Soil color as an indicator to predict some of it's properties and suitability for agricultural uses in Iraqi Kurdistan Region

Other Title(s)

لون التربة كمؤشر لتخمين بعض صفاتها و ملائمتها للأغراض الزراعية في إقليم كردستان، العراق

Dissertant

Yahya, Izzat Fandi

Thesis advisor

Karim, Tariq Hama

University

Salahaddin University-Hawler

Faculty

Agriculture College

University Country

Iraq

Degree

Ph.D.

Degree Date

2012

English Abstract

Soil is one of the most important national resources of any country.

Not only it grows a variety of food and fodder crops, but also produces raw materials for various industries.

Field trips throughout the mountainous area revealed that there are numerous patches of colorful soils.

While substantial progress has been made in description of normal soils.

Much less is known about the characteristics of these abnormal soils.

Furthermore, the difficulties of the standard methods relative to the ease of identifying soil colour has resulted in many attempts to predict many soil properties from soil color.

So the present study has been undertaken to widely describe the dominant colored soils in the studied region and to assess their suitability for agricultural and non-agricultural uses plus the possibility of predicting some soil components from color measurement.

To achieve the above objectives, representative soil samples were collected from a total of 42 locations distributed throughout Iraqi Kurdistan Region.

A broad range of colored soils were included.

Before performing a series of laboratory and field experiments, representative subsamples were taken for physical, chemical, geotechnical, microbiological and mineralogical analyses.

To develop relationships between soil organic matter content and soil colour, samples from three cultivated soils were treated with finely ground sheep manure equivalent to organic matter percent ranging between 0 and 10 %.

Soil color was measured with Munsell Color book in both dry and wet states.

To predict soil moisture content from soil color measurement, six different soil samples with water content varying from 0 to 0.35 kg kg-1 were prepared.

After taking photos with a digital camera, the images were compared with different gray scale colors another attempt was made to determine the comparative effectiveness of colored soils on soil temperature moderation red, chalky and gray soils were used as mulching materials and spread over the surface of the soil at Sumail site in a layer 5 cm in depth.

Following mulching, a metal thermometer was buried at a depth of 5 cm below the soil surface to note the soil temperature at the indicated depth over a period of 33 days.

In order to investigate the response of corn growth grown in coloured soils to fertilizers, a pot experiment was also laid in completely randomized block design using three replicates.

Each block consisted of 12 combination treatments of colored soil (red, gray, white, yellowish brown) and type of fertilizer (No fertilization, N, NP, and NPK).

At the end of the experiment, the plant height was measured and the crop was harvested to determine fresh and dry weight under each treatment.

To detect the magnetic suitability of the soils, which have a considerable amount of iron; four red beside soils two cultivated soils were tested using low frequency measurements.

Eventually, standard procedures were followed to determine the swelling pressure and California bearing ratio for 6 coloured soils after remolding.

The tested specimens covered two gray, two red and two white soils.

The specific objective was to study the suitability of these soils as subgrade materials.

The main results can be portrayed as follows : I.

Brief Characterization of the Studied Soils 1.

In general, the investigated soils were non-saline, neutral to mildly alkaline in reaction, calcareous and low in soil organic content 2.

There was a broad variation in clay content.

It ranged between 5.6 % and 76.35 % 3.

The majority of soils at their site were in a loose state or uncompacted.

4.

The liquid limit of the majority of the soil samples was less than 50 %.

5.

Based on clay activity (Ac), values of the studied soils were classified as inactive clays (Ac < 0.7).

Further, the majority of the investigated soils fell in clay of low plasticity.

6.

It was also noticed that the percent of linear shrinkage for nearly all the investigated samples was less than 9 %.

7.

Different colored soils offered different mineralogical composition.

8.

With exception of the white soils, SiO2 constituted a major portion of the majority of the investigated soils.

Apart from this, CaO constituted a high percentage of the white soils.

9.

The Fe2O3 content of the red soils was higher compared to that of the remaining soils.

Estimating Soil Water Content from Soil Color Using Munsell Color Book and Image Analysis : 1.

The results indicate that the addition of moisture to the investigated soils had little effect on both the hue and chroma.

2.

The decrease in value occurred primarily between air dryness and a threshold value with no significant change in value above this limit.

The upper limit, over which the Munsell value changed, ranged from 5 to 15 %.

3.

