Emily Payne - - Agtech

Soil Moisture Sensors Mean Savings for Growers

Seventy percent of the world’s freshwater is used for agricultural purposes. Compared to rainfed farming, growers have been able to achieve an estimated two to four times greater yield through irrigation practices, providing about 40 percent of the world’s food.

But often, improper irrigation management leads to suboptimal yields.

With soil sensors constantly tracking moisture levels, growers can make more informed decisions about irrigation, adjusting levels based on data from the ground rather than weather predictions or guesswork. This means growers save water, increase yield, increase crop quality, and reduce labor.

Real-Time Data, Better Crop Quality

Over-irrigated soil will become oversaturated, preventing crop roots from accessing oxygen. Oversaturation can also wash fertilizer away, taking important nutrients along with it. While oversaturation can be corrected, depriving plants of oxygen and nutrients for these periods of time can stunt growth. When this occurs frequently or at multiple times throughout the season, the damage will be reflected in growers’ yields.

As opposed to aerial imagery or drone technology, using in-ground soil sensors allow farmers to receive real-time information on their soils, knowing exactly where oversaturation might occur and when. A grower can look at how much moisture is lost each day in the fields, factoring in the stage of growth of each individual crop type, and make informed decisions on irrigation timing.

As opposed to aerial imagery or drone technology, using in-ground soil sensors allow farmers to receive real-time information on their soils.

The Cost of Water

The cost and profitability associated with irrigation varies based on a few factors: available water sources, type of irrigation system, type of crops, energy source used, and whether or not there are water costs for off-farm water supplies. While irrigation is often supplemental in the Eastern United States, irrigation is required in much of the West to provide most of the soils’ moisture. And in the West, water laws and allocations rule farmers’ irrigation practices.

According to the USDA, U.S. farms spent about $2.64 billion on irrigation facilities and equipment in 2013 (the last time these numbers were reported). About 72 percent ($1.91 billion) of these investments were on land in the West, where most of the Nation’s irrigated land is concentrated.

In an April 2018 study published by the University of Florida, one participant said soil moisture probes “take the guesswork out,” estimating that he is saving 50,000 gallons of water each day through the precision agriculture techniques.

The study interviewed nine growers who adopted multi-depth, 24-hour soil moisture sensing. Researchers found that eight out of nine (89 percent) have changed how they irrigate, 89 percent saw savings in water, fuel, fertilizer, or electricity, and 78 percent showed labor reductions.

“In the right circumstances, moisture sensors can save a turn in a single week. Beyond diesel savings, remember that equipment, labor, time, and pickup trips are all affected,” Chris Henry, associate professor and water management engineer at the University of Arkansas (UA) Rice Research and Extension Center, tells Farm Journal AgTech.

For a pivot making a 40-hour turn and using 4 gallons of diesel per hour at $2.50 per gallon, a single revolution will cost $400. According to Henry’s estimation, that’s up to $1,600 saved per month of the growing season in irrigation costs alone.

According to Henry’s estimation, that’s up to $1,600 saved per month of the growing season in irrigation costs alone.

State-Mandated Savings

For Patrick Troy, Regional Specialized Agent focusing on best management practices for agronomic crops in North Florida, the need for soil moisture sensors partially stemmed from governmental regulations: the farmers he works with are under a Basin Management Action Plan (BMAP), put in place by the Florida Department of Environmental Protection.

In areas like where Troy is operating in North Florida, there’s no question—soil moisture monitoring has to be adopted. Soil moisture sensors provide documentation that can be reviewed over the course of a season. The alternative would be to have the Department of Environmental Protection come in and do monthly monitoring, which, according to Troy, would cost about $8,000 per year. He and the growers he works with chose to not take this penalty, and instead adopted constant soil monitoring that can easily be reported.

While there is no public data measuring savings, Troy estimates that the average farmer using in-ground soil moisture saves one irrigation per corn season. He did some quick calculations: This amounts to 27,154 gallons per acre, so if farmers spend between $6 and $9 per acre on irrigation and the average farm is 800 acres, that’s a savings of $4,800 to $7,200, on average.

Adopting Tech

With farmers across the globe operating on thin margins, precise water management is an important tool towards gaining profitability. And the savings go beyond pure irrigation cost.

“If you look at how much you save both on the nutrients and the water. Somewhere between 20 and 30 percent of all nutrients—and nitrogen is the most mobile—is lost by over-irrigation,” according to Troy. “You’re wasting your water and the nutrients if you’re letting it percolate deeper.”

Irrigating efficiently within the root zone keeps nutrients where the crops can access them. New, multi-depth sensors allow constant monitoring of these root zones, so it’s easy to tell when irrigation is or isn’t needed.

While numerous factors that make each farm unique will inform each farm’s irrigation practices, the benefits of precise irrigation management can be seen across the board.

“It’s pure profit,” says Troy.

For those just starting with more precise irrigation management, the USDA Natural Resources Conservation Services posts free resources online.