Nutrient transformations based on sampling scheme and cropping system following subsurface-banded poultry litter

Authors: Ashworth, Amanda; AMORIM, HELEN - University Of Arkansas; Moore, Philip; Adams, Taylor; Nieman, Christine; Owens, Phillip

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2024
Publication Date: 7/10/2024
Citation: Ashworth, A.J., Amorim, H., Moore Jr, P.A., Adams, T.C., Nieman, C.C., Owens, P.R. 2024. Nutrient transformations based on sampling scheme and cropping system following subsurface-banded poultry litter. Soil Science Society of America Journal. 88(4):1285-1296. https://doi.org/10.1002/saj2.20672.
DOI: https://doi.org/10.1002/saj2.20672

Interpretive Summary: Poultry manure land application has the proven ability to substantially increase crop yields and enhance soil health. However, surface applications have been scrutinized for water quality concerns from excess nutrient runoff into neighboring waterbodies, as well as for greenhouse gas emissions that are released to the air during nutrient breakdown. In efforts to address these concerns and improve management options that prevent nutrient losses and conserve poultry litter nutrients and improve crop yields, a research team at the United States Department of Agriculture, Agricultural Research Service developed a prototype tractor-drawn implement for subsurface applying poultry litter in conservation tillage systems. This 'ARS Subsurfer' has proven to reduce nutrient losses to air, soil, and water by 90%, but no recommendations currently exist for how frequently to apply poultry litter when using the ARS Subsurfer and how to soil sample in Subsurface applied poultry litter systems in both perennial and annual cropping systems. To address this gap, ARS researchers conducted field studies to evaluate nutrient losses and transformations based on two sampling methods (composite and systematically measuring nutrients at specific distances from the Subsurface poultry litter band) 0, 1, 6, 12, 18, and 24 months after applying Subsurface litter in annual and perennial systems. Researchers found that, on average, 15, 96, and 72% greater nitrogen, phosphorus, and potassium were conserved under subsurface compared to surface applications. Compared to surface applications, the Subsurfer increased crop nutrient removal 70-75%, which translated into 78-80% increases in yield and N-use efficiency. This further translated into poultry litter applications with the ARS Subsurfer needing to be applied every other year (rather than every year for surface applied systems), which saves farmers resources and time. Therefore, Subsurface applying poultry litter conserved nutrients in the soil for crop use and decreased the amount of nutrients lost to the environment, which positivity impacted crop use and air and water quality.

Technical Abstract: Poultry litter (PL) is an excellent source of micro-and macronutrients; however, surface PL applications result greater nutrient runoff and nitrogen loss via ammonia volatilization. Subsurface banding PL is a promising technology for combating these challenges, but scant information exists on proper soil sampling techniques and management recommendations for subsurface applied PL. Therefore, objectives were to quantify nutrient transformations (relative to surface applications) based on sampling depth (0-15 and 15-30 cm) and schema [systematic [(0, 3, 7, and 10 cm from PL bands) and composite] to develop subsurface PL recommendations per cropping system (annual cropping and perennial pasture) following PL application and 1, 6, 12, 18, and 24 months thereafter. On average, total N, and Mehlich-3 extractable P, and K were 15, 96, and 72% greater, respectively, under subsurface compared to surface applications. Further, Mehlich-3 and water-soluble P at the 0-15 cm depth was 4-5 and 2-3 x greater in soils receiving subsurface PL in perennial pasture and row crop systems, respectively, compared to surface applications based on composite sampling. Two and 4 x greater NH4-N and NO3-N levels occurred one month after subsurface PL applications (0-15 cm). Compared to surface applications, subsurface- PL increased (p < 0.05) N, P, and K crop removal by 75, 70, and 72%, respectively, and resulted in 80 and 78% yield increases and N-use efficiency, respectively. Consequently, subsurface PL conserved greater N, P, and K at the 0-15 cm depth, thus increasing nutrient-use efficiency in row crop systems and improving water quality in sensitive watersheds.