The Nitrogen Cycling Key Functional Genes and Related Microbial Bacterial Community α−Diversity Is Determined by Crop Rotation Plans in the Loess Plateau

Abstract

Soil nitrogen cycling microbial communities and functional gene α−diversity indicate soil nitrogen cycling ecological functions and potentials. Crop rotation plans affect soil nitrogen fractions and these indicators. We sequenced soil samples from four crop rotation plans (fallow, winter wheat monoculture, pea-winter wheat-winter wheat-millet rotation, and corn-wheat-wheat-millet rotation) in a long-term field experiment. We examined how microbial communities and functional gene α−diversity changed with soil nitrogen fractions and how nitrogen fractions regulated them. Planting crops increased the abundance and richness of nitrogen cycling key functional genes and bacterial communities compared with fallow. The abundance and richness correlated positively with nitrogen fractions, while Shannon index did not. The abundance increased with soil total nitrogen (STN) and potential nitrogen mineralization (PNM), while Shannon index showed that nitrogen cycling key functional genes increased and then decreased with increasing STN and PON. Introducing legumes into the rotation improved the α−diversity of nitrogen cycling key functional genes. These results can guide sustainable agriculture in the Loess Plateau and clarify the relationship between nitrogen fractions and nitrogen cycling key functional genes.

Variations in the Diversity and Biomass of Soil Bacteria and Fungi under Different Fire Disturbances in the Taiga Forests of Northeastern China

“…The observed changing patterns in Menhinick and Margalef indices of the soil communities in the past fire sites were consistent and correlated with the levels of soil TN, AN and MC. Possibly, soil water content and soil nitrogen can promote the increase in some microbial abundance [48,49]. In addition, we found that the Menhinick and Margalef indices in soil of past and more recent moderate fire sites were similar to those of the control sample, which is consistent with the "intermediate disturbance hypothesis theory" proposed by Connell from the point of view of the species richness and diversity of the biological communities [50].…”

Soil depths and microhabitats shape soil and root-associated bacterial and archaeal communities more than crop rotation in wheat

“…However, the gene copy numbers associated with N-cycling in the rhizoplane samples exhibited variations across different soil depths, and no disparities were observed between WM and WR. Liu et al (2023) noted that crop rotation is a significant factor influencing nitrogen-cycling functional genes. They found that crop rotation increased the richness of bacterial communities associated with functional genes involved in nitrogen cycling.…”

“…This observation does not align with existing research in the field. For example, a diversified cropping system has shown positive effects on the soil microbiome, which can be observed by the increase in alpha diversity and expanded network structure in soils under conventional N application (Liu et al, 2023). A meta-analysis conducted by Venter et al (2016) found that higher microbial diversity was generally observed in soils with a greater diversity of crops.…”

“…The plant is rewarded with increased nutrient and phosphorus availability through microbial mining, enzymatic soil organic matter mobilization, and fast-cycling N reservoir degradation (Bulgarelli et al, 2013;Hosseini et al, 2022). These conversion processes are primarily conducted by microorganisms nourished by root exudates (Meier et al, 2017), which host the enzymes responsible for facilitating nitrogen transformation processes, including diazotrophs, denitrifiers, and nitrifiers (Das et al, 2022;Liu et al, 2023). The rhizoplane also encompasses a communication portal between the plant and the microorganisms, supporting the transit of biomolecules, nutrient uptake, the availability of root exudates, controlling the entry of harmful microorganisms into the plant tissue, and microbiota-assisted priming against plant diseases (Edwards et al, 2015).…”

“…Crop rotations offer a sustainable alternative to monoculture by preserving soil fertility and increasing productivity (Leteinturier et al, 2006;Tiemann et al, 2015;Babin et al, 2019;Woo et al, 2022). Crop rotation also contributes significantly to biodiversity enhancement (Albrecht, 2003) and improvements in the soil microbiome (Liu et al, 2023). Prior research on various crop rotations has primarily examined the overall soil microbiome, often overlooking distinctions among plant microenvironments, such as rhizo-compartments or soil depths.…”