Fertiliser Guide for Indian Farmers (2026): NPK Grades, Water-Soluble Fertilisers, Micronutrients and Mixing Rules

A farmer may buy the correct fertiliser and still get a disappointing response, because it was applied at the wrong stage, placed away from active roots, used in unsuitable soil or mixed with an incompatible product. Good crop nutrition starts with a better question: which nutrient does my crop need, how much of it, at what stage, and by which method?

This guide explains urea, DAP, SSP, MOP, complex NPK fertilisers, water-soluble fertilisers such as 19:19:19, 12:61:0, 13:0:45 and 0:52:34, secondary nutrients, micronutrients, biofertilisers and the mixing mistakes that cost money. It is written for farmers, agri-input retailers and crop advisers who want to decide with reasons rather than by habit. Every grade below links to its specification in NanoKheti's FCO Fertiliser Library.

Why Choosing the Right Fertiliser Matters

An ICAR–Indian Institute of Soil Science article in Indian Farming (December 2025) puts nutrient-use efficiency in Indian cropping systems at roughly 30–50% for nitrogen, 15–20% for phosphorus, 50–80% for potassium and below 5% for micronutrients. These are broad ranges, not a prediction for your farm. And a nutrient the crop does not take up this season is not always wasted: some stays in the soil, while some is lost through leaching, run-off, gases or fixation into forms the crop cannot easily use.

India's soils are also short of more than nitrogen, phosphorus and potassium (NPK). A nationwide study of about 2.4 lakh soil samples from 615 districts found sulphur deficient in 58.6%, zinc in 51.2% and boron in 44.7% of soils (counting acute, ordinary and latent deficiency together). That is why more NPK alone may not fix a nutrition problem. The deficiency in your own field still has to be confirmed by a test.

The practical lesson is simple: improve what you apply and how you apply it before you increase the dose.

How to Read a Fertiliser Grade: N, P₂O₅ and K₂O

A grade such as 19:19:19 gives the declared percentages by weight of nitrogen (N), phosphate expressed as P₂O₅, and potash expressed as K₂O.

Fertiliser grade	What the numbers mean	Nutrients in 10 kg of product
19:19:19	19% N, 19% P₂O₅, 19% K₂O	1.9 kg N + 1.9 kg P₂O₅ + 1.9 kg K₂O
12:61:0	12% N, 61% P₂O₅, no declared K₂O	1.2 kg N + 6.1 kg P₂O₅
13:0:45	13% N, no declared P₂O₅, 45% K₂O	1.3 kg N + 4.5 kg K₂O
0:52:34	No declared N, 52% P₂O₅, 34% K₂O	5.2 kg P₂O₅ + 3.4 kg K₂O

These are labelling conventions: P₂O₅ and K₂O are not the same as elemental phosphorus and potassium (16% P₂O₅ is about 7% P). Always compare grades in the same units.

Urea, DAP, SSP and MOP: The Common Fertilisers in India

Fertiliser	Declared nutrients (FCO minimum)	Main role	What to keep in mind
Urea	46% nitrogen	Nitrogen for leaf, stem and vegetative growth	Split doses usually match crop demand better; too much N creates imbalance
DAP (diammonium phosphate)	18% N + 46% P₂O₅	Nitrogen and phosphorus, mostly as a basal dose	Check whether the soil actually needs more phosphorus
SSP (single superphosphate)	16% available P₂O₅ + 11% sulphur	Phosphorus and sulphur	Useful where sulphur is short; not interchangeable with DAP kilogram for kilogram
MOP (muriate of potash)	60% K₂O	Potassium	Contains chloride; crop sensitivity and soil and water conditions matter
SOP (potassium sulphate)	50% K₂O + 17.5% sulphur	Potassium and sulphur	Sometimes preferred for chloride-sensitive crops; weigh cost against need

Example: a 50 kg bag of urea at 46% N contains 23 kg of nitrogen. That tells you how much nutrient you bought, not how much the crop will take up, which depends on moisture, soil, timing and crop demand.

Complex NPK Fertilisers: Which Grade Does What?

Complex fertilisers combine two or more nutrients in each granule. A bigger number is not automatically better; the right ratio depends on what the soil supplies and the crop demands.

Grade	Nutrient emphasis	When to consider it
10:26:26	More phosphate and potash than nitrogen	A P- and K-weighted basal dose, where justified
12:32:16	Higher phosphorus, with N and K	Basal nutrition matched to crop and soil needs
14:35:14	Higher phosphorus	Where the nutrient plan supports a high phosphate demand
20:20:0:13 (ammonium phosphate sulphate)	N, P and 13% sulphur; no K	When sulphur is needed and potassium comes from elsewhere or is already sufficient

Do not choose a grade only because a neighbour got a good result with it. The same fertiliser can be right in one field and unnecessary in the next.

