Soil pH is important• Soil pH (a measure of the acidity or

alkalinity of the soil)  • Soil pH is one of the most important soil

properties that affects the availability of nutrients.  – Macronutrients tend to be less

available in soils with low pH (acidic soils)

– Micronutrients tend to be less available in soils with high pH (alkaline soils).

Macronutrients: Primary Nutrients

• Macronutrients are those elements and compounds needed in large quantities for a plant to grow.

• The primary nutrients are nitrogen (N), phosphorus (P), and potassium (K).

• These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and

survival. 

Macronutrients: Secondary Nutrients

• The secondary nutrients are calcium (Ca), magnesium (Mg), and sulfur (S). There are usually enough of these nutrients in the soil so fertilization is not always needed. – Large amounts of Ca and Mg are

added when lime is applied to soils. – Sulfur is usually found in sufficient

amounts from the decomposition of soil organic matter.

Micronutrients

• Micronutrients are those elements essential for plant growth which are needed in only very small (micro) quantities and are sometimes called minor elements or trace elements.

• Micronutrients include boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn).

Neutralizing soil pH If the soil is acidic, an alkali called lime can be added to neutralise the soil. If the soil is alkali, fertilizer can be added to neutralise the soil. Most plants like a neutral soil. Note: (some plants need acidic soil to grow and some need alkali soil to grow). The farmer will need to first test the pH of his soil and decide which plants will thrive best on the soil or he can adjust the pH of the soil to suite the plants he wants to grow.

It is your job to determine what is causing the problems at the Botanic Gardens. Let’s begin!

Before a farmer can plant crops in soil he has to make sure that the pH is right for the crops he is going to plant.

You are going to do an experiment to test the pH of 3 soil samples from the botanic garden. You will then try to neutralise the acidic and alkali soil.

Use the pictures in these boxes as a guide.

Step 1 -Mix Step 2 -Filter Step 3 -Test

Soil Sample Colour with pH Acid/alkali or neutral universal indicator

A

B

C

Follow the steps to carry out the test on the 3 soil samples. Put your results in this table:

For a merit: Try to get your acidic soil neutral by adding the alkali lime. You only need a tiny bit! Try to get your alkali soil neutral by adding fertilizer. You only need a tiny bit!

Part A: What do you know? 

1.What are the problems that are concerning the Botanical Gardens Committee?

Pink hydrangeas are growing on one side of the gardens and white and blue on the other side.

The vegetable patch on one side of the gardens is healthy but not on the other side. 

2. What do you predict are some possible reasons for the problems at the Botanical Gardens?

The limestone is affecting the pH of the soil and therefore the plants

The fertiliser is affecting the pH of the soil and therefore the plants 

3. What do you know about the pH of soil and how it affects the way plants grow?

Some plants need acidic soil to grow where as some need basic soil to grow.

 

1. Using the results from the soil test, label on the site map with letters A, B and C where:

Basic soil would be found?

Neutral soil would be found?

Acidic soil would be found?

2. Explain why you chose to label the site map as you did in question 1?

From the pH value for each soil sample also limestone is alkali and fertilizer is acidic. So the quarry side will contain the alkali soil, the golf course will contain the acidic soil and the car park in the centre of the garden away from the limestone and the fertilizer will contain the neutral soil.

3. On the site map label what macro nutrient is lacking in the quarry area and what micro nutrient is lacking in the golf course area.

4. Using your knowledge and results suggest some ways in which the Botanic Garden Committee can even out the pH of the gardens?

Sprinkle limestone on the acidic side, and fertiliser on the basic side.

5. Imagine your neighbour wants to grow some tomatoes for the Easter Show Largest Tomato Competition. What advice would you give them about the conditions of the soil?

Tomatoes grow best in acidic soil therefore using fertiliser will optimise growth.

6. If they planted hydrangeas next to the tomatoes what colour would they be?

White/blue

7. What will happen if you add lime and ammonium fertilizer at the same time to the soil?

There will be no beneficial effects of both. The two react to make a salt, ammonia gas and water.

Part B: What analysis you made?