Extended Abstract

Background and objectives

Low rainfall, low soil organic matter, poor vegetation and the 120-day winds of Sistan have made the rangelands of this region highly susceptible to wind erosion. Wind erosion has caused a lot of damage to the people of this region, among these damages can be mentioned the reduction of visibility and the occurrence of road accidents, the reduction of human health, the loss of soil, the reduction of the potential of agricultural lands, etc. Therefore, it is necessary to investigate ways to increase soil resistance against wind erosion. The present research was conducted in order to study the effect of humic substances on increasing soil stability in the degraded rangelands of Taghzi, Zabul city.

Methodology

This research was conducted as a factorial experiment in the form of a completely randomized design with 3 replications. The first factor was soil type in 3 levels: soil with low sensitivity to wind erosion (S1), medium sensitivity (S2) and high sensitivity (S3). The second factor of humic substances was considered in 2 levels including: humic substances (combination of humic acid + fulvic acid: H1) and without humic substances (H0). In one step, humic substances were added to the soil of the pots in the form of irrigation. The amount of humic material required for each pot was calculated based on its soil content and added to each experimental unit along with 200 ml of water. Also, in the control treatment, 200 ml of water was added to the soil. After three months, the effect of humic substances on the amount of acidity, electrical conductivity, lime percentage, organic matter, nitrogen percentage, soil microbial respiration, microbial population, soil stability including the weight percentage of soil grains in wet sieve and dry sieve and the mechanical resistance of wet soil were measured. After determining the normality of the data distribution and homogeneity of the variances, analyzing the variance of the data with Statistix 10 software and average data comparison was done with LSD test at 5% probability level.

Results

The results showed that the highest amount of lime (37.17%), microbial respiration (0.14 mg of carbon dioxide per gram of soil per day) and nitrogen (0.33%) were measured in the application of humic substances in soil with high sensitivity. In soil with low sensitivity, the lowest amount of lime (19.50%) was observed in the application of humic substances. The minimum microbial respiration (0.03 mg of carbon dioxide per gram of soil per day) was measured in all soils without the use of humic substances. The lowest amount of nitrogen (0.03%) was measured in soil with medium sensitivity and without humic substances. The highest percentage of dry soil grains was measured in the application of humic substances in 11.2 mm sieve in soil with high sensitivity and 2 mm sieve in medium sensitivity soil. The most wet soil grains in the 11.2 and 8 mm sieve were related to soil with high and medium sensitivity in the application of humic substances. Humic substances caused the maximum increase of wet soil grains in low sensitivity soils in 4.75 mm sieve. The most wet soil grains in the 1.8 mm sieve were related to highly sensitive soils. In general, the lowest amount of wet soil grains was observed in the absence of application of humic substances. The use of humic materials increased the maximum mechanical resistance of soils with medium and low sensitivity.

Conclusion

In general, the results of the present study showed that the application of humic substances was effective in improving the physical and chemical properties of the degraded soils of the researched rangelands. The use of humic substances had positive effects in increasing nitrogen and soil microbial respiration and subsequently creating suitable conditions for the activity of existing soil microorganisms. Overall, the application of humic substances compared to Solutions such as the use of chemical fertilizers in soils sensitive to destruction and wind erosion as an accessible and environmentally friendly soil conditioner can be a completely sustainable solution in improving the physical and chemical properties of the soil and as a result Increase soil stability. The cost of using these materials is often negligible compared to the damages caused by erosion (such as reduced soil fertility, loss of vegetation, increased costs of rangeland restoration, and environmental risks), making it economically justified in most cases. However, for more accurate decision-making and to recommend this method for enhancing rangeland sustainability, conducting an economic analysis tailored to the conditions of each region is essential.