• What is ph ?• What is soil ph ?• How does soil ph affect soil growth?• How to measure soil ph ?• Symptoms of Soil Acidity• How does soil ph change ?• How to restore soil ph ?• Soil Permeability• Factors affecting soil permeability• Measurement of Soil permeability• Percolation Rate
• pH is the measure of acidity. More correctly it is the measure of the potential of Hydrogen ions.• The higher the concentration of hydrogen ions in the soil, the lower the pH and vice-versa.• The level of acidity (low pH) or alkalinity (high pH) is measured on a scale of 1 to 14 with 7 being neutral.• For instance, pH of: caustic soda = 13.8 seawater = 8.0 soft drink = 2.8 etc.
• Soil pH is an indicator of the acidity or alkalinity of a soil.• Extremes in pH level may affect the plant growth.• Some plants can grow over a wide range of pH; others are sensitive to acidity or alkalinity.• Soil pH is affected by soil chemistry and soil biology.• It is also affected by the physical characteristics of the soil via aeration of soil and soil water.
• At extreme pH, the availability of some nutrients is decreased. E.g.: phosphorous and molybdenum at low pH and zinc at high pH.• Solubility of elements is toxic to the plants is increased. E.g. : aluminium and manganese at low pH.• Extremes in pH level may also affect the production of many plant species and may disturb the symbiotic relationship with Rhizobia.• In alkaline soils where the trace elements iron, manganese, copper, zinc and boron, so readily available in acid soils, may be unavailable to plants, even though they are present in the soil in adequate amounts, and molybdenum is readily available.
• In laboratories, soil pH may be measured by using prepared sample of soil and a pH probe.• On the site, the soil pH is measured using a colorimetric kit and a fresh sample of soil.
• Nodulation failure of legumes - reddening of stems andpetioles on pasture legumes, or yellowing and death of oldestleaves on grain legumes indicate nitrogen deficiency.• Deficiency symptoms ofsulphur, phosphorus, molybdenum, calcium or magnesium.• Root growth poor, with stubby roots and few fine roots.• Crop yields / pasture growth are poor even in good seasons.
• Agricultural activities often decrease the soil pH of soil which is also called acidification.• Some processes involve in acidification of soil are :i. Sowing annual dominant pastures.ii. Cropping with legumes.iii. Application of nitrogen fertilizers.iv. Product removal, especially hay and grain.
• The most common way of regaining the soil pH is by adding agricultural/quick lime.• Successful use of lime occurs where the farmer: Knows the target pH for the plants being grown. Incorporates lime by cultivation. Matches the quantity and quality of lime with amount needed for the pH buffering capacity of the soil. Can get it on the ground at a sufficiently cheap price.• Other important factors include: The type of lime Cost Plant response Timing Application method Soil texture Organic matter content
• Soil permeability is the property of the soil to transmit water and air and is one of the most important qualities to consider for fish culture.• The more the permeability of the soil, the greater the seepage.• Some soils are so much permeable that it is not possible to build a pond without special construction technique.• The soil is divided into many layers and each layer has different soil permeability.
• Many factors affect soil permeability such as:1. soil texture2. structure3. layering4. consistency5. color6. holes/spores7. depth SOIL TEXTURE PERMEABILITY CLAYEY FINE VERY SLOW LOAMY MODERATE MODERATE SANDY COARSE RAPID
• Soil permeability is generally measured in :1. Centimeters per hour (cm/h)2. Millimeters per hour (mm/h)3. Centimeters per day (cm/d) etc.• It is also measured in terms of coefficient of permeability in meters per second (m/s) or in centimeters per second (cm/s).• In fields, soil permeability can be measured by:i. The visual evaluation of the permeability rate of soil horizons.ii. A simple field test for estimating soil permeability.iii. A more precise field test measuring permeability rates.
• Perculation rate is the measurement of the permeability.• It is expressed in the terms: amount of water/time taken to perculate = ml/sec