Skip to main content

More crop per drop

FARMERS CAN’T SET MARKET PRICES for their crops. They can’t stop government from creating new regulations. They can’t control the cost of inputs or keep land values from rising.

But they can make rain—with irrigation, that is.

“So much about farming is out of our hands, but irrigation is one thing you can control. It takes away a lot of the risk,” said Robert Lange, who raises corn and soy­beans on 400 irrigated acres in the Missouri Bootheel, just outside Cape Girardeau. His grandfather, also named Robert, graded all the fields, installed wells and started farming with furrow irrigation here in the mid-1980s. The younger Lange took over a portion of the farm from his uncle, David, when he retired in 2020.

With water being one of the biggest factors in determining yield, irrigation can help improve both productivity and profitability in crop production. Only about 15% of harvested land in the U.S. is irrigated yet those acres contribute 40% of the country’s agricultural production, according to the 2017 Census of Agriculture, the latest figures available. Data from the 2022 census will likely show an increase in those numbers, although cost, water availability and suitability of the land for irrigation are barriers to more widespread adoption.

In Missouri, irrigation is found on some 1.5 million acres, representing about 10% of the state’s total cropland. Around 800,000 of those acres are set up for surface irri­gation—furrow or flood—while center pivot sprinklers make up most of the rest.

“It costs a lot and is a lot of work, but it by far pays for itself,” MFA District Agron­omist Jesse Surface said. “In general, irrigating soybeans gives you an increased yield of 10 to 20 bushels per acre over dryland beans. In corn, we see a 50- to 60-bushel increase. And the biggest benefit is yield stabilization, knowing from year to year what your production will be. That allows growers to more confidently market their crops.”

As an MFA agronomist, Surface works with growers throughout the Missouri Bootheel, where more than 85% of the state’s irrigated acres are located. Furrow irri­gation is the most common system in the region. This gravity-powered method works by creating furrows between elevated crop beds and pumping water into these sloping channels through poly pipes with strategically placed holes. This system requires rela­tively level land that can be precision-graded to allow for the ideal flow of water.

On the other hand, center pivots, the second-most prevalent irrigation system in Missouri, offer the ability to water fields where surface irrigation is impossible or impractical. In this method, an overhead sprinkler system rotates around a central point connected to a water supply. Pivots are best suited for large square-, rectangular- or circular-shaped fields free of obsta­cles such as trees, fences, roads and power poles.

No matter what type of system, making every drop count through proper irrigation scheduling is both environmentally and economically important. However, determining when to irrigate and how much water to apply during the growing season can be a challenge. With too little water, the crop is stressed. With too much water, plants are stunted and fertilizer leaches below the root zone. Either way, the crop suffers.

“People talk about the science, but irrigation is truly an art form,” Surface said. “The biggest thing to under­stand is when crop needs its water the most, especially when we talk about soybeans. They almost use more water than corn when they get to the grain fill stage. Knowing when the crop really starts ramping up water intake helps you stay on top of it. And sometimes, you have to just trust your gut.”

From emergence to maturity, corn typically uses around 26 inches of water, with peak demand during reproductive stages from tassel (R1) to beginning dent (R4). Similarly, soybeans will use nearly 23 inches of water during the growing season, needing the most moisture from beginning bloom (R1) to pod fill (R5-R6). Unless the soil is extremely dry, supplemental irrigation is generally not needed during germination or vegetative growth stages.

When soil moisture becomes limiting, that’s the time to turn on the water for the first time each season, Surface said. In making that decision, growers must not only consider the soil moisture but also factors such as crop stage, soil type and weather forecast.

“Nobody likes to get started until they have to, because the general rule is, once you start irrigating, you don’t stop,” Surface said. “A lot of guys will wait too long on this step, and it hits them in the back end. Once you get behind on irrigation, there’s no catching up. You’re just behind all year.”

One of the biggest mistakes growers make, he added, is trying to make irrigation decisions by the “window farming” method.

“You can’t evaluate soil moisture from the highway,” Surface said. “You have to get out there and dig with a shovel. It may look dry, but is it really? You need to know how deep the mois­ture is in the soil profile.”

Knowing the soil type can also help. The water-holding capacity varies with the soil’s texture, structure and infiltration. For example, coarse-textured and sandy soils hold less water and need to be irrigated more frequently than loam and clay soils.

The weather forecast should also be considered when sched­uling irrigation. If precipitation is expected in the near future, the first watering could be delayed without detriment to the crop, Lange said.

“You don’t want to be watering the crop right in front of rain,” he said. “You’ll just waste water and oversaturate the field, and that’s never a good thing.”

Along with when to start irrigating, the second-most common question is when to stop, Surface said. While this decision, too, can be subjective, he said the rule of thumb is, “You don’t want to keep watering after your crop is already made.”

In corn, the timing is relatively cut-and-dried. When the ker­nels reach black layer, irrigation can be stopped. Soybeans take a little more work. Surface suggests walking fields, pulling a few pods from the top three nodes and opening them.

“Inside, there will be a membrane that should peel off the beans,” he explained. “When it does, you know a majority of moisture is already in that bean. At the most, you’ll only need one more watering at that point. Corn is easier. You just break open a kernel, and when it’s at black layer, it’s done. Corn is very distinct on when to quit irrigating.”

Despite its benefits, Lange warns that growers can’t count on irrigation to be a crop’s savior when conditions are extreme. He said last year was the driest since 2011 on his farm. Irrigation started early, and there were no breaks. Yields reflected the challenges.

“The biggest thing we learned from last year is that Mother Nature still holds the cards,” he said. “I wouldn’t want to farm without irrigation, yet it doesn’t alleviate all the risk.”

MFA agronomists and crop consultants can help growers in making irrigation decisions. Check with your local MFA for more information.

READ MORE from the June/July 2023 Today’s Farmer’s Magazine, the MFA Incorporated member magazine.

  • Created on .
  • Hits: 474