Microbial community structure is affected by cropping sequences and poultry litter under long-term no-tillage

Authors: Ashworth, Amanda; DEBRUYN, JENNIFER - University Of Tennessee; ALLEN, FRED - University Of Tennessee; RADOSEVICK, MARK - University Of Tennessee; Owens, Phillip

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2017
Publication Date: 7/29/2017
Citation: Ashworth, A.J., DeBruyn, J.M., Allen, F.L., Radosevick, M., Owens, P.R. 2017. Microbial community structure is affected by cropping sequences and poultry litter under long-term no-tillage. Soil Biology and Biochemistry. 114:210-219.

Interpretive Summary: Soil microbes play important roles in forming soil carbon and cycling nutrients, and consequently are perceived as indicators for soil health. However, it is largely unknown how soil bacterial abundance and community structure is affected by crop rotation and soil amendments (poultry litter and cover crops). To better understand how management effects microbial function and diversity, a research team assessed soil bacterial composition after 12-years of crop rotations (ranging from monocultures to more temporally diverse sequences of soybean, corn, and cotton) and soil amendments. Researchers found that micobial composition differed among crop rotations, with continous cotton being the most different and least diverse community structure. Soil amendments greatly impacted soil microbes, with poultry litter amended soils differing from wheat and hairy vetch cover crops. Therefore, soil microbial diversity was greatest under poultry litter and less pesticide-intensive crop rotations of corn and soybean. These results suggest that soil ecosystem services and soil health are improved under nutrient-rich soil amendments and high residue producing crop roations.

Technical Abstract: Soil microorganisms play essential roles in soil organic matter dynamics and nutrient cycling in agroecosystems and have been used as soil quality indicators. The response of soil microbial communities to land management is complex and the long-term impacts of cropping systems on soil microbes is largely unknown. Therefore, changes in soil bacterial community composition were assessed in response to cropping sequences and bio-covers at long-term no-tillage sites. Main effects of four different cropping sequences of corn (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean (Glycine max L.) were rotated in four year phases for 12-yrs at two Tennessee Research and Education Centers in a randomized complete block design with split-block treatments of four winter bio-covers: hairy vetch (Vicia villosa L.), wheat (Triticum aestivum L.), poultry litter, and a fallow control. Using Illumina high-throughput sequencing of 16S rRNA genes, bacterial community composition was determined. Composition, diversity, and relative abundance of specific taxa were correlated per cropping system, bio-cover, and their interaction. We found that i) richness and diversity varied temporally and spatially, coinciding with soil carbon, pH, nutrient levels, and climatic variability; ii) community composition varied by cropping system, with continuous corn, soybean, and the corn-soybean rotation presenting a hybrid of the continuous corn and soybean communities; however, continuous cotton resulted in the most varied assemblage; iii) bio-covers asserted the greatest influence on microbial communities; specifically poultry litter treatments differed from cover crops (all of which received inorganic-N). Consequently, microbial diversity was greatest under nutrient rich bio-covers (poultry litter) and high residue producing, less pesticide-intensive cropping sequences (soybean and corn compared to cotton), suggesting a more dynamic soil ecology under these no-till cropping systems. This suggests that nutrient management (inorganic fertilizers vs. animal manure) and greater crop rotations (within 4-yr phases) may directly drive phylogenetic community structure and subsequent ecosystem services across agricultural landscapes.