Researchers are hoping a new, on-farm study using soil moisture sensors will help transform the art of irrigation timing to the science of irrigation timing.

A panel at Cotton Incorporated’s Crop Management Seminar in Tunica, Miss., discussed the results of the study recently, as well as other irrigation research and their thoughts on why irrigation efficiency is critical to Mid-South producers.

The study took place on the farm of Chris Bush, a third generation row crop farmer from Greenwood, Miss., who produces cotton, corn and soybeans on about 12,000 acres. The farm is about 95 percent irrigated, mostly by furrow. The study evaluated Decagon and WaterMark soil moisture sensors equipped with wireless communication, for their ability to schedule irrigations.

“We all know that timing is critical,” Bush said. “It is easy to manage water when the weather is hot and dry, because you can get in a rotation. The challenge for me is knowing when to resume watering after a rain, and this is when the sensors really help.”

The sensors were placed at 8 inches, 16 inches and 24 inches deep, in an approximately 100-acre field divided into quadrants. They provided season-long information to Bush and researchers for the project, which was funded by Cotton Incorporated.

This season’s results were surprising, according to Mississippi Extension cotton specialist Darrin Dodds, who helped with the study.

“It’s interesting that the quadrants we watered three times averaged about 1,400 pounds. The ones we watered twice averaged 1,500 pounds. We watered (the higher yielding quadrants) a little later, which is a little bit contradictory to the information coming out of Arkansas, which indicates you should water beginning about a week prior to bloom. Certainly rainfall plays into this. And we need to come back and tie some rainfall data into the results.”

Dodds said irrigation results can often be mixed, depending on factors like rainfall, temperature, soil type and even variety. But irrigation methods, and research, can always be fine-tuned for better results. “One of the biggest questions that comes to mind are the intervals between watering,” Dodds said. “If we stretch those out and put a little stress on the crop before we give it some water, what is it going to do to our yields? Where is that edge? We want to push that crop to make the best crop at the least amount of cost.”

Mississippi State University agricultural engineer Lyle Pringle, said that soil sensors can provide the type of quality information that moves irrigation away from art and toward science. “The biggest gap for the producer is what's going on below the soil surface,” Pringle said. “How much water is there? What are the critical soil moisture levels where we need to irrigate to prevent a yield-reducing stress?”

For Pringle, the irrigation demonstration on the Bush farm indicated “that the later initiations on deeper soils can save an irrigation without reducing yield and possibly increasing yield. And it doesn’t take an engineer to do this. The producer or consultant, if he has the interest, can install and operate the systems, and understand the data.”

Pringle says the bigger picture is conserving water for future generations.

“We have been put on notice in the Mississippi Delta that we are mining our aquifer. That aquifer is not supporting any drinking water, so it’s mainly our irrigation wells that are pulling those levels down. Static water surveys have shown that there is a (cone of depression) that has developed in the middle of the Delta and (it’s) getting deeper and wider every year. Our recharge for the aquifer comes from the bluff hills on the east side and from the Mississippi River on the west side. This is a Delta wide problem, not just for the people who are in the (depression).”

Pringle suggests that agriculture use more surface water and create more surface water supplies. “We can divert water and we can build reservoirs. In the short term, it’s about conservation. We can increase our water application efficiencies and our water-use efficiencies through irrigation scheduling.”

Irrigation systems are important too, noted Pringle. “A drip system is one of the most efficient systems. A well-managed drip system does not have run-off, deep percolation loss and very little evaporative loss.

“But in the Mississippi Delta, water quality in our shallow water aquifer is not very good for a drip system. We have iron and magnesium in the water, and we tend to have clogging problems. For the cost of a drip system, we have to have the drip system last for 20 to 25 years. Now they last about 10 years.”

A sprinkler system is the next most efficient system, at 80 percent efficiency on average, Pringle noted. “We have to keep those systems maintained so they continue to run at the designed efficiency.”

Furrow irrigation, at 60 percent efficiency, can have losses due to run-off, deep percolation and evaporation, noted Pringle. “There are programs like the PHAUCET program to help size holes (in rollout pipe) and get a more uniform distribution of water down the row. In certain situations, furrow diking, alternate row irrigation and surge flow irrigation can help.”

Pringle noted, “If everybody properly irrigated, we may not save a lot of water, because we have some producers who over irrigate, and some producers who under irrigate. But my view is that if you are irrigating properly, you’re maximizing your yields and you have a better bottom line. Then you can invest more in irrigation conservation practices. The goal is to have adequate water for all users in the Delta.”