“North Carolina growers should not manage for average corn yields, because ‘average’ is not profitable,” says North Carolina State University Corn Specialist Ronnie Heiniger.
Speaking at the recent North Carolina Corn Producers Association meeting, Heiniger says there are five basic keys to managing a corn crop for high yields.
First, he says is to select high yielding hybrid varieties that have a history of high, uniform stands and yield stress tolerance. Heiniger points out that 70 corn growers in North Carolina were recognized at the annual meeting for producing 200 bushels or more per acre and that one consistent variable among their production practices was use of proven varieties.
After selecting the optimum variety, it is critical to plant enough seed to get an optimum stand without wasting money on over-seeding. Seed cost is a variable often not managed well by corn growers, Heiniger contends.
Though many production factors influence precise seeding rates, in statewide testing on sandy soils, the optimum seeding rate was 40,000 seed per acre. On heavier soils with more organic matter, 35,000 seed per acre provided maximum yields, Heiniger explains.
Depending on soil dynamics and other factors, growers can adjust precise rates up or down from these average rates, Heiniger points out. In 2005, the state yield champion, Hardy Farms planted 35,000 seed per acre and runner up, Justin Carter planted 24,000 seed per acre. Row spacing 30-inch versus 20-inch for the top producer is one factor accounting for the difference in seeding rates.
A simple thing like planter calibration can play a bigger role in reaching yield potential than most growers think, Heiniger contends. “Calibrating the seeder correctly is simple and doesn't take a lot of time, but not paying attention to this detail can be the limiting factor in reaching 200 bushel per acre yields, the North Carolina corn specialist stresses.
The optimum seed spacing for 30-inch rows is six inches, he notes. Research, he explains, demonstrates that every one inch variation from the standard deviation caused a five bushel per acre drop in yield in field testing in 2005. “When you see a corn field with some plants bunched together and others with wide plant spacings, it's easy to see how a grower can lose 35-40 bushels per acre just from poor planter calibration, clogging or other mechanical problems that can easily be avoided,” Heiniger stresses.
Quick exploitation of the vertical root system is another of the keys to producing 200 bushel per acre corn, Heiniger contends. In addition to the cost of yield reductions, the high cost of fertilizer makes it doubly important for growers to choose the optimum starter fertilizer that gives corn plants the best chance to establish a strong root system, according to Heiniger.
Proper fertilization is the last key, though it directly affects the other four. “How do we respond to higher fertilizer costs is a question every corn grower is asking, Heiniger says. For growers trying to make maximum yields it is another of those two-edged swords — on one side using enough fertilizer to make maximum yield, and on the other side, not using more than is needed.
Richard Reich, assistant commissioner of agriculture in North Carolina, says their labs completed over 300 corn tissue analyses in 2005, and surprisingly, more samples showed low and deficient sulfur than nitrogen.
Heiniger agrees that low sulfur in 2005 was a more limiting factor on corn yields than nitrogen. Though stopping short of recommending grid sampling in corn fields, the North Carolina State specialist did urge growers to test more thoroughly in low-producing areas of their farm to ensure adequate use of sulfur and other fertilizers.
Potassium is another critical factor affecting corn yield. Heiniger points out that for every 100 pounds of K applied to a corn field, takes $6.25, or about three bushels of corn to pay for it. “Growers can't cut back on K and expect to produce a top yield, yet in the overall budget for fertilizer there is a set amount for potassium. Thus, putting K in the places in a field where it will do the most good is critical to both yield and profitability.
Determining precise amounts of fertilizer to use is critical in that fertilizer prices are high and corn is a high-demanding crop. The best approach, according to Heiniger is to use 25-50 pounds of N at planting, then use a simple color test, in which small strips are analyzed, to determine which areas of the field used the N and which areas need additional amounts.
Armed with strip test color analysis and well thought out soil testing, growers can make better decisions on which fertilizers to use. Knowing how much nitrogen carryover is in the soil can allow growers to cut back on N in some fields, or even parts of fields.
By carefully managing these five keys, Heiniger contends, North Carolina corn growers can maximize yields and profitability.
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