Liquid feeding

Abstract

When plants are grown for long periods in small volumes of media, the supply of available nutrients becomes depleted, growth ceases and symptoms of nutrient deficiency may spoil the general appearance of the plants. Years ago, the grower’s remedy was either to occasionally add to each pot a teaspoonful of powdered fertilizer which was washed into the media at the next watering, or to make up a liquid feed by suspending animal manure in coarse sacking in a barrel of water and allowing the soluble nutrients to diffuse into the water. This solution was then applied to the pots with a watering can. These methods of liquid feeding are too imprecise and time consuming to be used today and the practice of adding soluble chemicals to the irrigation water has steadily gained in popularity since it was first used in the 1930s. Factors contributing to the growth of this system of liquid feeding have been:

• (a) the large increase in the cost of labour;

• (b) the need to obtain the maximum growth rate and the greatest number of plants per year from each glasshouse;

• (c) the development of automatic or semi-automatic systems of pot watering, which, together with fertilizer injectors or diluters, provide an efficient and easy means of combining feeding with watering;

• (d) the increased use of loamless mixes, which have a greater need for liquid feeding than the older, loam-based composts.