Organic fertilizer can improve soil management and alleviate soil nutrient loss caused by excessive fertilization. This study determines a fertilization scheme that can achieve high and stable crop yield and effective soil fertilization by exploring the effects of different organic fertilizer proportions on soil nutrient content, fertilizer utilization rate, and wheat yield. The experiment was conducted from 2018 to 2020 using the Xinchun 38 wheat variety and gray desert soil. The experiment used six treatments: no fertilizer (CK), with normal nitrogen and phosphorus fertilizer (CF). The amount of conventional chemical nitrogen fertilizer was reduced by 6%, 12%, 18%, and 24%, respectively, and supplemented with organic nitrogen fertilizer of the same proportion. The experimental treatment codes were SF6, SF12, SF18, and SF24, respectively. Plant samples from six wheat growth stages and 0–20 cm soil samples were collected to analyze the nitrogen and phosphorus content and organic matter; dry matter accumulation, crop yield, and yield components were measured at the harvest stage. Soil available nitrogen, phosphorus, potassium, and soil organic matter contents increased with the replacement ratio of organic fertilizer after three consecutive years of application. The available nutrients and organic matter in soil treated with SF18 and SF24 were significantly higher than those in CK and CF. The dry matter accumulation and nutrient accumulation of wheat increased with increasing organic fertilizer replacement rates of SF18 and SF24, respectively. Nitrogen and phosphorus fertilizer utilization rates, partial productivity, and agricultural use efficiency also increased, with the SF18 and SF24 treatments having higher organic fertilizer replacement rates than those in the other treatments. The number of ears, 1000-grain weight, and yield of wheat treated with SF18 treatment produced the best results. Therefore, continuously using organic fertilizer as a partial replacement for conventional fertilizer can increase wheat growth and soil nutrient availability, which can improve the utilization rate of fertilizer, thereby achieving stability and even a significant increase in yield.

Sugar beet production is threatened by beetroot rot, which can be triggered by consecutive monoculture. Previous studies have shown the beneficial function of microbes affiliated with different plant compartments in inhibiting various plant pathogens. However, whether sugar beet root can recruit particular microbes at the risk of beet rot is still unclear. Therefore, this study explored the composition and community structure of bacteria and fungi of the different compartments (endosphere root, rhizosphere, bulk soil) under two farming modes (monoculture and rotation). Our result showed that the farming mode significantly affected the community structure of bacteria and fungi in bulk soil. In the rhizosphere, the community structures of bacteria between the two varieties were similar under rotation mode, and markedly different under monoculture mode. The bacterial and fungal diversity in the rhizosphere and endophytic root of the rot-suppressive variety was higher than in the rot-conducive variety. Under monoculture mode, the beneficial microbes as biomarkers were enriched in the rot-resistant variety, e.g., operational taxonomic units (OTUs) affiliated to the genus of Sordariomycetes, Cordycipitaceae, Lecanicillium, Plectosphaerellaceae, S085, Pedosphaeraceae in the rhizosphere and the genus of Actinobacteria, and Pseudonocardia, Exobasidiomycetes in the endophytic root, while for the rot-conducive variety, OTUs affiliated to the genus of Chitinophagaceae, Flavisolibacter in the rhizosphere and the Novosphingobium, Sphingobacterium, Tilletiopsis_washingtonensis, and Flavobacterium in the endophytic root. The network analysis showed that OTUs affiliated to the order of Saccharimonadales, Anaerolineae, the family of Saprospiraceae, the genus of Subgroup_10 (belonging to the family of Thermoanaerobaculaceae), Lysobacter, and AKYG587 were the keystone taxa in the rot-suppressive variety, while both beneficial and harmful microbes in the rot-conducive variety, such as Pedobacter, Ferruginibacter, and P3OB-42, were present. The variation in soil pH was shown to be the critical contributor to the microbial difference. In summary, the farming mode is critical in shaping bulk soil microbial structure by changing soil pH. Under monoculture mode, the rot-suppressive variety has more microbial diversity in both the rhizosphere and endophytic root, and enriched different beneficial microbes relative to the rot-conducive variety; the underlying mechanisms and associations of critical microbes are worth further investigation.

This study aimed to investigate the effects of varying organic fertilizer substitution ratios on soil nutrients, organic matter, enzyme activities, and microbial communities, with the goal of optimizing fertilization strategies, enhancing soil fertility, and promoting sustainable agricultural development. Experimental Design: A three-year consecutive field experiment was conducted using an equal nitrogen application design with the following treatments: no fertilizer control (CK), conventional farmer fertilization (CF), and organic fertilizer substitutions at 10% (SF1), 20% (SF2), 30% (SF3), 40% (SF4), and 50% (SF5) of chemical fertilizer. Key soil parameters were analyzed, including available nutrients (alkali-hydrolyzable nitrogen, available phosphorus, and available potassium), organic matter content, enzyme activities (e.g., urease and phosphatase), and microbial community structure (bacterial and fungal diversity and abundance). Results: Partial substitution with organic fertilizer significantly enhanced soil available nutrient content and organic matter levels, with the 30–50% substitution treatments (SF3–SF5) demonstrating particularly pronounced effects. Moreover, organic fertilizer amendments markedly improved soil enzyme activities and altered microbial community composition, notably increasing the abundance of beneficial taxa such as Gemmatimonadota. These modifications further facilitated soil nutrient cycling and utilization efficiency. Conclusions: The findings demonstrate that appropriate organic fertilizer substitution not only improves soil fertility but also enhances microbial activity, thereby creating a healthier soil environment for crop growth. This study provides critical theoretical and practical insights for optimizing fertilization regimes, reducing chemical fertilizer reliance, and improving soil ecosystem functionality.