Some aeration parameters of the dominant soils in Erbil region and their responses to agricultural machinery compactions

Other Title(s)

بعض معالم تهوية الترب السائدة في منطقة أربيل و استجابتها لانضغاط المكائن الزراعية

Dissertant

Muhammad, Kamyar Muttalib

Thesis advisor

Karim, Tariq Hama

University

Salahaddin University-Hawler

Faculty

Agriculture College

University Country

Iraq

Degree

Master

Degree Date

2012

English Abstract

Soil air permeability is one of the most important parameters which governs the aeration in agricultural soils and has a significant effect on the plant growth and crop production.

It is closely related to soil capacity parameters such as air-filled porosity.

The air-filled porosity and permeability relationships are different for different soils and compaction can change the air-water relationships.

Furthermore, air permeability is an easily measured parameter, closely related with water permeability and useful in soil remediation studies Notwithstanding extensive studies on air permeability determination for single and multi-phase flows on a global scale, there is lack of knowledge on air permeability and capacity parameters of the existing soils in Iraq Accordingly, this study was conducted with the main objective of determining the aeration parameters of the existing soils, highlighting the effect of compaction on air capacity and the possibility of predicting unsaturated hydraulic conducting from air permeability.

To achieve the above objectives, representative disturbed and undisturbed samples were collected from different depths from twelve different sites from across Erbil governorate.

Air permeability was measured by using constant pressure gradient method.

Air-filled porosity was measured by core method for soil samples obtained from uncompacted soils and for compacted soil samples receiving different number of passes (different trafficking intensities).

Also the unsaturated hydraulic conductivity for a set of soil samples was measured by upward infiltration method.

The main results of the present work can be summarized as follows : It was noticed that the air-filled porosity hardly fell below the lower limit of its critical range of 5 – 15 %, implying that the air capacities of the study soils were adequate.

With a few exceptions, it was noticed that the measured air permeability values fell in the fast (350 x 10-10 – 700 x 10-10 cm2) and very fast (> 700 x 10-10 cm2) air permeability classes.

Irrespective of soil type and soil depth, there was a sudden increase in air permeability over the lower range of air-filled porosity.

Thereafter, the air permeability curve flattened off over the upper range of air-filled porosity in most cases, implying that the air permeability (Ka) increased exponentially as air-filled porosity increased.

The results also revealed that the pore continuity index varied from a minimum value of 5.47 μm2 / m3 m-3 for Ainkawa soil sample obtained at a depth of 0.30 – 0.60 m to a maximum value of 181.48μm2 / m3 m -3 for the Qushtapa soil sample obtained from the same depth.

As regards, the air permeability at a matric potential of -100cm ranged from a minimum of 0.5 μm2 for Gomaspan soil to as high as 35.32 μm2 for Ainkawa soil.

The ratio of air-filled porosity to the air-filled porosity at a matric potential of -100cm explained more than 95 % of variations in the ratio of air permeability to the air permeability at the reference point in five selected soils.

The findings also indicated that the first six passes of the tractor wheel caused a major portion of the total soil compaction.

At a given time, there was a steady decrease in air-filled porosity with increase in degree of compaction.

The air-filled porosity decreased linearly with an increase in degree of compaction.

The field observation has shown that the soil at Grdarasha site can attain an adequate air-filled porosity value even after 1-2 days from rainfall events in the coldest month of the year when evaporation rate is very slow.

Additionally, linear regression analysis revealed that more than 90 % of variation in K (ө) was attributed to variation in air permeability.

Main Subjects

Earth Sciences, Water and Environment

Topics

• Soil conservation
• Soil mechanics
• Iraq
• Irbil

No. of Pages

118

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-314418