To study the characteristics of the β–glucosidase enzymatic reaction in wheat field soil under the condition of reducing the application of chemical fertilizer, five fertilization treatments were established, including no fertilizer (CK), chemical fertilizer (F), organic fertilizer (OF), 25% organic fertilizer plus 75% chemical fertilizer (25% OF), and 50% organic fertilizer plus 50% chemical fertilizer (50% OF). The activity of β–glucosidase and its kinetic and thermodynamic characteristics were analyzed by using microplate p–nitrophenol colorimetry. The results showed that the V_max values of soil β–glucosidase in the organic substitution of chemical fertilizer treatment were higher than those in the chemical fertilizer and no fertilizer treatments, and the K_m values were lower than those in the chemical fertilizer and no fertilizer treatments at the different growth stages. The V_max value in the 25% OF treatment was the highest at the jointing stage and that of the OF treatment was the highest at the booting stage; the K_m value in the 50% OF treatment was the lowest at the different growth stages. Compared with the chemical fertilizer and no fertilizer treatments, the application of organic fertilizer effectively reduced thermodynamic parameters such as E_a, Q₁₀, ∆H, ∆G, and ∆S at the jointing and booting stages of wheat. The thermodynamic parameters in the 25% OF treatment were the lowest at the jointing stage and those in the OF treatment were the lowest at the booting stage. A reasonable amount of organic fertilizer is more beneficial to enzymatic reactions and improves the soil quality and the ability to supply nutrients to wheat cultivation.

Soil organic carbon (SOC) and microbial biomass carbon (MBC) are highly correlated with enzyme activities. Specific enzyme activities can exclude the autocorrelation between enzyme activity and SOC and MBC. However, the responses of absolute and specific enzyme activities to saline–alkali properties remains unclear. In this study, the absolute and specific enzyme activities of cellobiose hydrolase, β-glucosidase, arylsulfatase, alkaline phosphatase, and urease were measured in soils with 10, 15, 18, 21, and 26 years of organic fertilizer application in contrast to soils without organic fertilizer application. The results showed that long-term organic fertilizer application led to significantly increased in the absolute and specific enzyme activity and decrease in pH, electrical conductivity (EC), exchangeable sodium percentage (ESP), as well as sodium adsorption ratio (SAR_5:1). In the structural equation model (SEM), the EC extremely limited the geometric mean of specific enzyme activity per unit of MBC (MBC-GMSEA) (path coefficient, −0.84, p < 0.001). Pearson’s correlation analysis showed that the correlations between EA/MBC and pH, EC, ESP, and SAR_5:1 were higher than between the absolute soil enzyme activity and pH, EC, ESP, and SAR_5:1. Of the parameters tested, EA/MBC was a more sensitive index to reflect the improvement effect of organic fertilizer on soils and evaluate the saline–alkali barrier.

Inversion tillage and organic fertilizer application can break the plow pan and improve soil quality. However, the effects of combining these practices on the soil microbial resource limitation and maize yield in Haplic Chernozem are unclear. In this research, a field experiment was established in 2018, and soil samples were collected in 2021 in Longjiang County in Northeast China, which is a Haplic Chernozem region. Four treatments comprising conventional tillage (T15), conventional tillage with organic fertilizer (T15+M), inversion tillage (T35), and inversion tillage with organic fertilizer (T35+M) were randomly arranged with four replications. Compared with T15 and T15+M treatments, soil bulk density significantly decreased by 11.1–16.3% in the 15–35 cm layer under T35 and T35+M treatments, accompanied by the improvement in soil pore structure (e.g., soil porosity, circularity, and Euler number). T15+M treatment significantly increased soil organic carbon and soil nutrient contents by 11.1–16.3% and 3.9–24.5% in the 0–15 cm layer compared with other treatments. However, soil organic carbon, total nitrogen, available phosphorus content, microbial biomass, and enzymatic activities reached the maximum values in the 0–35 cm layer under T35+M treatment. In addition, T35+M treatment had the highest maize yield and sustainable yield index. Extracellular enzymatic stoichiometry suggested that soil microorganisms are generally co-limited by carbon and phosphorus in Haplic Chernozem. However, T35+M treatment significantly reduced soil microbial resource limitation, which was one important factor impacting maize yield and sustainability. Random-forest and partial least-squares path modeling showed that T35+M treatment could reduce soil microbial resource limitation and increase the stability and sustainability of the maize yield by improving soil available nutrients, microbial biomass, and pore structure. Therefore, the incorporation of inversion tillage and organic fertilizer is a suitable soil management practice in view of increasing soil quality and crop yields in a Haplic Chernozem region.

