State farmers change way they grow rice

STARKVILLE, Miss. -- When a system works, there is little reason to change and many reasons to stick with success; any change in that system is often small things to improve efficiency.

Mississippi’s rice industry is not following that pattern.

Rice has been grown around the world for about 5,000 years on flat land that is flooded with immense amounts of water and then drained at crucial times. Rice is from Asia, and its growth is limited to areas where these conditions could be met.

In the Midsouth, rice is drill seeded then grown in upland, or non-flooded conditions for roughly six weeks. Water is typically pumped from ground wells to flood rice fields once seedlings are established. That flood is maintained for the next ten to fourteen weeks as the rice grows.

Dave Spencer, irrigation specialist with the Mississippi State University Extension Service, said in Mississippi, that water comes primarily from the Mississippi River Valley Alluvial Aquifer.

“Rice is only about 20% of acres in the Mid-South, but it uses 45% of the water we draw from the alluvial aquifer,” Spencer said. “Rice markets are down this year, and with margins being tighter, it becomes that much more important to manage your risks more effectively.”

The MSU Extension Service records that Mississippi’s modern commercial rice production began in 1948 when Rex Kimbrell produced about 300 acres just south of Greenville in Washington County. By 1954, about 77,000 acres were harvested.

Rice acreage was limited by U.S. government acreage controls from 1954 to 1973, and rice production began to increase dramatically after those limits were removed. Rice in Mississippi reached a high of 335,000 harvested acres and 14.4 million hundredweight in 1981.

Spencer said under a traditional system, rice uses 30-36 inches of water a year. The majority of rice acres in the state and across the U.S. are grown using a traditional flood system.

But research has shown that rice can be grown without the flood.

MSU researchers are testing various methods of successfully growing rice without the traditional flood. Over the years, research has focused on precision land leveling, use of polypipe for flooding rice fields and furrow irrigation for the fields.

Recently, MSU researchers have investigated alternative irrigation methods, including automating alternate wetting and drying. The system of alternate wetting and drying, called AWD for short, does things very differently but produces similar yields as flooded fields.

“Instead of maintaining the flood at 2 to 4 inches of standing water, you let water levels drop before putting the flood back on it,” Spencer said.

Over three years, MSU researchers tested rice in side-by-side plots using various amounts of water. In some fields, a 2- to 4-inch flood was maintained, while in other fields, the water level was kept at the soil surface, and at varying depths below the surface. That means rice was grown in fields where the soil was dry for several inches down.

“We took the water level to 16 inches below the soil surface before reapplying the flood,” Spencer said. “There was not a yield crash, but there was a yield loss. But we showed that you can grow rice on fields that only have water 16 inches below the soil level.”

The data indicates that the best rice performance happens when the water level is not allowed to drop lower than 4 inches below the soil surface. When managed at this rate, AWD maintained rice yields at typical levels and reduced water use 23% to 39%. This efficiency saved growers $25 an acre, on average.

“We substantially reduced the amount of water needed to grow the rice crop,” he said. “When we drop the water level we require for a field, we can capture some of those rainfall events.”

After validating the method of AWD and determining its effectiveness, MSU researchers coupled the intermittent flooding strategy with automation technology in a project led by Drew Gholson, MSU Extension irrigation specialist.

Using a system of water level sensors, actuated valves and pump controllers, water is applied to the crop precisely when sensors indicate it is needed. Water supply is shut off when water levels are full. This reduces overpumping and labor requirements.

“Employing automation in on-farm AWD management reduced water use 15% and even increased yield 4% relative to a continuous flood,” Spencer said.