امکان‌سنجی استفاده از بنتونیت در احیای پایداری خاکدانه در خاک کاربری‌های مختلف پس از وقوع آتش

Soil stability refers to the resistance of the soil structure against external forces such as the impact of raindrops and splash erosion. Some human factors, such as fire, not only cause the vegetation reduction, the bare becomes soil surface and its vulnerable, but also have the destructive effects on the aggregates stability of surface Fire causes the soil to be susceptible to erosion by reducing organic matter, reducing the aggregates stability and reducing soil quality. Considering that the vegetation establishment in the affected areas by fire requires a lot of time and money, the application of soil conditioners in order to vegetation restoration and increasing the aggregates stability in affected areas by fire is an important step in restoration of these areas. Landuse has the significant effects on changes of soil erodibility factor, and the studies have shown that the forest landuse has the lowest amount of soil erodibility factor compared to pasture and cropland landuses. The present study was conducted with the investigation aim of aggregates stability before and after fire using bentonite conditioner with different levels in forest, pasture and agricultural landuses.
Materials and methods: At first, the collected soil from each landuse was placed in plots and compacted to specific weight to natural conditions and subjected under mean-fire conditions. Then, the remaining ash was collected from the surface of the fire plots and rainfall simulation with rainfall intensity of 90 mm h-1 and duration of 10 min was performed in the control treatments (soil without conditioner, burned and un-burned soil), fired and unfired soil containing different levels of bentonite with rates of 15, 30 and 45 percent in three replications. The used rainfall simulator in this study is placed on a metal structure in the form of A, with the ability to adjust the height from 2 to 2.7 m. To stability measurment of the aaggregates stability, surface soil was collected to depth of two mm with an amount of about 50 g from the surface of the splash cups, and the aggregates stability was calculated using the sieve method. Excel and SPSS software were used to performance of all statistical analyses. In order to extraction of the grading components, including the mean, standard deviation, skewness, and kurtosis and as well as all variables, D10, D50, D90, D90/ D10, D75/ D25, D75-D25 was used from GRADISTAT macro in different treatments under Excel software.
Results: The conditioner effect of bentonite on forest landuse showed that the bentonite with level of 15 percent compared to the other two levels increased the aggregates stability in finer particles and levels of 30 and 45 percent increased the stability in coarser aggregates. In rangeland landuse, bentonite conditioner, all three levels of conditioner increased the average diameter of coarser aggreagets. In agricultural landuse, bentonite conditioner, in level of 15 and 30 percent showed that the more effect on aggregated stability on finer aggregates stability. The landuses effect on the stability of soil aggregates showed that this parameter had the significant effect on the variables D10, D50, D90, D90/ D10, D75/ D25, D75-D25, sorting, skewness and kurtosis at the level of 99 percent. The fire treatment was also significant on the variables D90, D90/ D10, D90- D10 sorting and kurtosis at the level of 99 percent, D75-D25 at the level of 95 percent. The conditioner effect of bentonite at before and after fire on the stability of soil aggregates also showed that it was significant on the variables D10, D50, D90, D90/ D10, D90- D10, D75-D25and skewness at the level of 99 percent. The interaction effect of landuses and fire on variables D90, D90/ D10, D90- D10, sorting and kurtosis of soil aggregates were significant at the level of 99 percent. Also, the intraction effect of landuses and bentonite conditioner on variables of D10, D50, D90, D90/ D10, D75-D25, and skewness was at the level of 99 percent and also on skewness and kurtosis significant at the level 95 percent. The results showed that conditioner can act as a soil amendment and by creating adhesion on the soil surface, it can stable the soil aggregates against raindrop impact and reduce soil erosion. According to the results of the present research, it can be stated that the usage of bentonite clay was beneficial in managing and reducing erosion and making executive decisions, although the final conclusions depend on conducting more extensive research in natural fields.
Results: The conditioner effect of bentonite on forest landuse showed that the bentonite with level of 15 percent compared to the other two levels increased the aggregates stability in finer particles and levels of 30 and 45 percent increased the stability in coarser aggregates. In rangeland landuse, bentonite conditioner, all three levels of conditioner increased the average diameter of coarser aggreagets. In agricultural landuse, bentonite conditioner, in level of 15 and 30 percent showed that the more effect on aggregated stability on finer aggregates stability. The landuses effect on the stability of soil aggregates showed that this parameter had the significant effect on the variables D10, D50, D90, D90/ D10, D75/ D25, D75-D25, sorting, skewness and kurtosis at the level of 99 percent. The fire treatment was also significant on the variables D90, D90/ D10, D90- D10 sorting and kurtosis at the level of 99 percent, D75-D25 at the level of 95 percent. The conditioner effect of bentonite at before and after fire on the stability of soil aggregates also showed that it was significant on the variables D10, D50, D90, D90/ D10, D90- D10, D75-D25and skewness at the level of 99 percent. The interaction effect of landuses and fire on variables D90, D90/ D10, D90- D10, sorting and kurtosis of soil aggregates were significant at the level of 99 percent. Also, the intraction effect of landuses and bentonite conditioner on variables of D10, D50, D90, D90/ D10, D75-D25, and skewness was at the level of 99 percent and also on skewness and kurtosis significant at the level 95 percent. The results showed that conditioner can act as a soil amendment and by creating adhesion on the soil surface, it can stable the soil aggregates against raindrop impact and reduce soil erosion. According to the results of the present research, it can be stated that the usage of bentonite clay was beneficial in managing and reducing erosion and making executive decisions, although the final conclusions depend on conducting more extensive research in natural fields.