Abstract
Some soil properties were studied in relation soil aggregate along a climatologically region and different crop land use in the Northeast of Sulaimani City/Kurdistan Region of Iraq. Five locations were selected along these regions ranging from semiarid to sub-humid climatologically conditions. The soil physical, chemical properties, aggregate stability and size distribution were analyzed. A mean-weight-diameter (MWD) value was determined on 5 soils, which was the sum of the percentage of soil on each sieve (6, 3, 1.5, 0.75, 0.375 and 0.125 mm). The results of the measurements could evaluated with linear correlation coefficients for the relationships between aggregate stability (MWD) and soil physical and chemical properties of the different crop land use. The correlation coefficient for the relationship between aggregate stability and organic matter was highly significant (P < 0.0l%) which is in agreement with the findings of [1]. Generally large aggregates (large 6, 3, 3 - 1.5 mm) were present in highest proportions in the most semiarid of the studied areas. Aggregates 0.75 - 0.125 mm were positively correlated to fine, very fine sand and silt fractions and to organic matter. Stability of aggregates showed a positive correlation with clay content and organic matter content, while the carbonate content was strongly correlated with aggregate stability. The land use history affecting soil overlaps the pattern of climatological situations and cultivated crop lands and has to be taken into account. Aggregate size distribution and stability can be used as indicator of soil conservation and productivity.
Highlights
Soil aggregation is defined as the group of soil particles in which the forces held the particles together [2]
The objective of this study was to predicate the relationships between the soil aggregate stability and the soil surface coverage factors, these relationships will predicate the conditions raising the stability of soil aggregates, which may participate to the increase of efficient soil management to increase the soil aggregate stability
Effect Organic Matter Content on Aggregate Stability (MWD) More techniques were used for evaluating soil aggregate stability, like: changes in moisture characteristic, changes in permeability, and wet-sieving [21]
Summary
Soil aggregation is defined as the group of soil particles in which the forces held the particles together [2]. The aggregation is formed by some processes like physical, chemical and biological forces which are mainly responsible for their stabilization [3] [4]. The formation of aggregates are affected by some factors that are involves wetting and drying, and freezing cycles, All these processes are able to bring soil particles close together that the physical and chemical forces between them hold the particles [3]. Plasticity refers to the response of a soil to changes in moisture content (Coduto, 128). The plasticity index is a measure of the range of moisture contents that encompass the plastic state (Coduto 130) and is the numerical difference between the liquid and plastic limits. Soil aggregate stability is widely used to measure change in soil structure due to different management options [6] [7]. The extent of aggregate disintegration by wetting depends on aggregate stability which is related to organic matter, and clay content [8] [9]
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