High salinity and low fertility have restricted crop production in primary saline-alkali soils. Soil organic carbon (SOC) and surface charge characteristics affect the soil fertility and soil colloid characteristics of primary saline-alkali soils, respectively. In this paper, the SOC and surface charge properties of primary saline-alkaline soil under organic wastes applications were assessed. Five treatments were involved in this experiment: chemical fertilizer combined with sheep manure (SM), corn straw (CS), fodder grass (FG), and granular corn straw (GS), while chemical fertilizer only was used as control (CK). The content of SOC was significantly different under different organic wastes application (p < 0.05). Treatment GS recorded the highest content of SOC compared with the other treatments. In addition, the content of each SOC density fraction increased after the application of organic wastes. Similarly, the application of organic wastes, increased the proportion of organic carbon in free light fraction (Fr-FLOC) and organic carbon in occluded fraction (Oc-FLOC) in the soil however the proportion of organic carbon in heavy fraction (HFOC) decreased. In this study, we found that treatment GS has a greater impact on soil surface charge properties than other treatments, and through redundancy analysis (RDA) the content of SOC and Fr-LFOC (F = 24.704, p = 0.004; F = 19.594, p = 0.002) were identified as the main factors affecting the surface charge properties of soil organic carbon. In conclusion, GS is the recommended organic waste for ameliorating primary saline-alkali soil, as compared to the other organic waste treatments.
Innovative agricultural technologies such as organic fertilization have provided long and short-term benefits as far as sustainable soil management is concerned. In this study, five treatments were applied: cow manure (CM), chicken manure (JM), poplar tree leaves (TL), maize straw (MZ), and control (CK). The aim was to evaluate the long-term effects of applying organic materials on soil chemical and electrochemical properties. The highest pH and EC were recorded in JM and CM respectively. The highest cation exchange capacity (CEC) and specific surface area (SSA), were recorded in treatment TL while the application of organic materials increased the CEC and SSA by 24.9-85.5% and 6.9-52.4% respectively. The surface charge characteristics were significantly improved by the organic treatments compared with CK (P<0.05). The application of organic materials increased the surface charge potential (φ0) by 28-35.9% and the surface charge density (σ0) by 21.42-35.71%. Moreover, the electric field strength (E0) and surface charge number (SCN) were increased by 16.6-27.8% and 21.7-94.9% respectively. The soil chemical and electrochemical properties decreased along the soil profile with the exception of pH and EC, which increased with depth. The granulometric properties of organic matter and other physical attributes affected the chemical and electrochemical properties of the soil. The surface charge characteristics were significantly positively correlated with each other and the soil chemical properties as shown by the correlation analysis. The application of organic materials especially treatment TL is recommended as it had a more advantageous effect on enhancing the surface charge characteristics and could improve the quality of agricultural soils.
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