Effects of long term interplanting forage on soil humus content in orchard

Archis pintoi cv. Amarillo and Chamaecrista rotundifolia cv. Fuyinn No.1 were interplanted in hilly orchard for water and soil conservation in subtropical red soil region in Fujian Province in 1996. The contents of humus organic carbon and the combining between organic matter and minerals were measured in 2007. The results showed that the humus organic carbon content in surface soil (0 to 15 cm) of treatments interplanted A. pintoi cv. Amarillo and C. rotundifolia cv. Fuyuan No. 1 were increased by 2.56 g/kg and 1.90 g/kg respectively compared with the control (clean tillage). But the change of humus organic carbon content in subsurface soil (15 to 30 cm) was weaker than surface soil. The combining degree of original soil in surface was 83.09% to 96.75%, higher than that in subsurface (77.73% to 92.14%). And the increased combing degree in surface soil of interplanting treatments was 70.52% to 83.42%. Among different treatments and control, the order of combining degree was clean tillage interplanting A. pintoi cv. Amarillo interplanting C. rotundifolia cv. Fuyuan No. 1. The treatment of interplanting A. pintoi cv. Amarillo showed better performance than C. rotundifolia cv. Fuyuan No. 1, and the increased combing degree was 83.42% which was 12.9% more than latter.