Water-Soluble Fertilisers (WSF): Grades and Uses

Water-soluble fertilisers dissolve completely for drip (fertigation) and, where the label allows, foliar sprays. They let you feed smaller amounts more often, where irrigation and crop management permit.

WSF grade	Common name	Nutrients	Common purpose
19:19:19	Balanced water-soluble NPK	Equal N, P and K	Balanced supplementary feeding during active growth
12:61:0	Mono ammonium phosphate (MAP)	Phosphorus with some nitrogen	When a high dose of soluble phosphorus is needed
17:44:0	Urea phosphate	Phosphorus and nitrogen	Phosphorus through drip, subject to water and system compatibility
13:40:13	High-phosphate NPK	More P, with N and K	A phosphorus-weighted soluble grade, where justified
0:52:34	Mono potassium phosphate (MKP)	Phosphorus and potassium, no N	P and K, often around flowering and fruit set
13:0:45	Potassium nitrate	Potassium with nitrate nitrogen	K-focused feeding, often during fruit development
0:0:50	Sulphate of potash (SOP)	Potassium and sulphur	K and S, when indicated
18:18:18 + S	Sulphur-containing soluble NPK	Balanced NPK plus sulphur	Balanced feeding with sulphur; check the declared S on the label
Calcium nitrate	Calcium nitrate	15.5% N + 18.5% calcium	Calcium and nitrate nitrogen, where suitable

Two kinds of 19:19:19. The FCO also lists an NPK 19-19-19 complex fertiliser in which only 16.5% of the 19% phosphate has to be water-soluble. For drip, buy a pack that says 100% water soluble on the label.

What Is 19:19:19 Used For?

19:19:19 is a balanced NPK fertiliser. It is used when a crop needs nitrogen, phosphorus and potassium together rather than a grade weighted towards one nutrient. It is not automatically the best fertiliser for every crop or every stage.

What Is the Difference Between 12:61:0 and 0:52:34?

12:61:0 (MAP) gives phosphorus and nitrogen but no potassium. 0:52:34 (MKP) gives phosphorus and potassium but no nitrogen. Choose by the whole nutrient programme, not simply by whether the crop is flowering.

When Is 13:0:45 Useful?

13:0:45 (potassium nitrate) is rich in potassium and also carries nitrate nitrogen. It may be used when potassium demand rises, including during fruit development. It does not replace other nutrients, and its nitrogen must be counted in the crop's total. The FCO also lists a prilled 13-0-45 for soil application.

Important: soluble does not mean any strength is safe to spray or inject. Follow the label for the crop, dilution, water quality, spray volume, injection strength and interval. A foliar spray can scorch the crop when the strength, weather or mixture is wrong.

Which Fertiliser at Which Crop Stage?

Use this as a way of deciding, not as a day-by-day prescription for tomato, chilli, sugarcane, paddy or any other crop.

Crop stage	The nutrition question	Practical direction
Establishment and early rooting	Is phosphorus available, and are roots growing in good soil conditions?	Correct a confirmed phosphorus shortage; protect seedling roots from excess salts
Vegetative growth	Is there enough nitrogen, without excess?	Give N in suitable splits while keeping P, K and other nutrients in place
Bud initiation and flowering	Are P, K, boron and other nutrients adequate?	Correct specific shortages; do not assume every flower drop is boron deficiency
Fruit, grain or tuber development	Is potassium enough? Is calcium or water movement limiting quality?	Match K and Ca to crop need and irrigation; keep incompatible concentrates apart
Maturity	Is more fertiliser still worth paying for?	Avoid unnecessary late doses; follow crop recommendations and harvest restrictions

The stage matters, but so do the soil test, irrigation water, variety, expected yield, weather and what has already been applied.

Secondary Nutrients: Calcium, Magnesium and Sulphur

NPK does not tell the whole story.

• Calcium (Ca) builds cell walls and growing tissue. Calcium disorders in fruit can appear even when the soil has calcium, if water movement and uptake are disturbed.
• Magnesium (Mg) sits at the centre of the chlorophyll molecule. Shortage shows as yellowing between the veins, usually first on older leaves.
• Sulphur (S) is needed for amino acids, protein and quality, and matters especially for oilseeds, pulses, onion and garlic when the soil runs short.

Common sources include calcium nitrate, magnesium sulphate (9.5% Mg + 12% S), gypsum, SSP and sulphate of potash. Choose the source by the deficiency and the way you will apply it, not by brand name.

Micronutrients: Zinc, Boron, Iron, Manganese and Copper

Micronutrients are needed in small amounts, but a shortage can hold back a crop even when NPK looks adequate.

