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Published October 20, 2011, 06:12 AM

SDSU offers help coping with field losses due to fire

BROOKINGS, S.D. - Fires in early October not only consumed standing crops and crop residue, but they could lead to soil nutrient loss according to SDSU Extension experts at South Dakota State University.

BROOKINGS,S.D. - Fires in early October not only consumed standing crops and crop residue, but they could lead to soil nutrient loss according to SDSU Extension experts at South Dakota State University.

"From an agronomic point of view, there is not only the loss of the current crop, but also loss of nutrients and soil cover to consider," said Dwayne Beck, manager of Dakota Lakes Research Farm.

Ron Gelderman, SDSU Extension soils specialist explained that any time crop residues are burned, the nitrogen and sulfur in the residue is mostly lost to the atmosphere.

"Depending on the temperature of the burn, potassium and other nutrients may also be lost either directly to the atmosphere or lost with blowing ash leaving the field. The hotter the fire, the more likely other nutrients will be lost into the atmosphere," Gelderman said.

Beck encouraged growers to talk with their insurance agents, and with their neighbors where the fire involves more than one farm, and take care to document current grain loss as well as the loss of nutrients with burned residue. The SDSU Extension publication "Estimating nutrient loss from crop residue fires" at http://pubstorage.sdstate.edu/ AgBio_Publications/articles/E xEx8164.pdf is a resource growers can use to help calculate the loss.

"They should also document the extent of the fire on their land so that if future crops show a yield loss, they will have a means of documenting the loss," Beck said.

He said the use of an aerial map, satellite imagery, and/or a field mapping program might be helpful in this regard.

"If you want to directly measure loss of residue and duff, one way to do this would be to use a hula hoop or other device with a fixed area and take several geo-referenced samples of surface residues," Beck said. "One could use a hand-held vacuum to gather the duff in burned and unburned areas for comparison."

Samples can be dried, weighed, and sent to a lab for complete nutrient analysis. Documenting losses and mapping the extent of the fire are important for establishing the value of what was lost.

Cover crops help

prevent nutrient loss

What can growers do to their land to prevent further loss? SDSU Extension agronomist Peter Sexton, said that without residue, the soil surface is naked against the elements and prone to erosion and further loss of nutrients.

"In this situation, establishing a cover crop is of prime importance. However, before seeding a cover crop, the field should be inspected by an adjuster and released if there are any insurance claims to consider," Sexton said.

When selecting a cover crop mix, hesaid growers should select species which will establish quickly and grow into the fall.

Prime candidates for this purpose include oats, triticale, or winter wheat.

"To add some diversity to the mix including some flax or peas would also probably be a good idea," Sexton said.

Beckencouraged growers to use a high seed rate and plant the cover crop as soon as possible.

"There isn't much time left for it to get established," Beck said. "Even so, a small amount of growth is much better than nothing in terms of protecting the soil. If growers decide to go with winter wheat and keep it for a grain crop, then of course they would leave out any other cereals to avoid risk of contamination. Growers need to consider the disease hazard of planting wheat into corn or sunflower residue."

He reminded growers that the final planting date for winter wheat to be eligible for insurance is Oct. 15 in winter wheat counties. After Oct. 15 the level of coverage available declines the later the wheat is planted.

"With the loss of residue, not only are nutrients lost, but sustenance for the beneficial organisms in the soil food web is also lost. It is probably a good idea to rotate to high residue crops for the next year or two both to provide soil cover and to promote activity of the soil food web for future seasons," Sexton said.

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