To identify suitable soil amendments for the understory cultivation of Polygonatum kingianum and to address issues such as soil acidification, nutrient imbalance, and exacerbated soil-borne diseases resulting from continuous cropping of preceding Panax notoginseng, this study utilized two-year-old P. kingianum seedlings as experimental material. Three soil amendments—quicklime, wood ash, and tetramycinwere applied at three different concentration levels. After one year of planting, the yield, quality, and soil physicochemical properties of P. kingianum were measured to evaluate the effects of these amendments on agronomic traits, nutrient accumulation, and soil ecological and physicochemical characteristics. The results demonstrated that all tested amendments improved seedling survival rates and reduced the incidence of root rot in P. kingianum. All treatments effectively reduced the incidence of root rot in Polygonatum kingianum, with wood ash showing the greatest reduction (60%–80%), followed by quicklime (48%–72%) and tetramycin (58%–68%). A comprehensive evaluation using the entropy-weighted TOPSIS method indicated that all amendment treatments outperformed the untreated control group (CK). Among them, the wood ash C3 treatment (1200 kg hm-²) was the most effective, increasing yield by 51.96% compared to CK.
To evaluate the effects of maize straw return rate on soil mesofaunal community composition, diversity, and vertical distribution, four treatments were established: 0, 225, 450, and 900 g m⁻². In 2024, soil mesofauna and physicochemical properties were sampled at the maize seedling, jointing-tasseling, and pre-maturity stages from four soil depths (0–5, 5–10, 10–15, and 15–20 cm). A total of 8,122 individuals belonging to 20 taxa were identified. Dominant taxa were the suborders Oribatida, Mesostigmata, and Prostigmata, along with the family Onychiuridae, collectively accounting for 89.2% of total abundance. Straw return significantly increased mesofaunal abundance, species richness and Margalef’s richness (all p< 0.05), but not Shannon-Wiener diversity (p> 0.05). Pielou’s evenness index also responded significantly (p< 0.05). The Sørensen similarity coefficient was consistently lower than the Morisita-Horn index, indicating that straw return mainly altered less abundant taxa rather than the dominance pattern of major groups. Furthermore, straw return significantly enhanced the aggregation of mesofaunal abundance in the upper soil layer (0–5 cm). Canonical Correspondence Analysis revealed that soil organic matter and total potassium were the primary environmental drivers of community structure. Specifically, Onychiuridae was positively associated with pH, whereas Isotomidae and Hypogastruridae were linked to soil organic matter. Oribatida and Mesostigmata were positively associated with total potassium. Overall, the highest straw-return treatment (900 g m⁻²) showed greater mesofaunal abundance, richness and altered vertical distribution, correlated with variations in soil organic matter and total potassium.
Manganese (Mn) sorption plays an important role in controlling its mobility, bioavailability, and environmental behavior in calcareous soils. The current study examines the kinetics of manganese sorption in six calcareous soils sampled within the vertisols (Chromic Haploxererts) order in Duhok Governorate in Kurdistan Region, Iraq. A solution of manganese (MnSO4) 300 mg L-1 with 10 pore volumes (PV) at 298o K was added to soil. The findings indicate that the lowest Mn adsorption capacity was in the Imerik soil (1230.5) while Derabun soil having the highest value (1475.4 mg kg-1)by using miscible displacement technique. Mathematical description of Mn-adsorption according to kinetics approach gave the following best fitting: Power function, First order, Zero-order, Elovich equation, Parabolic equation, Second order, respectively, based on the highest R2 value and lowest SE. Rate coefficient of Mn adsorption ranges from (0.99 to 1) and (95 to 96) x 10-4 hr-1 with an average 96 x 10-4 hr-1 according to power function and First order, respectively. The physicochemical and mineralogical characteristics are reflected in variations of Mn adsorption in the investigated soils.
Saline-alkaline soil carbon reserve constitutes an important component of the terrestrial carbon pool; however, knowledge regarding soil organic carbon (SOC) stability in arid saline-alkaline loess remains limited. This study aimed to assess SOC stability by analyzing variations in organic carbon fractions and mineralization rates along a salinity gradient in the saline-alkaline loess of Middle Gansu Province, Northwest China; also the relationship between SOC stability and microbial diversity and community structure are discussed. The key results are as follows: (1) With increasing salinization levels, the diversity and abundance of bacterial and fungal communities significantly decreased, accompanied by marked shifts in microbial community structure. (2) Total carbon (TC) and SOC contents ranged from 12.19 to 32.00 mg g-1 and 6.58 to 14.31 mg g-1, respectively, while active organic carbon (AOC) and non-active organic carbon (NOC) contents varied between 1.44 to 5.57 mg g-1 and 3.46 to 9.12 mg g-1 —all of which showed a decreasing trend with escalating salinity. (3) After 40 days of incubation, the cumulative SOC mineralization in low, medium, and heavy saline-alkaline soils was 4833.77, 4287.74, and 3452.99 mg CO2 kg-1d-1, respectively, indicating that both the magnitude and rate of SOC mineralization declined progressively with increasing salinity. The carbon pool management index (CPMI) ranged from 0.73 to 2.17. Notably, the value of carbon pool management index (CPMI) was positively correlated with microbial community diversity and abundance (p < 0.051), indicating that SOC stability tends to be more stable with the decreasing microbial community diversity. These findings provide insights into the microbial mechanisms underlying changes in SOC stability in arid saline-alkaline loess.
Soil organic carbon (SOC) plays an important role in the global carbon cycle. However, there were few studies on SOC and its fraction of rhizosphere soil and bulk soil in the water-level fluctuation zone. Therefore, the study collected soil samples at three elevations (LP-145m, MP-155m and UP-165m) of four transects in the Pengxi River Nature Reserve. The contents of total SOC and its fractions (F1-very labile carbon; F2-inert carbon; F3-oxidizable resistant carbon) in bulk soil and rhizosphere soil were determined by using a modified Walkley-Black method. Results showed that content of total SOC, F1, F2 and F3 of rhizosphere soil at MP and UP were significantly higher than those of bulk soil, while there was no significant difference in SOC content between the two soil types at LP. The content of SOC fractions showed an upward trend with the increase of total SOC content, and the correlation coefficient with SOC was F2>F1>F3. F2 was the largest contributor to the total SOC content of rhizosphere soil in three altitudes, while in the bulk soil, the largest contributor was F2 at LP and MP and F3 at UP. In conclusion, the SOC content of rhizosphere soil was significantly higher than that of bulk soil at middle and high altitudes, and the F2 was the main contributor to the total SOC content.
