The decline in soil quality is becoming a significant process of soil degradation. Optimizing organic fertilizer incorporation practices in cropland is essential to enhancing crop productivity and soil health. However, that requires a comprehensive understanding of crop yield and soil quality reaction across an application gradient of organic fertilizer. We investigated the effect of organic fertilizer incorporation practices on crop yield, soil quality, and fauna feeding activity from fluvo-aquic soils on wheat (Triticum aestivum)-maize (Zea mays) rotation field. The six treatments included were unfertilized N control (UC), traditional chemical fertilizer application (TF, 600 N kg ha⁻¹ year⁻¹), and recommended chemical fertilization (RF, 400 N kg ha⁻¹ year⁻¹) with no organic fertilizer application rate, low-level 15.0 (RFLO), medium-level 30.0 (RFMO), and high-level 45.0 t ha⁻¹ year⁻¹(RFHO) application, respectively. The research findings show that the yield with organic fertilizer incorporation treatments increased 26.4%–44.6% for wheat and 12.5%–40.8% for maize compared to RF plots. The long-term organic fertilizer incorporation rate increased organic carbon from 54.7% to 110.6% versus UC plots and 27.9%–74.0% versus chemical fertilizer (TF and RF) treatments, and the total nitrogen content of soil increased from 41.8% to 59.2%, and 24.6%–39.2%. The long-term inorganic fertilizer combined with organic fertilizer incorporation practices significantly enhanced soil sucrose (30.1%–51.9%), urease (28.4%–38.3%), and β-1,4-glucosidase (34.6%–122.4%) activity. Still, nitrite reductase, polyphenol oxidase, and catalase significantly lower 27.3%–49.9%, 8.5%–26.3% and 23.3%–34.3% than single applications of inorganic N fertilizer groups. Meanwhile, the results showed that organic fertilizer incorporation practices improved soil fauna feeding activity by 35.2%–42.5%, and the excessive application of inorganic N fertilizer reduced the activity level of soil fauna.

According to its characteristics, biochar originating originating from biomass is accepted as a multifunctional carbon material that supports a wide range of applications. With the successfully used in reducing nitrate and adsorbing ammonium, the mechanism of biochar for nitrogen fixation in long-term brought increasing attention. However, there is a lack of analysis of the NH₄⁺-N adsorption capacity of biochar after aging treatments. In this study, four kinds of acid and oxidation treatments were used to simulate biochar aging conditions to determine the adsorption of NH₄⁺-N by biochar under acidic aging conditions. According to the results, acid-aged biochar demonstrated an enhanced maximum NH₄⁺-N adsorption capacity of peanut shell biochar (PBC) from 24.58 to 123.28 mg·g⁻¹ after a H₂O₂ modification. After the characteristic analysis, the acid aging treatments, unlike normal chemical modification methods, did not significantly change the chemical properties of the biochar, and the functional groups and chemical bonds on the biochar surface were quite similar before and after the acid aging process. The increased NH₄⁺-N sorption ability was mainly related to physical property changes, such as increasing surface area and porosity. During the NH₄⁺ sorption process, the N-containing functional groups on the biochar surface changed from pyrrolic nitrogen to pyridinic nitrogen, which showed that the adsorption on the surface of the aged biochar was mainly chemical adsorption due to the combination of π-π bonds in the sp² hybrid orbital and a hydrogen bonding effect. Therefore, this research establishes a theoretical basis for the agricultural use of aged biochar.

Although aboveground biodiversity has been extensively studied, the impact of nutrient enrichment on soil microbial populations remains unclear. Soil microorganisms serve as important indicators in shaping soil nutrient cycling processes and are typically sensitive to nutrient additions. For this, we employed a factorial combination design to examine the impact of nutrient additions on the composition and function of soil bacteria in a temperate steppe. Nitrogen addition promoted the growth of copiotrophic bacteria (Proteobacteria, Firmicutes, and Bacteroidota) but inhibited the growth of oligotrophic bacteria (Acidobacteria, Chloroflexi, and Verrucomicrobiota). Phosphorus addition alleviated phosphorus deficiency, resulting in a decrease in the abundance of phoD-harboring bacteria (Actinobacteria and Proteobacteria). Significant enhancement of soil bacterial alpha diversity was observed only in treatments with added phosphorus. Changes in NO₃⁻-N, NH₄⁺-N, available phosphorus, and dissolved organic carbon resulting from nutrient addition may have a greater impact on microbial community structure than changes in soil pH caused by nitrogen addition. Moreover, nutrient addition may indirectly impact microbial ecological function by altering nutrient availability in the soil. In conclusion, our study suggests that soil nutrient availability, particularly available phosphorus, affects soil bacterial communities and potentially regulates the biogeochemical cycles of soil ecosystems.

Major problems in China’s pursuit of sustainable agricultural development include inadequate, low-quality soil and water resources, imbalanced regional allocation and unreasonable utilization of resources. In some regions, overexploitation of soil resources and excessive use of chemicals triggered a web of unforeseen consequences, including insufficient use of agricultural resources, agricultural non-point source pollution and land degradation. In the past decade, China has changed its path of agricultural development from an output-oriented one to a modern, sustainable one with agricultural ecological civilization as its goal. First, the government has formulated and improved its laws and regulations on soil resources and the environment. Second, the government has conducted serious actions to ensure food safety and coordinated management of agricultural resources. Third, the government has planned to establish national agricultural high-tech industry demonstration zones based on regional features to strengthen the connection among the government, agri-businesses, scientific community and the farming community. As the next step, the government should improve the system for ecological and environmental regulation and set up a feasible eco-incentive mechanism. At the same time, the scientific community should strengthen the innovation of bottleneck technologies and the development of whole solutions for sustainable management in ecologically fragile regions. This will enhance the alignment between policy mechanisms and technology modes and effectively promote the sustainable development of agriculture in China.

CO₂ fixation by autotrophic microbes has a significant effect on the carbon cycle in temperate grasslands. Nitrogen (N) deposition in soil has been steadily increasing for decades, which has consequences for soil microorganisms. However, the impact of this deposition on the diversity and abundance of CO₂-fixing soil microorganisms remains unclear in temperate grasslands. In the present study, the cbbL gene, a key gene in the Calvin–Benson–Bassham cycle that encodes the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, was used to study CO₂-fixing microbes under different rates of N addition (0, 15, 30, 50, 100, and 150 kg N ha^–1 yr^–1) in a 9-year field experiment in a temperate grassland. The results showed that N addition led to significant reductions in cbbL gene abundance and genetic diversity and altered cbbL gene community composition. High N addition enhanced the relative abundances of Acidiferrobacterales and Rhizobiales but reduced those of Burkholderiales and Rhodobacterales. Structural equation modeling further revealed that N addition primarily reduced cbbL genetic diversity by increasing the soil NO₃-N content and decreasing the soil pH. N addition indirectly reduced cbbL gene abundance, possibly by increasing the soil N/phosphorus (P) ratio and decreasing the soil pH. These findings suggest that N addition increases the soil available N and causes soil acidification, which may inhibit growth of CO₂-fixing microbes to some extent.