ABSTRACT

There are various ways to determine the soil pH. Soil pH is essential for the

growth of the plant which determine colour of flower and also their growing state. Hence,

to study the effect of soil nature on crops that grow and to determine the types of crops

growth based on different soil pH, a natural way (red cabbage) is used as an indicator.

Red cabbage contains anthocyanin which will give rise to different colour in different pH

solution. Anthocyanin pigment is extracted from red cabbage using blender and immerse

it in hot distilled water. The initial colour of red cabbage solution is said to be neutral and

different solution of soil sample was tested using red cabbage solution. The result is then

analyzed.

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INTRODUCTION

Soil nature is simply the chemical characteristic of the soil either acidic or

alkaline. Soil acidity and alkalinity basically determine the plant nature that grow at the

soil such as color of flower of the same species plant. Different species of plant will grow

base on different soil nature.

Although typical garden soil pH never hit the extremes, slight change in acidity

and alkalinity can affect the health and hardiness of your plants. Extremely alkaline soils

and extremely acidic soils tend to stunt plant growth because plants can’t take up

nutrients effectively within these ranges. Highly acidic environments leach off plant

nutrients while highly alkaline soil locks up nutrients in the soil.

In this project, red cabbage juice is used as indicator to determine the soil either is

acidic or alkaline. Red cabbage juice contains anthocyanin which give the cabbage dark

red in color. Anthocyanins are water-soluble vacuolar pigments that may appear red,

purple, or blue depending on the pH. They belong to a parent class of molecules called

flavonoids synthesized via the phenylpropanoid pathway; they are odorless and nearly

flavorless, contributing to taste as a moderately astringent sensation. Anthocyanins occur

in all tissues of higher plants, including leaves, stems, roots, flowers, and fruits.

Anthoxanthins are clear, white to yellow counterparts of anthocyanins occurring in

plants. Anthocyanins are derived from anthocyanidins by adding sugars.

Anthocyanins can be used as pH indicators because their color changes with pH;

they are pink in acidic solutions (pH < 7), purple in neutral solutions (pH ~ 7), greenish-

yellow in alkaline solutions (pH > 7), and colourless in very alkaline solutions, where the

pigment is completely reduced. Anthocyanin generally degraded at higher pH to give a

lighter color solution.

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Method of preparing red cabbage juice to test the acidity and alkalinity of a

chemical mixture is by Mr. James Watt, Engineer; it is announced and communicated by

Sir Joseph Banks, Bart, P.R.S on May 27, 1784. "The syrup of violets was formerly the

test of the point of saturation of mixtures of acids and alkaline, which was principally

used; but since the late improvements in chemistry it has been found not to be sufficiently

accurate, and the infusion of turnsole, or of an artificial preparation called litmus, have

been substituted in the place of it. Having occasion in winter to repeat some experiments,

in which the phlogisticated nitrous acid was concerned, I found my stained paper almost

useless.  I was, therefore, obliged to search for some substitute among the few vegetables

which then existed in a growing state; of these I found the red cabbage (brassica rubra) to

furnish the best test, and in its fresh state to have more sensibility both to acids and

alkaline than litmus, and to afford a more decisive test ..."

Problem Statement:

What is the effect of soil nature on crops that initially planted?

Objective:

i) To study the effect of soil nature on crops that growth.

ii) To find the types of different medium of soil based on the soil.

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METHODOLOGY

Material and apparatus:

5 types of different soils (River Soil, Swamp Soil, Garden Soil, Forest Soil &

Farm Soil.)

red cabbage

knife

boiling distilled water

distilled water

filter paper

One large glass beaker

250 ml beakers or other small beakers

NaOH (aq)

Vinegar

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Procedure:

1. Chop the cabbage into small pieces until you have about 2 cups of chopped

cabbage. Place the cabbage in a large beaker or other glass container and

add boiling distilled water to cover the cabbage. Allow at least ten minutes for the

color to leach out of the cabbage.

 

2. Filter out the plant material to obtain a red-purple-bluish colored liquid. This

liquid is at about pH 7.

 

3. Pour about 50 - 100 mL of your red cabbage indicator into each 250 mL beaker.

4. Add vinegar, NaOH(aq) to two beakers of the red cabbage indicator. NaOH(aq) is

alkaline while vinegar is acidic.

5. Record down the colour change and determine the colour of acidic and alkaline in

the red cabbage indicator.

6. Five types of 50g soil are prepared and pour into 5 plastic cups. Then 100 ml of

distilled water is poured into each plastic cups. Filter out the soil solution with the

volume of 50ml.

 

7. Add the five types of soil solutions into each of the beaker which containing the

red cabbage indicator, observe and record down the final colour change.

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RESULT

Type of soil Observation ResultSwamp soil

Reddish purple to blue Alkaline

River bank soilRemain unchanged Neutral

Forest soilRemain unchanged Neutral

Farm soilReddish purple to red Acid

Highland soilRemain unchanged Neutral

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DISCUSSION

When swamp soil solution is poured into red cabbage solution, the initial reddish

purple colour of red cabbage solution turns blue. The result show that swamp soil is

alkaline as the anthocyanin degraded from quinonoidal base (reddish purple) to anionic

quinonoidal base (blue).Thus, mangrove plant growth better in swamp soil as it is

alkaline. Whereas soil solution of river, forest and highland do not show obvious changed

of red cabbage solution. Hence we deduce that river, forest and highland soil are neutral.

Example of mango trees usually growth in almost neutral soil. Farm soil solution changes

the red cabbage solution to red. This shows that farm soil is acidic as anthocyanin of red

cabbage degraded to flavyliumcation (red). Example of paddy plant is growth better in

farm soil as it is acidic.

Swamp soil is usually alkaline as its near seaside whereas farm soil is acidic due

to human activity. River, forest and highland soil are neutral because this contains

numerous mineral such as calcium carbonate which neutralize the soil and maintain its

neutrality.

In this experiment we have shown that colour of anthocyanin changes based on

different soil pH. Gardener usually cultures their plant in specific pH to control the

growth of their plant or to obtain different colour of flower. In example, hydrangeas

changes its colour based on soil pH from blue in acidic medium to red in alkaline

medium.

CONCLUSION

Usually, paddy plant growth better in farm soil as it is acidic. Whereas mangrove

plant growth better in swamp soil as it is alkaline. While mango tree usually growth in

almost neutral soil like river bank soil, forest soil and highland soil.

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REFERENCE

Website

http://chemistry.about.com/od/acidsbase1/a/red-cabbage-ph-indicator.htm

https://en.wikipedia.org/wiki/Red_cabbage

http://www.instructables.com/id/Red-Cabbage-pH-Indicator/

Books

Plant Soil Interaction at low PH: Principles and Management (Date R.A)

Field Experiments and Natural Experiments (Robert E. Goodin)

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