Correlation Between Soil Organic and Inorganic Carbon and Environmental Factors in Cotton Fields in Different Continuous Cropping Years in the Oasis of the Northern Tarim Basin

Abstract

Studying the characteristics of soil organic carbon (SOC) and soil inorganic carbon (SIC), and their relationship with environmental factors is helpful for understanding soil ecological processes, and providing theoretical support for research on the global carbon budget. Based on the oasis in the northern margin of Tarim Basin, this study analyzed the characteristics of the soil carbon pool, and, combined with redundancy and path analyses, explored the relationship between SOC and SIC, and their environmental factors. The results showed that there was a significant difference (P<0.05) in SOC and SIC contents in cotton fields with different continuous cropping years (P<0.05). With an increase in continuous cropping years, the SOC content increased firstly and then decreased, while the SIC content decreased firstly and then increased (P<0.05). The SOC content was the highest in the 0-20 cm layer, while the SIC content was the highest in the 20-50 cm layer. The importance of environmental factors on the characteristics of the soil carbon pool was deduced by redundancy analysis. The order of importance was phosphatase activity > pH > sucrase activity > catalase activity > total N > available P > available K > soil moisture content > urease activity > electrical conductivity (EC); phosphatase activity, pH value, invertase activity, catalase activity, total nitrogen, available phosphorus, and available potassium showed significant correlation with SOC and SIC (P<0.01). Soil moisture and urease activity showed significant correlation with SOC and SIC (P<0.05). The path analysis showed that available P had a direct effect on the SOC content; it was the main factor affecting it. The urease activity had a direct effect on SIC; it was the main factor affecting it. This study of soil carbon pools in arid and semiarid regions is the basis for evaluating the "source/sink" effect of soil carbon in farmland ecosystems, and is of great significance for studying the global carbon budget and land carbon cycle mechanism.