SOIL ATTRIBUTES, SOIL ORGANIC CARBON AND RELATIONS WITH RUBBER-TREE MORPHOLOGY IN A THREE-DECADE-OLD ORCHARD

Successful establishment of a rubber tree plantation may be affected by the initial soil management at the time of planting. However, research on the long-term development of rubber tree plantations and initial soil treatment is scarce. Thus, this study evaluated agronomic characteristics, organic carbon and its stock and their relation to soil attributes in a 32-year-old rubber tree plantation. The experiment adopted a randomized block design with two rubber tree clones (RRIM 600 and FX 2261) and five planting systems (P1: 0.4 x 0.6 m planting hole; P2: 0.35 x 0.4 m planting hole; P3: 0.45 x 0.45 m furrow; P4: 0.35 x 0.8 m planting hole; P5: 0.25 x 0.5 m planting hole) with four replications. The trunk circumference at breast height, height of first bifurcation, bark thickness, total organic carbon in litterfall and carbon stocks in soil were evaluated. The planting systems used for the rubber trees and clones did not influence the trunk circumference at breast height or height of first bifurcation. The bark thickness of FX 2261 was greater than that of RRIM 600. The soil’s physical attributes were not affected by different planting systems or clones. The soil of the rubber tree plantation includes significant amounts of carbon absorbed from the atmosphere as CO2.