A STUDY AND QUESTION ON THE DECOMPOSITION RATE OF ORGANIC CARBON UNDER UPLAND AND SUBMERGED SOIL CONDITIONS
Huang Dong-mai; Zhu Pei-li; Wang Zhi-ming; Yu Xiao-he (Institute of Soil and Fertilizer, Jiangsu Academy of Agricultural Sciences,Nanjing 210014)
14C-labelled goat manure, elephant grass and its root were incubated with alfisol at 30℃ for 365 days, under 70%WHC (upland) and submerged condihons. Another set of incubation experiments using 14C-labelled rice straw and maize stfaw with ultisol and vertisol were conducted at 30℃ for 112 days under the same water regimes.The rate of decomposition of 14C-labelled goat manure and all the related plant materials or residues obviously revealed faster in submerged soils than those in 70% WHC soils irrespective of soil types, consequently the amount of residual 14C remained in soils showed the opposite trend. The half life of added organic substrates was l.4 to 2.0-fold greater in 70% WHC condition than that in submerged condition.Contrary to the traditional concepts of decomposition rates of organic matter in upland soil and submerged soil, it is considered that either the rate or the amount of organic carbon decomposition in submerged soil is substantially greater than that in upland soil if both soil conditions are adequate to microbial metabolism.