Macronutrients are vital for strong and healthy growth. Compound NPK fertilizers contain a mix of these macro nutrients in the right proportions, when they are tailored to meet local requirements.
Nitrogen activates vegetation, and is essential for assimilation and respiration. It is a key component of protein and chlorophyll. Lack of nitrogen is recognizable by yellowish vegetation and slow growth. Nitrogen also requires the contributory effect of other macronutrients because sole nitrogen fertilization program, while increasing yield in the short term, depletes other nutrients, will result in long-term yield decline in yield.
The need for phosphorus is greatest at the beginning of the growing period. Several plant processes, such as photosynthesis, glycolysis, respiration, and protein and fatty acid syntheses, depend on the presence of phosphorus. A phosphorus deficiency results in small plant size, a reduced number of seeds, delayed maturation, and a reddish tinge to the plant.
Plants need potassium most at the end of the growing period. It controls plant respiration and the transportation of photosynthesis products. Potassium activates several enzymes involved in carbohydrate metabolism. Potassium concentrates in the straw of cereal grains, meaning that if the straw is harvested along with the grain, the soil may face a shortage of potassium. Deficiency is apparent as slow growth, a poorly developed root system, and a grayish tinge to the plant.
In granular fertilizers, Potassium source is normally Potassium Sulphate (SOP) or Potassium Chloride (MOP) or a mix of these two. SOP is more expensive and it should be used for crops sensitive to Chloride, as well as crops requiring larger amounts of Sulphur.