Sulphur-Deficient Soil in India: Impacts on Crops and Human Health

The Problem of Sulphur-Deficient Soil and Its Implications for Human Health in India

Tejasvani Knowledge Desk | Soil Health • Food Quality • Human Nutrition

Introduction: An Essential Nutrient Beneath Our Feet

When we discuss soil health, we often focus on nitrogen, phosphorus and potassium. However, another essential plant nutrient deserves greater attention: sulphur.

Sulphur plays an important role in plant growth, protein synthesis, enzyme activity and the production of several biologically important compounds. Yet, research indicates that sulphur deficiency is widespread across agricultural soils in India. This raises an important question: if the soil that nourishes our crops is deficient in essential nutrients, what could this mean for the quality of the food we eat?

The connection between soil health and human nutrition is complex. Soil nutrients influence plant growth and metabolism, which can affect the composition and nutritional quality of agricultural produce. Although this does not automatically translate into a specific nutritional deficiency in humans, it highlights why soil fertility should be considered an important part of the broader conversation about food quality and public health.

1. Sulphur Deficiency in Indian Agricultural Soils

The scale of the problem is significant.

A national study conducted under the All India Coordinated Research Project on Micro- and Secondary-Nutrients and Pollutant Elements in Soils and Plants analysed 242,827 surface-soil samples collected from agricultural fields across 615 districts in 28 Indian states.

The study reported that 58.6% of the analysed samples showed some degree of plant-available sulphur deficiency, encompassing acute deficiency, deficiency and latent deficiency categories. The findings also revealed substantial variation between regions.

These findings are important because plant-available sulphur is necessary for healthy crop development. They do not mean that every Indian farm is deficient, but they demonstrate why location-specific soil testing and nutrient management are essential.

Several agricultural factors can contribute to sulphur depletion:

• Intensive cropping: Repeated cultivation and harvesting remove nutrients from the soil.

• Imbalanced fertilisation: Fertilisers supplying nitrogen, phosphorus and potassium may not provide sufficient sulphur.

• Leaching: Sulphate can move below the root zone, particularly in susceptible soils and under heavy rainfall or irrigation.

• Low organic matter: Soils with limited organic matter may have smaller reserves of organically bound sulphur.

• Reduced atmospheric deposition: Cleaner air has reduced one historical source of sulphur replenishment in many agricultural regions.

ICAR has also highlighted sulphur as an often-overlooked essential plant nutrient, particularly in relation to crop productivity and the nutritional quality of agricultural produce.

2. Why Do Plants Need Sulphur?

Sulphur is involved in several fundamental plant processes.

Protein synthesis and amino acids

Plants absorb sulphur primarily in the form of sulphate and use it to synthesise sulphur-containing amino acids, particularly methionine and cysteine. These amino acids are necessary for producing proteins and supporting normal plant metabolism.

A shortage of available sulphur can interfere with protein synthesis, restrict growth and reduce crop yields.

Crop quality and nutritional composition

Legumes and oilseeds have important sulphur requirements. Adequate sulphur nutrition supports their growth, protein formation and other metabolic processes involved in seed development.

Sulphur also participates in the synthesis of compounds found in crops such as mustard, garlic and onion. The effects of sulphur fertilisation on grain, seed and oil composition can vary by crop and growing conditions, and additional crop-specific research is needed to quantify these effects consistently.

This distinction matters: healthy soil nutrition supports the potential of a crop to grow and develop normally, but the precise nutritional composition of the harvested food depends on several factors, not just sulphur availability.

3. From Soil to Food: Understanding the Human Health Connection

Humans obtain sulphur mainly through dietary compounds, especially proteins containing methionine and cysteine. Methionine is an essential amino acid that must come from the diet, while the body can produce cysteine from methionine under normal physiological conditions.

These amino acids contribute to protein formation, cellular function and the body's antioxidant and metabolic systems.

When a crop grows in sulphur-deficient soil, its growth and metabolism may be affected. In some circumstances, sulphur deficiency can also influence the concentration of particular sulphur-containing compounds in the harvested crop.

However, low sulphur levels in soil do not automatically mean that the people consuming its produce will develop sulphur deficiency. Human nutrition depends on total dietary intake, food variety, protein quality, absorption and the body's metabolic requirements.

The concern is therefore broader than one nutrient: agricultural practices should protect the ability of soils to support nutritious, good-quality food.

Sulphur-containing amino acids and protein quality

Methionine and cysteine are important components of dietary protein. They contribute to protein synthesis, tissue maintenance and other physiological functions.

For people consuming predominantly plant-based diets, the quality and variety of dietary protein deserve particular attention. Pulses, cereals, soybeans, nuts and seeds can contribute to protein intake, but their amino acid profiles differ.

Sulphur deficiency in crops can affect plant protein metabolism. Nevertheless, the extent to which this changes the amino acid composition of a particular food must be established through crop-specific nutritional analysis. It should not be assumed that all wheat, pulses or oilseeds grown in deficient soil contain inadequate amounts of these amino acids.

A diverse diet containing sufficient protein remains an important foundation of human nutrition.

4. Sulphur, Antioxidant Defences and Cellular Health

One of the important biological roles of sulphur is its contribution to molecules involved in cellular protection.

The role of glutathione

Glutathione is a major antioxidant produced by the human body. It helps regulate oxidative stress, supports cellular defence mechanisms and participates in the metabolism of certain potentially harmful substances.

Cysteine is an essential building block for glutathione synthesis, linking sulphur-containing amino acid metabolism to the body's antioxidant systems.

This makes sulphur-containing nutrients biologically important. However, it is important to distinguish between the established role of glutathione and the more specific claim that sulphur-deficient agricultural soils cause glutathione depletion in people.

