| The red soil hilly region is located in the south-center Hunan province. With hightemperature,rainy days, clear wet, dry seasons, the soil in red soil hilly region of southern Hunanprovince is low fertility and general lack of potassium and phosphorus the and it has become a limitingfactor of crop high yield in this region. When developing and utilizing the slope land of hilly red soilregion of southern Hunan province, the question that soil erosion causes loss of soil nutrient and leads todegradation of land produetivity has received many attentions. Based on the experimental data indoorand infield from runoff plots located in Qiyang county, Hunan province during2011, the characteristicsof potassium and phosphorus the loss by runoff were studied by the continuous observation of theamount and nutrient content of runoff under8-different ecological planting patterns, The main resultsand conclusions are given as follows:（1） There were17times runoff which occurred from March to November,2011,13times of themconcentrated in May, June and August to October. The distribution characteristics of runoff were thesame as rainfall. The average annual total runoff of8ecological patterns was866.0m3·hm-2with a rangefrom238.1m3·hm-2to1422.1m3·hm-2. The average annual total soil loss of8treatments was25.2t·hm-2with a range from0.1t·hm-2to67.6t·hm-2. The differences of annual runoff and soil loss amongdifferent ecological patterns were both significant （P<0.01）. The soil and water losses of treatment withtea-oil tree planted in terrace was very serious when tea-oil tree was young, the losses amount was onlyless than the treatments of the wasteland pattern（control）and natural sloped cropping patterns. Howeverthe soil and water losses were much less if the terraces planted tea-oil tree were covered with rice strawor intercropped forage legume or peanuts.（2） The amount of phosphorus loss from sloped land of wasteland pattern（T1） was the biggest,then were the natural sloped cropping patterns（T2,T3）, while the treatments of terrace patterns（T4,T6,T7,T8） were much less, only9.9%,0.68%,2.3%and1.9%of T1, respectively. The ecologicalplanting patterns affected directly forms of phosphorus lost from sloped land, the particulate phosphorus（PP） lost from sloped land in T1T5were more than90%of total phosphorus （TP）, while the dissolvedphosphorus （DP） was the main form in T6. The loss of soil available phosphorus was very small, only3.9%of TP.96.8%of phosphorus loss was PP form. In case of rainstorm （dayly rainfall>50mm）, theimpact of rainfall on PP and DP was not significantly different, however, with rain intensity increased,the loss amount of PP increased significantly, the ratio of DP and PP became small, and the loss amountof TP increased significantly. Soil phosphorus loss mainly occurred during June to September. Bothrainfall and rain intensity directly affected time distribution of phosphorus loss.The loss amount of total potassium（TK） by runoff under8ecological planting patterns followed asort order:T1(1265.4kg·hm-2)>T2(940.8kg·hm-2)>T3(611.8kg·hm-2)>T5(404.0kg·hm-2)>T4(103.0kg·hm-2),T6(6.2kg·hm-2),T7(28.3kg·hm-2),T8(31.9kg·hm-2); The amount of TK loss by runoff mainlyoccurred in June and September and concentrated in4storm-runoff, the monthly distribution characteristics of potassium loss under each planting pattern was incomplete similarity with rainfall.The loss of potassium mainly through particulate was98.5%of the total. To sum up, the loss ofpotassium in the wasteland pattern （control） was most, then were the natural sloped cropping patterns,the last were the terraces cropping patterns, and T1was99.4%, T6was only20.3%.To sum up, T6,T7and T8had very good effect not only on reducing the soil and water losses butalso on potassium and phosphorus losses, The three kinds of mode had reduced potassium andphosphorus losses by runoff under heavy rain, it was of great significance and they are should bevigorously promoted when developing and utilizing in hilly red soil region of southern Hunan province. |
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