Irrigating Cotton With Sensors

By Rad Yager

Whether you’re a cotton breeder, researcher or grower, it’s time to consider using soil moisture sensors if you irrigate. Basically, they will help you understand what’s going on deep below the soil surface. Here are some tips on how to get started with the technology.

Soil moisture sensors continue to improve and the network of consultants using them continues to grow, making the technology easier for irrigators to use. The data sensors generate is like the emergency room sending you home with a 24/7-heart monitor. The monitor senses and measures every heartbeat – strong or weak, regular or erratic. With this information, your doctor can better diagnose any current or future problems. The longer soil moisture sensors are in a cotton field, the more understanding you and your consultant will have about your irrigation management and how it affects cotton yield.

Below The Soil Surface

Soil moisture data can be accessed 24/7 through the wireless cellular network.
Soil moisture data can be accessed 24/7 through the wireless cellular network.

The first thing to keep an eye on is how full or empty your soil moisture “tank” is at any point throughout the season. Unlike the fuel tank on your tractor, the level of moisture in your active root zone can have a big effect on the cotton plant’s “horsepower” or growth rate. Knowing this can help with not only irrigation decisions but also fertilizer and growth regulator applications. Growers in some production regions start measuring and managing their soil moisture tank even before planting because of limited water resources. The critical refill level can be adjusted throughout the growing season to match the ever-changing daily water needs of the crop.

Secondly, because cotton is a deep-rooted crop (studies show roots more than 6 feet deep), it is important to document and measure root activity by depth. Multi-level probes have built in sensors, measuring moisture at 4-inch intervals down to 60 inches if needed. Just like measuring height-to-node ratios above ground, with sensor data we can better manage the crop by knowing where root activity is and track that progression during the season. If a field shows limited rooting depth, it may be time to check for hard pans or other restricting factors, such as nematodes.

A third thing to measure and manage is irrigation depth. Many producers prefer multiple, light irrigation applications but are very surprised to see how little, if any, water gets deeper than 4 inches. Of course soil type, tilth and current moisture greatly impact this movement, but sensors will give you a clear picture of the difference between light and heavier irrigations. Irrigating to deeper levels (when possible) will result in less evaporative losses and more water available to the crop. Tracking water movement with sensors works well with most irrigation methods, such as drip, flood, seep or overhead.

Tips On Getting Started
The most important tip to get started with sensors is to plan on paying for good support. Soil moisture sensors require a fairly precise installation process, maintenance and sometimes repair. Having someone responsible for doing these things on a regular and timely basis will yield many years of service from the equipment. Additionally, data calibration and interpretation requires some training and experience. You will have a lot of questions at first, so having reliable, available and trained support will give you the answers that lead to better management decisions.

The second tip is to consider leasing rather than purchasing if possible. This will enable you to try several configurations of sensors and data display without getting locked in to your first choice. Follow the advice of your local support but don’t hesitate to change things up to better match your irrigation needs. Most real-time soil moisture systems rely on the wireless cellular network to get the data to a website or app for viewing. When you lease, you can check out the reliability of the data transfer and display. These days you should expect reliable data transfer with little to no data gaps and convenient data display on your mobile devices.

The last tip is to go ahead and get started. Yes, the technology will get better and less expensive, but it’s already come a long way. There are many good companies offering solid equipment choices and good warranty policies. Your first unit should cost from $1,000 to $3,000, depending on leasing or buying. Growers everywhere are feeling the pressure to increase yields using less water. Now is the time to invest in equipment that will help you become an even better irrigation manager.

Rad Yager is co-owner of Certified Ag Resources in Camilla, Ga. Contact him at

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