The crucial role of the secondary nutrients in sustainable agriculture
|Secondary nutrients deficiencies are increasingly becoming an important limiting factor in intensive crop production systems|
|Dr. Patricia Imas, Chief Agronomist, ICL Fertilizers, Patricia.email@example.com|
|October 17, 2019|
Sulphur (S), magnesium (Mg) and calcium (Ca) are essential plant nutrients. They are called “secondary” nutrients because plants require them in smaller quantities than nitrogen (N), phosphorus (P), and potassium (K). On the other hand, plants require these nutrients in larger quantities than the “micronutrients” such as iron, zinc and boron.
Secondary nutrients deficiencies are increasingly becoming an important limiting factor in intensive crop production systems, especially in soils fertilized only with N, P and K. Many soils worldwide are poor in fertility - specifically in secondary nutrients - as they have consistently been depleted of their native nutrients due to continuous cultivation. This has resulted in the soil becoming a poor food crop producer.
Crops such as corn that have a high dry matter production generally require the greatest amount of sulphur. Also potatoes, cotton, sunflower, canola (rape seed), Brassicas (cabbage, broccoli, cauliflower) and many other vegetables require large amounts of S.
Many coarse-textured, sandy soils and low-organic matter are found to be sulphur deficient for crop production. Farmers usually apply S fertilizers before planting, so it is prone to losses by rains or irrigation that will leach out the S from the soil profile and will not be taken up by the crop.
Sulphur deficiency in maize (USA)
Magnesium (Mg) is an essential component of the chlorophyll molecule, with each molecule containing 6.7% Mg. It is essential for photosynthesis, cell division, protein formation phosphate metabolism, plant respiration and the activation of several enzyme systems.
Magnesium deficiency in soybean (Brazil)
Calcium (Ca) is responsible for proper plant cell division and for strengthening cell walls. Calcium improves the absorption of other nutrients by roots and their translocation within the plant. It activates enzyme systems, helps convert nitrate-nitrogen into proteins and contributes to improved disease resistance. Without enough Ca, roots become stunted with impaired activity.
Ca deficiency in grapes (China)
Polysulphate is mined in the UK by ICL Boulby, from the polyhalite layer of rock deposited 260 million years ago over 3,300 feet below the North Sea off the North Yorkshire coast.
Being a natural crystal, it has a very unique dissolution pattern, which releases its nutrients gradually after being applied to the soil. While most sources of S have high rates of dissolution, releasing S immediately with the risk of losing S as leached sulphate - Polysulphate provides a prolonged availability of S. This prolonged release pattern of S from Polysulphate matches the uptake timing of S by crops and minimizes the risk of loss of sulphate by leaching.
Agronomic and environmental benefits of Polysulphate for farmers
The steady, prolonged release of S over a longer period than other fertilizers is a key advantage of Polysulphate. Along with S, Polysulphate provides three other nutrients (K, Mg and Ca) in one single application and has a positive effect on crop growth, yield and quality – many experiments worldwide show this steady yield response to Polysulphate application. For example, in a trial in Indonesia. rice paddy plants fertilized with Polysulphate fertilizer are 8-10 cm taller than those grown according to farmer’s practice. Importantly, the Polysulphate grown plants are also more tolerant to lodging:
Trial in Popowo, Poland investigating the effect of Polysulphate on the yield and quality parameters of Brook variety of potato.
Polysulphate also improves the quality of produce. There is a growing body of evidence for this in crops in many parts of the world. For example, in an experiment with wheat carried out by Southeast Missouri State University, USA, Polysulphate improved N:S ratio in grains and thus enhanced baking quality of the flour.
For more info please contact: Patricia Imas
This article was published in the special issue for FWD 2019