Investigation of the Relationship between Natural Hydrophobicity and Physicochemical Properties of Soil in Different Land Uses in the Coastal Areas of West Guilan

Soil water repellency is a dynamic property that delays the infiltration of water into the soil and increases the potential for runoff and erosion. Accurate knowledge about the existence and severity of soil water repellency (SWR) in the coastal areas of Guilan, which are under different land uses, is very important. The present study evaluates the effects of land uses on soil water repellency in three areas: 1) Forested area with Pinus Teda, 2) forested area planted with Pinus Teda in some parts and covered with natural wild pomegranate in other parts 3) Agricultural land covered with Diaspyros Kaki. Soil water repellency was measured using three tests of the water drop penetration time (WDPT), the molarity of ethanol droplet (MED) and the soil wetted area (SWA). Significant differences in soil water repellency were found among the different land uses. Forest soils under pinus Teada showed the highest SWR and the soils under wild pomegranate and persimmon cultivated area showed the lowest SWR. Also, the relationship between SWR and soil properties (soil organic matter, pH, total nitrogen, phosphorus, Cation Exchangable Capacity, Electrical Conductivity, sodium, potassium, calcium, magnesium, soil texture, bulk and particle density) was investigated in 200 samples. Principal component analysis (PCA) showed that organic matter, total nitrogen with a positive effect and soil acidity with a negative effect are the most important parameters controlling repellency in these soils. To investigate which component of the soil particles have a more important role in creating water repellency, the intensity of water repellency was examined in six particle sizes of the soil (1-2, 0.5-1, 0.25-0.5, 0.125-0.25, 0.05-0.125 and less than 0.05 mm). The results showed that although coarse-textured soils are more prone to repellency, the smallest particle size in these soils plays a very important role in the intensity of soil water repellency.