Formation And Development of Vertisols in Selivany Plain at Duhok Governorate, Kurdistan Region, Iraq

Abstract

The study area located at the Selivany plain in Duhok governorate, Kurdistan Region, Iraq. Forty- three soil samples were taken from horizons in all studied pedons then physically and chemically analyzed according to standard methods. The studied soils were slightly alkaline non- saline. The values of CEC increased with increasing clay content. The Studied soils considered Vertisols and occurs pedoturbation, in turn, trans-locating organic matter from surface to subsurface and deep horizons, additionally, existing plant roots contribute in increasing organic matter in these horizons, and the humification process can occur in different soil horizons. Total carbonate content increased with increasing depth in subsurface horizons this due to the origin of limestone parent materials. The differences in carbonate distribution manner indicated to development. The studied soils contain a considerable amount of active carbonate that affecting different soil properties. Relatively high clay content in studied soils and its content at the surface horizons are lower than it at subsurface horizons. The high value of clay and silt content indicates to soil development. The following pedogenic processes can be specified loss, gain, leaching, illuviation, eluviation, alkalization, humification, lessivage, desalinization, calcification, decomposition, synthesis, pedoturbation, and braunification. Humification processes of organic matter are predominate because the ratio of carbon to nitrogen (C / N) is less than 25. According to the criterion (Total clay in B-horizon / Total clay at A-orizon) most of the studied pedons (1, 3, 6, 7, 8, 9, 10, 12, 13, and 14) considered as well developed soils. The ratio of (Active carbonate/ Total carbonate) was high ranged between (0.31-3.14%), and this may be due to the high weathering intensity of parent material, as a result of increased the ratio mass of active carbonate to total carbonate.

Study Soil Development and Classification in Erbil Province, Kurdistan, Iraq Using Mathematical Indices

“…Argillic horizon existed in development pedons (2, 4, 5, and 7) because the clay content in the previous pedons corresponding to the requirement of Argillic horizon formation (48). Silt fraction ranged between (175-391) g Kg -1 and there is no constant manner of silt distribution along studied pedons, which sometimes increase with depth (27), and in other times decreased with depth (2), additionally may be fluctuated between increase and decrease in other pedons (1). The results of sand content illustrate an increase in their amount in less developed soils and the absence of (B) horizon therefore the high sand values were found in pedons (1, 3, and 6).…”

“…The ratio of active CaCO 3 /total CaCO 3 is another index used for illustrating the degree of soil development. Increasing this ratio is an indicator for an increasing the intensity of pedogenic processes and soil horizons will be more distinct (1). The active CaCO 3 /total CaCO 3 ratio increases with depth in pedons (1, 2, 3, 4, 5, and 7), while, slightly fluctuated with depth in pedon (6).…”

“…Figure 2. Interpolated map for C/N ratio Increasing of C/N ratio is an indicator of the soil organic matter decomposition is slow, and littering is a common process that indicates a high C/N ratio and decrease in organic matter decomposition in the soil (1). In line with this idea, and as a result of low C/N ratio in study soils (1.1-5.7), therefore, these soils have a highly decomposed organic matter and dominance of humification process this was related with high rainfall amount and the existence of considerable amount of plant residuals particularly for forest trees in study locations.…”

Hydrological Evaluation in Dohuk-semel Area

“…The study area soils are of mixed type, consists of grain size ranges from fine clay to coarse sand (Khasback, 1973;Jassim and Sisakian, 1978). In addition, according to (Abdulrahman et al, 2020) the accuracy types of study area is represented group D and the vegetation cover during rainy season consists of wheat, and straight row cultivation is used for soil treatment, therefore according to this specifications, the soil is of class A type (according to the classification proposed by this method). Soils in Group D have strong runoff potential and a relatively slow infiltration rate.…”

“…Finally: Numerous agro-hydrological studies have been conducted in the subject area, including those by Parson Co. (1955), Taufiq and Domas (1977), Yaqo (1990), Hameed (2006, Fayadh (2010), and Abdulrahman (2020). Due to the world's changing environment, additional study was required to resolve agricultural issues.…”