by John Hart, Southeast Farm Press
Irrigation significantly improves peanut yields in all rotation systems while the length of rotations also influences yield, according to research conducted in Georgia.
In a paper presented to the annual meeting of the American Peanut Research and Education Society, Marshall Lamb, research leader and scientist at the USDA Agricultural Research Laboratory National Peanut Research Laboratory in Dawson, Ga., presented findings that show there was no statistical difference in peanut yield when either corn or cotton was the prior crop to peanuts. But the research shows the length of rotation did make a difference.
The irrigation and crop rotational studies were conducted from 2001 to 2015 at the USDA/ARS multi-crop irrigation research farm in Shellman, Ga. Six sequences from continuous peanut; one year out, alternating with corn and cotton; two-year out rotations of corn, cotton and cotton, corn; and three-year out rotations of corn, cotton, corn were examined.
“In the three-year out rotation, we averaged roughly 5,800 pounds per acre,” Lamb said. “In the two- year out rotations, we averaged roughly 5,100 pounds per acre. When we get down to a one-year out rotation on irrigated land, we were averaging roughly 4,200 pounds per acre. Continuous peanuts yielded roughly 3,300 pounds per acre irrigated.”
On non-irrigated land, the three-year out rotation averaged 3,500 pounds per acre while the two-year out rotation yielded 3,300 pounds per acre and the one year out rotation produced 3,000 pounds per acre. The yield on continuous dryland peanuts was 2,500 pounds per acre.
Lamb said the research shows that peanut yields are significantly impacted by rotational years out of peanuts but not by the prior crop planted. “Irrigation significantly increased peanut yield within all rotations. The rotational crops did not affect peanut yield,” he said.
In addition, Lamb said the research validates a 2010 study commissioned by the United Nations Educational, Scientific, and Cultural Organization (UNESCO) that shows peanuts use less water per ounce than almonds, pistachios, walnuts and animal protein.
The UNESCO study examined the water footprint of 126 crops worldwide and defined water in three ways: “green water” which is basically rain; “blue water” which is irrigation, surface and ground water; and “gray water” which is water required to disperse nutrients, primarily nitrogen.
“What they found is that peanuts on a gallon per gallon basis on blue and gray water footprint use about 4.7 gallons of water per ounce of peanuts,” Lamb said. “But when we look at some of the competing plant protein crops, we find that almonds use 80 gallons of water per ounce, walnuts use 73 gallons of water per ounce, and pistachios use just under 20 gallons of water per ounce. Peanuts have a very good water footprint, especially when you look at the blue and the gray.”
Lamb said the blue water footprint of peanuts is positively influenced by the length of rotation. “The longer the rotation, the better we are on our footprint. There is concern because we have had increased acreage of peanuts over the past couple of years which could be affecting our rotation potentially and could affect our blue water footprint as well,” he stressed.