High Plains farmers realize that their most valuable resource, water, is too precious to waste. They also understand that the Ogallala Aquifer continues to decline.
On top of that, the cost of running irrigation systems stretches production budgets.
Cotton farmers Jeff Pate, Idalou, Texas, and Lloyd Arthur, Ralls, Texas, say technology offers opportunities to save money and preserve the resource.
They each started using soil moisture sensors about seven years ago and say the investment makes economic and environmental sense.
“The money I spend on moisture probes is the best money I spend all year other than soil testing,” Pate says.
Arthur agrees. “If technology doesn’t make money or save money, it doesn’t matter if it works.”
He’s convinced it’s been a good investment.
“The first time I used moisture sensors, the pivots went by twice and the sensors were not registering. I thought it was not working. I discovered that I was putting water out too fast. It was not soaking into the root zone.”
He says he was not putting out enough water on each pass to last until the next application.
Pate says he demonstrated the value several years ago with an experiment comparing a field on his farm with a neighbor’s.
“We both have subsurface drip. We started our wells at the same time, but I shut off mine intermittently as the probe said I had sufficient soil moisture. I could shut it off for two, three, even four days.
“At the end of the season, I had applied 4 inches less per acre, and yields were almost identical.”
He says his yield was only about 4 pounds per acre less. “But I used less water and about the same amount of fertilizer.”
Pate and Arthur say saving 2 inches a year is not difficult by using sensor data to schedule irrigation. Scheduling is a key.
“Early season is a good time to save water,” Pate says. “At two to six true leaves, cotton does not use much water. We can put too much out early in the season and waste some. The goal is to give it exactly what it needs when needs it.”
Efficient water use
“We’re in an area of deficit irrigation,” Arthur says. “We need rainwater in addition to irrigation. Some farmers use half-pivots, cotton on one half and dryland or an alternate crop on the other. I have not adopted that yet. I am looking at areas with better soil, better yield potential, and that hold water better, where I might slow the pivot down. On sandier soils, with lower yield potential, I might speed up, apply less. I want to place water where I can get maximum yield.”
“We typically get some rain during the summer, maybe just three-quarters of an inch,” Pate adds. “But that can justify shutting off the irrigation for two or three days.
If we don’t know what we have in the soil profile, we might keep running. I don’t want to stress plants, but I also do not want to apply so much the water runs out the bottom.”
More with less
“We want to grow more with less,” Arthur says.
Pate says water savings can pay for the probe. “Every year, we can save from 2 to 4 inches. And we save water in the aquifer. Once it’s lost, we don’t get it back.”
Sensors work on subsurface drip systems, too. “I use them on drip,” Arthur says. “I put in the first drip system about 20 years ago. Drip is more efficient with no evaporation, but we were not putting enough water on to carry the rootzone to the next application. Now, we slow to a 24-hour setting instead of 4 hours.” He said rains this summer allowed him to change up some fields but not across the board.
“My crop consultant checks fields at least once a week, so I have a backup on fields without probes. I might speed up or slow a pivot on one side of the farm or the other.”
Arthur says he got interested in soil moisture sensors through the Texas Alliance for Water Conservation (TAWC) back in 2012.
“TAWC researches various irrigation systems, including pivots and drip, and different techniques. They also use Mesonet, water meters, soil moisture probes and irrigation scheduling.
“What caught my eye,” Arthur says, “was what technology showed me that I had not seen before. I was running pivots on a three-day rotation. That’s what we had been doing since the 90s. We went around once at night and the next time during the day because of evaporation losses.
“I started slowing the pivots. In a hot, dry year, it might go five days, sometimes seven. That seems like a long time, but we still had moisture in the rootzone. I thought that if I had done that years ago, fewer passes would have meant less wear and tear on the pivots.”
“I think this is one of the best pieces of technology made available to producers over the last few years,” Pate adds. “I depend on them. I check my phone every morning. I get an email about 5:30 that tells me the soil root depth, how much moisture is available at depth, air temperature, and soil temperature. Last year, during the early freeze, the probe showed the ground frozen to 18 inches.”
Arthur hopes to tie the soil moisture sensors into other technology to use variable rate irrigation. One product he’s looking at is a radar unit from Israel. It attaches to the pivot arm and makes readings across the field as the pivot moves.
“It takes readings all the way around the pivot path at the one location on the pivot arm. A soil probe is stationary. This product allows us to see moisture availability all the way around. Even though the sensor is in the same spot on the pivot, it records across all quadrants.”
He says the additional data account for different soil types and slopes in all pivots. “This technology allows me to do more variable rate irrigation.”
Variable Rate Option
He hopes to tie this system into his FieldNet technology to provide more data and better opportunities for variable rate applications across the board.
“I can log where yields are best. With the yield monitor on the stripper, I can enter data into my computer and use variable rate irrigation, along with other practices.”
Pate says typically one soil sensor is adequate for one field.
“If the field is level, no bad slopes, I use one probe per field, around 120 acres. That fits most pivots; most drip fields also are 120 acres. One is 80 acres.
“I place probes in areas representative of the entire field.
I place them at a 36-inch depth. When the soil profile is full, it does not make sense to irrigate more, especially with a caliche layer. We rarely hit 100% field capacity unless we get big rains.”
He said timely rains this summer filled the profile, “unusual for this area.”
“Each field is different,” Arthur says. “On one field where we’re using VR, we have three sensors and are comparing to the radar unit.
“Usually, one in a field is OK. We might not need one in every field, if the pivots are all in good areas. One probe might show what’s going on across much of the farm.
“A farmer can tell if a crop is stressing by looking at it from the road, but if he does not dig or use a probe, he can’t tell how long it will stress.”
Experience with soil moisture monitors makes a difference in efficiency and confidence, Arthur and Pate say.
“I’m comfortable with the information from the probes,” Pate says. “The first year or so was a learning curve. I had to learn to look at the data and understand what I was seeing and understand what it was telling me to do and not do.
“We can only see if the soil surface is wet or dry. The probes tell us how much moisture is available.”
He says products available now are improved from early versions. “I used to use probes that I pushed down by hand. Those told me if it was wet or dry but not what was available.”
“The first ones I used, I had to take readings in the field,” Arthur says. “Now, the data comes to my smartphone, several times a day, every time a pivot passes.”
Pate and Arthur both work with TAWC on water management projects.
“What I learn from them, I use in the field,” Pate says. “It is an advantage to be on the front line of a project and put in practice.”
“It’s always a learning curve,” Arthur says.