Study On The Water, Soil And Nutrient Loss From Gneiss Mountainous Area Under Simulated Rainfall

Soil erosion is a serious ecological problem of our country. Hebei Province’s Taihanggneiss region belongs to the northern mountainous area. It is one of the more serious soilerosion areas, of which soil texture and other factors have big difference with other regions,so it is necessary for soil erosion research to this area. A artificial simulated rainfall devicewas used in this study to research the effects of different slopes, rainfall intensities andfertilizations on soil and nutrient loss in gneiss slopes and has certain significance to thecontrol of soil erosion in mountainous area and small watersheds’ non-point sourcepollution. The main conclusions were as follows:1. Runoff-yielding time decreased with increasing slopes. Under different rainfallintensity, the runoff-yielding time of5°slope is significant longer than the25°slope.The5°slopes’ total runoff and total sediment were the lowest. What’s more, the totalrunoff and total sediment did not increase with the increasing slopes. Except the5°slope’s sediment concentration is stable, the others were lowed fast at the beginning andthen tended to stable. Nutrient content was low in the runoff’s water samples of varioustreatments, and the scope of the change was also small. Before the rain stopped, thesediment’s total phosphorus content still changes much, and contents of the total nitrogen,total potassium, available phosphorus and available potassium were trended to stable.The sediment’s nutrients did not have significant relationship with slope and the rainingtime.2. In each slope, runoff-yielding time under60mm/h rainfall intensity wassignificantly higher than which under80mm/h and100mm/h. On each slope, both of thetotal runoff and total sediment were descended the order of100mm/h>80mm/h>60mm/h. In the case of rainfall intensity smaller, lower sediment amount and concentration.In the runoff’s water samples, total nitrogen concentration and rainfall intensity wasnegatively correlated. At different slope conditions, dissolved potassium content in samplesproduced by60mm/h rainfall is at a high level. The sediments’ nutrients had no significantrelationship with the rainfall intensity and raining time. For each runoff plots, the range ofthe total nitrogen’s cumulative loss is0.27g～7.20g, the range of the total phosphorus’scumulative loss is0.07g～1.52g, and the range of the total potassium’s cumulative loss is3.16g～72.85g. Although the concentration of the nutrients in the sediment did not havebig differences, the total losses have big differences due to the sediments’ amount. Thenitrogen, phosphorus and potassium are mainly lost with the sediment. The highestavailable phosphorus content is in the sediment produced by the60mm/h rainfall intensityat different times. The sediment’s available potassium content is stable late in the rain.3. The research results of gneiss slopes’ soil erosion and nutrient loss under differentfertilizer levels showed that: the total loss of sediment of the excessive fertilizationtreatment was significantly higher than the unfertilized treatment; the total nitrogen, totalphosphorus and potassium content in the runoff’s water gradually reduce with thecontinuous rainfall time and remained stable at the end of the rainfall; The total nitrogen,total phosphorus, total potassium in the sediment of each treatment accounted for49.7%-55.4%,71.8%-96.4%and93.4%-94.0%of the nitrogen, phosphorus, potassium’stotal loss. There was a significant difference of total nitrogen loss between the two fertilization treatments and no fertilization. The total nitrogen losses of the unfertilized,common fertilized and excessive fertilized treatments are0.53g,0.81g and1.03g. Therewere also significant differences of the total loss of the phosphorus, and the total loss ofare0.07g,0.38g and0.49g. The total potassium loss of the excessive fertilized treatmentsand unfertilized treatments were exist significant differences, and the total loss are3.35g,4.73g and5.51g.