Land surface cover affects runoff generation and soil loss processes. Splash erosion occurs by the impact of raindrops on the soil surface. As a result of this process, raindrops detach soil particles, destroy soil structure, and finally, increase runoff and erosion. Amendments improve and reinforce soil aggregates and some physical barriers against raindrop impacts and runoff. The present research was an attempt to determine the efficiency of straw mulch applied at a rate of 0.5 g m−2 in changing the runoff commencement time, runoff amount, splash erosion, and sediment yield from eroded mid‐sized plots at different rainfall intensities under laboratory conditions. The research was conducted on a sandy loam soil taken from summer rangeland in the Alborz Mountains, northern Iran, with simulated rainfall intensities of 30, 50, 70, and 90 mm h−1 and a slope of 30% in three replicates. The collected data from 36 splash cups showed that the straw mulch played an effective role in reducing the splash erosion in both up and down directions, with the maximum reduction occurring at a rainfall intensity of 70 mm h−1. The results of the research also showed that the straw mulch had a significant effect in changing runoff and soil erosion characteristics at a confidence level of 99%. The maximum increase in runoff commencement time (110.10%) was observed for the rainfall intensity of 90 mm h−1. The runoff coefficient had a maximum reduction at rainfall intensities of 30 and 90 mm h−1. The maximum decrease in sediment yield (63.24%) also occurred at the rainfall intensity of 90 mm h−1.

The sediment yield model of the MUSLE (modified universal soil loss equation) is applied extensively throughout the world, but different performances have been reported of its success relative to measured data. A review of all the available literature is presented to assess the application of the model under different conditions and, ultimately, make a comprehensive judgement on the different aspects to allow readers to adjust their further research. A review of 49 papers showed the variable accuracy of the model, which depends on the manner of calculation and determination of the input and output, and the study time and space scales. There were differences in land use, in correspondence of the physiographic characteristics with those of the original conditions of model development, and even in the experience of researchers in applying the model. The results also show the need to consider the original application of the model, as proposed by its developers, to achieve comparable results.

Abstract. Amendments can control the runoff and soil loss by protecting the soil surface. However, scale effects on runoff and soil loss control have not been considered yet. The present study has been formulated to determine the efficiency of two plot sizes of 6 and 0.25 m 2 covered by 0.5 kg m −2 of straw mulch with regard to changing the time to runoff, runoff coefficient, sediment concentration and soil loss under laboratory conditions. The study used a sandy-loam soil taken from summer rangeland, Alborz Mountains, northern Iran, and was conducted under simulated rainfall intensities of 50 and 90 mm h −1 and in three replicates. The results of the study showed that the straw mulch had a more significant effect on reducing the runoff coefficient, sediment concentration and soil loss on a 0.25 m 2 plot scale. The maximum effectiveness in time to runoff for both the scales was observed at a rainfall intensity of 90 mm h −1 . The maximum increasing and decreasing rates in time to runoff and runoff coefficient were observed at a rainfall intensity of 90 mm h −1 , with 367.92 and 96.71 % for the 0.25 m 2 plot and 110.10 and 15.08 % for the 6 m 2 plot. The maximum reduction in the runoff coefficient was in the 0.25 m 2 plot for the two rainfall intensities of 50 and 90 mm h −1 , with rates of −89.34 and −96.71 %. The maximum change in soil loss at the intensities of both 50 and 90 mm h −1 occurred in the 0.25 m 2 plot, with 100 %, whereas in the 6 m 2 plot, decreasing rates of soil loss for the intensities of both 50 and 90 mm h −1 were 46.74 and 63.24 %, respectively.

