• By Larry Oldham •
Editor’s note: Here are highlights of Larry Oldham’s broiler litter article. To see the complete report, go to https://bit.ly/2TTx6X1.
Extensive research has been conducted with poultry litter as a nutrient source for row crops within Mississippi. Here are several considerations about including poultry litter in the nutrient program.
▶ How much is it worth and what equipment is needed?
The nutrient content of litter varies from integrator to integrator (about seven operate in Mississippi) due to different bird growing management techniques. Litter is a relatively light material (31 pounds per cubic foot) compared to inorganic fertilizers (46 to 70 pounds per cubic foot). Therefore, transport expense can be high.
Proper spreading equipment is necessary and should be calibrated and maintained regularly. The Mississippi State University guidance for “Calibrating Poultry Litter Spreading Equipment” was recently updated.
▶ When should I apply litter for my cotton?
Litter is most effective when applied close to when the crop will use the nutrients. Conversion of nitrogen in the litter to plant available forms, whether nitrate or ammonium, will begin one to three weeks after application.
Litter is most efficient when applied a few days before planting row crops. Each year, only about 50 to 60 percent of N in spring-applied litter is used by plants. Research in north Mississippi found that with no actively growing cool-season crop, fall-spread litter provided no N to the next season cotton crop.
Significant amounts of the P in the litter applied in the spring and practically all the K in the litter is plant-available from spring applications. Phosphorus applied in excess of the amount used by plants will be stored in the soil. No carryover credit can be given for litter K to subsequent crops.
▶ How much litter do I use?
The U.S. Department of Agriculture-Agricultural Research Service in cooperation with MAFES conducted six studies using litter on cotton in 2002-2005. Yields were generally higher at five locations for poultry litter-based fertility programs. The only location that did not result in an advantage for broiler litter over standard inorganic nitrogen fertilizer was a Dubbs silt loam soil near Cruger, Mississippi, with a 3- to 4-bale yield potential for cotton.
The most effective application rate of litter as cotton fertilizer is 2 tons per acre applied a few days before planting, and then sidedressed with an additional 60 pounds of inorganic fertilizer N. This calculates to 180 pounds N applied per acre using average nutrient contents.
However, if about 120 pounds of N is added in the preplant litter application, half of that amount or 60 pounds of N is the plant available quantity in the course of the growing season. Another 60 pounds N should be sidedressed using inorganic fertilizers at layby, thus the net application rate is 120 pounds of N per acre from both sources that will be used during the growing season.
Further work has shown that because litter provides all nutrients, it can be difficult to decide which limiting nutrient was alleviated by the litter application. However, as the Cruger location demonstrated, if no soil-based nutrients are limiting production, litter and inorganic nitrogen are roughly equal. Therefore, a sound soil testing program must be in place to make sure balanced plant nutrition is provided.
▶ Application Rates
With the fertilizer content of the litter and calibrated spreading equipment, application rates using litter can be calculated. Remember that only about 50 percent of the N in the litter will be available to growing plants during the application season of application. Zero will be available if fall-applied for next year’s crop.
Six studies in Mississippi have shown that broiler litter can provide enough nutrients at 2 tons per acre applied shortly before planting cotton with supplemental sidedressing of 60 pounds nitrogen per acre at lay-by. Litter has distinct properties that must also be considered in the economics of transportation and application.
It is always best to have a recent nutrient analysis of actual litter to be applied. A sound soil test-based soil fertility management program is required to maximize the overall efficiency of litter used as fertilizer.
Larry Oldham is an Extension soils specialist at Mississippi State University.