Soda saline–alkaline soils have seriously restricted the sustainable development of agriculture in the Songnen Plain, China. Applying soil amendments has proven to be an effective remediation strategy for these sodic soils; however, conventional amendments face limitations, including prolonged remediation periods and the potential to cause secondary pollution upon misapplication. In this study, we combined three different amendments and applied them as four distinct treatments—citric acid + nano-silica (CS), citric acid + nano-silica + humic acid (CSH), nano-silica + humic acid (SH), and citric acid + humic acid (CH)—with no amendment used as the control (CK). The effects of these treatments on improving the soda saline–alkali soil was evaluated using a field positioning experiment. The results indicate that, compared to the CK treatment, applying the amendments significantly increased the concentrations of available phosphorus (AP) (9.19% to 44.43%) and organic matter (SOM) (3.53% to 16.48%) while decreasing alkalinity and salinity indicators (pH, EC (electrical conductivity), ESP (exchangeable sodium percentage), SAR (sodium adsorption ratio), and TA (total alkalinity)) and soil alkali stress ions (water-soluble and exchangeable Na⁺, CO₃²⁻, and HCO₃⁻). The partial least squares path modeling analysis (PLS-PM) demonstrated that the application of the amendments improved soil quality by changing its alkalinity and ion composition, thereby increasing the maize yield (from 3.01% to 9.80%).

The NH₃, N₂O and CO₂ emissions from farmland soil pose a great threat to the environment, and the application of organic fertilizer and other reasonable fertilization measures can reduce soil gas emissions. However, research into greenhouse gas emissions and environmental benefits under the combined measures of partial substitution of organic fertilizer and phased application of chemical fertilizer is limited. Herein, a field experiment involving soil gas emission monitoring was conducted to study the effects of chemical fertilizer application in stages on Mollisols’ gas emissions and environmental benefits based on the partial replacement of chemical fertilizer with organic fertilizer. Five treatments were set up, including conventional nitrogen application (CF); no nitrogen application (N0); and one-stage (N1), two-stage (N2) and three-stage (N3) application of chemical nitrogen based on 25% of chemical nitrogen being replaced with organic fertilizer. The results showed that N1 had the best emission reduction. Compared with CF, N1 reduced NH₃ volatilization and N₂O and CO₂ emission accumulation by 27.64%, 12.09% and 15.48%, respectively. Compared with N2 and N3, N1 could better reduce the soil urease, nitrate reductase, catalase and β-glucosidase activities, reduce the rate of the conversion of urea and organic carbon, increase the content of NH₄⁺-N in the soil and reduce the NH₃ volatilization rate and N₂O and CO₂ emission rates. A comprehensive analysis showed that N1 showed the best effects in reducing the soil gas emission rate, and environmental cost.

Aims Many previous studies have focused on crop yields, but there is a knowledge gap regarding the environmental benefits of phased fertilization and organic substitution. To study the effects of phased fertilization and organic substitution on soil gas emissions and spring wheat yields, a field experiment was conducted using Mollisols. Methods Five treatments were set up: conventional nitrogen application (CF); no nitrogen application (N0); one-time (N1), two-stage (N2) and three-stage (N3) application of chemical nitrogen based on 25% of chemical nitrogen being replaced by organic fertilizer. The changes in NH₃ volatilization, N₂O and CO₂ emissions, soil-related carbon and nitrogen invertase activities and soil carbon and nitrogen contents under different treatments were analyzed and compared. Result The results showed that N1 had the best emission reduction and yield increase effects. Compared with CF, N1 reduced NH₃ volatilization, N₂O and CO₂ emissions accumulation by 28.94%, 10.29% and 17.21%, respectively, and increased spring wheat yield by 21.33%. Compared with N2 and N3, N1 could better reduce soil urease, nitrate reductase, catalase and β-glucosidase activities, reduce the conversion rate of urea and organic carbon, increase the content of NH₄⁺-N in soil, and reduce the NH₃ volatilization rate and N₂O and CO₂ emissions rates. Conclusions Comprehensive analysis showed that the N1 treatment had the best effect on reducing the soil gas emission rate, emission reduction rate and environmental cost as well as on increasing yield.