Soil pH and Nutrient Availability By Dr. P.C. Patel

Soil pH is the foundation of soil fertility:
Soil pH is a master variable in the soil. It plays an important role in the soil in biological, chemical or even physical in some instances. Managing soil pH is a critical part of a soil fertility plan.
It has been observed that soil reactions play a pivotal role in determining the nutrient availability for the plants. Soil pH affects nutrients available for plant growth. In highly acidic soil, Al and Mn can become more available and more toxic to plant while Ca, P and Mg are less available to the plant. In highly alkaline soil, P and most micronutrients become less available.
The soil pH also influences plant growth by the effect of pH on activity of beneficial microorganisms.
Fertilizers and Soil Acidity
• Soil acidification is a natural process in high rainfall environments where leaching slowly acidifies soil over time.
• Intensive agriculture can speed up soil acidification through many processes - increasing leaching, addition of fertilizers, removal of produce and build-up of soil organic matter.
• Of all the major fertilizer nutrients, nitrogen is the main nutrient affecting soil pH, and soils can become more acidic or more alkaline depending on the type of nitrogen fertilizer used.
• Nitrate-based products are the least acidifying of the nitrogen fertilizers, while ammonium-based products have the greatest potential to acidify soil.
Importance of buffering in agriculture:
• The buffer solutions can be broadly classified into two types. They are acidic and alkaline buffers. These solutions are used to maintain acidic conditions.
• The stabilization of soil pH, so the regulates plant nutrient availability.
• The amounts of amendments required to change in soil reaction. Calculations of amount of amendment necessary to affect a certain change in soil reaction.
• When hydrogen ions in the soil solution are neutralized by lime, hydrogen ions from the soil surfaces are release into the soil solution to maintain equilibrium and resist increase in pH. Better buffered soils are slower to acidify but require more lime to lift pH when they do acidify.

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