
Researchers at Mississippi State University are always studying new ways to utilize and protect the Delta’s most valuable resources for farmers - soil and water. The Mississippi Delta offers some of the most abundant farmland in the world, but with great assets also come great challenges.
In this case, the challenge was efficiently irrigating high-clay soils in a quick and conservative way without impacting yield. Sounds simple, but in practice an ever-changing target.
“A lot of soil, especially in the Delta, where we have almost half of those soils could be classified as a shrinking clay or vertisol clay,” said National Center for Alluvial Aquifer Research coordinator Drew Gholson. “Once it cracks open, we have really excessive infiltration and it creates problems with waterlogging, and it can stay saturated for too long.”
Getting creative
When cracked soils become waterlogged, especially if a rain event follows irrigation, yield penalties are almost inevitable. To prevent waterlogged losses, researchers needed to get creative about how and where water was applied on field.
“We know these soils, when they are cracked open, fill from the bottom to the top,” Gholson said. “We wanted to know if there were ways we could move that quicker, and potentially put less water down.”
As a result, research began on furrow-irrigated corn and soybeans planted in 40-inch rows. Water was applied to every row, every other row, every four rows and every eight rows. Eight rows represented the initial widest distance at 26.7 feet from one irrigation point to another.
“If it's every row, we're still applying the same amount of water as the eight row skip. We're just concentrating the entire amount of that water for those eight in that one row,” Gholson said. “It stays the same amount of flow. I think it's important to make sure that flow is higher on our wide space irrigation, to move through those cracking plates.”
In theory, water applied this way would move more quickly across the field and fill cracked clay more efficiently, thereby saving both time and water. After irrigation, the data collected showed promise for a smooth water application.
“The field gets really wet on the surface adjacent to the eight-row skip, and then you can walk across the middle with it being really dry,” Gholson said. “It was 100% saturated, about three inches down, and we got some sensor data to show how fast that moved collaterally across, and it filled up from the bottom and then left a little trough in the middle.
However, the crops harvested from those trials still had to pass the yield test. If the irrigation applications cost yield rather than added it, there would be cause for concern.
“We saw no yield difference, which is what we're looking for,” Gholson said. “Then we broke it down a little bit further to look at the top side of the field and the bottom side of the field. We saw higher yield in the top side of the field compared to our every row, and in our 26.7, which is our eight-row skip, we saw higher grain yield.”
Other benefits
In addition to a higher grain yield in the top side - the longest under irrigation, researchers also saw some other small benefits to wider spread irrigation points.
“We saw higher protein content and kernel weights,” Gholson said. “The furthest we took this was at every two rows. So, the two rows that were the drop the furthest away from the water furrow had the highest protein and highest kernel weight.”
In thermal imaging to monitor the water advancement between the single row, every other row and four and eight row skips, water moved almost twice as fast across the field in the eight row skips versus every row irrigation.
“We know that in these heavy cracking clay fields, if it cracks open too wide, then we're irrigating sometimes twice as long as we felt like we should, or we normally would,” Gholson said. “This is another advantage that we were picking up on, that we could push that water twice as fast, but we're still getting that water moving across. Then we felt like maybe we can use less water.”
In 2024, researchers were able to test the wide row skip method at another level. Previous testing occurred in wet years, which was suited to the purpose of reducing waterlogging after irrigation events. The big questions about potential success in dry conditions and how wide would be too wide to separate the skips needed further testing.
So, how wide is the limit? About 40 feet.
“What we saw is the yield increased with higher inflows,” Gholson said. “We really needed that higher flow and that concentrated flow, and we did have yield decrease once we got to our furthest point from the irrigated furrow on as we moved further away, so we felt we hit the point of 40 feet being too long.”
Even in a dry year, researchers were encouraged by the continued success of wide row skips.
“I think we can irrigate faster and then we can put less water out,” Gholson said. “This was in a year where we didn't have subsequent rains. And so, it is encouraging. Even with drier weather conditions that we had in 2024, yield loss was not observed.”
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