旱地和水田有机碳分解速率的探讨与质疑

A STUDY AND QUESTION ON THE DECOMPOSITION RATE OF ORGANIC CARBON UNDER UPLAND AND SUBMERGED SOIL CONDITIONS

14C标记的羊粪、杂交狼尾草（象草）及其根部分别施于淋溶土中，在30℃培养365天。土壤保持旱地（70％WHC）和淹水两种状态，进行有机碳在土壤中分解的对比试验。另一组试验采用14C标记的水稻秸和玉米秸，分别施于老成土和变性土中，在上述相同的水分条件下于30℃培养112天进行对比。所有加入的不同有机物料。不论是在何种土壤，其在淹水土壤中的有机碳分解速率均快于旱地土壤，而前者的残留率却明显低于后者。淹水处理中各种不同有机物料的分解半衰期约为旱地相应处理的1．4—2．0倍。这和有关有机质在旱地和水田土壤中分解速率的传统概念相反。作者认为如果旱地和水田的土壤条件均适宜于微生物的代谢作用，水田土壤中不论是有机碳的分解速率还是分解量实质上均大于旱地土壤。

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.