Why Does Soil pH Matter More Than the Fertilizer You Choose?

Introduction

A lot of Indian farmers are wasting thousands of rupees in a season by spending them on fertilisers, and not getting good yields. In fact, the most common is not the type of fertiliser they selected, but the pH of the soil that they ignored. Soil pH will influence whether the nutrients already in your soil and/or fertilisers you add them to your soil are available for your crop roots, or bound in a chemical form which is not taken up by your plant roots. This blog describes how soil pH affects the availability of nutrients, what can happen to your fertiliser investment when the pH is wrong, and how to correct the pH – all with the help of the Government of India.

What Is Soil pH and Why Does It Control Everything?

A lot of Indian farmers are wasting thousands of rupees in a season by spending them on fertilisers, and not getting good yields. In fact, the most common is not the type of fertiliser they selected, but the pH of the soil that they ignored. Soil pH will influence whether the nutrients already in your soil and/or fertilisers you add them to your soil are available for your crop roots, or bound in a chemical form which is not taken up by your plant roots. This blog describes how soil pH affects the availability of nutrients, what can happen to your fertiliser investment when the pH is wrong, and how to correct the pH – all with the help of the Government of India.

How pH Locks Up Your Fertiliser Investment

The most dramatic is the case of phosphorus which is locked up in Indian soils. Under acid conditions (pH<5.5) phosphorus combines with Fe and Al in the soil that become unavailable to the crop. Phosphorus also is bound by calcium in alkaline soils with pH greater than 7.5. Research indicates that as much as 80% of applied phosphorus fertiliser may be unavailable to the crop if the soil pH is not within the optimum range — and a farmer who applies DAP on the wrong pH is wasting up to 80% of his or her investment. Zinc deficiency is also pH dependent. India has the largest soil zinc deficient region in the world with an estimated 49% agricultural soils being zinc deficient. The main cause is not lack of zinc in soil but high alkalinity of the soil which binds the zinc into unavailable forms. A farmer spraying zinc sulphate on alkaline soil without correcting the pH first is treating the symptom rather than the cause — with poor and short-lived results.

Nutrient Availability by pH: A Quick Reference

The table below shows how soil pH affects the availability of the six most critical nutrients for Indian crops — and what correction is needed when pH is outside the optimal range:

How to Correct Soil pH: Practical Steps for Indian Farmers

Agricultural lime (calcium carbonate) at the recommended rate based on a soil test is the standard soil amendment for acidic soils (pH below 6.0). Lime is used to improve soil pH levels by reducing soil acidity and moving them closer to the desirable levels and supplying calcium, a secondary benefit. Dolomitic lime also provides magnesium, which is often lacking in acid soils. In most of the acidic Indian soils, the application of 2–4 t/ha of lime will increase the pH of the soil by 0.5–1.5 units in 1–2 seasons. Elemental SULPHUR is applied at 200-500 kg/ha depending the degree of alkalinity to correct alkaline soils (pH > 7.5), found throughout Rajasthan, Punjab, Haryana and some parts of Gujarat. Sulphur is converted to sulphuric acid by soil microorganisms which progressively lowers the pH. Gypsum (calcium sulphate) is also applied extensively in sodic and alkaline soils for structure and nutrient availability, but not to significantly alter the pH. The most successful saline-alkaline (usar) soil correction practice is the combination of gypsum, green manuring and rice-wheat rotation as recommended by ICAR. The most important step in all cases is soil testing — before you can make any amendments they can only be a guess since you don't know what the nutrient and pH levels are. The India Soil Health Card scheme is being implemented on soil testing on the basis of 12 parameters such as pH, electrical conductivity and organic carbon; and recommends soil corrections specifically for each crop for each farmer.

Government of India Resources for Soil pH Management

The Soil Health Card (SHC) scheme, launched by the Ministry of Agriculture and Farmers Welfare, tests soil pH alongside 11 other parameters and provides specific liming or sulphur recommendations tailored to each farmer’s field. Over 22 crore soil health cards have been issued to Indian farmers across two cycles. Getting your soil tested under this scheme is free of cost. For the official Soil Health Card scheme details:

https://www.pib.gov.in/FactsheetDetails.aspx?Id=148602

The National Mission for Sustainable Agriculture (NMSA) supports soil health management including pH correction, integrated nutrient management, and organic matter improvement across India’s diverse agro-climatic zones. For official NMSA guidelines:

https://nmsa.dac.gov.in/

The 2024–25 update on the New Soil Health Card Scheme — covering the rollout of 665 Village Level Soil Testing Labs across 17 states — is available at:

https://www.pib.gov.in/PressReleaseIframePage.aspx?PRID=2099759

Conclusion

Soil pH is not the only soil parameter, but it is the most controlling one—it determines if all other inputs put into the soil are effective. A farmer who is using ₹5000 on the fertiliser on soil with pH imbalance could be getting the benefit of ₹1000 only from his crop. Soil health card testing is free and the most cost-effective practice that Indian farmers can do to improve soil pH is to apply lime or sulphur. Fix the pH first. Then the fertiliser will take its effectAGBLOG151

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