force a plant has to impose the less water that is in the soil. The less force the more freely available water that is in the soil. It is equivalent to soil moisture,” Ortiz explained.


There are three sensors on each probe because it measures the soil moisture at three different levels. This is important because there may not always be roots in all three sections of the soil. When the growing season first starts, the roots are only in the first layer of the soil, so data from the first section is the only one used. Then as the plants grow, the roots expand to the other sections so then the average of the sections is used to determine the total moisture content available for the plant.

On top of these probes is an antenna that has a radio that communicates to a computer base in the field. This allows farmers to access the data from anywhere and helps reduce the time involved in making the decision of whether or not to irrigate. Farmers will use this data to decide when to apply a uniform rate of water to an entire field.

“We are running tests where we apply water at different times. Sometimes early, sometimes late depending on the thresholds. We are comparing the yields between all of the plots to see how and if applying water too early or too late affects yield, explained Ortiz. “My goal is to expand this work to other fields and other farms to demonstrate how the technology works and show farmers the benefits and implications of using more or less water.”

This technology is applicable to anyone involved in using water to grow plants, it is also already available to those farmers. If farmers want to use this technology, there are a few ways to make it cost effective.

“Farmers can build the probe with a PVC pipe and they can go to the field and read the sensors manually. It will still be greatly beneficial in making educated decisions about whether it is time to irrigate or wait,” Ortiz said.

Each sensor costs about $300, but the return in improved yield could be worth the investment.


This technology is great for the agriculture industry, but it is not perfect. The main issue with this technology is that fields are not uniform — there is variability either in soil type, aka texture or in topography. But yet, farmers are applying water uniformly across the field, whether the plants need it or not. Ortiz is also studying how to account for natural variability and apply different rates and frequency of water based on that variability. This is called Variable Rate Irrigation. This means that some areas of a field may get watered, while others do not. Or that some areas of a field receive more water than others.

This technology can be used on a center pivot irrigation system, which is what most farmers use to irrigate their crop land. The system will require some modifications, and a GPS must be used, along with the sensors. The GPS creates what is called a variable rate prescription map that tells the computer which areas of the field are on for irrigation and what areas are off for irrigation. The sensors help with deciding when to irrigate or whether they can wait longer without being damaged.

This technology will be incredibly beneficial for farmers to prevent wasting resources by overwatering fields or watering parts of the field that are not being utilized. This research and technology could help increase yield, because it provides farmers with the best times to apply water and how much to apply for the maximum yield. It will also help decrease water wastage, by over-watering. If research can prove the perfect time to water crops, then farmers would be able to create a more uniform yield across the farm and across the region.

The goal of most agriculturalists is to feed the world, while being sustainable, environmentally and economically. This variable rate irrigation research will help the agriculture industry do just that. The best thing is that this research can be applied to all aspects of the agriculture industry, not just for large-scale production agriculture. It can be used for small, organic, or even backyard gardens. Water is necessary for all plant life, and knowing how much is available in the soil profile will help everyone know how much is needed. This helps agriculturalists become better farmers, growers and most importantly better stewards of the land.


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