| Soil erosion is the world's largest environmental problems;there are different degrees of land degradation for 65 per cent of the land globally.The world's major land loses topsoil 24 billion t each year, over the past 20 years,the world's lost topsoil is the sum of arable land in the United States,and the situation is still deteriorating in many countries.Thus,soil erosion captured the widespread concern as a hotspot.At present,China's northeast district has black soil erosion area of 275,900 km,27.09 percent of the total black soil area.The soil erosion of black soil area is mainly the loss of slope land,accounting for more than 80 percent of the black soil erosion area.According to the survey,black soil zone loses 0.3～1 cm black topsoil at an average annually,because of years of serious soil erosion,now the black soil layer is only 20～30 cm,which is thick before.Some localities have even been exposed loess parent material, basically losing production capacity.Therefore,we must analyze the reasons for the loss of the black soil, identify controlling measures and counter-measures.This paper,through artificial rainfall method,is to study,at different slopes,different vegetation coverage,different treatment,the loss of soil sediment,the level of wastage of tablets,a class reunion of the loss of soil moisture changes,changes in soil nutrients, soil pH changes in runoff and nutrient content in water samples,the results of the study are as follows:(1)As to the sediment loss in the black soil runoff,the loss of sediment is:9 degree＞7 degree＞5 degree＞3 degree.(2)The general trend is:with the increase in slope,the black soil runoff increases and growth trends:9 degree＞7 degree＞5 degree＞3 degree.(3)The black soil moisture content:different slope,the same rainfall,soil moisture content increases with the decline of the slope.Soil moisture:9 degree＜7 degree＜5 degree＜3 degree.(4)After the loss of black soil,rapid N increased and then dropped,and finally achieved a smooth.P went up first,then decreased.The loss of K increased with the time and frequency of rainfall.Organic matter content:9 degree＞7 degree＞5 degree＞3 degree.(5)The movement of soil pH:the slope has no obvious impact on pH,the slightly higher trend of pH may be due to the hot weather,making the soil compaction,resulting in an increase of anion concentration and pH.(6)The impact of fertilization treatment on the black soil nutrient loss:on 3°slope,the imposition of chemical fertilizers,soil nitrogen content is the highest;the impact of different treatment on black soil organic matter:on 9 degrees the soil organic matter,under the use of chemical fertilizers,is higher than the counterpart group.The movement on 7 degrees:increase and then decrease..(7)the soil micro-aggregates in black soil runoff,on different slopes,the trend of all micro-aggregate＞0.25 mm the aggregate loss of less,0.25-0.05 mm the aggregate loss to the maximum.After fertilization treatment for the micro-aggregates,the second after the artificial precipitation＞0.25 mm of soil micro-aggregates relatively large percentage of,0.25-0.05 mm there and＞0.25 mm of soil micro-aggregates of the same.(8)the changes of soil nutrient in black runoff water,from 7 degrees slope,5 of the slope under the base of compound fertilizer runoff water changes of nitrogen,5 degrees slope,the first decline after rising and further,and a smooth transition.3 degree slope under the(fertilizer+chemical fertilizer,fertilizer and CK treatment)of nitrogen runoff water base,a small slope in the circumstances,the simple use of chemical fertilizers,N the inevitable loss of more than other groups.P steep slope under the present law of the loss of changes,have shown a downward trend.Runoff water samples in the loss of potassium in the slope of 9 degrees slope of the circumstances and 3 slope CK under the control group,each rainfall,with rain washed away the runoff water,K is the overall show a downward trend And the flow of quick-impact K:9 degree＞3 degree.Note slope of the loss of K had an impact.
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