| چکیده انگلیسی مقاله |
Introduction and Goal
Soil is the basis of biological resources and life on the earth. Soil stability is one of the key indicators that it used to performance evaluation of soil structure against soil erosion. In fact, the aggregates stability indicates the resistance of the soil structure against external forces such as the raindrops impact and splash erosion. The raindrops energy is one of the main factors in the disintegration of soil aggregates in water erosion. The usage of different conditioners on the surface or inside soil is closely related to various processes such as surface sealing, infiltration, runoff, evaporation and finally soil erosion. Considering the importance of the aggregates stability soil erosion control, increasing the particles diameter on the soil surface can be one of the ways to prevent their movement and by erosive factors. The literatures review showed that the bentonite conditioner as a mineral conditioner can play the effective role in stability changes of aggregates, especially in degraded soils. Therefore, the purpose of present research is to the usage of bentonite conditioner on the changes of soil surface aggregates.
Materials and Methods
In the present research, the conditioner of bentonite mineral used in amounts of 30, 15 and 45% of soil surface coverage and in three replications. At the first, collected soil from rangeland land to depth of 20 cm transferred to laboratory and was exposed to air-dry and passed through sieve of 4-mm. Then the soil was poured into the splash cups and placed under rainfall simulator with a rainfall intensity of 90 mm h-1 and a duration of 10 min. Surface soil before and after application of rainfall simulator was collected with depth of 2-mm with amount of about 50 g of the surface of splash cups and the aggregates stability was calculated using the method of wet sieve. In the method of wet sieve, the remaining soil on each sieve was drained into marked containers using washing method and then and was put to rest for 24 h. After draining the excess water of samples, the remaining sediment was transferred the appropriate containers with specific weight. Finally dried for 24 h at oven with temperature of 105˚C. Finally, the application effect of the bentonite conditioner on the variables of aggregation and aggregates stability was calculated using SPSS software.
Results and Discussion
According to the conservation function and the average diameter of the soil aggregates using bentonite conditioner in three values of 15, 30 and 45 percent and based on diameter classes >500, 250-500, 125-250, 100-125, 100- 53, 38-53 and <38 micrometer, the results showed that the average diameter of soil aggregates significantly changed under the effect of bentonite conditioner. The average mass of the aggregates in the control treatment was with rates of 0.82, 1.88, 6.82, 3.37, 9.53, 4.62 and 20.36 g respectively, in the mentioned diameters, and with bentonite conditioner in the amount of 15% was with rates of 1.16, 2.63, 8.17, 4.46, 10.81, 4.02 and 17.68 g, respectively. Also, in the conditioner with the amount of 30%, this variable was the rates of 0.84, 2.42, 93. 7, 4.32, 11.03, 3.46 and 17.38 g and in the amount of 45% was the amounts of 0.81, 1.96, 6.95, 3.53, 10.01, 3.51 and 31 It was 19 g, respectively. The results of GLM test showed that the effect of bentonite conditioner on the variables D10, D10/ D90 and sorting was significant in level of 95% and on the variables D50, D90, D90- D10, D75- D25 and skewness was significant in level of 99%. But the bentonite effect was not significant on the variable D75/ D25 and kurtosis. Also, the results of Duncan test showed that the bentonite conditioner with rates of 15 and 30% had the better effects on the stability of soil aggregates and increasing the average aggregates diameter.
Conclusion and Suggestions
The obtained results from this research showed that bentonite conditioner can act as a protector against the raindrops and reducing soil erosion with creating adhesion on the soil surface. According to the results of the present research, it is suggested that the first, the more researches be conducted due to the soil conditions and natural rainfall and then the optimal values of bentonite be determined by erosion management and runoff. |