October 18, 2000 | By: Laura Skillman

When the poultry industry first moved into Kentucky more than a decade ago, University of Kentucky agronomists began looking at how to best utilize the litter to fertilize crops.

That research is ongoing but has resulted in recommendations for farmers on when to fertilize and how much litter should be used to gain optimum benefit.

"The primary interest I've had is in getting information for farmers on how to utilize the litter as a nutrient source for growing crops," said Monroe Rasnake, Extension agronomist in the UK College of Agriculture.

The research has focused on yields and comparisons with commercial fertilizers - especially nitrogen.

Fall is a good time to add litter to some forage crops and wheat. Tall fescue can utilize not only the nitrogen in the litter but also the phosphate and potash. The state has a large amount of tall fescue and many of it is low in fertility, Rasnake noted. Four tons of litter per acre a year is the most that should be used on fescue pastures.

An additional benefit found by using the litter was that it did not lessen the soil's pH as much or at all compared to nitrogen fertilizer. As a result, farmers may not have to lime fields as often. Since litter can be placed on fescue fields in the fall, the need for litter storage is also reduced.

Some wheat fertilization research has been done but more is needed, Rasnake said. The advantage with using wheat is that the litter can be applied either in late fall or winter. Most litter applications to other crops such as corn and tobacco are done in the spring.

Putting it on those crop fields in the winter would result in too much loss of nitrogen. Wheat, on the other hand, is growing during that time frame and can use the nitrogen, Rasnake said.

The best results with wheat has been using a combination of litter and commercial fertilizer with the litter applied in the fall and other fertilizer in the spring.

Most of the research initially was on corn and on farms in western Kentucky with the focus on nitrogen use. Litter is high in nitrogen and corn uses much of the nutrient.

"Part of what we recommend is that they not put litter on the same field year after year," Rasnake said. "Most of our farmers don't grow just one crop, so what they can do is use the litter on their corn so they can get the benefit of the nitrogen and get the build-up of the potash, phosphate and other nutrients in the soil for use by their soybean crop. So they can essentially fertilize two crops at one time that way."

Forage crops need to also be watched for build up especially if grazing it, because they are recycling the nutrients, he said.

Some work has also been done looking at litter use on tobacco as a possible replacement for at least some commercial fertilizer. Both yield and quality of the crop were reviewed with a particular eye toward chloride. Poultry litter contains chloride and if applied to tobacco at too great an amount can hurt the crops quality, Rasnake said.

"Essentially our recommendations are that farmers not apply more than 4 tons per acre for growing tobacco mainly because of the chloride and balance the remainder of their fertilizer needs with commercial fertilizer," he said.

Rasnake has also been researching the use of litter on Bermuda grass. When it is cut for hay, this summer forage crop removes large amounts of nutrients from the soil.

Litter is used on this crop in June or July when it is growing vigorously.

"We've been looking Bermuda grass as a forage crop that would take the litter at a different time of year and also one that would use a lot of nutrients," he said.

Rasnake's research is also looking at the accumulation and movement of these nutrients through the soil using corn plots sponsored by the Kentucky Corn Growers Association. In the finer textured soils, there seems to be little movement of these nutrients down into the soil profile, he said.

For more information on using animal manures as nutrient sources contact your local Extension office and ask for publication AGR- 146.


Monroe Rasnake, (270) 365-7541