Variation in Bacterial Community Structure Under Long-Term Fertilization, Tillage, and Cover Cropping in Continuous Cotton Production

Abstract

Agricultural practices alter the structure and functions of soil microbial community. However, few studies have documented the alterations of bacterial communities in soils under long-term conservation management practices for continuous crop production. In this study, we evaluated soil bacterial diversity using 16S rRNA gene sequencing and soil physical and chemical properties within 12 combinations of inorganic N fertilization, cover cropping, and tillage throughout a cotton production cycle. Soil was collected from field plots of the West Tennessee Agriculture Research and Education Center in Jackson, TN, United States. The site has been under continuous cotton production for 38 years. A total of 38,038 OTUs were detected across 171 soil samples. The dominant bacterial phyla were Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia, and Chloroflexi, accounting for ∼70% of the total bacterial community membership. Conventional tillage increased alpha diversity in soil samples collected in different stages of cotton production. The effects of inorganic N fertilization and conventional tillage on the structure of bacterial communities were significant at all four sampling dates (p < 0.01). However, cover cropping (p < 0.05) and soil moisture content (p < 0.05) only showed significant influence on the bacterial community structure after burn-down of the cover crops and before planting of cotton (May). Nitrate-N appeared to have a significant effect on the structure of bacterial communities after inorganic fertilization and at the peak of cotton growth (p < 0.01). Structural equation modeling revealed that the relative abundances of denitrifying and nitrifying bacteria were higher when conventional tillage and vetch cover crop practices were applied, respectively. Our results indicate that long-term tillage and fertilization are key factors increasing the diversity and restructuring the composition of bacterial communities, whereas cover cropping may have shorter-term effects on soil bacteria community structure. In this study, management practices might positively influence relative abundances of bacterial functional groups associated with N cycling. The bacteria functional groups may build a network for providing N and meet microbial N needs in the long term.

Effects of restructuring tilth layers on the occurrence of Verticillium wilt and the soil microbial community in a continuous rotary tillage cotton field

“…RTL did not change the dominant soil bacterial and fungal phyla or families (Fig. 5), which agrees with the results of previous research [31,32], These ndings suggest that these communities are likely dominated by taxa that have adapted to the environmental conditions or that a stable dynamic balance mode was formed after long-term manual management [33]. However, the relative abundance of microbial communities changed signi cantly after RTL.…”

Identification of Novel Viruses and Their Microbial Hosts from Soils with Long-Term Nitrogen Fertilization and Cover Cropping Management

“…In this study, inorganic N-fertilization positively influenced viral community diversity and played a role in shaping viral community structure. It is likely N-fertilization positively influenced viral population through increasing abundance of host communities ( 53 – 56 ). Also, a strong positive correlation between the abundances of Verrucomicrobiota and its vOTUs was observed, and N-fertilization influenced the abundance of genus PSRF01 affiliated with Blastocatellia ; the abundance of Blastocatellia was correlated with nitrogen availability in soils ( 57 ), which might indirectly influence the viruses related to Blastocatellia .…”

“…The ongoing long-term conservation management experimental site used in this study is located at the West Tennessee Research and Education Center (WTREC; Jackson, TN), established in 1981, and the soil type was Lexington silt loam (fine-silty, mixed, 127 thermic, Ultic Hapludalf) ( 56 ). The continuous cotton production experiment was arranged in a randomized complete block with a split-split plot design.…”

Long‐term no‐tillage and rye cover crops affect soil biological indicators on Andosols in a humid, subtropical climate

“…The tillage systems substantially altered the soil microbial structure and communities, whereas cover crop treatments did not (Figure 5). Duan et al (2022) found that the effects of cover crops on bacterial community structure were observed only after the retention of cover crops, which led to a relatively short‐term effect (approximately 1 month). In the present study, soil samples were collected approximately 3 months after cover crop termination in the summer and 2 months after cover crop sowing in the winter.…”

“…The tillage systems substantially altered the soil microbial structure and communities, whereas cover crop treatments did not (Figure 5). Duan et al (2022) found that the effects of cover crops on bacterial community structure were observed only after the retention of cover crops, which led to a relatively short-term effect (approximately 1 month).…”