1. SOIL CHEMISTRY

2. Acidic or Basic; also known as . . .
SOIL pH
A measure of the degree to which the soil is
Acidic or Basic; also known as . . .
Soil Reaction

3. SOIL pH
Technically:
expressed as the negative logarithm of the hydrogen ion (H+) concentration

4. SOIL pH At pH 7: - neutral pH - indicates H+ concentration of . . .
10-7 mol/L

5. SOIL pH
Since the product of normalities of H+ and OH- ions is always 10-14, OH- is also 10-7 mol/L
mathematically . . .
(10-7)(10-7) = 10-14

6. SOIL pH therefore . . . at neutral pH (pH 7 on a scale from 0 to 14)
amount of H+ ions = amount of OH- ions
solution is neither acidic nor basic

7. common productive agriculture soils fall
SOIL pH
Most agricultural soils pH range from 4 to
common productive agriculture soils fall
between pH 5 to 8

8. SOIL pH 2 factors affecting pH are: 1) Amount of precipitation
2) Type of vegetation

9. SOIL pH AMOUNT OF PRECIPITATION –
HUMID AREAS (heavy rainfall)  ACID SOILS
Ca+, Mg+, and Na+ are leached downward and replaced by H+ ions

10. SOIL pH TYPE OF VEGETATION –
Vegetation affects pH over period of years:
grasslands – higher pH
forests – lower pH

11. SOIL pH The most critical effects of soil pH are indirect . . .
the availability (unavailability) of certain nutrients is greatly influenced by soil pH

12. SOIL pH Nutrients UNAVAILABLE at higher pH: Cu – Copper Fe – Iron
Mn – Manganese
Zn – Zinc

13. Critical with beans and peas
SOIL pH
additionally . . .
nitrogen-fixing bacteria associated with
legumes are seriously hindered in acid soils
Critical with beans and peas

14. SOIL pH ADJUSTING SOIL pH
- Crops vary considerably regarding soil pH preferences

15. SOIL pH
AZALEA
BLUEBERRY
RHODODENDRON
ACID SOILS

16. SOIL pH
Mildly Acid Soils:
Wheat
Corn
Soybean
Apple
Tomato

17. SOIL pH
Neutral to Slightly Acid Soils:
Alfalfa
Lettuce
Muskmelon

18. SOIL pH ADD LIME RAISING Soil pH: Factors to consider before applying
- soil type
- how much to raise the pH
- fineness of lime
- type of lime

19. Sandy Loam < Clay Loam WHY?
SOIL pH
AMOUNT OF LIME NEEDED TO RAISE pH:
Sandy Loam < Clay Loam
WHY?
Cation Exchange Capacity (CEC) of clay particles

20. SOIL pH Add Sulfur LOWERING Soil pH:
- May be necessary for acid-loving crops
- May also benefit potato production by reducing potato scab