Improvement of Karst Soil Structure and Microbial Community by Organic Mulch

Abstract

In karst regions with severe soil erosion, improving soil quality plays a crucial role in ecological restoration and boosting agricultural productivity. The purpose of this study was to reveal how organic mulching modifies karst soil physicochemical properties, nutrient content of orah mandarin (Citrus reticulata cv. Orah) leaves, soil microbial community diversity, and soil enzymes. Experimental conditions with no mulching (control), corncob, or rice husk mulching were set up. Both corncob and rice husk mulching treatments significantly reduced soil bulk density (BD), increased total soil porosity (STP) by 9.13%, soil moisture (WC) by 87.50%, and electrical conductivity (EC) by 63%, compared to control. Corncob mulching significantly enhanced the activities of soil acid phosphatase (S-ACP) by 104% and soil urease (S-UE) by 86%, and significantly increased the contents of soil organic carbon (SOC) and total nitrogen (TN) by 210% and 88%, compared to control. The total phosphorus (TP) content in orah mandarin leaves significantly increased in corncob mulching. The bacterial diversity significantly increased under the two types of mulching, and corncob mulching significantly increased the abundance of Actinobacteriota, Gemmatimonadota and Acidobacteriota. Functional prediction showed that microbial metabolism was the main pathway. SOC and available phosphorus (AP) were key influencing factors of soil bacterial communities. The results indicate that corncob mulching had a remarkable effect when applied on the soil surface of young orah mandarin orchards. Such application not only may enhance soil quality and promote synergistic nutrient transformation by microorganisms but may also effectively facilitate the resource utilization of agricultural waste.

Keywords: soil erosion, mulching treatment, Soil physicochemical properties, soil microbiota biodiversity, leaf nutrient content