Nutrient	Possible signs of shortage	FCO grades (minimum)	Caution
Zinc (Zn)	Stunting, short internodes, typical symptoms in rice and maize	Zinc sulphate heptahydrate 21% Zn; monohydrate 33% Zn; zinc chelates	Soil pH and the form decide availability
Boron (B)	Damaged growing points, poor pollination or fruit set in sensitive crops	Borax 10.5% B; boric acid 17% B	The gap between shortage and toxicity is narrow
Iron (Fe)	Yellow young leaves with greener veins	Ferrous sulphate 19% Fe; iron chelates	Some sources work poorly in high-pH soils
Manganese (Mn)	Yellowing between veins or spotting, depending on crop	Manganese sulphate 30.5% Mn	Symptoms resemble other deficiencies
Copper (Cu)	Growth and tissue symptoms that vary by crop	Copper sulphate 24% Cu	Too much harms the crop and soil life

Never diagnose a micronutrient deficiency from leaf colour alone. Root damage, waterlogging, salinity, disease, herbicide injury or several imbalances together can look the same. Use a soil test, and a leaf test where it helps.

Biofertilisers and Mycorrhiza: Where Biology Fits

Biofertilisers are living organisms that help the crop get nutrients. They are not ordinary chemical fertilisers, and their results depend on viability, placement, soil conditions and crop compatibility.

• Rhizobium: fixes nitrogen with the right legume; match the strain to the crop.
• Phosphate-solubilising bacteria (PSB): can release some fixed phosphorus under suitable conditions.
• Potassium-mobilising bacteria (KMB): may help release potassium from certain soil minerals.
• Arbuscular mycorrhizal fungi (VAM/AMF): live with the roots of compatible crops and extend a network that reaches nutrients and water beyond the roots.

Biological products need careful storage and use. Check the label for the organism, its live count, the expiry date, how to apply it and what it can be mixed with. No biofertiliser replaces a whole recommended NPK programme. For more, read our guide to mycorrhiza, PGPR, PSB, Azotobacter and Rhizobium and Dr. Abhishek Mathur's note on biofertiliser pack sizes from 1 April 2026.

What About Nano Urea?

Nano fertilisers are covered by their own schedule of the FCO (Schedule VII, for example nano nitrogen), and products differ in formulation and nitrogen content. Judge each one by its notified specification and label, not as one uniform category. Research results vary with crop, place, how much conventional nitrogen was replaced and management, and some published field comparisons have reported lower yields where nano urea sprays replaced a large share of conventional nitrogen.

Practical advice: do not drop a proven soil nitrogen programme just because a nano product is marketed as highly efficient. Go by current crop research, the product's instructions and locally tested recommendations before you change nitrogen rates.

Fertiliser Compatibility: What Should Not Go in the Same Tank?

Incompatible fertilisers can form a precipitate that locks up nutrients and blocks filters and drippers. The risk depends on strength, water chemistry, temperature and formulation, and is highest in concentrated stock tanks.

Combination	Main risk	Safer practice
Calcium nitrate + phosphates (MAP, MKP, phosphate NPK)	Calcium phosphate precipitate	Separate stock tanks; apply one after the other and flush if needed
Calcium nitrate + sulphates (magnesium sulphate, SOP, zinc sulphate)	Calcium sulphate (gypsum) precipitate	Keep concentrated stocks apart; follow the equipment guidance
Zinc sulphate + concentrated phosphate	Insoluble zinc phosphate	Apply separately unless compatibility is documented; a chelate is not automatically safe in every mix
Any fertiliser + pesticide	Physical incompatibility, crop injury or weaker performance	Mix only if both labels allow it and a jar test passes
Several soluble fertilisers + hard water	Cloudiness, precipitate, blocked drippers	Check water pH, bicarbonates and hardness; do a jar test

A jar test with your actual irrigation or spray water is a useful first check, but it does not prove the mixture is safe for the crop. Follow the mixing order and restrictions on each label. In a two-tank drip system, the common rule is calcium in one tank, phosphates and sulphates in the other.

This table is not a ban on using these nutrients in the same field. It is about risky mixtures, especially concentrated solutions; the nutrients can be applied separately within a sound programme.

How Much Fertiliser per Acre?

There is no single reliable per-acre dose of urea, DAP, 19:19:19, 13:0:45 or any micronutrient that suits every crop and field. The right dose depends on:

• the crop, variety, plant density, age and a realistic yield target;
• the soil test: nutrient levels, pH, salinity and organic matter;
• what has already been supplied through basal fertiliser, manure and earlier doses;
• the irrigation method, water quality and expected losses;
• the product's analysis, the way it is applied and the manufacturer's instructions.