The addition of moisture caused the value of Qelachwalan, Spelik, Makhmor1and Swaretoka 1 soils to decrease by 2 units, compared with a decrease of only 1 unit for the Dukan 2 and Bajlor1 soils.

4.

The darker the soil color the less will be the change in Munsell value renotation due to increase in soil moisture 5.

The regression models for the linear portion of the curves indicated that ³ 90 of variation in soil moisture could be explained based on variation in Munsell value in majority of the investigated soils.

6.

The variation in gray scale explained more than 80 % of variation in soil moisture content in most cases.

III Prediction of Soil Organic Matter Content from Soil Color Measurements 1.

Munsell hue and chroma did not appear to be a good predictor of SOM.

2.

The range over which the Munsell value changed became narrower upon soil moistening.

Stronger relationships existed between dry Munsell value and soil organic matter content (SOM) for the investigated soils than for moist Munsell value and SOM.

3.

Munsell value did not respond to variation in soil organic matter content in the range of 10 to 40 g kg-1, but there was an abrupt decrease in Munsell value as the soil organic matter increased from 50 to100 gkg-1 in most cases 4.

Transforming soil organic matter SOM by log10 resulted in a more normal distribution of values and increased the coefficient of determination for the most relationships.

IV.

Comparative Effectiveness of Colored Soil Materials on Soil Temperature Moderation 1.

The order of effectiveness of soil temperature moderation was : Spirez chalky mulch > Sheqlawe1 chalky mulch > Sinjar1 red Gercus mulch > Hejran Gray mulch > check.

2.

The soil temperature at a depth of 5 cm under the Spirez chalky mulch was lower by as much 7.5 o C compared with the check treatment.

3.

The soil temperature under the check treatment and the Spirez chalky mulch averaged about 1.1 and 0.89 times as much as the air temperature respectively.

V.

Soil Magnetic Susceptibility of Some Selected Soils 1.

With no exception, each of the studied soils offered a permeability value less than that of air.

This gave rise to a negative susceptibility value for each soil, but close to zero.

It varied from as low as -0.076 for Makhmor1 soil to as high as -0.036 for the Sinjar 1 soil.

2.

The investigated soils were grouped under diamagnetic class.

3.

There was an indication of a direct relationship between magnetic susceptibility and soil free iron oxides content VI.

Evaluation of Colored Soils for Engineering Uses 1.

The C.B.R.

values ranged from as low as 2.91 % for Basifr 1 gray soil or Bajlor 1 red soil to as high as 19.32 % for Spirez white soil 2.

The white soils offered the best performance compared with the remaining colored soils.

In contrast, the red soils offered the least performance.

3.

The swelling pressure ranged from 0.00 for the white soils to 61.03 kPa for the Basifr 1 gray soil.

4.

The gray soils can be categorized under the group which had medium degree of soil expansion (swelling pressure).

On the other hand the red soils were classed under low swelling potential group.

VII.

The Number of Viable Microorganisms in Some Selected Colored Soils 1.

The results indicate that the Sheqlawe 2 soil yielded the least number of microorganisms and the Bajlor 1 the second lowest.

On the contrary the Pshtgry cultivable soil yielded the highest number of microorganisms.

2.

Regression analysis indicate that the number of microorganisms was linearly and negatively correlated with the soil iron oxide content VIII.

Biological Experiment 1.

In general, there was a slight response to type of fertilizer in the colored soils without a defined trend.

2.

Planting in colored soil, irrespective of fertilizer type, led to more than a 10-fold reduction in dry matter compared planting in Sumail soil.

IX.

Correlations and Prediction Equations 1.

among an array of the studied variables, the organic matter and iron oxides were negatively and high significantly correlated with the Munsell value.

But the calcium carbonate was positively and high significantly.

2.

Only calcium carbonate and iron oxide affected the Munsell chroma significantly.

3.

No statistically significant correlation existed between Munsell colour variables and each of sand, silt and clay content.

4.

The average error of prediction of iron oxide, calcium carbonate and organic matter content from Munsell value were 1.34, 13.3 and 0.72 % respectively.

5.

Multiple regressions showed that both organic matter content and calcium carbonate content explained about 51 % of variability in the Munsell value.

Main Subjects

Agriculture

Topics

• Quality control
• Iraq
• Kurdistan
• Colors

No. of Pages

140

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-314539