Effects Of Straw Application On Soil, Water, Nitrogen And Phosphorus In The Slope-farmland Of Northeast China

It has been a long term problem for water and soil loss in slope-farmland of Northeast China. Besides, most of the crop straw is burned in the field without cutting the field, and most the farmlands only use chemical fertilizer rather than organic fertilizer. This will results in organic material decrease topsoil layer, black soil degradation due to water and soil loss, soil plough layer decrease, bad water and fertilizer conservation, low utilization efficiency of chemical fertilizer, decrease of anti drought and water logging capability, smaller root developing space, thus influence the growth of crops and improvement of crop output. Moreover, the problem of the farmland diffused pollution resulting from water and soil loss is more highlighted.The research is on the effect of crop straw cutting field to the nitrogen and phosphorus in the water and soil, based on the requirements for conservation of nitrogen and phosphorous and crop straw cutting field inslope area of Northeast China. The test consists five treatments: corn stubble with less plough+ horizontal ridge(CN), crushing alfalfa cutting field +horizontal ridge(MR), crushing corn straw cutting field(CR), crushing soybean straw cutting field +horizontal ridge(SR), conventional planting +longitudinal ridge. Through observing nitrogen and phosphorus loss quantity in the water and soil of the slope farmland, the research achieves the following results.Straw cutting field has no significant effect to the increase of soil total nitrogen, with no significant difference among corn, alfalfa and soybean straw cutting. However, the soil total nitrogen for crushing corn is 20.6% higher than straw returning field, thus the crushing method is more beneficial to conservation and improving nitrogen content in the soil. Crop straw cutting field is in favor of reducing available nitrogen content in the topsoil layerl, and can reduce the nitrogen loss in the slope-farmland during runoff process; there is no significant difference among crushing corn, alfalfa and soybean cutting field. Crushing crop straw cutting field can reduce 46.4%-58.4% of nitrate nitrogen content in topsoil layer and can reduce nitrate nitrogen loss in surface runoff, without significant different among MR, CR, SR. The concentration ratio of nitrate nitrogen in topsoil layer has increased 54.0%which is liable to soil nitrogen loss, indicates that the slope-farmland is not suitable to corn stubble straw cutting.Crop straw returning to field has no effect to total phosphorus content in the topsoil layer, without significant difference among MR, CR and SR, or between CN or CR. The effect of crop cutting to the soil rapid available phosphorus is equal to the total phosphorous. For the reason that the content rapid available phosphorus in CN soil is 77.4% higher than MR, because the alfalfa had absorbed much more soil phosphorus.Crop straw cutting field has no significant effect to the improvement of organic material in surface soil, without significant difference among MR, CR and SR,or between CN and CR. It may be because the test period is too short, so the straw has not made the recarburization effect.Crop straw cutting field and horizontal ridge plough can reduce soil loss load in slope cropland effectively. Compared with CK, soil loss load of CN, MR, CR, SR has reduced 24.1%, 53.95, 37.1%, 49.1%respectively. Compared with CN and CR, CR is more favorable to soil conservation. Crop straw cutting field and horizontal plough can reduce volume of runoff in slope farmland. Compared with CK, the runoff load of CN, MR, CR, SR has reduced 51.2%、54.2%、52.2%、61.0%, respectively. There is no difference for surface runoff in slope farmland for three crushing corn, alfalfa and soybean, and CN is 2.30% higher than CR, both of these indicate that the crushing crop straw has more free soil effect than crop straw.The total nitrogen pollution load resulted from soil loss in corn longitudinal ridge of slope land is 1.95kg/hm2, and the total nitrogen pollution load for CN, MR, CR and SR has reduced 48.7%、65.9%、51.0%、62.0% respectively. The total phosphorus pollution load resulted from soil loss in corn longitudinal ridge of slope land is 0.75kg/hm2, and the total phosphorus pollution load for CN, MR, CR and SR has reduced 45.3%,66.7%,50.7%,60.0% respectively.The total nitrogen pollution load resulted from farmland runoff in cornlongitudinal ridge of slope land is 5.81g/hm2, the total nitrogen pollution load for CN、MR、CR、SR has reduced 60.1%、32.2%、77.1% respectively, and MR has raised 21.2%. The total phosphorus pollution load resulted from farmland runoff incorn longitudinal ridge of slope land is 3.77g/hm2, and the total phosphorus pollution for CN, MR, CR, SR has reduced 44.8%、67.1%、91.8%、70.3% respectively. From above we can see, farmland runoff in slope area doesn’t exist nitrogen and phosphorus pollution.The test results of crop straw indicate that, compared CN and CR with CK, there is no significant difference for their corn output. For crushing corn straw cutting field, there is significant difference between output of second year 8961 kg/hm2 and output of first year 7989 kg/hm2, which indicates the crushing corn straw is favor for the increasing production of corn, but the corn straw cutting has no effect of increasing production.The output of soybean in two years is 2366.7 and 2365.6 kg/hm2 while the output of alfalfa is 5697.9 and 5885.4 kg/hm2. Thus we can see that the technology of crushing corn straw cutting for horizontal ridge plough is helpful to improve nitrogen and phosphorus conservation for soil and water in slope farmland. Based on proper fertilizing, crushing alfalfa and soybean cutting can also realize the effect of nitrogen and phosphorus conservation for soil and water.