In agroecosystems, fungi not only attract attention as crop pathogens, but also play crucial roles in nutrient cycling as decomposers and arbuscular mycorrhizal mutualists. Consequently soil fungi strongly influence agroecosystem function, and are conspicuously influenced by agricultural practices. We examined the effects of four compost rates (0, 11.25, 22.5, and 45 Mg ha⁻¹) on soil fungal community compositions and network patterns in soybean at seedling, flowering, and mature stage in a field experiment in black soil of Northeast China. Miseq sequencing was used to characterize the soil fungal community. Our results revealed that soil fungal richness was unaffected by compost addition, while soil fungal community composition was significantly influenced by compost addition across the growing season. Among the combined “top 20” fungal OTUs, 15 OTUs positively responded to compost addition, while 10 negatively responded. The abundance of predicted pathotroph was greatly decreased by the 45 Mg ha⁻¹ compost addition. Network analysis indicated that the fungal networks in compost amended soils were more complex and harbored more positive links than the control. Fungal network harbored more positive links among saprotroph-saprotroph and saprotroph-symbiotroph in moderate level of compost amended soils than other networks. In conclusion, this study revealed that compost addition impacted positively both the soil fungal communities and network patterns within a single growing season. Thus, compost addition could be a good practice to enhance the soil fungal community and function and ultimately soil health and quality.

This study aimed to elucidate the effects of various doses of compost amendment on bacterial community compositions and co-occurrence network patterns across the growing season in black soil, Northeast China. Bacterial richness was unaffected by compost addition in seedling and flowering stage, whereas significantly enhanced by high level of compost addition (45,000 kg ha⁻¹) in mature stage. Non-metric multidimensional scaling analysis revealed distinct bacterial communities in response to compost addition across the growing season. At phylum level, copiotrophic groups of bacteria including Bacteroidetes and Firmicutes gradually increased in relative abundance along with compost rate, while oligotrophic groups (Planctomycetes and Verrucomicrobia) showed opposite tendency. Notably, these enrichment or reduction was most pronounced in seedling stage. Abundant genera including Actinomadura, Aminobacter, Cellvibrio, Devosia, Luteimonas, Microbacterium, Nonomuraea, Promicromonospora were positively and consistently correlated with compost rate, whereas Arthrobacter, Flavisolibacter, Janthinobacterium, Kaistobacter negatively correlated. Network analysis indicated that compost amended soils (40.0, 49.0, and 64.0%) harbored more positive links than control (37.6%). In addition, the soil bacterial network connectivity and connectedness generally increased along with the compost rate, while modularity exhibited opposite trend. Overall, our findings show that compost addition modified the bacterial community compositions and network patterns in soybean agroecosystem in Northeast China.

The germination of halophytes in saline-alkali substrates is a useful criterion for selection tolerant alfalfa (Medicago sativa L.) cultivars. The experimental conditions consisted of five levels of salinity (24, 48, 72, 96 and 120 mM) and four pH levels (7, 8, 9 and 10). The results showed that under saline conditions, the germination percentage (Gp), plumule length (Pl) and radical length (Rl) also decreased with increasing concentration. However, under low or moderate saline conditions, Pl and fresh weight decreased sharply but Rl was the longest at 48 and 72 mM and pH 7.1, which indicated that low salinity may promote radical growth appreciably. Salinity and alkalinity stresses had synergetic effects on Gp, Ge and Gi but not on Pl, Rl and fresh weight. The results confirmed Gp, Gi and Ge are important indices for assessing germinated energy of alfalfa in salinity-alkalinity soils. Moreover, three alfalfa cultivars tested were relatively tolerant of salinity and alkalinity and Stockpile was the most tolerant cultivar in the present experiment.

The aim of this study is to improve the utilization of phosphorus (P) in soil, and to study the effects of phosphate-solubilizing bacteria (PSB) on P fractions and bacterial communities. In this experiment, we reduced the amount of P fertilizer by 30 % and 40 % respectively to studied the effects of combined application of bacterial fertilizers on soil microbial community and phosphate transformation process under different fertilization rates. The results showed that the application of PSB affected the transformation process of different P fractions. PSB had the most significant impact on organic phosphorus (p < 0.05). Correlation analysis showed that the abundance of bacteria was significantly correlated to the P fractions, indicating that the application of PSB had affected the bacterial community structure. In addition, Structural Equation Model (SEM) analysis showed that there was a causal relationship between the various visual variables. SEM confirmed the response relationship between bacterial communities and P components. Based on these results, we concluded that the application of PSB increased the sensitivity of P components, especially Olsen-P and MBP, to soil microorganisms. The application of PSB is an effective method to improve P utilization.