Like all living beings, plants too need light, water and nutrients to grow. Light comes from sun, water comes from rain or irrigation and nutrients from fertilisers.
Though fertilisers help in growth, plants grown in poorly drained soils, excessive shade, or in places where there is overcrowding do not respond to fertilisers. So before you go ahead with a fertiliser, you must also take care that the soil is well-drained and there is optimum sunlight.
Fertilisers are either organic (plant or animal based) like manure, bone meal, cotton seed or inorganic that are made from chemicals.
The three main ingredients of a good fertiliser
The three numbers written on any fertiliser container stand for the percentage of nitrogen, phosphorous and potassium. These figures are always listed in the order N-P-K. For example, a 100 kg bag which has 10-20-10 written on it means it has 10kg nitrogen, 20kg phosphorus and 10kg potassium.
The rest of the content is a carrier like sand, perlite or rice husk. A good fertiliser is one that has all these three ingredients.
Nitrogen is essential for the overall growth of a plant, be it roots, leaves, stems, flowers or fruits. Nitrogen gives a plant its green colour and is needed to form protein. Lack of nitrogen turns a plant into pale green while excess will kill it.
Phosphorus helps form roots, flowers and fruit. Its deficiency stunts the growth of a plant and results in poor flowering and fruiting.
Potassium is required for many of the chemical processes that allow a plant to grow. Shortage of this ingredient results in stunted growth and yellowing of lower leaves.
Choosing the right fertiliser
A good fertiliser is one that has twice the amount of phosphorus than that of nitrogen and potassium like 10-20-10 or 12-24-12. These fertilisers are usually easy to find.
But guard against over-feeding your plants with fertiliser as it can damage or even kill them. Also, before putting any fertiliser, get the soil tested so that you can select the type and formula that is required.
The best time to put fertiliser
Fertiliser is most effective when used on plants at the peak of their growing cycle. This is when the plant is leafing out in case of deciduous species, flowering, or gaining new growth after leaving the dormant winter stage.
During the monsoon season, the pores in the plants open up, so spraying a fertiliser helps them absorb these easily.
Fertiliser should be added to a potted plant once in every three months, and the best time to add fertiliser is early morning. The author is a landscape designer, architect and founder of Sunshine’s Nest & Gardens