Furrow-dike irrigation promising

With temperatures topping the century mark and the region stuck in a prolonged drought, it was appropriate that several stops along a recent National Peanut Research Laboratory (NPRL) Field Day in southwest Georgia featured irrigation options for farmers.

Furrow-diking — long a staple of irrigation in the West — is now being considered for Southeastern farms, says Russell Nutti of the NPRL. “We're working with furrow-diking to help conserve water and to help capture rainfall and irrigation water,” says Nutti. “We've been doing replicated field trials for the past three years, and we've done most of our research with a two-row Brown Chiselvator with a two-paddle furrow-diker behind it. We've also looked at reducing a pass in the field by putting the furrow-diker on back of the planter itself.”

Researchers have planted cotton, peanuts and corn and are using the Irrigator Pro computer software program to schedule irrigation.

“With Irrigator Pro, you input soil moisture data, crop age, soil type and rainfall. It then gives you a basis on whether or not to irrigate. It gives you an idea of the soil moisture before the plants show stress. We've used Irrigator Pro both on diked and non-diked fields,” he says.

Furrow-diking is a tillage operation that creates a series of basins and dams in the furrow to catch and absorb water delivered by either rainfall or irrigation. “If it's diked, we'll hopefully capture more water per irrigation and rainfall, and there will be less runoff. That should extend the amount of time the soil will provide water to the plant,” says Nutti.

There was plenty of rainfall in 2005, he says, and the peanut and cotton crops required only one irrigation. Furrow-diked corn received three irrigations and non-diked corn required five irrigations. Despite abundant rainfall, higher levels of soil moisture were maintained in plots with furrow-dikes compared to conventional plots. Similar yields were attained regardless of furrow-diking. No detrimental effects such as water logging or digging losses in peanuts were observed with furrow-diking.

“In 2006, we had a very dry year, and we were able to save 1 inch of irrigation on cotton,” says Nutti. “Also, in one of our trials, we saw a 21-bushel increase in corn yield when we irrigated a diked plot alongside a non-diked plot. In our cotton crop so far this year, we've saved 3 inches of irrigation by furrow-diking.”

From June 30 until about two weeks into July, the furrow-diked plots were irrigated three times while the non-diked plots were watered four times, he says. “During this period, we received about 1.4 inches of rain on this farm — that is part of the 6 total inches we've received since March,” says Nutti.

“We were able to save 3 inches of irrigation because the soil moisture status in the dike stayed wetter for the season compared to the non-diked area. Because of that, when we finally received a rain, each irrigation appears to be more efficient. We were able to avoid irrigating on this date in the diked area versus requiring an irrigation in the non-diked,” he says.

Clinton Truman of USDA-ARS says he has constructed a small rainfall simulation project to help support the furrow-diking research. “Our dikes are about 5 feet apart in plots that are 6 feet wide by 10 feet long. We simulated a 2-inch rainfall per hour, comparing diked with non-diked, looking at erosion, runoff and infiltration as a percent of rainfall. The plant availability water value was estimated based on ET and infiltration rates,” he says.

Furrow-diking, says Truman, increased infiltration by 38 percent. “The dike treatment was capturing more water, and more water was going into the soil surface in the dike treatment compared to the non-dike treatment. In our study, if water is not going in, then it must be running across, and that's when run-off occurs,” he says.

In the conventional or non-diked treatment, 53 percent of the rain that fell ran off compared to 15 percent for the diked treatment, says Truman. “Diking was originally designed to help capture more water, whether it's rainfall or irrigation. One of the added benefits we've seen is a significant decrease in the amount of soil loss that occurs from dike treatments — that's also about three and a half times the diked treatments.

“If you take all the infiltration and assume it's available for the plant, and assume an ET value, you can come up with an estimated plant-available water, and we've expressed that in terms of days of water use. With that 2 inches of water, the non-diked treatment had only about four days' use of water. For the diked treatment, we had about seven days of use. That's a difference of about 82 percent. In this study, if you're not furrow-diking, you'll irrigate every four days. If you're furrow-diking, you'll irrigate every seven days. That's a significant water savings,” he says.

If a farmer doesn't have to run the diesel to turn on irrigation, then he'll obviously be adding to the profit in his overall operation, says Truman. “Initial results look very good in terms of natural resource conservation, soil loss prevention and adding to the profit margin,” he says.

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