It is important for farmers to know which fertilisers are best suited to their soil to enable them to make good use of the nitrogen-phosphorus-potassium ratio and increase yields

A proper understanding of the nitrogen-phosphorus-potassium (NPK) ratio will ensure that the crop is properly fed and nourished. For Tata Chemicals, educating farmers on the proper use of fertilisers to optimise crop output has always been a crucial objective.

Stripped of complexity, the NPK ratio is simply a way of specifying the nutrient content of the fertiliser, in terms of percentages, by weight. For example, a fertiliser with an NPK ratio of 10:15:5 (2:3:1) contains, by weight, 10 per cent nitrogen (N), 15 per cent phosphorous (P) and 5 per cent potassium (K).

The remaining 70 per cent, by weight, of the fertiliser is inert material: substances that are bound to or carry these three principal nutrients. What this means is that in any 100-kg sample of the fertiliser there are 10 kg of nitrogen, 15 kg of phosphorous, 5 kg of potassium and 70 kg of inert material.

Tailor-made nutrition
Plants need different nutrients at different stages of their growth. In the root stage they need what are called root fertilisers, or potassic fertilisers. In the growing stage they need 'leaves-and-foliage fertilisers' (nitrogenous fertilisers). In the flowering and fruit stage they need 'fruit-and-flowering fertilisers' (phosphatic fertilisers).

Urea, which is manufactured by TCL, is a nitrogenous fertiliser. Being a leaves-and-foliage fertiliser, it has wide application in the growth of plants.

The constitution and application of various types of fertilisers and their NPK ratios are as described below:

Nitrogenous fertilisers
Nitrogenous fertilisers (or urea) support the plant during the growth of leaves and foliage. The NPK ratio of nitrogenous fertilisers varies, but in India a ratio of 4:2:1 is considered to be optimum for food crops, especially rice and wheat (where nitrogen is present in 4 parts, phosphorus in 2 parts and potassium in 1).

Phosphatic fertilisers
Phosphatic fertilisers are also called fruit-and-flowering fertilisers since they aid the growth of flowers and fruits in plants. Ideally, the NPK ratio of phosphatic fertilisers is in the ratio of 2:3:2 (where nitrogen is present in 2 parts, phosphorus in 3 and potassium in 2).

Potassic fertilisers
Potassic fertilisers are called root fertilisers since they stimulate the growth of roots of plants. Ideally, the NPK ratio of potassic fertilisers is in the ratio of 2:2:3 (where nitrogen is present in 2 parts, phosphorous in 2 and potassium in 3).

By the judicious use of nitrogenous, phosphatic and potassic fertilisers, a farmer can optimise the yield from his land.