The Impact of Land Use on Erodibility and Soil Quality (Case Study: Hashtian Catchment, Urmia Lake)

Soil erosion is considered as an important factor in reducing soil quality and degradation. One of the important and influential parameters in soil erosion is the types of land use. Each of the land uses directly and indirectly affects the erodibility of the soil and as a result the quality of the soil. Heshtian Catchment area needs monitoring of soil quality and erodibility due to natural conditions, human interventions and diversity of land use. Therefore, the purpose of this research is to investigate the effect of land use on erodibility and soil quality in Hashtian Catchment. In this research, 21, 18 and 14 samples of agriculture, pasture, and garden land use were taken from the basin by systematic-random method, respectively. By performing statistical analyses, the physical and chemical characteristics of the samples, including sodium, potassium, total phosphorus, organic carbon, electrical conductivity, pH, calcium, saturated percentage, bulk density, particle density, and soil texture were determined. Using variance analysis, the relationship between the measured parameters and land uses was determined. The results showed that most physical and chemical parameters of soil with P value less than 0.05 have a significant relationship with land use. Also, the results showed that soil quality index with P value (0.17) has no significant relationship with land use, and soil erodibility with P value less than 0.001 has a significant relationship with land use. Also, using Post-hoc test and Tukey's method, it was determined that agricultural use with better quality soil due to aeration and remaining straw and stubble during plowing and vegetation is suitable, and pasture use is suitable due to excessive livestock grazing and the reduction of soil nutrients has a high erodibility compared to agricultural and garden use.
 Extended Abstract
1-Introduction
Soil assessment is important to achieve sustainable development in any region because soil is a vital component of ecosystems and plays a major role in habitat characteristics, ecosystem stability and biogeochemical cycles. Soil conditions and stability are closely related to human health and sustainable development of the natural environment. Considering that manufactured products support the human population, therefore, sustainable use of soil resources is necessary for the long-term health of soil quality and sustainable development. Soil characteristics that are sensitive to changes in land use and management can be used as indicators and criteria of soil quality. Choosing the suitable number of criteria is the most important step in the evaluation and monitoring of soil quality and sustainable development, which is called the minimum data set. The methods of measuring individual criteria or the set of minimal data are used in the direction of temporal and spatial monitoring of the stability of soil quality and evaluation of land management and use. Multivariate statistical techniques and modeling approaches are among the tools to determine and detect suitable parameters in choosing the minimum data set. Hashtian watershed is also very sensitive to erosion due to natural conditions and human interferences and variety of land use, and inappropriate use of land, cultivation on steep slope, non-compliance with the principles of soil conservation operations and grazing more than livestock has increased the intensity of erosion, reduced soil fertility and increased runoff in the basin, and ultimately caused pollution of water sources and environmental problems.
2-Materials and Methods
Hashtian watershed is located in West Azarbaijan province, Urmia city, which is located in the west of Urmia lake. Soil sample of 0-20 cm was collected to determine the characteristics of the soil. After air drying, the samples were passed through a 2 mm sieve. In all the samples, sodium and potassium were measured by flame photometry, total phosphorus by spectrophotometry (Nasrati and Majdi, 2016), organic carbon by Walky-Black oxidation method (Mylavarapu, 2014), pH with a pH meter, electrical conductivity with an EC meter, total soil lime with a calcimetric method, soil texture with a hydrometric method (Nosrati and Collins, 2019). Apparent specific gravity using untouched samples by Sampling ring, true specific gravity by weight method, soil porosity by calculating the percentage of available pores (Carter and Gregorich, 2006), saturated moisture capacity was obtained from the difference in the weight of saturated mud, before and after drying in the oven. The accessible water of the samples was determined using the soil water pressure device. In this research, mainly in all stages of the investigation, multivariate statistical techniques such as factor analysis, principal component analysis and variance test were used. was used. The decision-making method in the analysis of variance method is based on the value of the F statistic and P value. The soil quality index and the soil erodibility was obtained.
3- Results and Discussion
The results showed that among physical and chemical characteristics, land use has an effect on apparent specific gravity, true specific gravity, soil texture (sand, clay, silt), organic carbon, electrical conductivity, sodium, potassium, percentage of saturated moisture and lime. Other physical and chemical characteristics of the soil due to the high amount of P (more than 0.05) do not have a significant correlation with land use. Also soil quality index was calculated based on minimum data set, results showed that the average values ​​of soil quality in agricultural land uses are better than pasture and garden land use. Also, after calculating the erodibility of the soil, the analysis of variance statistical test was used to investigate the effect of land use on soil erosion. According to the results of variance analysis, land use has an effect on soil erodibility with P value (0.00) and has a significant correlation. Also, based on the post-hoc test and Tukey's method, it was determined that the average values ​​of soil erodibility in land use have a significant correlation. Among the three land uses, the amount of soil porosity is higher in pasture land use. The lack of cultivation and plowing in the garden has reduced the density of the soil and the stability of the soil grains (Chen et al., 2010), which is similar to Wang et al. (2010) in this respect, and does not match with results of Alinejadbidabadi and Kiani (2016). Considering the greater adhesiveness of clay compared to silt particles and the low mass of silt particles compared to sand particles along with excessive livestock grazing and also the slope of the catchment, silt particles have been eroded and its amount in pasture land use have been decreased compared to agricultural land use and garden and instead increased the amount of sand, which is similar to the results of Karimi et al. (2017). The reduction of organic matter has also reduced the percentage of saturated moisture
 
4- Conclusion
In this research, the impact of land use on erodibility and soil quality in the Hashtian watershed was investigated using statistical analysis. According to the results, most of the physical and chemical parameters of soil have a significant relationship with land use, which means that land use affects these parameters and there is a significant relationship between other parameters and land use. According to the results and the chart of the soil quality index, agricultural use has better quality soil than pasture and garden use, the reason for this is the remaining straw and stubble and soil aeration due to plowing and lack of excessive erosion by protecting the cover. It is a plant in the rainy season. Also, pasture use has the highest rate of erosion due to the reduction of nutrients and vegetation as a result of excessive grazing.