Avoiding soil degradation and improving crop productivity could be achieved by performing sustainable soil nutrient management with an appropriate understanding of soil properties’ spatial variability. The present fertilizer recommendations for the region where the study area is located are typically symmetric for large regions. This leads to the under-application of fertilizers in zones with low nutrient contents and over-application in zones with high nutrient contents. Therefore, this study was conducted to assess soil management zones (MZs) in the study area for effective soil nutrient management and to evaluate soil properties’ spatial variability. A total of 100 geo-referenced soil samples were collected at a depth of 0–20 cm, processed and analyzed for pH, available nitrogen (AN), available phosphorus (AP), available potassium (AK), soil organic carbon (SOC), total nitrogen (TN) and total phosphorous (TP), while C:N, C:P and N:P ratios were calculated. Soil properties’ coefficients of variation (CVs) widely varied from low (1.132%) to moderate (45.748%). Ordinary kriging and semi-variogram analysis showed differed spatial variability patterns for the studied soil properties with spatial dependence ranged from weak to strong. MZs were delineated by performing principal component analysis (PCA) and fuzzy K-means clustering. Four PCs with eigen values more than 1 dominated 84.44% of the total variance, so they were retained for clustering analysis. Three MZs were delineated based on the two criteria modified partition entropy (MPE) and fuzzy performance index (FPI). The studied soil properties differed significantly among MZs. Thus, the methodology used for MZ delineation could be used effectively for soil site-specific nutrient management for avoiding soil degradation concurrently with maximizing crop production in the study area.

Soil acidification is a severe environmental problem around the world. Soil pH buffering capacity (pHBC) is the intrinsic factor affecting the soil acidification rate and is intensively impacted by anthropogenic and natural conditions. However, composite assessments of the effects of land use and soil type on soil pHBC are still limited. Therefore, we collected samples of five soil types (red soil, lateritic red soil, latosol, paddy soil and acid sulphate soil) from two land use patterns of agricultural and adjacent forest fields at different depths (0–10 cm, 10–20 cm and 20–30 cm) in South China, aiming to investigate the effects of land use and soil type on soil pHBC in this region. The results show that land use, soil type and their interactions greatly influence soil pHBC and physico-chemical properties. Forest soils have a significantly higher pHBC (11.40–49.50 mmol·kg⁻¹ soil·unit⁻¹ pH), cation exchange capacity (CEC), exchangeable Al³⁺ (EAl³⁺) and clay content than agricultural soils. Acid sulphate soil has the highest pHBC (49.27–117.83 mmol·kg⁻¹ soil·unit⁻¹ pH) values and exchangeable acid (EA) content among all investigated soil types, whereas lateritic red soil has the lowest pHBC (10.56–31.71 mmol·kg⁻¹ soil·unit⁻¹ pH). In agricultural fields, soil pHBC is positively related to CEC, soil organic carbon (SOC) and EA, indicating that agricultural soils may be in a cation exchange buffering stage. The soil pHBC of forest fields is positively correlated with SOC and EAl³⁺, implying that forest soils may be in the Al buffering stage. In conclusion, soil pHBC would vary with different land use forms and soil types, in which a series of key complex physico-chemical processes and interactions would occur to regulate soil pH buffering capacity.

Due to rapid population growth and pressure on water resources, it is necessary to use economic and non-traditional techniques for irrigation. One of these techniques is the use of salt water after treatment with a magnetic force. A simulation experiment was conducted with soil columns using three quantities of saline water: 0, 3, and 6 g L⁻¹ (S₀, S₃, and S₆). Magnetic forces of 0, 1000, 2000, 3000, 4000, 5000, 6000, and 7000 gauss were used to study the effects of magnetic forces on leachate and soil physicochemical properties at different depths. The results at all soil depths showed that the pH decreased with increasing salinity from S₀ to S3 and S₆ by an average of 8.44, 8.28, and 8.27%, respectively. Soil EC decreased significantly with depth by 10–35%. The maximum SAR, SSP, and CROSS values (16.3, 51.1, and 17.6, respectively) were reported when no magnetic force was used, while the lowest values (13.9, 49.9, and 15.3) were recorded when using 3000 gauss under S₆ within the soil profile. Magnetizing the water halved the EC of the leachate under S₀, while it decreased the EC by 12.4% under S3. Increasing the magnetic force enhanced the leachate SAR, SSP, and CROSS values by 4.9–20.4% on average under S₃ and S₆. Magnetic forces augmented the hydraulic conductivity at the same salinity level and with increasing salinity, resulting in an increment of 50% at S₃ and S₆ compared with S₀. After nine hours, the maximum cumulative infiltration rate was under 1000 and 4000 gauss. Our results demonstrated the important effects of magnetically treated irrigation water and could therefore support its application in agriculture under conditions of low water resources and quality.