Soil Organic Carbon Components and Influencing Factors of Rubber Plantations of Different Ages in Qiongzhong, Hainan

Purpose To study the relationship between organic carbon components and physicochemical properties of rubber forest soil, providing theoretical basis for soil quality and efficient development of natural rubber industry in China.

Method Several soil physicochemical properties and soil organic carbon components were tested by agrochemical analysis method in five rubber plantation soil samples (2, 9, 12, 27 and 31 a) of Qiongzhong Dafeng Farm in Hainan Province.

Results 1) The soil pH in 9-age rubber plantations was the highest, the water content of 31-age rubber plantations was the highest and the bulk density was the lowest. The contents of total nitrogen, total phosphorus and total potassium in each forest age were lower than, equal to and higher than the national level, respectively. 2) The contents of soil organic carbon in different aged rubber plantations were different. The content of total organic carbon changed from 4.58 to 8.52 g/kg, the content of easily oxidized organic carbon changed from 1.72 to 4.66 g/kg, and the content of stable organic carbon changed from 2.05 to 3.27 g/kg, the content of water-soluble organic carbon changed from 0.23 to 0.48 g/kg. 3) The content of total soil organic carbon was extremely positively correlated with the content of easily oxidized organic carbon and the content of stable organic carbon (P<0.01), with correlation coefficients of 0.321 and 0.333, respectively.

Conclusion The soil organic carbon content of 27 and 31 aged rubber plantations is higher than that of low aged rubber plantations because of the accumulation of organic matter under the forest. Due to rigid planting, the vegetation under the 2-age rubber forest is exposed, and the 12-age rubber forest is cut, so the organic matter loss is more.