27/05/2019
SOIL REACTION...............
Soil Acidity and Alkalinity are both termed soil reaction or soil condition or soil pH.Adversely, high pH can disrupt the soil structure.
The standard soil reaction scale ( soil pH) ranges from 1 to 14, the soil reaction is acidic when it is below 7 but alkaline when it is above 7. At 7, the soil reaction is regarded as neutral but in practical terms soils between 6.5-7.5 is regarded as being neutral.
SOIL ACIDITY.
soils in the range 5.6-6.0 are moderately acidic and below 5.5 are strongly acidic. The more Hydrogen ion held on the soil, the greater the acidity of the soil. Soil acidity is formed as a result of the inputs of carbonic, sulfuric and nitric acid from the atmosphere, plant exudates and the decay of plants and animals residues. Also caused by the continuous use of acid forming fertilizers. It is common in areas with high rainfall.
EFFECTS OF SOIL ACIDITY
Soil acidic leads to the following problems
• Aluminum Toxicity
• Manganese Toxicity
• Iron toxicity
• Calcium deficiency
• Magnesium deficiency
• Molybdenum deficiency
• Very slow organic decomposition
• Decrease in Calcium and Phosphorus availability.
HOW TO CORRECT SOIL ACIDITY
When a particular soil is acidic, it can be corrected to suit ones choice for planting. This can be done using the following methods:
• Flooding
• Addition of organic matter
• Addition of wood ash
• Liming: This is the traditional method used to correct soil acidity and to improve soil productivity. Common liming materials are: limestone, dolomite, hydrated lime, quicklime.
SOIL ALKALINITY
they are mostly clay soils with poor structure and low infiltration capacity. They have hard calcareous layer of about 0.5 to 1 metre depth. Alkaline soils also called Sodic soils contain sodium carbonate which causes the soil to swell and difficult to settle.
They are mostly found in arid areas (region with uneven rainfall) . They have high salt content.
EFFECTS OF ALKALINE OR SODIC SOILS
• Due to the presence of high content of salt, it causes an osmotic pressure in plants leading to plasmolysis ( the contraction of the protoplast of a plant cell as a result of loss of water from the cell.)
• The quality of water produced to the plants are reduced due to the presence of salt.
• Inability of the plant to absorb nutrients needed from the soil.
• The alkalinity causes corrosive action on the bark of roots and stems.
• Sodium ion has an adverse effects on the plant metabolism.
• The soil has low infiltration rate.
• Rain water stagnates in the soil easily.
HOW TO CORRECT SOIL ALKALINITY
• Good drainage to allow the salts drain with fresh water.
• Leaching and flushing out of the salts from the soil by keeping the soil free of vegetation for about a year to accumulate enough water to pe*****te beyond the root depth.
• Addition of gypsum or sulphur to the soil.
THE SOIL pH OF COMMON CROPS
Individual crop has its own specific soil pH some crops can also thrive well on acidic and slightly acidic soil to slightly alkaline soil, these crops are:
• Pineapple (4.5-5.5)
• Egg plant (5.5-6.5)
• Watermelon (6.0-6.8)
• Potatoes (4.5-6.0)
• Tomatoes (5.5-7.5)
• Black berry (5.0-6.0)
• Blue berry (4.5-6.0)
• Raspberry ( 5.5-6.5)
• Pumpkin(6.0-6.5)
• Peanut (5.0-7.5)
• Pepper(5.5-7.0)
• Garlic (5.5-7.5)
• Cucumber(5.5-7.0)
• Apple(5.5-6.0)
• Carrot(5.5-7.0)
• Corn(5.5-7.5)
• Radish (6.0-7.0)
• Sweet potatoes (4.5-5.5)
• Beans (5.5-7)
• Cabbage (5.5-7)
• Onion (5.5)
• Squash(5.5-7.0)
• Grape (5.5-6.5)
• Cassava (5.5-6.5)
• Rice (6.0-6.7)
These values can only be gotten through soil testing..
