Efficient Water User
Efficient Water User: Sunflower second only to peas in water use efficiency study
Sunflower is one of the best broadleaf crops at converting water to seed yield, according to a three-year study completed at the USDA-ARS Northern Great Plains Research Lab in Mandan, ND.
From 1995-97, crop scientists at Mandan compared water use and seed yield of broadleaf crops, with the objective of identifying broadleaf crops best suited to the drier conditions of central and western ND, in cereal-based cropping systems. Donald Tanaka and Steve Merrill, USDA-ARS soil scientists at Mandan, and Randy Anderson, now at South Dakota State University, Brookings, were the crop scientists involved in the study.
They compared four early-season crops (peas, crambe, canola, safflower) and three late-season crops (sunflower, soybeans, beans). Precipitation was above average in 1995 (11.99”) close to average in 1996 (8.41”) and below average in 1997 (5.87”)
Sunflower used the most water, followed closely be safflower, then soybeans, black beans, crambe, peas, and canola. Root growth plays a key role in water use. The study of crop root growth has shown that depth of rooting for a given crop can vary somewhat from year to year, but that the relative rooting depth of one crop type compared to another is consistent.
Sunflower and safflower are the most deeply rooted (5 to 7 feet), and these oilseed crops tend to be moderate to large water users. The mustard family crops canola and crambe, along with spring wheat, show an intermediate range of rooting depths (generally 3 to 4 feet) and moderate amounts of water use. The annual legume crops field pea, dry bean, and soybean have the shallowest rooting depths (generally 2 to 3 feet), and can vary considerably in water use, running from relatively lower water use by the shorter-season pea crop to the greater water use by soybean.
In the water-use study at Mandan, peas were the most efficient at converting water to yield, averaging 2,350 lbs per acre. Next was sunflower (1,780 lbs/acre) followed by black beans (1,200 lbs) crambe (1,190 lbs), canola (875 lbs), safflower (1,180 lbs), and soybeans (910 lbs).
The price that would have been received from the sale of each crop included in the three-year study was also calculated. In that comparison, black beans offered the best return, at $19 per inch of water that the crop used. Peas were second ($16/inch water used) and sunflower third ($14/inch water used) followed by canola ($12), safflower ($11), crambe ($10), and soybeans ($7).
Bear in mind that different prices would likely change these return rankings today. Still, water-use comparisons are worthwhile in helping producers determine what crops to include in their cropping systems. “Sunflower, even though it is a higher water user, is very good at coverting water into seed,” says Donald Tanaka, USDA-ARS soil scientist in Mandan—Tracy Sayler
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