Soil Microbiological Impact of Cover Crop and Fall-Applied Poultry Litter in Subsurface Bands.

Most benefits associated with modern agronomy consider crop yield as a function of nutrient inputs and abiotic factors such as climate and soil type. Few studies consider the effect agronomy has on biotic factors such as soil microbiological populations. The current study considered the application of poultry litter as conventional surface broadcast versus subsurface banding application, cover crop versus no covercrop, and seasonal application. The study was conducted on cotton (Gossypium hirsutum L.) in Mississippi. A previous study determined that fall, subsurface band application of poultry litter can be applied to these soils without yield penalty; whether there’s an associated effect on soil biology is unknown. Surface soil samples (0-15 cm) were collected from 2008 through 2013 and processed for the presence of heterotrophic plate count bacteria and fecal indicator bacteria (Enterococcus, Clostridium perfringens, Escherichia coli, and staphylococci). Additionally, DNA was extracted from soil collected in 2009, 2012, and 2013; extracts were quantified for the presence of 16S rRNA  and other soil health gene indicators as well as subjected to high throughput 16S rRNA sequencing. Overall, cultivation based approaches demonstrated that subsurface banding enriched and sustained some fecal indicators as well. Cover crop versus no cover crop plots were not significantly different, nor was seasonal application. The use of Illumina MiSeq 16S rRNA sequencing and Mothur analysis allowed detailed examination of microbial populations and demonstrated significant differences between treatments, particularly a more enriched and diverse population in banded and cover crop treatments. Using the non-treated control as a base showed that agronomical management plays a large role on soil microbiology, however positive or negative microbiological effects associated with these approaches cannot yet be determined.