Grass residue decomposition is crucial for nutrient cycling in agro-ecosystems, enhancing nutrient utilization efficiency and supporting sustainable crop management. While grass mulching has been widely studied for improving orchard soil fertility, the role of soil microbial communities in decomposing different plant organs remains unclear. Before decomposition, the aboveground and belowground plant parts were harvested and placed in separate litterbags, which were later used for evaluating the decomposition rate and chemical characteristics of the shoots and roots for 40 days (at 10 days intervals). The changes in soil fertility, soil microenvironment, soil microbial community were measured after 0, 1 and 3 months, alongside analysis of key microbial taxa under different residues treatments. The remaining mass of root litter treatment was significantly higher than that of other treatments by 72.97%, 17.53% during 1–10 days and 30–40 days, respectively. During the 40-days period, the release of potassium (K) from root litter reached 58.61%, and the decomposition of lignin was recorded at 56.94%, whereas the release of carbon (C), nitrogen (N), and phosphorus (P) remained relatively stable. Despite no significant changes in nodes, edges, and links at 30 and 90 days, the co-occurrence network of root litter exhibited modularity values of 0.774 and 0.773, respectively. The values were higher than those observed in random networks, indicating the presence of functional modules and enhanced stability within the root microbial community. Litter organs enhanced decomposition rates by positively influencing soil fertility and keystone microbial decomposers, while its soil microenvironment affects decomposition rates. Despite its recalcitrance, the chemical composition of root litter plays a key role in regulating soil microbial community structure and improving soil fertility, thereby maintaining orchard ecosystem functionality.

Silicon (Si) is widely distributed in nature and can promote plant growth under various biotic and abiotic stresses. Drought stress seriously affects plant growth and the concentration and ecological stoichiometry of nutrients. Integrated nutrient management effectively protects plants from stresses. However, the role of water and Si availability on element concentrations and stoichiometry in plantain (Plantago lanceolata L.) are unclear. Accordingly, this study observed changes in the concentration and stoichiometry of macro- and micro-elements in plantain leaves supplied with various levels of Si under variable water availabilities through a greenhouse experiment. Supplemental Si increased Si concentration of leaves under both well-watered and drought conditions. Without supplemental Si, drought conditions decreased concentrations of carbon (C), C: nitrogen (N), C: phosphorus (P), silicon (Si):N, Si:P and increased concentrations of N, P, N:P, Si:C, calcium (Ca²⁺), magnesium (Mg²⁺), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu). Increased Si under water stress increased concentrations of C, C:N, C:P, Si:C, Si:N, and Si:P, and decreased concentrations of Ca²⁺, sodium (Na⁺), and Mg²⁺. These results suggested that exogenous Si changed the concentrations and ecological stoichiometry of macro- and micro-elements.

To investigate the effects of row ratio configurations on intercropping advantages and related rhizosphere microbial communities, a field experiment involving five treatments of different rows of broomcorn millet, i.e., P1M1 (1 row of broomcorn millet intercropped with 1 row of alfalfa), P2M3, P1M2, P1M3 and broomcorn millet alone (SP), was conducted on the Loess Plateau of China. We analyzed the yield, nutritional content of broomcorn millet, the soil nutrient availability and the diversity and community composition of AMF (arbuscular mycorrhizal fungi) and diazotrophs in the rhizosphere of broomcorn millet. The results showed that compared with monocultures, alfalfa-millet intercropping system under different row ratio configurations significantly increased the yield of broomcorn millet and the absorption of PTP and PTK (total phosphorus and potassium of broomcorn millet). In addition, the broomcorn millet-alfalfa intercropping system also improved soil nutrition, with the decrease of the row ratio of broomcorn millet, the changes of TN, NH4+-N and microbial biomass in the rhizosphere of broomcorn millet were consistent, which was opposite to NO3−-N. Moreover, co-occurrence network and PLS-PM (partial least squares path modelling) analysis showed alfalfa-broomcorn millet intercropping system changed the community diversity and composition of soil microorganisms, increased the improvement of soil nutrition (TN, NH4+-N and microbial biomass), and promoted the absorption of different nutrients by plants (N, P and K) mainly through the negative regulation of AMF and the synergistic effect of AMF on diazotrophs, and finally increased crop yield. This shows that broomcorn millet-alfalfa intercropping can increase plant nutrient content by adjusting soil nutrients and soil microbial activities, thereby increasing yield. Furthermore, we found that 1P2M was the best ratio of alfalfa-millet intercropping system, which may provide reliable suggestions and selection basis for future agricultural production practices.

Soil microorganisms play a key role in soil fertility. Exploring the microbial community composition and diversity in response to cover crops is important for improving soil fertility in orchards. This study investigated how cover cropping can improve soil fertility by altering microbial community composition and the interrelations among soil microorganisms. Soil physicochemical and biological indicators and microbial community composition were evaluated after a 6-years application of cover cropping in an apple (Malus pumila cv. Fuji) orchard located on the Loess Plateau, China. Three treatments were applied: Trifolium repens treatment (TR), Lolium perenne treatment (LP), clear tillage treatment (CT). The soil of the cover crop treatments had a more complex microbial co-occurrence network than that of the clear tillage treatment; in particular, the correlations among fungi were significantly increased. Cover cropping increased the levels of soil organic matter (SOM), microbial biomass carbon (MBC), and total nitrogen (TN) in orchard soil. Changes in the fungal community were more related to microbial biomass nitrogen (MBN), TN, and carbon-nitrogen ratio (C:N). This indicates that cover cropping not only increases the diversity of soil microorganisms but also increases the interrelations between microbial groups, thereby improving the soil fertility of apple orchards on the Loess Plateau.

Soybeans can simultaneously form tripartite symbiotic associations with arbuscular mycorrhizal fungi (AMF) and diazotrophs. However, no studies have explored whether soybean genotypes differing in their maturity groups (MGs) may have implications for the recruitment of rhizosphere soil AMF and diazotrophs. We investigated the diversity and community compositions of AMF and diazotrophs in three soybean genotypes differing in their maturity groups (MG) using high-throughput sequencing. The soybean MGs were MG1.4, MG2.2, and MG3.8, representing early, standard, and late maturity, respectively, for the study region. Soil chemical properties and yield-related traits were determined, and co-occurrence network patterns and drivers were also analyzed. The results obtained demonstrated that AMF richness and diversity were relatively stable in the three soybean genotypes, but noticeable differences were observed in diazotrophs, with late maturity being significantly higher than early maturity. However, there were differences in AMF and diazotrophic composition among different MG genotypes, and the changes in the proportion of dominant species in the community were necessarily related to MG genotypes. Co-occurrence network analysis showed that the positive correlation between AMF and diazotrophs gradually decreased in earlier MG genotypes than in the other later MG genotypes. The results of the structural equation model analysis showed that soil organic carbon, AMF, diversity of soil nutrients, and extracellular enzyme activities were important factors driving soybean yield change, with organic carbon accounting for more than 80% of the pathways analyzed. These results suggest that soybean genotype selection based on MG plays an important role in recruiting both AMF and diazotrophic communities, and in comparison to AMF, diazotrophs are more responsive to the different MG genotypes.