In a business where rain makes grain, water is a crop input that seems to fall free-of-charge from the sky. But specialists at Syngenta say there are definite costs associated with water, whether it comes directly from rainfall or through irrigation.
“We should approach water the same way we approach fertilizer or any other crop input that carries a price tag,” says Chris Zinselmeier, program leader for water optimization with Syngenta Seeds, Inc. “We can’t control the rain, and sometimes we can’t even predict it, but that doesn’t mean we can’t manage soil moisture for maximum return on investment.”
Just how much does water cost? Under irrigation, growers can spend up to $10 per acre-inch on energy alone. Figuring the cost in dryland farming is tougher.
For example, a deep-tillage pass can remove 1 acre-inch of water through evaporation. That might cost an irrigator an extra $10 per acre in pumping costs, but for the dryland farmer, it could cost much more in lost yield potential if the crop is stressed for moisture.
Too much water also has a price tag. Wet springs delay planting. Standing water promotes nitrogen loss, disease and stalk rot. Intense rain events wash away productive topsoil. How much is this costing farmers? A recent Iowa State University report pegs the price of soil erosion at $10 per acre for every ton lost.
“That's why we are focused on best management practices and technologies that apply to a broad spectrum of water issues,” Zinselmeier says.
When the problem is not enough water, a large share of the discussion has focused on genetics: breeding crops with specific genes to make plants more tolerant to drought. Syngenta says drought tolerance falls under a broader umbrella of water optimization — making the best use of available water across a range of geographies, crops and agronomic disciplines. The company is developing a line of water-optimized corn hybrids bred for both full-water and drought conditions.
“The technical target for our water-optimized corn hybrids is to reduce the yield penalty associated with drought stress by 25%, says Wayne Fithian, head of technical information services with Syngenta Seeds.
Under full-water conditions, these hybrids yield as well as leading conventional genetics. That’s an important distinction, says Fithian, because it takes water optimization beyond the traditional boundaries of drought.
“Yes, we can use these genetics to increase dryland yield potential in drought areas,” he says, “but we also can use them to reduce the cost of water in irrigated farming and to hedge against unexpected drought stress in areas with more consistent rainfall.”
Even as genetics generate waves of excitement, Kendall Lamkey, agronomy chair at Iowa State University, encourages growers to consider soil, weather and overall crop management as equal partners in the drive for higher yields.
“We’re not going to double crop yields with genetics alone,” says Lamkey, pointing to the growing need for soil management to stem erosion, adding that Iowa leads the nation in soil loss by water. “Fields here lose an average of 5 tons per acre per year."
With every ton of soil erosion, fields also lose water infiltration and holding capacity, as well as organic matter.
“Topics like soil erosion may not be as exciting as molecular plant breeding,” adds Lamkey, “but they figure largely in water management, crop yield and return on investment.”
Many established no-till farmers report that their fields drain better and support planting and harvesting equipment better than tilled fields in wet years. But no-till also conserves soil water for the crop in dry areas.
Growers can save 1/2 to 3/4 inches of soil moisture by eliminating one pass with a field cultivator, even more when they eliminate deep tillage. No-till is the crown jewel: researchers at the University of Nebraska report saving 3 to 5 acre-inches of water when no-tilling under center pivot irrigation.
Similar water savings can come from early season weed control. In ongoing corn studies conducted by Syngenta, researchers consistently see a 3:1 water advantage in plots treated with pre-emergence herbicides.
“For every inch of water removed in the weed-free plots, we see 3 inches of water removed in the weedy plots,” reports Bob Kacvinsky, Nebraska-based technical support representative with Syngenta. In corn plots, 2-inch weeds remove about 2 acre-inches of water. Two- to 4-inch weeds remove almost 4 acre-inches of water. Results have been similar in soybean and milo tests.
“Depending on your irrigation system and your energy source, the cost of replacing water lost to weeds is about $7 to $10 per acre for every inch of weed growth,” Kacvinsky says. “The longer you delay herbicide application, the more it costs you in lost water.”
Water loss has a direct impact on potential corn yields, adds Kacvinsky.
“Over the past 4 years, the plots treated with either Lumax or Lexar pre-emergence herbicides averaged 16 bushels better than the total post herbicide plots,” he says.
Pre-emergence herbicides also enable reduced-till and no-till systems by partially or completely replacing mechanical weed control. Atrazine, one of three modes of action in Lumax and Lexar herbicides, replaced up to four tillage trips when it was first introduced in 1959. Today, atrazine is used on more than 60% of conservation-tilled corn.
Increasingly, the savings in tillage and time and the increase in yield are tipping the scales in favor of pre-emergence weed control, but it’s a prescription that can be difficult to follow when rain delays planting.
“Extremely wet springs can make it difficult to get a residual herbicide applied before planting,” says Mike Leetch, Syngenta technical support representative based in Iowa. “We know that allowing the corn to germinate with weeds and pushing all of our weed management to post-emergence applications is not our best management practice, but sometimes it’s unavoidable.
"If you’ve got to plant before you apply herbicides, we recommend adding residual weed control to your glyphosate. It will help to prevent yield loss due to weed competition, prevent late-season weed flushes and provide additional management against glyphosate resistance.”