Saline–alkali soil is common in north China, especially in the Datong district in north Shanxi province. Improving the soil will benefit the environment and society. Graphene oxide (GO) has been shown to benefit agricultural and forest soils. Herein, we explore three different experimental conditions of CK (CK means irrigated with tap water), CJ (CJ means 0.2 g of bacteria addition and irrigated with tap water), and CJ25 (CJ25 means 0.2 g of composited bacteria plus 25.0 mg/L of GO added and irrigated with tap water) for saline–alkali soil by the addition of optimized amounts of GO and external bacteria. Our results show that the addition of 25.0 mg/L GO and microbial agents increases the number of bacteria and fungi in the soil and improves the species abundance of bacteria and fungi in the saline–alkali soil, while having little effect on species richness. The GO and bacterial treatment increased the abundance of Proteobacteria, Actinobacteriota, Chloroflexi, Pseudomonas, Ascomycota, Mortierella, and Fusarium. These bacteria have been shown to produce proteolytic enzymes and cellulases that decompose lignin and cellulose in litter, and thus play important roles in carbon and nutrient cycling. The addition of GO and microorganisms provides a viable way to improve saline–alkali soils.

Soil compaction, a result of mechanical resistance to penetration, has a direct impact on yield potential by limiting root access to water and nutrients. Factors such as inadequate crop rotation, intensive mechanization, and trampling by animals contribute to compaction. Mitigation strategies include crop rotation, control of machinery traffic, the use of cover crops, and the use of mechanical techniques. Geostatistical methods in pedostatistics evaluate the spatial variability of soil properties. The aim of this study was to determine the penetration resistance in five soil layers (10, 20, 30, 40, and 50 cm), identify critical compaction regions, and quantify the economic impact of compaction management in a 230 ha farm in Alegrete, Brazil. A digital penetrometer was used to measure resistance and semivariograms were calculated using classical and robust estimators for interpolation. The evaluation of the economic impact took into account the variable cost differences between the total area and the area required for compaction. The analysis showed a gradual increase in compaction from the surface to the subsoil, with a highly compacted zone occurring at 20–30 cm, signaling the need for monitoring and intervention. The dependency analysis showed a well-defined structure. The results show that geostatistical tools can be used in the assessment of soil penetration resistance, especially in layers from 10 to 20 cm. An efficient identification and quantification of compacted zones within the cultivation area was achieved. This approach proves to be economically viable, especially in extensive farming, suggesting a wide application in agricultural compaction management.

We conducted incubation experiments with paddy soil collected from a long-term field experiment to explore the effect of Chinese milk vetch (Astragalus sinicus L., CMV) application on potential nitrogen (N) denitrification (PDA), nitrification (PNA), mineralization (PNM), soil chemical properties, microbial communities, enzyme activities, yields, and nutrient uptake of rice under different fertilization treatments. Five treatments were included: no chemical fertilizers (C₀), chemical fertilizers (C₁₀₀), Chinese milk vetch (M), CMV combined with 100% chemical fertilizers (MC₁₀₀), and with 80% chemical fertilizers (MC₈₀). Results showed that the M, MC₁₀₀, and MC₈₀ treatments significantly increased PNM and PNA compared with the C₁₀₀ treatment (P < 0.05). Meanwhile, the CMV application significantly increased total N, microbial biomass N, and carbon (C) concentrations, the abundances of the bacterial phylum Actinobacteria and the genera Bradyrhizobium, Mycobacterium, Streptomyces, and Reyranella, N-acetyl-glucosaminidase (NAG) activity, yields, and N nutrient uptake of rice grain compared with the C₁₀₀ treatment (P < 0.05). Correlation analyses indicated that grain yield and N uptake of rice, soil total N, microbial biomass C and N, the bacterial phylum Actinobacteria, the genera Bradyrhizobium, Mycobacterium, Streptomyces, Reyranella, and NAG were significantly correlated with PNM under different fertilization regimes, while microbial biomass C and N, Actinobacteria, Bradyrhizobium, and Reyranella were positively related to PNA (P < 0.05). Together, the application of CMV alone or in combination with chemical fertilizers can improve soil properties and rice growth, which may accelerate N mineralization and nitrification in this soil.

The factors influencing the spatial distribution of fungal communities are commonly examined over large spatial scales but not at smaller scales. Given this, the extent to which soil properties and topographic features contribute to the diversity and distribution of fungal communities in an agricultural field needs to be further explored. We investigated the spatial distribution of soil fungal community composition from an ∼1100 m long transect with 83 sampling points in a commercial potato field with a rolling landform. The relative abundance of Ascomycota, Basidiomycota, and Mortierellomycota showed medium to strong spatial dependence with an autocorrelation range varying from ∼43 to 92 m, similar to the autocorrelation range of soil properties and topographic features. Most of the variability in fungal and saprotrophic community composition was explained by soil properties (15% and 11%, respectively) and spatial distance (16% and 15%, respectively) while topographic features contributed 8% and 5% of variability to total fungi and saprotrophic community composition, respectively. The fungal and saprotrophic community compositions were correlated with soil organic carbon, pH, and slope curvature, however, richness and Pielou’s evenness of the fungal communities and fungal biomass were not correlated with soil properties or topographic features. The results suggest that the spatial variation in fungal and saprotrophic community composition in response to soil properties and topographic features in this agricultural landscape was due to differences in assemblages of fungal amplicon sequence variants (ASVs) but not in differences in the number of fungal ASVs or fungal biomass measured using phospholipids fatty acids.

Improving the concentrations and bioavailability of micronutrients, especially iron (Fe) and zinc (Zn), in crop grains is important to alleviate their deficiencies in humans. Inoculating crops with arbuscular mycorrhizal fungi (AMF) can potentially enhance soil nutrient supply and crop yield, but the effectiveness is influenced by soil factors, particularly soil phosphorus (P) availability. A greenhouse pot experiment was conducted to evaluate the effect of a commercial AMF product on spring wheat (Triticum aestivum L.) yield and grain concentrations of Zn and Fe under different soil P addition levels (0, 5, and 20 mg P kg^–1 dry soil). Results showed that AMF inoculation significantly increased root colonization rate of wheat across all P addition levels. Wheat growth, as evidenced by dry weights of shoot and grain, was significantly enhanced by AMF and high P addition treatments. AMF inoculation did not affect grain Zn concentration, but significantly increased grain Fe concentration compared to the un-inoculated control. As expected, P addition resulted in a significant reduction in grain concentrations of Fe and Zn, primarily due to a growth dilution effect. An integrated analysis using the radar plot concludes that AMF inoculation is most effective in increasing crop yield and grain micronutrient concentrations when soil P levels are low. Importantly, while adequate P supply is crucial for maintaining crop productivity, it may decrease grain micronutrient availability without complementary strategies.

Given potato farm cropping history, the recent introduction of C4 cover crops may provide an in situ opportunity to track their residues by δ¹³C techniques. From 2019 to 2022 soil (0–15 cm) samples were collected on Prince Edward Island potato farms from 15 paired strips of sorghum sudangrass (SS) and C3 crops. Under C3 crops, soil δ¹³C was remarkably uniform at −27.7‰ ± 0.26‰, while SS cover cropping (aboveground biomass −12.8‰) significantly enriched soil δ¹³C values to −27.4‰ ± 0.38‰. This study demonstrates proof of concept that δ¹³C techniques can quantify the dynamics of C4 cover crop residues in potato farm soils.