| The relation between soil quality and environment highlighted due to the trend of agricultural sustainable development. In the present, soil erosion has done severely harm to living and development for human being. Ferrisols, located in South China, are the most important food production area. It was being seriously eroded by water because of long-term's unreasonable utilization and weak ecological system, which harmed the development of national economic greatly. From the aspect of soil characters, aggregate distribution and stability as well as aggregate stability mechanism of Ferrisols were studied in this paper, which would have great importance in reducing water erosion danger, stabilizing and improving agricultural production, preserving soil resources and balancing soil ecological system. The main results were summarized as follows:1. Aggregate stability was closely related to the research method. After wet sieving, water stable aggregate showed the highest fraction at the size of <0.25mm,while micro-aggregate was distributed from 0.25mm to 0.01mm size. Aggregate stability of soils increased with an increased clay content. Either >5mm size or >2mm size, the relative percentage of aggregate destruction (PAD) was over 60%. It was found that forest soils were stronger in aggregate stability compared with parent material or bare soils.The particle size distribution (PSD) and mean weight distribution (MWD) after mechanical shaking treatment and chemistry dispersion treatment, were significantly different. The latter treatment enhanced the destruction though samples showed different susceptibility. In aggregates distribution after two treatments, the size of <0.05mm was the highest percentage while 0.25-0.15mm size was the lowest for the initial 5-2mm size aggregate. It also concluded that garden area soils showed the strongest stability among all soils.2. The results of aggregate distribution and stability on Ferrisols used by Le Bissonnais's method suggested that, treatment method and initial size had greatly affected on aggregate stability and aggregate distribution. Fast wetting (FW) treatment had the largest disruption while wet-stirring (WS) treatment had the lowest disruption. It concluded56that Ferrisols aggregate breakdown was caused by the pressure produced by the entrapped air in the soil porosity when fast wetting, which indicated that Ferrisols erosion was most severe in the sudden heavy rain in the nature. The more initial aggregate was, the bigger the MWD of products was, and the higher aggregate stability was. The MWD value of this method was bigger than the routine methods one, and the MWD index of FW and slow wetting (SW) treatment were agreed significantly to the >0.25mm size percentage given by wet sieving in the routine methods.The three treatments of fast wetting, slow wetting and the wet-stirring had significant difference. FW treatment had more significant relationships with SW but no significant relationships with WS. The three initial sizes of aggregate had also significant relationships. All of the three treatments and three initial sizes, MWD value was the biggest produced by big aggregate after WS treatment. In addition, the big aggregate of parent material layer and bare soils had the biggest slaking index (RSI) and the cultivated soils ranked the next place.3. The relationships between soil aggregate stability and soil characters demonstrated that, soil aggregate stability index was only related to the certain soil characters. The soils were ranked differently according to different aggregate stability index.4.The contribution values of organic matter and free iron oxide to aggregate stability were less than 10 percent among all the samples. The free iron oxide contribution had the trend of increasing with the size being smaller. Organic matter contribution of the 0.25-0.05mm aggregate size surpassed that of 1-0.25mm aggregate and <0.05mm aggregate size, and the contribution value was bigger than corresponding one of free oxide. It was found tha... |
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