Types of Fertilizer: Nutrient Content of Nitrogen, Phosphate, Potash and NPK Grades

Crops take most of their nutrients from the soil, and fertilizers top up what the soil cannot supply in sufficient quantity. Bulk mineral fertilizers are either manufactured industrially or mined, and each product carries a defined, declared nutrient content.

Besides the nutrient carrier itself, a product may contain additives such as anti-caking agents, coatings or inhibitors that slow down its conversion in the soil.

• Nitrogen fertilizers: urea, ammonium nitrate, calcium ammonium nitrate (CAN), ammonium sulphate, urea ammonium nitrate solution (UAN)
• Phosphate fertilizers: diammonium phosphate (DAP), monoammonium phosphate (MAP), triple superphosphate (TSP)
• Potash fertilizers: muriate of potash (MOP), sulphate of potash (SOP)
• Compound fertilizers: NPK, NP and PK grades in many formulations

Sulphur (S) and magnesium (Mg) are secondary nutrients and are supplied, for example, through ammonium sulphate or SOP.

For the most widely traded solid nitrogen fertilizer, see our urea 46 % guide.

Figures are typical commercial grades; the binding values are those in the contract specification.

Ammonium phosphates are made from phosphoric acid and ammonia and rank among the most traded phosphate fertilizers worldwide; they are also a common base for blends. SOP is low in chloride and also supplies sulphur, which is why it is used for chloride-sensitive crops, whereas MOP is the standard potash source.

Phosphorus and potassium are expressed as oxides by convention, not as the pure element. Additions such as “+ 2 MgO + 6 S” declare secondary nutrients. The numbers stay well below 100 % because the rest of the weight is made up of bound elements such as oxygen, hydrogen or chloride and of other constituents.

NPK products are sold either as complex (compound) fertilizers, where every granule contains all nutrients, or as bulk blends mixed from straight components.

• Ammonia: nitrogen from the air reacts with hydrogen, usually obtained from natural gas.
• Urea: synthesised from ammonia and carbon dioxide.
• Ammonium nitrate: made from ammonia and nitric acid, which itself is produced from ammonia.
• Phosphates: phosphate rock is digested with sulphuric acid to make phosphoric acid, which reacts with ammonia to form DAP and MAP.
• Potash: potash ore is mined or extracted from brines and refined into potassium chloride.

Because natural gas is both feedstock and energy source for nitrogen products, gas prices weigh heavily on production costs.

Which product, and how much of it, makes sense depends on soil type, nutrient status, crop, climate and local regulation – and is worked out through soil analysis and agronomic advice. This guide does not give application rates.

Overuse matters too: surplus nitrogen can leach into groundwater as nitrate, which is why the EU Nitrates Directive restricts nitrogen inputs.

We only broker bulk mineral fertilizers, not organic products.

• Specification: nutrient content, moisture, granule size, physical form, impurities
• Certificate of analysis (CoA) and certificate of origin, ideally confirmed by independent inspection at loading
• Packaging: 50 kg bags, big bags or loose in bulk
• Compliance: labelling, registration and safety rules, for example for ammonium nitrate

Our guide to inspection and CoA/CoO certificates explains the documents in detail. See the fertilizers section for the products we broker, or send your specification and volume via contact.