Soil fertility is the ability to supply plant nutrients in adequate amounts and right properties and produce high yields.


Factors that contribute to soil Fertility

Soil depth

Deeper soils can anchor plant roots better and can hold enough was for use by the crops even in a dry season.  Plant roots will be able extend and absorb nutrients.

Soil Structure

This is the arrangement of soil particles and nit will affect air and water movement, heat transfer, root penetration creating an ideal environment for plant growth.

Soil Drainage

Is the ease with which excess water can move out of the soil.  This will influence proper movement and heat transfer.  It will also influence soil pH.  It also influences the presence of living organisms and root development.

Soil Aeration

Poor root development is encouraged where there is poor respiration.  Living organisms can only function well when there is enough soil air to break down organic matter and release nutrients that will be taken up by plant roots.

Water holding capacity

The ability of the soil to retain enough water for plant growth will influence nutrient up take since all nutrients have to be dissolved in water before they can be taken up in plants.  Poor water holding capacity will encourage loss of nutrients through leaching.

Availability of plant nutrients

This is when nutrients are in a soil in a form at which plant roots can take them in.  This is greatly affected by the amount of soil water and pH for example in acidic soils, phosphorus becomes un available to plants or fixed.  In extremely alkaline soils Baron, potassium, zinc and Magnesium   are un available.

Soil pH

This will influence nutrient availability presence and activity of soil organisms and presence of disease causing organisms in the soil.

Experiment I

Experiment to compare the rate at the rate at which water rises by capillarity in different soils.


3 long glass tubes                      –        Dry sand, clay, loam high in organic matter

Cotton wool

Water                                        –        Retort sand

Large glass beaker

A clock

A ruler


  • Close the bottom of each glass tube with cotton
  • Fill one f the tubes with dry sand another with dry, clay and dry loam.
  • Tap the tubes gently on the bench to tightly pack the soil.
  • Set the tubes at the same time in a large beaker containing water up t a depth of about 5cm.
  • Support each tube with a clamp and time.

Note or measure the height reached by the water in each time at intervals record your results in the table below.

Soil Sample After 5min After 10min After 15min After 20min After 25min
Sand 10cm 12cm 13cm 14.2cm
Clay 4cm 6cm 6.5cm 7.5cm
Loam 3.5cm 4cm 5cm 6cm



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