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The Key Metrics of Agriculture- Soil pH

In a nation characterized by diverse terrains and geographies, soil undergoes inevitable variations. As Kerala grapples with the challenge of elevating its low pH as a result of intense rainfall, Tamil Nadu faces the opposite battle as its soils struggle with high alkalinity and salinity amidst declining groundwater. The fluctuation in soil pH, along with its sensitivity to atmospheric changes, raises concerns, particularly given its pivotal role in plant nutrient management.

Comprehending Soil pH 

The term pH is from the French pouvoir hydrogen or hydrogen power. Soil pH or soil reaction is an indication of the acidity or alkalinity of soil.

It is measured in pH units and is classified as acidic (<6.5), neutral (6.5-7.5), saline (7.5-8.5), and sodic/alkaline (>8.5).

Soil pH categorization

1) Acidic soil (<6.5) 

  • Poor fertility status due to Aluminum, Manganese, and Iron toxicity.

  • Nutrient immobilization and reduced microbial activity as pH lowers.

2)  Neutral soils(6.5-7.5) 

  • The optimal medium for maximum nutrient availability, ensuring soil productivity.

3) Saline soils (7.5-8.5)  

  • Toxic concentrations of soluble salts of chlorides and sulfates of sodium, calcium, and magnesium affect water availability to plants.

  • High osmotic pressure retards plant growth and germination.

4) Sodic soils/ Alkaline soil (>8.5)

  • Formed due to exchangeable sodium, limiting Calcium and Magnesium availability.

  • Causes physical deterioration of the soil.

What influences soil pH?

A report by ICAR-Central Salinity Research Institute states that in India, 6.73 million ha (M ha) area has been characterized as salt-affected, out of which 3.77 M ha is alkali and the remaining 2.96 M ha is saline, While about 11 mha of land suffers from acute soil acidity with very low productivity thus threatening livelihood security of the farming community. Uttar Pradesh has the largest alkali area of 1.35 M ha accounting for 35.75 percent of the total alkali-affected area followed by Gujarat (14.36%), Maharashtra (11.21%), Tamil Nadu (9.41%), Haryana (4.86%) and Punjab (4.02%). These six states have about 80% of the total alkali lands of India.

Addressing the drastic changes in soil pH, whether man-made or a result of biological processes over time, is a crucial topic for environmental stewardship.

Soil pH influential factors


Excessive water washes out the essential nutrients in the soil that alter the soil pH.

Nitrogen fertilization

Something as common as urea can acidify your soil as the higher the percentage of ammonium in a given fertilizer higher the acidifying potential, reducing the pH.

Climate and temperature 

Soils from arid climates are commonly alkaline and soils from humid climates are mostly acidic. In warm and humid temperatures, soil pH decreases due to soil acidification caused by leaching due to high rainfall or due to mineralization of soil organic matter. In arid regions, the high rate of chemical weathering of earth materials results in the accumulation of salts resulting in alkaline pH.

Land use and management

Not only do land use practices (i.e. mode of vegetation, cultural and mechanical practices, etc) influence the soil surface but also the sub-surface characteristics influencing the soil dynamics.

The buffering capacity of soil

Sandy loam soils with low buffering capacity(The natural resistance of soil to change of pH)compared to the high buffering capacity of clayey soils are easily susceptible to pH change.

Know your soil pH

The significance of something's presence only truly manifests when it becomes accessible, and in the realm of soil nutrients, pH stands as the sole arbiter of this accessibility. Soil pH is, therefore, described as the master soil variable that influences myriads of soil biological, chemical, and physical properties and processes that affect plant growth and biomass yield.

As per estimates of ICAR-CSSRI, every year, India loses 11.18 million tonnes (M t) of cereals, oilseeds, pulses, and cash crops from 3.77 M ha alkali affected area, which is equivalent to the monetary loss of 1,50,000 million (15,000 Crores). 

The first step to retaining and repairing your soil is to know your soil and this is to be achieved by soil testing. 

A stitch in time saves a nine, by checking your soil pH before growing your plants saves your time and energy in adopting reclamation practices in the later stage. Test your soil samples today in your nearest soil laboratory but if you want your soil test results fast, precise, and detailed, Ekosight soil doctor is your go-to soil testing solution.

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