April 6, 2007

High corn prices have many Nebraska farmers switching their usual planting rotations from corn following soybeans to corn following corn.

However, a University of Nebraska-Lincoln soils scientist said producers need to keep cost in mind if making the switch.When calculating which crop would be most profitable, farmers need to figure the continuous corn crop yield will be reduced 10 to 15 percent, and it will take 30 to 45 pounds more nitrogen to raise that crop, said Charles Shapiro, soils specialist at the university's Haskell Agricultural Laboratory near Concord. At today's prices on irrigated corn, that could cost about $116 more per acre compared to corn following soybeans. Planting corn one year and following with corn the next year will reduce yields slightly and require more nitrogen fertilizer.

"One cannot just take the net income from soybeans and corn and compare them if the cropping sequences have changed," the Institute of Agriculture and Natural Resources specialist said. "Other practices will change as well. It also is important to factor in timeliness of operations. Corn yields will be reduced about a bushel per day if they are planted late."

As a farmer increases corn acres, there is more chance that some of them will not be planted at the optimum time, he said. A farmer needs to make sure all other operations can be done in a timely manner as well, such as weed control and irrigation."A farmer told me he made $150 more on his corn than soybeans last year." So, if a farmer made the switch it could give him a potential $34 extra per acre.

"I've talked to seed corn dealers and farmers and a lot are making the switch at least for one year," Shapiro said. "With high corn prices and the ethanol boom, it's going to happen."

Decades of university research in eastern Nebraska on silt and clay loam soils also quantify the difference in yields and reduced nitrogen needs.

Research found corn following soybeans usually produces optimum yields with about 45 pounds less nitrogen than following corn. When planting corn following corn, farmers will have to buy that nitrogen. Currently the average price of nitrogen is about 48-cents per pound.

Two years of university research have shown similar results in sandy soils.

"Last year the best yield corn on corn was 200 bushels per acre and the best corn following soybeans yield was 225 bushels per acre," he said. "It also took 30 pounds less nitrogen to grow corn following soybeans."

Basically, farmers considering planting corn on corn just need to "do the math and figure out what the costs are," Shapiro said.In addition, planting corn on corn also can result in a possibility of increased corn rootworm problems, said Bob Wright, UNL field crops specialist.

Rootworm beetles lay eggs in corn fields, and after overwintering they hatch in the spring. However, the beetles can't survive in soybeans.

"The more years you have corn on corn the more populations can build up," Wright said.

Wright said the best thing farmers can do is to count beetles during the summer. If there are high numbers, there are several options to protect against corn rootworms, including using Bt corn varieties active against rootworms or a planting-time insecticide.

"However, if they don't have that scouting information, they can't make those judgements," he said.

Sandi Alswager Karstens
IANR News