| چکیده انگلیسی مقاله |
The development and creation of new ways to protect water and soil lead to either educing or controlling soil loss which are considered as vital issues. In this study, the effect of vermicompost and straw as a soil organic conditioner on reducing runoff and sediment is investigated in the plots with two square meters area. For this purpose, 400 g of straw and 500 g of vermicompost per square meter were mixed with the topsoil of plots. Besides, the rainfalls with 51 and 65 mm/h intensities were simulated by portable rainfall simulator in field with natural condition. The results showed that straw could decrease runoff volume up to 16.84 % compared to the control treatment, while suspended sediment load is increased by 9.06 % at 51 mm/h intensity. Vermicompost, the runoff volume and suspended sediment increase up to 2.37 and 11.04 %, respectively. However, statistical criteria showed that none of these results was significant in this intensity. By the rainfall intensity increase from 51 to 65 mm/h, wheat straw treatment reduces the runoff volume at a significant level (p< 0.01) and suspended sediment load at a significant level (p< 0.05) by 64.91 and 45.46 % respectively. Moreover, vermicompost treatment reduces runoff volume at a significant level (p< 0.01) and suspended sediment load at a significant level (p< 0.05) by 47.18 and 35.85% respectively. These results imply that the inherent of protecting the amendments has not appeared in the low rainfall intensity. But at higher levels of intensity, both amendments have been able to reduce the destructive effects of increasing rainfall. Extended Abstract 1-Introduction One of the approaches to protect water and soil resources is the use of amendments. The organic amendments, by having advantages, including nutrients and organic matter, aggregating stability, increasing infiltration, and reducing bulk density can control and reduce the various phase of erosion process. Therefore, in this research it is tried to assess impacts of two organic amendments on important parameters of erosion and sediment. 2-Materials and Methods The study area in this paper is located along the longitude of 47 ̊ 6 ꞌ east and latitude 34 ̊ 19 ꞌ northeast in the province of Kermanshah. Its area is 3000 m 2, the average slope is 8-12% and the average annual rainfall is 437.92 mm. The effect of straw and vermicompost modifiers was simulated in two maximum intensities of 51 and 65 mm / hr, based on 66 years of precipitation of the synoptic meteorological station of Kermanshah for 15 minutes and the return period of 100 years, in the plots with two square meters area. With the appearance of the first runoff droplets in the outlet of plots, sampling was performed at 3-minute intervals. One-way analysis of variance (ANOVA), two way (GLM) and independent t-test were used to analyze the results. 3-Results and Discussion At 51 mm/h intensity for straw treatment, the runoff volume and coefficient drops to 16.84 and 17 percent, respectively, compared to control treatment, but the suspended sediment load increases by 9.06 percent. For vermicompost treatment, the parameters like runoff volume, runoff coefficient and suspended sediment load have increased by 2.37, 2.17 and 11.04 percent, respectively, compared to control treatment. The results showed that runoff volume and coefficient for the vermicompost are almost the same as the bare soil treatment, but the suspended load has increased. One-way analysis of variance showed that there was no significant difference between treatments at 51 mm / hr in all parameters. With increasing rainfall intensity from 51 to 65 mm / h, in straw treatment, the runoff volume, suspended sediment load and runoff coefficient decrease to 64.91, 45.46 and 64.90 percent respectively, compared to bare soil treatment. These parameters in vermicompost treatment, have decreased by 47.18, 35.85 and 47.18%, respectively. The results of univariate analysis for variance in intensity 65 (table 3) for the modifiers implied that decreasing changes of runoff volume and runoff coefficient in the confidence level of 99% and the suspended load parameter in the 95% confidence level are significant. At a lower intensity (51 mm / hr), the positive effects of the modifiers are less appeared, while at a higher intensity (65 mm / hr) both amendment treatments have been able to play their protective role and reduce the parameters of erosion and sediment load at a meaningful level. Independent t-test results show that with increasing rainfall intensity, only control treatment has shown that the parameters of runoff volume, suspended sediment load and runoff coefficient have increased by a confidence level of 99%; however, with two wheat straw and Vermicompost, the soil has been able to reduce the destructive effects of increasing rainfall intensity. The results of two-way analysis of variance indicate that there is a significant difference in the confidence level of 99% between volume and coefficient of the runoff variables and 95% confidence level in suspended sediment variables. This is a drastic effect that, by increasing the intensity from 51 to 65 mm / hr, with the change of treatment from bare soil to vermicompost and then wheat straw, the decomposition conditions have been found on these parameters. 4-Conclusion The results showed that using two wheat straw and vermicompost amendments at levels of 400 and 500 g / m2, and in two-square meter plots with completely normal conditions, at 51 mm / hr, straw treatment has been able to reduce the volume and coefficient of runoff compared to the control treatment, but the suspended sediment load has increased. In vermicompost treatment, all of these parameters increased in comparison with control treatment, but in both treatments these differences were not significant. With increasing intensity to 65 mm / hr, both amendment treatments reduce the runoff volume, sediment load and runoff coefficient at a significant level and it can be said that these two amendments showed their positive and protective roles at 65 mm / hr intensity. |