Agronomic and economic productivity of summer annual forage systems under different poultry litter application methods

Authors: MEYER, IVANELLE - University Of Arkansas; POPP, MICHAEL - University Of Arkansas; Nieman, Christine; Ashworth, Amanda; Owens, Phillip

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2024
Publication Date: 5/15/2024
Citation: Meyer, I., Popp, M.P., Nieman, C.C., Ashworth, A.J., Owens, P.R. 2024. Agronomic and economic productivity of summer annual forage systems under different poultry litter application methods. Crop, Forage & Turfgrass Management. https://doi.org/10.1002/cft2.20281.
DOI: https://doi.org/10.1002/cft2.20281

Interpretive Summary: Poultry litter is a common fertilizer source for pastures in the mid-southern US. Broadcast application is common practice and leads to nutrient losses in runoff and via nitrogen volatilization. Application of litter below the soil surface is a solution, but is costly. At the same time, heat-stress during summer months may be addressed by sod-seeding summer annuals in pastures. We evaluated sorghum-sudangrass, cowpeas, and their mixture in pastures fertilized in 2021 using 3 ton/acre of litter that was either broadcasted or sub-surface applied in comparison to no poultry litter to determine yield and nutritive value across treatments. Sorghum-sudangrass had highest yields regardless of fertilizer treatment. Mixtures did not improve yield nor nutritive value as cowpeas were outcompeted sorghum-sudangrass. Sub-surface litter application increased plant crude protein concentration. Soghum-sudangrass only with sub-surface applied litter was the preferred treatment as it had highest relative profit over the course of this 2-yr study that was characterized by summer drought.

Technical Abstract: Poultry litter is a nutrient dense fertilizer that increases nutritive value and yield in pastures in the mid-southern US. Nutrient losses due to runoff and nitrogen volatilization are common when broadcasting poultry litter. As such, incorporating litter below the soil surface (sub-surface) was evaluated in comparison to broadcasting in 2021 and 2022 by evaluating yield and nutritive value of annual forage species. The study was a randomized complete block design with three forage species or species mixtures - sorghum-sudangrass only, cowpea only, and a mixture of sorghum-sudangrass and cowpea. The other main effect was poultry litter application method – broadcasted, subsurface, and no poultry litter. All treatments were replicated four times. Poultry litter was applied in 2021 only as biennial application is common to save on application cost. Forage was harvested twice per year and yields presented are total annual yields. Nutritive analyses included neutral detergent fiber, acid detergent fiber, and crude protein (CP). Partial budgeting led to relative profitability estimates by accounting for yield and cost differences across production systems. Sorghum-sudangrass had the greatest yields across fertilizer treatments. Mixing sorghum-sudangrass and cowpea did not improve yields nor forage nutritive value, as cowpeas were vastly outcompeted and did not average more than 5% of the total forage harvested in mixtures. Cowpea yields did not benefit from poultry litter application. Sub-surface application resulted in greater CP content for all forage species. Sorghum-sudangrass with sub-surface applied poultry litter was superior in terms of relative profitability compared to other treatments.