Fertiliser Introduction | A Series

Fertilisers are essential to modern agriculture. Growing populations and subsequently increasing farming intensity require nutrient supplementation. Fertilisers provide plants with macro and micro nutrients, purchased and applied by farmers depending on plants’ stage of growth and development, and what their soils are deficient in.

Macro Nutrients are the N, P, K’s (Nitrogen, Phosphorus and Potassium) and Sulphur.

Nitrogen supports growth. It is a vital component of chlorophyll, the molecule responsible for photosynthesis. In supporting photosynthesis, supplementing of Nitrogen directly impacts the accumulation of energy and growth of the plant. Nitrogen based fertilisers are typically applied during the early stages of stem and leaf growth to best prepare the plant for production of seed and grains. Stunted plants and yellowing leaves are typical symptoms of low Nitrogen availability. The first step in the production of Nitrogen is Ammonia, produced through the Haber-Bosch process (developed in 1913) by pressurising air (150-200 bar)  and heating it (400-500 degrees Celsius) to combine Hydrogen gas and Nitrogen.

Phosphorus is used by plants for root establishment, flowering, and fruiting. It is a component of the ATP Molecule (Adenosine Triphosphate) which powers metabolic processes, including the nutrient uptake for growth. Phosphorus is typically applied early to support plant establishment, and later, prior to fruiting and flowering when it is again needed to ensure flower health and fruit production.

Phosphorus is derived from Phosphate Rock, which has formed in areas that were ancient seabeds, and which have undergone mineralisation or have been uplifted through tectonic movements or erosion. Morocco and the Western Sahara are estimated to hold over 70% of the world's known accessible reserves, with locations such as the USA, China, and the Middle East also having reserves. Norway currently has “reserves” estimated to be larger than even Morocco, but currently there is no access.

Potassium operates as the quality enhancer. It supports water regulation and movement in cells, improves cell wall and disease resistance, and improves the size, taste and texture in fruits and grains. Potassium is generally applied during or preceding a drought to maintain productivity, and prior to fruiting in order to maximise crop quality and volume.

The main source of Potassium in fertilisers is from Potassium Chloride, commonly known as Muriate of Potash (MOP). MOP is formed where ancient seabeds went through repeated cycles of flooding and evaporation, and then have been buried under sediment, compressing and preserving them for mining. The largest reserve of Potash is in the Saskatchewan province in Canada, formed from the ancient seabed called the Prairie Evaporite Formation. Belarus, Russia, Germany, China and the Middle East also are home to potash deposits.

Sulphur supports protein synthesis and enzyme activity in plants, aiding in chlorophyll formation and improving nitrogen efficiency. It plays a critical role in enhancing crop quality, including the taste, size, and nutritional value of produce, while also bolstering drought tolerance and disease resistance. Sulphur deficiencies typically present as yellowing of younger leaves and stunted growth, often mistaken for nitrogen deficiency.

Sulphur is primarily sourced as a by-product of petroleum refining and natural gas processing, where hydrogen sulphide is converted into elemental sulphur through the Claus process. It is widely used to produce sulphuric acid, a key ingredient in fertilisers like SSP, TSP, and Ammonium Sulphate. Sulphur is also directly included in sulphate-based fertilisers like SOP, providing essential nutrients for plant growth.