- Organic and synthetic fertilisers provide nutrients in different ways. Nutrients in organic fertilisers are not water soluble and are released slowly over months or years. They, however, stimulate soil microorganisms and improve the soil structure. In most cases, organic fertilisers and compost will provide all the secondary and micronutrients the plants need.
- Synthetic (chemical) fertilisers are water soluble and can be taken up by the plant almost immediately. This means that too much of it can ‘burn’ the plant. They give the plants a quick boost but do little to improve soil texture, stimulate soil life or improve soil fertility.
- Some organically-based fertilisers, such as PHC (all-purpose fertiliser) also contain small amounts of synthetic fertilisers to ensure the availability of nutrients.
- Farmers advised to test soils every three years.
- Plants can absorb nutrients eight to 20 times more efficiently through their leafs than roots. As a result, spraying foliage with liquid nutrients can produce remarkable yields. For the best results, spray plants during their critical growth stages such as transplanting time, blooming time and just after fruit sets.
- Plants require six primary nutrients for growth. Of the six, carbon, hydrogen and oxygen are derived from the air and water, while nitrogen, phosphorus and potassium are injected through the use of fertiliser. Most packed fertilisers contain these three nutrients.
- Plants also require micronutrients in small quantities, including calcium, magnesium, sulphur, boron, copper, iron, and zinc. Healthy soil that has sufficient organic matter will always contain adequate amounts of each of them.
Uses of the different elements
Nitrogen: It helps plants to make the proteins they need to produce new tissues. In nature, nitrogen is often in short supply so plants have evolved to take up as much nitrogen as possible even if it means missing other necessary elements. If too much nitrogen is available, the plant may grow abundant foliage, but not produce fruit or flowers. Growth may actually be stunted because the plant is not absorbing enough of the other elements it needs.
Phosphorus: It stimulates root growth, helps the plant set buds and flowers, improves strength and increases seed size. It does this by helping transfer energy from one part of the plant to another. To absorb phosphorous, most plants require a soil pH of 6.5 to 6.8. Organic matter and the activity of soil organisms also increase the availability of phosphorus.
Potassium: Improves overall vigour of the plant and helps plants make carbohydrates and provides disease resistance. It also helps regulate metabolic activities.
Special formula fertilisers: They are specially designed to meet the adequate nutrient needs of a particular plant in order to grow optimally. Some plants are choosy and they will require a special formula fertiliser. This type is normally used when a plant is over fertilized or under fertilised.
Liquid fertiliser: It is effective when the nutrient required is to be delivered through the roots, where the plant will immediately take up the necessary nutrient. This is, however, a short-term remedy and should not be used in a large piece of land because it uneconomical, or in well drained soil.
Time release fertiliser: This is released slowly over a certain period of time – about two to six months – which is appropriate for the plants’ chances of getting burnt are minimal because they do not receive the nutrients in full blast. Warm weather improves their performance; it is therefore, important to water the plants if the weather is not favourable.