Extended Abstract
Introduction: Land degradation in arid and semi-arid regions, such as Iran, poses a serious challenge to sustainable agriculture and ecosystem health. Approximately 100 million hectares of Iranian land are currently exposed to desertification, driven by both natural and anthropogenic factors. Agricultural activities, while essential for food security, often contribute to soil degradation through practices such as over-cultivation, improper irrigation, and excessive use of chemical inputs. In regions like the Saravan Plain, increasing population pressure has led to the conversion of rangelands to agricultural lands without adequate soil management. These land use changes have adversely affected key soil health indicators, including nitrogen (N), organic matter, salinity, and pH, accelerating degradation processes. Understanding the impacts of different agricultural land uses on soil quality is critical for developing sustainable management strategies in arid regions with limited soil resources. This study aimed to evaluate the effects of different agricultural land use types on soil quality indicators in the Saravan Plain and to identify management practices that can mitigate degradation and enhance soil sustainability.
Materials and methods: This field research was conducted in the central part of the Saravan Plain to assess the impact of agricultural land use types on soil degradation. A split-plot design based on a completely randomized block design with three replications was employed to compare four dominant land use types: irrigated monoculture, irrigated polyculture, orchard, and rangeland (as control). Soil samples were collected from two depths (0–40 cm and 40–80 cm) using random sampling to ensure representative coverage of each land use type. Samples were air-dried, passed through a 2 mm sieve, and analyzed using standard laboratory methods. Measured parameters included micronutrients (Mn, Zn, Cu, Fe) via atomic absorption spectrophotometry, electrical conductivity (EC) using a conductivity meter, pH using a pH meter, and organic matter content via the Walkley-Black method. Data were categorized into ameliorative factors (N, P, K, organic matter, sulfate, Mg, Mn, Zn, Cu, Fe, Ca) and degradative factors (chloride, pH, EC). Statistical analysis was performed using ANOVA to examine significant differences between treatments, followed by Duncan's multiple comparison test. All analyses were conducted using SPSS, SAS, and Excel software.
Results and Discussion: The results revealed significant differences in soil quality among the four land use types. In general, irrigated monoculture and polyculture lands exhibited higher levels of ameliorative factors, while rangelands showed higher levels of degradative factors. In the surface layer (0–40 cm), mean organic matter content was significantly higher in monoculture (0.34%) and polyculture (0.30%) lands compared to rangelands (0.18%). Similarly, N levels were significantly higher in monoculture (0.037%) and polyculture (0.032%) compared to rangelands (0.02%). Among degradative factors, pH showed significant differences, with orchards exhibiting the highest acidity (8.23) compared to rangelands (7.71). EC was highest in monoculture lands, likely due to chemical fertilizer application and salt accumulation, showing significant differences from other treatments. Chloride concentration was highest in polyculture lands (59.64 meq/L). In the subsurface layer (40–80 cm), monoculture lands consistently performed better, with organic matter (0.26%) and nitrogen (0.027%) significantly higher than rangelands (0.14% and 0.012%, respectively). Micronutrient analysis revealed that Cu levels in monoculture lands (0.67 mg/kg) were significantly higher than in rangelands (0.21 mg/kg) in the surface layer. Based on a scoring system that integrated all soil quality indicators, monoculture lands received the highest score (+10), indicating the most suitable conditions for soil improvement. In contrast, rangelands received the lowest score (-19), reflecting the least favorable conditions for soil ameliorative properties across both soil layers.
Conclusion: This study demonstrates that agricultural land use type significantly influences soil quality in the Saravan Plain. Irrigated monoculture lands exhibited the greatest potential for soil improvement, as reflected in higher organic matter and N content, along with reduced chloride and pH levels. Conversely, rangelands were the most vulnerable, characterized by the lowest ameliorative factors and the highest degradative factors. These findings underscore the importance of targeted agricultural management practices for improving soil health and reducing desertification risk in arid and semi-arid regions. Future research should focus on long-term monitoring of soil dynamics and validate these findings in other arid regions using complementary technologies such as remote sensing to enhance the generalizability of results.