Soil Preparation Course: To Prevent Blossom End Rot (BER)

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UNIT 4: Soil pH

Objectives
1.  Identify the important pH level for balanced tomato soil,
2.  Identify why soil pH imbalance (too acidic or too alkali) affects plant calcium intake,
3.  Identify two methods for pH soil testing,
4. Identify two methods for bringing soil into pH balance,
by correctly answering true/false and multiple choice items.

Humor
1. Reason to become a chemist - it's pHun.
2. The science teacher was going to drop a nail into a glass of Coke to show an acidic reaction.   The girl sitting next to him raised her hand and asked, "Do you mean a real fingernail or a Lee Press-on nail?"
... So you can see we are already ahead of this class!

Content

What is balanced pH soil?
The pH is an abbreviation for the 'power of Hydrogen'. It represents the concentration of hydrogen-ions. In gardening terms - when the pH reading is optimum, the nutrient reactions will be most effective.

The pH readings show degree of acid or alkaline in a substance. These readings range from 1 to 14, with 7 being neutral. Any number below 7 is acidic, and the any number greater than 7 is alkali. If a pH reading is 5, it is in the acidic range.

The ideal pH level for tomato soil preparation is 6.5.

If a pH soil reading of 6.0 or less is obtained, it is important to add materials to bring the pH up to at least 6.0, but preferably to 6.5.

If a pH soil reading of greater than 7.5 is obtained, it is important to add materials to bring the pH down from the alkali range, toward 6.5.

It is much more difficult to bring a pH level down from alkali ranges then it is to bring a pH level up from an acidic range.

0                                 7                                  14
Acidic                    Neutral                     Alkali

Practice #1
Determine if a pH reading is acid, neutral or alkali.
1. 6.0
2. 7.5
3. 3.0
4. 13.0

5. What is the most ideal pH reading for tomato soil?
6. Mona's soil pH is 6.0. Should she treat soil to raise the pH?

How does unbalanced soil pH affect tomatoes?
A chemical (pH) soil imbalance, either too acidic or too alkali, will prevent calcium uptake from the soil into the tomato plant.

Practice #2
1. Describe the pH imbalance that blocks plant calcium uptake.
2. How does a lack of calcium plant intake relate to the disorder of BER?

How do I perform a pH test?
The chemically soil testing method can be completed at home with a pH soil test kit purchased at most local garden centers. The pH reading will be a color reading that is compared to a color chart showing pH levels. Also pH sampling may be tested professionally.

One advantage of home testing is that after performing a soil treatment, one may perform a second test to assess the results of the treatment. A re-test is a verification of successful chemical soil balance.

How do I treat soil to get pH balance?

Additives to improve soil pH:

0                                 7                               14
Acidic                   Neutral                    Alkali
(Add lime)                                    (Add sulfur)

To raise pH levels (if pH is lower than 6.0), add lime at a rate of 1 lb/30 square feet*. If a grower has only one tomato plant lime may be added at 2 cups per plant.
To lower pH levels (if pH is greater than 7.5), add aluminum sulfate (15% sulfur) at a rate of 1 lb/100 square feet**.
It takes 1 lb/100 square feet to lower pH 0.2. Therefore, to lower pH one whole point, it takes 5 lbs/100 square feet.

*30 square feet may be 5 feet x 6 feet ... or 3 feet x 10 feet, etc.
**100 square feet may be 10 feet x 10 feet ... or 5 feet x 20 feet, etc.

Practice #3
1. Sally's soil is extremely alkali. She needs to lower the pH 2.0 points. How many lbs. of aluminum sulfate (15% sulfur) should she add if she has 100 square feet of soil?
Answer: It takes 1 lb. to lower pH 0.2, so it would take 10 lbs to lower it to 2.0 because 10 times 0.2 equals 2.0.

2. Ben's soil is acidic (below 6.0). He needs to raise his pH. How much lime should he use for 90 square feet of soil?
Answer: It takes 1 lb. to for 30 square feet, it will take 3 lbs. for 90 square feet, because 3 times 30 equal 90.

Assessment
On a separate sheet of paper, answer True or False, or select the appropriate letter (a, b, c...). Then check your work using the link below.

For questions # 1-3, for standardized pH ranges,
1. A pH level of 5 is:
     a. Alkali
     b. Neutral
     c. Acidic

2. A pH level of 9 is:
     a. Alkali
     b. Neutral
     c. Acidic

3. A pH level of 7 is:
     a. Alkali
     b. Neutral
     c. Acidic

4. For tomato soil, a pH level of 6.5 is:
     a. pH balanced
     b. pH imbalanced

T   F   5. Alkaline soil prevents plant calcium uptake.
T   F   6. Acidic soil prevents plant calcium uptake.
T   F   7. Chemical pH testing may be completed with a home kit, or tested professionally.
T   F   8. Lime is used to neutralize (lower the pH of) alkali soil.
T   F   9. Sulfur is used to neutralize (raise the pH of) acidic soil.

10. Jack's soil is acidic. He should add:
       a. 2 cups of lime per tomato plant
       b. 1 cup of lime per tomato plant
       c. 2 cups of sulfur per tomato plant.

Link to Answers

References

Proceed to Unit 5