That direct relationship has not been established simply by measuring sulphur deficiency in soil. Dietary protein intake, the body's metabolic processes, illness and other factors can all influence glutathione status.

Skin, hair, nails and connective tissues

Sulphur is particularly relevant to keratin, a protein rich in sulphur-containing amino acids that gives hair, nails and the outer layers of skin many of their structural properties.

Sulphur-containing compounds also participate in processes that maintain tissues and cellular function.

However, there is insufficient evidence to conclude that sulphur-deficient agricultural soils directly cause hair loss, brittle nails, arthritis or degenerative joint disorders in the people consuming crops grown in those soils.

The scientifically meaningful concern is ensuring adequate dietary protein and essential nutrients while maintaining the soil conditions necessary for healthy crop development.

5. Sulphur and the Nutritional Quality of Food

Sulphur has a role in the formation of certain vitamins and plant compounds.

Thiamine, or vitamin B1, contains sulphur in its molecular structure. Plants and microorganisms also produce various sulphur-containing compounds that contribute to their normal biological functions.

Research on sulphur fertilisation has identified its relevance to crop yield and the synthesis of particular nutritional compounds. However, evidence relating sulphur fertilisation to changes in the nutritional composition of individual foods remains incomplete for several crops.

For this reason, sulphur management should be viewed as one part of improving agricultural productivity and food quality, rather than as a guaranteed method of preventing vitamin deficiencies in humans.

Human vitamin status depends on the full diet, absorption, physiological requirements and other health factors. A soil test alone cannot determine whether a person has a nutritional deficiency.

6. Sulphur and Gut Health: An Emerging Area of Research

Sulphur also has a role in the complex relationship between the human body and its intestinal microbiome.

Gut microorganisms produce several sulphur-containing metabolites, including hydrogen sulphide. Research indicates that hydrogen sulphide can act as a biological signalling molecule and influence intestinal mucus, the gut lining, inflammation and tissue repair.

Importantly, its effects depend on the concentration, source and biological environment. Low levels can contribute to normal physiological functions, while excessive concentrations in certain circumstances may damage the intestinal lining or contribute to inflammation.

This makes sulphur metabolism an interesting area of gut-health research.

However, the sulphur available to intestinal microorganisms is influenced by dietary substrates, microbial activity and the body's metabolism. There is currently insufficient evidence to claim that sulphur-deficient agricultural soil directly causes gut disorders through reduced hydrogen sulphide production.

The more useful takeaway is that healthy diets, appropriate soil nutrition and a better understanding of the gut microbiome are all important areas of ongoing research.

7. What About Brain Health and Neurological Disorders?

Sulphur-containing molecules participate in several processes relevant to the nervous system.

Glutathione helps protect cells from oxidative damage, while other sulphur-containing compounds are involved in cellular signalling and normal metabolic activity. Sulpholipids, including sulfatides, also contribute to the structure and function of myelin, the protective material surrounding many nerve fibres.

These biological relationships have attracted scientific interest in neurological and metabolic research.

Nevertheless, it is essential to distinguish between the role of sulphur-containing compounds in the nervous system and evidence that a particular environmental or nutritional exposure causes disease.

Understanding these mechanisms remains valuable, but stronger evidence is required before specific disease outcomes can be attributed to agricultural sulphur depletion.

8. What Can Be Done to Address Sulphur Deficiency in Soil?

Addressing this problem starts with recognising that sulphur is an essential component of balanced soil nutrition.

Soil testing and nutrient management

Farmers should use soil tests, including Soil Health Card recommendations, to assess nutrient availability and identify deficiencies. Sulphur application should be based on the crop, soil characteristics and locally appropriate recommendations rather than a universal fertiliser dose.

Balanced fertilisation

Using suitable sulphur-containing fertilisers where indicated can help correct deficiencies and support crop growth. Nutrient management should consider nitrogen, phosphorus, potassium, sulphur and relevant micronutrients together.

Improving organic matter

Appropriate use of compost, farmyard manure, retained crop residues and other organic materials can contribute to soil organic matter and nutrient cycling. Their effectiveness depends on their composition, application rates and local soil conditions.

Reducing nutrient losses

Appropriate irrigation, drainage, erosion control and soil-management practices can help limit nutrient losses and improve the efficiency of nutrient use.

Continued research into food quality

More crop-specific research is needed to measure how sulphur availability affects the concentration of essential amino acids, vitamins and other beneficial compounds in edible plant tissues.

Combining agricultural soil testing with food-composition research would help establish where sulphur management can make the greatest contribution to crop productivity and nutritional quality.

The Indian Council of Agricultural Research recommends soil-test-based, balanced and integrated nutrient management, including appropriate combinations of inorganic and organic nutrient sources.

Conclusion: Human Nutrition Begins with Healthy Soil

The sulphur status of agricultural soils deserves greater attention in India. Large-scale research has documented widespread deficiencies of plant-available sulphur, highlighting the need for balanced nutrient management and region-specific agricultural practices.

Sulphur is essential to plants, contributes to the formation of important compounds in food, and is involved in human protein metabolism, antioxidant defence and other biological processes. These connections make soil nutrition a meaningful part of the wider discussion about food quality and public health.

At the same time, good science requires us to recognise the limits of current evidence. Soil sulphur deficiency is not, by itself, proof of human sulphur deficiency or a direct cause of chronic or neurological disease.

The way forward is to combine better soil testing, scientifically guided nutrient management, diverse diets and further research on crop nutritional quality.

At Tejasvani, we believe that understanding the relationship between soil, plants and human well-being is an important step towards a more informed approach to natural living.

Healthy soil supports healthy crops. Understanding the journey from soil to food helps us make better decisions for agriculture, nutrition and long-term well-being.