Abstract: A study was carried out in a long-term field experiment to assess the influence of 19 years of application of mineral fertilizers and organic manure on soil organic carbon (SOC) pools of Mollisols in Northeast China. We used soil aggregate and soil organic matter fractionation techniques to isolate SOC pools (total coarse particulate organic matter (total cPOM), total fine particulate organic matter (total fPOM) and total silt and clay (total s+c)). We found that the application of chemical fertilizers alone did not affect SOC contents and the mean weight diameters (MWD) of aggregates, while combination of mineral fertilizers with organic manure facilitated the macroaggregation processes and greatly increased SOC content and stock by 36% and 18%, respectively, over the unfertilized control. Compared with the control, chemical fertilizer application had no influence on SOC pool and its stabilization, while integrated use of manure and chemical fertilizer significantly increased the SOC content located in total cPOM and total fPOM and thus decreased the stabilization of SOC pool. The increase of labile C in manure-added soils benefits the SOC mineralization to increase crop yield; on the other hand, it intensifies the greenhouse effect. Given these effects, application of manure at appropriate rates is a better way to solve the contradiction between agricultural production and environmental protection in Mollisols of Northeast China.

Key words: wild Ussurian pear, leaf morphological characteristics, chlorophyll, photosynthetic characters.