Abstract:Based on field simulated rainfall experiments, the study preliminarily investigated the effects of water and nutrient loss on loess slope with drill fertilization of different nano carbon contents (0 kg/kg, 0.01 kg/kg, 0.05 kg/kg, 0.07 kg/kg, 0.10 kg/kg) under 90 mm/h rainfall intensity. The results showed that: (1) The nano carbon had a significant influence on the rainfall infiltration process and the slope runoff amount. With the increasing content of nano carbon, the average infiltration rate tended to increase, and the runoff tended to decrease. (2) Compared with the control treatment, nano carbon could significantly alleviate soil erosion. The plots with 0.01 kg/kg, 0.05 kg/kg, 0.07 kg/kg and 0.10 kg/kg nano carbon reduced runoff amount on slope by 40%, 41%, 68% and 74%, respectively, and reduced sediment yield on slope by 27%, 50%, 68% and 79%, respectively. (3) Drill fertilization of nano carbon could effectively maintain the soil nutrient content on the loess slope, and compared with control treatment, the plots of 0.01 kg/kg, 0.05 kg/kg, 0.07 kg/kg and 0.10 kg/kg nano carbon reduced the loss of nitrogen in runoff by 47%, 52%, 74% and 79%, respectively, reduced the loss of nitrogen in sediment by 47%, 52%, 74% and 79%, respectively, reduced the loss of phosphorus in runoff by 63%, 63%, 88% and 86%, respectively, reduced the loss of phosphorus in sediment by 29%, 56%, 86% and 83%, respectively, reduced the loss of potassium in runoff by 43%, 46%, 81% and 83%, respectively, and reduced the loss of potassium in sediment by 25%, 62%, 78% and 87%, respectively.

Abstract:The objective of this study was to investigate the characteristics of the natural rainfall, runoff and sediment yield of sloping cropland during the whole growth period of corn. Field runoff plots and laboratory analysis were used to measure rainfall, runoff and sediment yield at different stages of the corn growth period (seeding stage, jointing stage, tasseling stage, and maturing stage) under 3 tillage practices (cross ridge planting, flat planting, and downslope ridge planting) based on natural rainfall of the study area. The results showed that the rainfall of the study area was 676.71 mm from May to August in 2015. The amount of erosive rainfall was 411.71 mm and accounted for 69.85% of the cumulative erosive rainfall at maturing stage. During the whole growth period of corn, the runoff was significantly influenced by rainfall and corn growth stages. Sediment yield under the cross ridge planting was significantly influenced by rainfall amount and intensity. However, sediment yield under flat planting and downslope ridge planting was significantly influenced by rainfall amount and corn height. The runoff and sediment yield increased with the growing of corn, and sediment yield was significantly influenced by the runoff. The sediment yield under cross ridge and flat planting decreased at first, then increased and finally decreased, while it decreased at first and then increased under downslope ridge planting. At tasseling stage, the runoff amount under cross ridge planting was significant lower than that under downslope ridge planting, while the sediment yield under cross ridge planting was significant lower than those under flat planting and downslope ridge planting. At maturing stage, the runoff and sediment yield under cross ridge planting was significantly lower than those under flat planting and downslope ridge planting. Rainfall was the main factor that influenced runoff and sediment yield of the sloping cropland under the condition of natural rainfall. The sediment yielding time was longer than that of runoff. Soil erosion at the maturing stage was the most serious among all growth stages of corn. The results indicated that cross ridge planting was an effective practice to prevent soil erosion. Therefore, this study would provide the theoretical basis for the soil erosion prevention, and sustainable development of agriculture in the yellow soil area.

Abstract:In this study, field experiments with water scouring were conducted to analyze the characteristics of runoff and sediment yield, and nitrogen and phosphorus loss under the conditions of different slope lengths. Results showed that with a fixed inflow rate, the amount of infiltration along slope land increased, but the runoff decreased with the increase of slope length. Notably, there was a critical slope length, where the amount of infiltration equaled to runoff, but there was the negative linear relationships between the slope length and accumulated runoff. Similarly, the sediment yield also increased with the increasing slope length, but the total loss of sediment of per unit length was not significant (P＞0.05). The cumulative sediment yield increased with the extension of slope length. For nutrient transport, power function was superior than exponential function in describing the changing process of nitrate nitrogen and soluble phosphorus. And the concentrations of nitrate nitrogen and effective phosphorus in sediment decreased over time. The nutrient enrichment ratio became greater as slope length increased. Also, there was a critical slope length inducing the total loss of nutrient to be maximum with the increase of slope length. Besides, the concentration of nitrate nitrogen in soil profile showed a peak feature with the increase of soil depth, and the peak occurred at different depths of soil. Furthermore, soil available phosphorus mainly distributed in 0—5 cm soil layer, and it was extremely low below 5 cm of soil depth. These results mentioned above provide a reference value for further analysis on the effect of slope length on water and soil nutrient loss.

Abstract:A field water-scouring experiment was conducted with different flow rates (35 L/min, 45 L/min, 55 L/min) and different slope gradients (24°, 28° and 32°) in order to explore spatial-temporal characteristics of runoff and sediment yield on slopes of engineering accumulation body. The results showed that the runoff intensity was closely related to the intensity of discharge and sediment yield, and multiple linear correlations existed between them. The runoff intensity showed a fluctuated increasing trend with the increase of scouring time. Average sediment amount and sediment yield ratio increased at first and then decreased with the increase of slope gradients, and the peak value appeared when the slope gradient was about 28°.Runoff intensity and sediment yield showed the first peak values at 10 min. The sediment yielding process included3 stages: sediment yield rapidly increase, fluctuated and steadily developed. The cumulative sediment yield showed linear correlation with the cumulative runoff. The experiment results may provide validation data for the prediction model of soil and water loss in the production and construction projects.

Abstract:Simulated rainfall experiments were conducted to investigate the research on soil and sediment yield and nutrients loss characteristics on soil slope of subtropical evergreen broad-leaved forest. The results showed that: (1) The runoff occurring time shortened with the increasing rainfall intensity and slope gradient, and the influence of rainfall intensity on runoff occurring time was greater than that of slope gradient. (2) For the same slope gradient, the runoff intensity and the average infiltration rate increased with the increasing rainfall intensity, and the temporal change of runoff intensity followed a power function and that of the average infiltration rate followed a logarithmic function. (3) The runoff amount first increased and then tended to be stable with the increasing rainfall duration, and increased with the increasing slope gradient. For the same slope gradient, the runoff amount increased with the increasing rainfall amount. Soil slope gradient had less influence on the runoff at rainfall initial moment, and rainfall intensity and slope gradient had the greater influence on the runoff. The runoff-yielding rate showed an opposite temporal variation with the runoff amount, which first decreased and then tended to be stable with the increasing rainfall duration. The runoff-yielding rate decreased with the increasing slope gradient. For the same slope gradient, the runoff amount increased with the increasing rainfall amount. (4) Slope sediment yield increased with the increasing slope gradient, and also increased with the increasing rainfall duration, which reached the maximum in the first 10 min of the rainfall. For the same slope gradient and rainfall duration, sediment yield increased with the increasing rainfall intensity. The slope sediment yield and nutrient loss followed a power function. (5) For different slope gradients, positive correlations existed between slope sediment yield and nutrient loss, and the correlation coefficients on the slopes of 15°, 20° and 25° were much better than on the slopes of 5° and 10°, while the total phosphorus had no correlation with slope sediment yield (P＞0.05), which implied that the slope sediment yield could cause the increase of various kinds of nutrients in sediment.