FACTORS INFLUENCING NUTRIENT AVAILABILITY IN THE SOIL

The factors which influence the availability of nutrients in the soil include the following:

a) Soil pH: The degree of acidity or alkalinity of the soil affects the availability of nutrients, both in the soil and also to plants.

1. A low pH (high acidity) will encourage the disintegration of clay minerals like calcium, iron and aluminium, which are leached away from the soil.
2. At high pH (high alkalinity), calcium and magnesium ions accumulate in the soil, and this affects the growth of plants.
3. A low pH also reduces the activities of soil living organisms which aid the decomposition of organic matter.

 

b) Concentration of Other Nutrients

1. The presence of certain element(s) in high concentration may prevent the absorption or utilisation of other elements.
2. The concentration of nitrogen and phosphorus in the soil results in the non-availability of potassium.
3. This condition results in retarded growth, low yield or even death of the plant.

 

c) Leaching

1. This is the removal of nutrients from the top soil to the inner parts of the soil beyond the reach of the roots of plant.
2. It results in the loss of nutrients such as calcium, magnesium, potassium from the top soil in solution.
3. It also results in the accumulation of aluminium and hydrogen ions which become acidic and toxic to plants.

 

d) Crop Removal

1. Nutrients are removed from the soil by crops for growth, development and production.
2. When the crops are harvested, the nutrients contained in the plants are never returned to the soil.
3. The rapid removal of nutrients from the soil by continuous cropping completely deprives the soil of such nutrients.

 

e) Oxidation and Reduction of Organic Material

1. Some compounds such as ammonium radicals are oxidised to gaseous ammonia.
2. Nitrates are also reduced to molecular nitrogen or oxides of nitrogen by denitrifying bacteria.
3. These products (i.e ammonium radicals and nitrates) which escape into the atmosphere in form of gases make the soil become poorer in nutrients.

 

f) Burning

1. It exposes the soil to erosion which can wash away plant nutrients in the soil.
2. It burns the organic matter content of the soil, thereby reducing the amount of nutrients in the soil.
3. It kills or reduces the number of soil organisms which aid decomposition of materials, and consequently, most nutrients may not be available to the soil.

 

g) Soil Texture

1. Fine texture, such as clay and silt, ensures the availability of nutrients in the soil.
2. But coarse texture like sand prevents the availability of nutrients in the soil.
3. Coarse texture encourages the leaching of nutrients from the soil.

 

h) Erosion

1. Heavy rainfall causes the washing or carrying away of top soil which is rich in plant nutrients.
2. Top soil can also be blown away by winds, resulting in nutrient reduction in the soil.

 

i) Soil Moisture Content

1. Soil moisture content determines the level of nutrients in the soil.
2. High level of soil moisture can lead to toxicity of nutrients in the soil.
3. High moisture content can lead to soil erosion that can wash away nutrients in the soil.
4. Moderate moisture in the soil ensures adequate availability of nutrients in the soil.
5. Very low soil moisture leads to dryness or non-availability of nutrients for plants.

 

j) Level of organic matter/microorganisms in the soil

1. High level of organic matter and micro-organisms lead to adequate availability of nutrients in the soil.
2. High level of organic matter ensures availability of water in the soil and vice versa.
3. High level of micro-organisms the soil ensures good growth for crop plants.
4. High level of organic matter in the soil helps to prevent soil erosion.
5. Adequate level of organic matter improves the activities of microorganisms in the soil.
6. Organic manure also helps to improve the structure of the soil.
7. It also reduces rapid soil temperature fluctuations.