The Effects Of Grass Buffer Strip Controlling Soil And Water Loss And Nitrogen And Phosphorus Output In Sloping Farmland

Water and Soil are the fundamental things for the survival and development ofhuman. As important technical means for human beings to protect soil and waterresources, and improve ecological environment, water and soil conservation has playedan important role in the process of human pursuing sustainable and coordinated economicand environmental development. Sloping land is the main farmland in yunnan province, itis the main type land of nitrogen and phosphate lose. With their large coverage andrelatively rapid growth etc, grasses are playing important roles in water and soilconservation. Through the field observations and indoor artificial rainfall simulated tests,the author preliminary studied runoff\sediment yield, nitrogen\phosphorus output, andreduce rates by grass buffer strip compared with contrast, further analyzed relationsbetween runoff\sediment yield and rainfall intensity, relations of runoff\sediment yieldand runoff time, the effects of rainfall intensity on the dynamic process ofrunoff\sediment erosion, relations between nitrogen\phosphorus output and rainfallintensity, the effects of rainfall intensity on the dynamic process of nitrogen\phosphorusoutput, relations between nitrogen\phosphorus output and initial pollutant concentration.And deeply revealed the regulatory effects of grass buffer strip on runoff\sedimenterosion and nitrogen\phosphorus output, which is of important significance on soilerosion, non-point source pollution control and ecological construction guidance. Theconclusions are as follows:（1） Grass buffer strip can reduce runoff\sediment erosion. In the field observations,the rate of reduced runoff and sediment by grass buffer strip was72.49%and82.12%. Inindoor artificial rainfall simulated tests, under rainfall intensity of20millimeter per hour,the rate of reduced runoff and sediment by grass buffer strip was55.28%and70.80%;under rainfall intensity of35millimeter per hour, the rate of reduced runoff and sedimentby grass buffer strip was42.40%and69.98%; under rainfall intensity of50millimeterper hour, the rate of reduced runoff and sediment by grass buffer strip was6.69%and52.16%. The effects of grass buffer strip to regulate and control sediment was better thanrunoff. With the increase of rainfall intensity, the effects of grass buffer strip to regulateand control runoff and sediment dropped off.（2） Grass buffer strip can control nitrogen\phosphorus output. Comparing withundisturbed sloping farmland, outputs of nitrogen and phosphorus in runoff decreasedobviously. TN output reduced73.59%, NH+4-N output reduced62.62%, TP outputreduced42.30%. Outputs of nitrogen and phosphorus in sediment decreased obviously Abstract: Water and Soil are the fundamental things for the survival and development ofhuman. As important technical means for human beings to protect soil and waterresources, and improve ecological environment, water and soil conservation has playedan important role in the process of human pursuing sustainable and coordinated economicand environmental development. Sloping land is the main farmland in yunnan province, itis the main type land of nitrogen and phosphate lose. With their large coverage andrelatively rapid growth etc, grasses are playing important roles in water and soilconservation. Through the field observations and indoor artificial rainfall simulated tests,the author preliminary studied runoff\sediment yield, nitrogen\phosphorus output, andreduce rates by grass buffer strip compared with contrast, further analyzed relationsbetween runoff\sediment yield and rainfall intensity, relations of runoff\sediment yieldand runoff time, the effects of rainfall intensity on the dynamic process ofrunoff\sediment erosion, relations between nitrogen\phosphorus output and rainfallintensity, the effects of rainfall intensity on the dynamic process of nitrogen\phosphorusoutput, relations between nitrogen\phosphorus output and initial pollutant concentration.And deeply revealed the regulatory effects of grass buffer strip on runoff\sedimenterosion and nitrogen\phosphorus output, which is of important significance on soilerosion, non-point source pollution control and ecological construction guidance. Theconclusions are as follows:（1） Grass buffer strip can reduce runoff\sediment erosion. In the field observations,the rate of reduced runoff and sediment by grass buffer strip was72.49%and82.12%. Inindoor artificial rainfall simulated tests, under rainfall intensity of20millimeter per hour,the rate of reduced runoff and sediment by grass buffer strip was55.28%and70.80%;under rainfall intensity of35millimeter per hour, the rate of reduced runoff and sedimentby grass buffer strip was42.40%and69.98%; under rainfall intensity of50millimeterper hour, the rate of reduced runoff and sediment by grass buffer strip was6.69%and52.16%. The effects of grass buffer strip to regulate and control sediment was better thanrunoff. With the increase of rainfall intensity, the effects of grass buffer strip to regulateand control runoff and sediment dropped off.（2） Grass buffer strip can control nitrogen\phosphorus output. Comparing withundisturbed sloping farmland, outputs of nitrogen and phosphorus in runoff decreasedobviously. TN output reduced73.59%, NH+4-N output reduced62.62%, TP outputreduced42.30%. Outputs of nitrogen and phosphorus in sediment decreased obviously millimeter per hour, dynamic processes changed similarly; under rainfall intensity of50millimeter per hour, initial concentration was high, then fell rapidly and achieved stabilityfinally. NH₄⁺-N concentration output in contrast plots had grater change than grass bufferstrip. The steepness of NH₄⁺-N concentration and output process was greatly affected byrainfall intensity. Under strong rain, decrease tendency waved greatly. Under light rain, itwas relatively steady. NO₃^--N concentration changed stable in grass buffer strip plots. Incontrast plots, NO₃^--N concentration was high in early runoff, and wave greatly. As timegoes by, NO₃^--N concentration curve decrease in wave.TP concentration dynamic output processes kept stable condition in the fluctuationsunder rainfall intensity of20or50millimeter per hour in two plots. Under rainfallintensity of35millimeter per hour, changes were complex. In grass buffer strip plots, itkept steady in early runoff, then quickly increased, and reached a stable condition in thefluctuations finally. In contrast plots, TP concentration slowly increase, then suddenlydecrease in anaphase of runoff, and reached a stable condition finally. PO3-4concentrationdynamic output process not obviously related to rainfall intensity in two plots.（5） TN NH₄⁺-N NO₃^--N TP PO₄^3-concentration dynamic output processes inrunoff of grass buffer strip and contrast plots were positively related to initial pollutantconcentration, their output directly affected by initial pollutant concentration.