For sprays, 1 g per litre means 15 g in a 15-litre pump; 2 g per litre means 30 g; 5 g per litre means 75 g. That is arithmetic, not a recommended dose. Choose a strength only after checking that it is right, and approved, for the product and the crop.

A Soil Health Card and a recommendation from your state agricultural university or Krishi Vigyan Kendra are a far better starting point than a one-size-fits-all social media chart.

Five Rules for Better Nutrient-Use Efficiency

• Right source: identify the nutrient needed before choosing a grade.
• Right rate: count the nutrient in every product, not just the bag weight.
• Right time: match supply to crop demand; split doses where recommended.
• Right place: put nutrients where active roots can reach them, or use a foliar spray for a clear, supplementary reason.
• Check the result: watch the crop's response, review irrigation and soil, and adjust the next programme on evidence.

The first four are the globally used 4R Nutrient Stewardship principles. The fifth is a reminder that every field decision deserves a review.

How to Check Fertiliser Quality and FCO Compliance in India

Before you buy, read the label and the papers: the fertiliser's name, grade and nutrient declaration, manufacturer, batch, date of manufacture (and expiry where it applies), net quantity, MRP and directions for use. Take an invoice from a licensed seller.

In India most fertilisers are governed by the Fertiliser (Inorganic, Organic or Mixed) (Control) Order, 1985, the FCO. Specifications are added, changed and sometimes omitted by later notifications. A product's marketing name is no substitute for checking its legal category and notified specification.

NanoKheti's FCO Fertiliser Specifications Library and FCO Biostimulant Library let you search every specification with its notification history, and the free label check reads a fertiliser or biostimulant label against the FCO. The latest Gazette notification remains the legally authoritative text.

For manufacturers, marketers and dealers, knowing the specification is not only about compliance. It prevents wrong product comparisons, misleading labels and avoidable complaints.

Frequently Asked Questions

What is the best fertiliser for plant growth?

There is no single best fertiliser. Nitrogen, phosphorus, potassium, secondary nutrients and micronutrients do different jobs. The right choice depends on the crop, the soil test and the growth stage.

Is 19:19:19 good for all crops?

19:19:19 is a balanced water-soluble NPK used in many crop programmes, but it is not automatically needed for every crop or right at every stage. Check your nutrient plan and the label, and for drip make sure the pack says 100% water soluble.

What is 12:61:0 used for?

12:61:0 is mono ammonium phosphate (MAP), a fully water-soluble source of nitrogen and a high level of phosphate. It is used where soluble phosphorus is needed, within the crop programme and the label directions.

What is 0:52:34 used for?

0:52:34 is mono potassium phosphate (MKP). It supplies phosphorus and potassium without nitrogen and is used in programmes that need both, including some flowering and fruiting stages.

What is 13:0:45 used for?

13:0:45 is potassium nitrate, supplying potassium and nitrate nitrogen. It helps when potassium demand is high, but its nitrogen must also be counted.

Can calcium nitrate and MKP be mixed?

Not in the same concentrated stock solution, because they can form a precipitate. Use separate stock tanks or apply them one after the other with flushing, and follow the manufacturer's compatibility advice.

Can I mix DAP and zinc sulphate?

Do not assume so in a concentrated spray or drip solution: zinc phosphate can precipitate. Look for documented compatibility or apply them separately.

Can nano urea replace ordinary urea?

Do not assume it can. Research results are mixed and depend on the product, the crop and how much conventional nitrogen is replaced. Do not cut conventional nitrogen on the strength of marketing claims alone.

Are biofertilisers enough to replace NPK fertilisers?

Not as a blanket rule. Biofertilisers support nutrient uptake and soil biology, but their contribution has to be judged within an integrated nutrient management plan.

How do I check whether a fertiliser is FCO-compliant?

Check the label against the notified specification, keep the invoice and refer to the official FCO and Gazette text. NanoKheti's searchable FCO library and free label check help you find and compare the entries.

A Note from the Founder

Working with farmers, dealers and manufacturers, I have seen the same problem again and again: a fertiliser is sold by its name or its popularity, not by the nutrient the crop actually needs. Good crop nutrition should be understandable, measurable and economically sensible.

The objective is not to sell a farmer more kilograms of fertiliser. It is to make every kilogram serve a clear purpose.

That is why we built NanoKheti's crop-nutrition resources and searchable FCO references. Farmers can use them to understand products, retailers to advise responsibly, and manufacturers to work with specifications more confidently.

Editorial disclaimer: This guide gives general educational information and is not a fertiliser prescription for any field. Follow your Soil Health Card, crop-specific recommendations, product labels and current regulations, and adjust diagnosis and rates to your actual soil, water and crop.

Editor's note: every fertiliser grade and minimum nutrient content in this guide was checked against the FCO as published in NanoKheti's FCO Fertiliser Library, and the research figures against the papers cited.