Abstract. Amendments can control the runoff and soil loss by protecting soil surface. However, scale effects on runoff and soil loss control has not been considered yet. The present study has been formulated to determine the efficiency of two plot sizes of 6 and 0.25 m2 covered by straw mulch with rate of 0.5 kg m−2 in changing the time to runoff, runoff coefficient, sediment concentration and soil loss under laboratory conditions. The study has been conducted for a sandy-loam soil taken from summer rangeland, Alborz Mountains, Northern Iran under simulated rainfall intensities of 50 and 90 mm h−1 and in 3 replicates. The results of the study showed that the straw mulch had more significant effect in in reducing runoff coefficient, sediment concentration and soil loss at 0.25 m2 plot scale. The maximum effectiveness in time to runoff for both the scales, observed in rainfall intensity of 90 mm h−1. The maximum increasing and decreasing rates in time to runoff and runoff coefficient observed in the rainfall intensity of 90 mm h−1 with the amounts of 367.92 and 96.71% for 0.25 m2 plot and the amounts of 110.10 and 15.08% for 6 m2 plot respectively. The maximum change of soil loss in both the intensities of 50 and 90 mm h−1 occurred at 0.25 m2 plot with the amount of 100% whereas at 6 m2 plot, decreasing rates of soil loss for in both the intensities of 50 and 90 mm h−1 were 46.74 and 63.24%, respectively.

Abstract. Although various organic and inorganic mulches are used for soil conservation purposes, the comparative effectiveness of them on soil characteristics has not been comprehensively considered from different aspects. The present study is therefore an attempt to determine the efficiency of straw mulch, manure and TA-200 polyacrylamide with respective rates of 500, 300 and 50 g m-2, respectively, in changing sediment concentration and soil loss. The experiments were conducted for sandy-loam soil (collected from the top 0–20 cm-layer) taken from a summer rangeland, the Alborz Mountains, Northern Iran under laboratory conditions with simulated rainfall intensities of 30, 50, 70 and 90 mm h-1 and the slope of 30%. The results showed that the straw mulch decreased soil concentration at rate of 45.60% compared to the control plots, and performed better than manure (8.98% reduction) and PAM (4.74% reduction). The results showed that the maximum reduction in sediment concentration and soil loss for all soil amendments occurred in the rainfall intensity of 90 mm h-1 with the rates of 58.69 and 63.24%, for straw mulch, 14.65 and 13.14%, for manure and 20.15 and 23.44% for TA-200, respectively.

Abstract. Various organic and inorganic mulches are used for soil conservation purposes, the effectiveness of which on soil characteristics has not been comprehensively considered from different aspects. The present study surveys the efficiency of straw mulch, manure and TA-200 polyacrylamide with respective rates of 500, 300 and 50 g m −2 in changing sediment concentration and soil loss. The experiments were conducted for sandy-loam soil taken from a summer rangeland, the Alborz Mountains, northern Iran. The experiments were performed under laboratory conditions with simulated rainfall intensities of 30, 50, 70 and 90 mm h −1 and a slope of 30 %. The results showed that the straw mulch decreased soil erosion at rate of 45.60 % compared to the control plots and performed better than manure (8.98 % reduction) and PAM (4.74 % reduction). The results showed that the maximum reduction in sediment concentration and soil loss for all soil amendments occurred at the rainfall intensity of 90 mm h −1 with the rates of 58.69 and 63.24 % for straw mulch, 14.65 and 13.14 % for manure and 20.15 and 23.44 % for TA-200.

This research surveyed the effects of land use changes on flow nitrate pollution in the Talar River (northern Iran), using Landsat images of 1991 and 2013 and the Soil and Water Assessment Tool (SWAT). The results indicated that forest areas decreased by 14.9% and irrigated crops, dry land farming areas, range lands and residential areas increased by 46.8%, 31.1%, 4.7% and 17.5%, respectively. To calibrate and validate the studied period, the Nash Sutcliffe model efficiency (NSE) and coefficient of determination (R 2 ) were applied, ranging from 0.57 to 0.75 and from 0.62 to 0.76 for flow simulation and 0.84 and 0.63 and 0.75 and 0.83 for nitrate simulation, respectively. The results of land use scenarios indicated that respective water flow and nitrate loads increased by 34. 4% and 42.2% in 1991-2013 and may even increase by 42.3% and 55.9% in the simulated period of 2013-2050 in all sub-basins. It is likely that the main reason for these results was due to the increase in agricultural activities and the decrease in forestry areas. Our findings showed the useful combination of modelling techniques (land cover changes and SWAT) to develop valuable maps able to design correct land management plans and nature-based solutions for water quality of runoff water harvesting systems in the future.

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