Abstract:

【Objective】 An attempt was made in this paper to investigate the dynamics of total organic C (TOC), labile organic C (CLOC) in relation to the system productivity of different black under soil long-term management strategies. 【Method】 The first experiment was designed to study the effects of different chemical compositions and complexity of residues in three grass and crop treatments, including bare fallow, grass fallow, plantation with no fertilizer on the contents of labile organic carbon of the black soil. The long-term fertilization experiment including three treatments was designed, i.e., plantation with on fertilizer (CK), chemical NP, and organic manure plus chemical NP. 【Result】 The result indicated that different residues returned into the soil had remarkable influence on the black soil labile organic carbon formation. The TOC and TN under bare fallow declined by 11.2% and 15.3% compared with those in 1985. The TOC and TN in the grass fallow was 13.2% and 5.8% higher than those in 1985. The storages of soil TOC in the plantation increased by 1.1% and TN declined by 15.5%. In contrast with the bare fallow treatment, the soil covered with plantation and grass fallow, increased by 13.9%, and 46.2% of light fraction organic nitrate and 36.48% and 62.0% of light fraction organic carbon, respectively. The sequence in the amounts of hot-water organic carbon and readily oxidizable carbon in different vegetations was grass fallow＞plantation＞bare fallow. In the second experiment, application of manure increased the concentrations of TOC by 25.5% and of TN by 18.6%.Compared with the CK treatment, the application of manure, fertilizer NP, increased the light fraction organic nitrate by 126.7%, and 12.17% and light fraction organic carbon by 125.14% and 17.14%, respectively. Compared with the CK and NP treatments, the application of manure increased the particulate organic nitrogen by 49.8% and 23.2% and 6.5%, and particulate organic carbon by 29.9%, respectively. The decline sequence in the amounts of hot-water organic carbon and readily oxidizable carbon in soils under cropping was CK＜NP＜NPOM. 【Conclusion】Grass cover and NPOM treatments are beneficial to the soil organic carbon and labile organic carbon accumulation.

Key words: Udic Mollisols')">Udic Mollisols, organic carbon, labile soil organic carbon, vegetation, long-term fertility