All plants need food if they are to thrive and grow. Contrary to the belief of some gardeners, the soil does not contain an endless supply of nutrients. They are eventually used up or leached out. They may not have even been there in the first place.
Apart from the fact that plants need food to sustain them, well-nurtured and healthy plants are far more likely to cope with adverse conditions like cold or drought. They become more resistant to the ravages of pests and disease and they will bear better and more prolific fruits and flowers.
The term fertilizer is a broad one that covers a range of plant foods of either organic or inorganic form. While the plants cannot tell the difference between the two, the long-term or short-term reaction of each kind of fertilizer is remarkably different.
Organic fertilizers are derived from plant or animal wastes. Compost, manure and derivatives like blood and bone and seaweed fertilizers are some of the better-known sources. Nutrients are released from decomposing residues which in turn becomes humus – a valuable soil additive. Humus increases the water and nutrient-holding capacity of the soil as well as making it more friable and easy to work.
There are a number of disadvantages of relying solely on organic fertilizers. Large amounts of it are regularly required to produce the required amount of nutrients. Most of the nutrients within are released only over a comparatively long period of time, and the composition of the fertilizer itself is variable. Animal manures vary according to the diet and the type of animal, and even plant residues may be deficient in either one or a number of elements.
The experienced gardener will recycle as much organic material as possible and supplement his plant feeding program with the minimum amount of inorganic (or chemical) fertilizers required to maintain good growth.
Nitrogen (N), phosphorus (P), and potassium (K) are the three major elements required by all plants. Nitrogen is necessary for leaf, phosphorus for root growth, and potassium to stimulate fruiting and flower production. Though a number of “micro” elements are also necessary for growth, sufficient, are added to proprietary “complete” fertilizers for most gardeners’ needs.
A plant that may be deprived of one of the major or microelements is said to be deficient. As plants invariably display some physical symptoms of deficiencies – for example, paler leaves or stunted growth – it becomes comparatively easy to rectify a problem.
Complete fertilizers are most effective when applied at the beginning of each growing season – spring and autumn. Soluble fertilizers that offer the home gardener ease of application as well as promoting a quick response in plant growth, are best used only through the growing season. As the weather becomes cooler the tender young growth which results from the high nitrogen feeds of liquid fertilizer is extremely susceptible to frost damage.
The balance of nutrients in the soil can be adversely affected by the wrong kind of feed. Fortunately, nowadays, much of the guesswork has been removed since the introduction of specially formulated packs with the correct amount of N-P-K for particular plants, such as azalea and camellias, citrus, and lawns and others.
Packet directions need to be followed carefully, though, for applying too much can cause problems of yet another kind. It may even kill the plant you are trying to nurture. Never apply chemical fertilizers to dry soil. Dampen the soil first then water it well into the ground afterward.
“Green manure” provides a first-time garden soil with much-needed vegetable matter. Barley, oats, wheat, and crops like peas, beans, and field lupins can all be profitably planted out in autumn. Grown to the point of flowering, they are later cut and then turned into the ground with a dressing of fertilizers, where they will quickly decompose, thus enriching and preparing the soil for spring planting.