CHENNAI: Plants must have light, moisture and nutrients to grow. The sun provides light. Moisture comes from rainfall or irrigation but nutrients come from fertilisers.
If plants are not growing well, fertilising them will help only if lack of nutrients is the cause of the problem. Plants grown in poorly drained soils, in excessive shade, or in competition with tree roots will not respond to fertiliser. Fertilisers are either organic or inorganic. Examples of organic fertilisers include manure (poultry, cow or horse), bone meal, cottonseed, vermicompost and other naturally occurring materials. Inorganic fertilisers are man-made products. They usually have a higher nutrient content.
Three main ingredients of a good fertiliser
The three numbers on any fertiliser container are the fertiliser analysis which stand for the percentage of N-P-K. They indicate nitrogen, phosphorus and potassium in the fertiliser, respectively.
These figures are always listed in the same order. So for eg, a 100kg bag of 10-20-10 fertiliser contains 10kgs of nitrogen, 20kgs phosphorus, and 10kgs of potassium. This equals a total of 40kg of nutrients. The rest of the fertiliser, or 60kg in this example, is a carrier or filler such as sand, perlite or rice hulls. A complete fertiliser is one that includes all three elements.
All parts of a plant need nitrogen for the growth of roots, leaves, stems, flowers and fruits. Nitrogen gives plants their green colour and is needed to form protein. A lack of nitrogen causes the lower leaves to turn yellow and the whole plant to turn pale green. On the other hand, too much nitrogen kills plants.
P-Phosphorus is needed for cell division and to helps form roots, flowers and fruit. Phosphorus deficiency causes stunted growth and poor flowering and fruiting.
Plants need potassium for many of the chemical processes that allow them to live and grow. A potassium shortage shows up in various ways, but stunted growth and yellowish lower leaves are common symptoms in many plants.
Choosing the right fertiliser
One should use a complete fertiliser with twice as much phosphorus as nitrogen or potassium. An example would be 10-20-10 or 12-24-12. These fertilisers are usually easy to find. When it comes to fertilising, more does not mean better. It is possible to overfeed your plants. Too much fertiliser can damage and maybe even kill your plants. Hence, before applying any fertiliser, it’s a good idea to have your soil tested, so you can select the type and formula that suits your plants’ needs. In return, your plants will reward you with bigger flowers, leaves, and fruits and vegetables.
What is the best time to fertilise plants?
Fertiliser is most effective when used on plants at their peak growing cycle. This is when the plant is leafing out for deciduous species, flowering, or putting on new growth after leaving the dormant winter stage.
During the monsoon season, the pores in the plants open up, so spraying a fertiliser helps the plants absorb them immediately. You should fertilise your potted plants once in three months. Remember to fertilise early morning for best results. You may use any kind of fertiliser, liquid or granules but make sure you do use something regularly.
The author is a landscape designer, architect and founder of Sunshine’s Nest & Gardens