Soil microbiological impact of cover crop and fall-applied poultry litter in subsurface bands

Authors: Brooks, John; Tewolde, Haile; Adeli, Ardeshir; SHANKE, MARK - Mississippi State University; Way, Thomas - Tom; Smith, Renotta; PEPPER, IAN - University Of Arizona

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2018
Publication Date: 4/26/2018
Citation: Brooks, J.P., Tewolde, H., Adeli, A., Shanke, M.W., Way, T.R., Smith, R.K., Pepper, I.L. 2018. Soil microbiological impact of cover crop and fall-applied poultry litter in subsurface bands. Journal of Environmental Quality. 47(3):427-435. doi:10.2134/jeq2017.09.0382.
DOI: https://doi.org/10.2134/jeq2017.09.0382

Interpretive Summary: Agronomy helps produce the greatest crop yield for a given amount of nutrient inputs and management. Something that is often ignored is the soil biology. While some agronomy addresses this, most management approaches fail to directly help the soil biology. Using manure such as poultry litter can help feed the soil biology and thus potentially can have long-term implications for crop yields. The purpose of this study was to compare typical fertilizer approaches with poultry litter applications delivered via surface broadcast and subsurface application and their effect on soil bacteria and fecal bacteria. A winter wheat cover crop was also applied to field plots. Overall, the presence of poultry litter increased most soil biological properties, but there were few differences between the application methods. Cover crop did not affect most measurements, but did increase soil moisture, which in turn could affect soil biological properties. Of noteworthy interest was the fact that some of the effects on the soil biology lasted four years after the final application of fertilizer; this effect was not noted for standard fertilizer plots. This study demonstrated the positive effects on the soil bacterial population of litter application over standard and untreated control plots, and additionally suggests there is a positive residual effect associated with the practice.

Technical Abstract: Agronomic management is aimed at managing the crop environment to maximize yield; an often ignored parameter is soil biology. Indirectly, some agronomic approaches feed the biological component of the soil, such as using “organic” amendments such as manure or municipal biosolids. This study aimed to compare the application of poultry litter via broadcast and subsurface banding versus standard inorganic fertilizer application to cotton and their effect on the soil bacterial population and fecal indicator bacteria. Additionally, the effect of application timing and winter wheat cover crop were also investigated. Overall, the application of poultry litter increased aerobic heterotrophic plate count bacteria, 16S rRNA, integron I, and urease C gene levels over standard and untreated control plots. More specifically, there were few differences between subsurface banding and broadcast application, while cover crop only increased soil moisture and urease C presence. Interestingly, cores collected 4 years post fertilizer or litter application suggested a positive residual effect of litter application with 16S, phosphatase A, and urease C gene levels were elevated over untreated control and standard fertilizer plots. Additionally, 16S rRNA high throughput analysis suggested increased diversity indices in litter plots over untreated controls, but not over standard fertilizer management. This study demonstrated the positive effects on the soil bacterial population of litter application over standard and untreated control plots, and additionally suggests there is a positive residual effect associated with the practice.