Soil amendments are
organic or inorganic matter added to the soil to improve texture, soil
physic-chemical properties like water retention, drainage, aeration, PH balance, nutrition availability and productivity.
Soil PH
and its characteristics
- The
availability of plant nutrients is optimum within the soil PH range 6.5
to 7.5.
- Below PH 5.5 soils
are referred to be acid soils and above PH 8.5
soils are known as alkaline/alkali soils.
- Accumulation of salts in soil also adversely affects the plant growth and nutrition. It is called soil salinity.
soil reactions
- Phosphate
applied through fertilizer gets converted into insoluble form as iron and
aluminium phosphates in acid soils.
- Solubility of a number of micro
nutrients is increased under acidic soil conditions and they may be
toxic to plants.
- With high PH (Alkaline Soil) many plant nutrients become
unavailable due to reversion into insoluble forms.
NOTES
- In
humid regions soils are generally acidic in reaction.
- Soil salinity and alkalinity
are the problems of arid regions.
- Acid soils
are to be corrected by Liming, alkaline soils are to be corrected by
gypsum.
- Rice has good tolerance to acidity since flooding of
rice fields raises the PH to almost neutrality.
Correcting soil acidity
- Soil acidity results from loss
of bases like calcium and magnesium. Soil acidity is reduced by
restoring the lost calcium and magnesium by applying lime to the
soil.
- Soils with low clay content
will require less lime. Soil with high clay content and soil with high
organic matter content need more lime.
- Excess doses of liming material
should be avoided, as over liming affects availability of nutrients like
iron, manganese, zinc, potassium, magnesium.
Method and time of Lime Application
- Liming
material are to be broadcasted at least a month before sowing.
- Nitrogenous and water soluble phosphatic fertilizers
should not mix with it, nor to be applied at the same time or immediately
after lime application, as it would result in ammonia being released and
lost to the atmosphere and availability of phosphate also being reduced.
Reclamation of saline and Alkaline soils
1) Saline soils
- In
this type of soil exchangeable sodium percentage is less than 15 and soil
reaction below PH 8.5.
- Crops growing on saline soils usually have barren
patches, foliage(leaf) has a deep green to deep blue colour and crop
yields are low.
Reclamation of saline soils
- By
applying rain or irrigation water for leaching out injurious salts to a
safe limit in the soil.
- By deep ploughing to break the pan followed by
irrigation and drainage.
2) Alkaline Soils
- In
these types of soils the percentage of exchangeable sodium is greater than
15 and the soil PH is usually in the range of 8.5 to 10.5.
- Poor aeration and high sodium content creates
difficulty in crop growth.
Reclamation of Alkaline soils
- alkaline
soils are to be corrected by gypsum.
- Press mud, a byproduct from sugar
factories, acts as a good reclamative material.
- Aluminium Sulphate,
Sulphur also act as a good reclamative material.
- By adding organic materials
such as farm yard manure, crop residues, green manuring crops.
- By deep ploughing followed by leaching with
irrigation water and drainage.
*Apply the above soil amendments after soil testing results and local agriculture officer’s guidance.
Conclusion
Soil amendments will help in maintaining PH balance in soil and it helps in increasing crop productivity by
better nutrient mobility in soil and available the nutrients to plants.
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