Rice cultivation is widely used to improve saline-sodic soils in Northeast China. However, the chronological effect of rice cultivation on soil fungal communities has not been studied. Therefore, this study investigated the variation of soil fungal communities in different rice cultivation years. Compared with the blank area, the rice cultivation for 20 years significantly decreased the pH and electrical conductivity by 16.6% and 70.1%, while significantly increased the soil organic carbon and available phosphorus by 90.6% and 17.4 times, respectively. Meanwhile, the relative abundance of Ascomycota and Basidiomycota significantly decreased and increased after rice cultivation, respectively. Moreover, some genera of arbuscular mycorrhizal fungi (AMF), e.g. Corymbiglomus, Glomus, and Rhizophagus, and pathogenic fungi (Thanatephorus cucumeris) disappeared, while Dentiscutata (one genus of AMF) appeared after rice cultivation. In addition, the fungal richness significantly increased when the rice cultivation less than 15 years and the fungal communities were similar between 15 and 20 years. Our findings showed that rice cultivation improved the nutrient availability and reduced salinity-alkalinity stress of sodic soils. After the rice cultivation for 15 years, the soil fungal community tended to be stable.

Converting natural vegetation to other types of land utilization is presently the most common land use change around the world. Conversion of grassland plays an important role in estimating the regional nutrients budget and assessing ecological effects. However, few studies have estimated the impacts of grassland conversion on soil nutrients under different soil pedogenic horizons. This study selected three sites, which were covered by grassland, shelterbelt, and cropland. The study evaluated the effects of grassland conversion and soil pedogenic horizon (to a depth of 100 cm) on the soil organic carbon (SOC), soil total nitrogen (STN), and soil total phosphorus (STP) concentrations and stocks in the Chinese Chernozem region. The results revealed that significant (p < 0.05) differences were seen after grassland conversion for concentrations and stocks of SOC, STN, and STP. The transformation from grassland to shelterbelt and cropland plantations caused soil carbon and soil nitrogen losses but caused soil phosphorus accumulations. Moreover, conversion of grassland made SOC, STN, and STP all drop below the B_k-horizon. Changes in the SOC and STP on an area basis were the greatest after conversion of grassland to cropland, for concentrations of −16% and 26% and for stocks of −15% and 32%, respectively. Land use change and soil pedogenic horizon primarily influenced the distribution patterns of nutrients concentrations and stocks. However, grassland conversion effects on nutrients were mainly at surface horizons. Soil properties, such as calcium carbonate (CaCO₃) and soil texture, affected the nutrients from the B_k-horizon to the C-horizon. This study indicates that land use management policies should protect natural grasslands to minimize losses of SOC, STN, and STP.

The implementation of scientific cultivation practices on soda saline–alkali land plays a pivotal role in safeguarding food security and promoting sustainable agro-economic development at the regional scale. However, there exists a critical knowledge gap regarding the optimization of tillage strategies for rain-fed maize (Zea mays L.) cultivation across heterogeneous saline–alkali soil matrices. This study selected meadow alkaline soil, saline meadow soil, and mild saline–alkali soil under the typical micro-landscape morphological characteristics of soda saline–alkali soil in the Songnen Plain as experimental plots. Under three tillage methods, namely no tillage (NT), rotary tillage + no tillage (RT), and subsoiling + rotary tillage + no tillage (SRT), the effects of the tillage methods on the soil physical properties at the seedling stage, root development at the V6 stage, and yield at the R6 stage during the process of cultivating maize in different types of soils were analyzed. The research results showed that compared with NT and RT, the SRT treatment better improved the physical properties, such as penetration resistance and the bulk density in micro-spaces (0–40 cm), of different soil types. The SRT treatment had a positive impact on the root development of maize seedlings in saline meadow soil and meadow alkaline soil. In terms of yield, compared with the NT treatment, the SRT treatment in meadow alkaline soil and saline meadow soil had a positive effect on the plant height, root dry weight, 1000–grain weight, and grain yield of maize. The increases in maize grain yield were 27.94% and 13.24%, respectively. Compared with NT, the differences in the effects of the SRT and RT treatments on maize yield in mild saline-alkali soil were the smallest, being 6.98% and 4.77%, respectively. The relevant results provide guidance on tillage methods and a theoretical basis for improving the properties of different types of soda saline–alkali soils and increasing maize yield.

The tillage method in farming systems is essential to develop strategies to increase fertilizer uptake by plant roots and to avoid environmental pollution. The field study aimed to investigate the characteristics of nitrogen and enzyme activities in rhizosphere soil with different tillage methods. Four treatment plots applied with fertilizers were established: continuous rotary tillage (CR), plowing-rotary tillage (PR), continuous no-till (CN) and ploughing-no-till (PN). The total content of nitrogen in chernozem was high during early stages of plant growth, and then it decreased with the maize growth. In the rhizosphere soil, the total N accounted 1314.45, 1265.96, 1120.47, 1120.47, 1204.05 mg·kg⁻¹ of CR, PR, CN, and PN, respectively, which were markedly greater than that of non-rhizosphere soil (1237.52, 1168.40, 984.51, 1106.49 mg·kg⁻¹ of CR, PR, CN, and PN, respectively). At first growth stages, content of NH₄⁺-N and NO₃⁻-N in two soil regions was low, then increased gradually, which followed the order of CR < PR < PN < CN. The rhizosphere soil showed slightly higher concentration of NH₄⁺-N and NO₃⁻-N than non-rhizosphere. The soil enzymes were more active in the rhizosphere soil than that of non-rhizosphere during the whole maize growth stages. Due to minimal damage to the soil environment and optimal soil moisture and temperature, the urease and catalase activities were greatest in the rhizosphere for CN treatment. Therefore, CN was recommended to be used by farmers for the improvement of macronutrient availability and soil enzyme activities in the soil.