Analysis on SOM and Available Nutrient of Mountain Red Earth in Karst Area

Mountain red earth is a kind of relic ancient clay remained on the Yunnan Plateau formed under the influence of paleo climate, but this soil has experienced degradation recently. To understand the mechanism and effects of such degradation, this study examined the mountain red earth based on the analysis of soil organic matter (SOM) and available nutrient. Particularly, soil samples were taken from area covered with pine, shrub land, grassland or uncovered red soil respectively in the karst area of east Yunnan. The results indicated that the highest SOM contents was grassland (5.00%), while bare land was the lowest (1.44%), average contents of vegetated land(4.48%) was 3.11 times of bare land; the highest Available K (AK) contents was shrub land (26.26mg/kg), while bare land was the lowest (1.36 mg/kg), average contents of vegetated land (22.39 mg/kg) was 2.75 times of bare land; the highest Available P (AP) contents was grass land (5.15 mg/kg), while bare land was the lowest (1.36 mg/kg), average contents of vegetated land(3.80 mg/kg) was2.79times of bare land. In addition, there was a significant and positive correlation of the contents of SOM with AK and AP. Thus, the red bare soil can be considered as the last stage to the rocky desertification. All these suggest one possible and viable way to improve the structural condition of a layer of red bare soil by increasing the contents of SOM. KeywordsKarst; Mountain Red Earth; SOM; Available nutrient; Rocky Desertification