Temporal Soil Bacterial Community Responses to Cropping Systems and Crop Identity in Dryland Agroecosystems of the Northern Great Plains

Abstract

Industrialized agriculture results in simplified landscapes where many of the regulatory ecosystem functions driven by soil biological and physicochemical characteristics have been hampered or replaced with intensive, synthetic inputs. To restore long-term agricultural sustainability and soil health, soil should function as both a resource and a complex ecosystem. In this study, we examined how cropping systems impact soil bacterial community diversity and composition, important indicators of soil ecosystem health. Soils from a representative cropping system in the semi-arid Northern Great Plains were collected in June and August of 2017 from the final phase of a 5-year crop rotation managed either with chemical inputs and no-tillage, as a USDA-certified organic tillage system, or as a USDA-certified organic sheep grazing system with reduced tillage intensity. DNA was extracted and sequenced for bacteria community analysis via 16S rRNA gene sequencing. Bacterial richness and diversity decreased in all farming systems from June to August and was lowest in the chemical no-tillage system, while evenness increased over the sampling period. Crop species identity did not affect bacterial richness, diversity, or evenness. Conventional no-till, organic tilled, and organic grazed management systems resulted in dissimilar microbial communities. Overall, cropping systems and seasonal changes had a greater effect on microbial community structure and diversity than crop identity. Future research should assess how the rhizobiome responds to the specific phases of a crop rotation, as differences in bulk soil microbial communities by crop identity were not detectable.

Las arvenses como hospedantes de microorganismos en un agroecosistema de sucesión Zea mays L.-Phaseolus vulgaris L.

“…El aumento de asentamientos antrópicos transforma o destruyen el hábitat natural de miles de especies, generando una pérdida considerable de la biodiversidad (Ouverson et al, 2021), lo cual afecta la comunidad edáfica también. Actualmente, factores de la biota edáfica, son usados como criterios del manejo de los suelos, permitiendo llevar la producción agrícola hacia nuevas técnicas de manejo sostenible que permitan la recuperación de los mismos (Karanja et al, 2020).…”

Soil bacterial community response to cover crops, cover crop termination, and predicted climate conditions in a dryland cropping system

“…Based on previous studies (Zhou et al, 2010;Eldridge et al, 2017;Ouverson et al, 2021), cattle grazed cover crop and fallow strip plots were expected to have higher bacterial diversity compared to glyphosate application and haying. However, no differences were found among soil bacterial communities based on cover crop termination method.…”

“…Environmental conditions strongly affect soil bacterial communities (Maestre et al, 2015;Naylor and Coleman-Derr, 2018;Ishaq et al, 2020;Ouverson et al, 2021). Precipitation in 2019 may have been a stronger influence on bacterial community alpha and beta diversity than the presence and composition of cover crops, termination methods, or simulated climate conditions.…”

“…However, no differences were found among soil bacterial communities based on cover crop termination method. In previous work, sheep grazing selected for dissimilar soil bacterial communities compared to tillage or chemical methods for cover crop termination and weed management (Ouverson et al, 2021). Long term exclusive cattle grazing and exclusive sheep grazing have different impacts on soil carbon storage, with no impact from cattle grazing observed in high diversity plant communities (Chang et al, 2018).…”

“…Interactions with physicochemical soil characteristics such as pH and soil moisture may also explain grazing-induced changes in soil bacterial community structure (Yang et al, 2019a). In a dryland USDA-certified organic cropping system, sheep grazing with reduced tillage intensity has been shown to foster distinct soil bacterial communities in comparison with organic tilled and conventional no-till systems (Ouverson et al, 2021).…”