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Fertilizers, Manures and Feeding

Plant nutrients are much the same as what we need. These are nitrogen, carbon, oxygen, hydrogen and minerals. The only real difference is in the form. While the plants take these in simpler forms, we take them as finished products, usually made by plants or by animals feeding on plants.

Nitrogen, Phosphorus and Potassium (detailed below) are categorised as Macronutrients as they are the main nutrients consumed maximally by the plants.

Nitrogen is the key element found in chlorophyll (photosynthesizer) and every other cell too. It is stored mainly in the seed in the form of protein. It is the most important element for plant development. Deficiency of nitrogen can be seen when the leaves are pale and thin, and growth is retarded. Excess of nitrogen increases stem and leaf growth at the expense of flowers making the leaves and stems tender, thus inviting pests.

Sources: Natural sources are animal excreta, bird droppings, dead animals and decaying proteins like seeds. Rainwater also contains nitrogen in the form of nitrous oxide, which is created by lightening.

Urea, though found naturally in the soil, is artificially produced and is the richest source of nitrogen (46 per cent). Urea acts very quickly, and is seen by the color of leaves becoming dark, within one or two days of application. Cowdung manure contains about two per cent of nitrogen, which is sufficient for flowers, indoor plants and low yielding crops. Another source is neem cake, which is made from neem seeds and contains 15 per cent nitrogen. This 'is a slow acting nitrogenous fertilizer, with sufficient nitrogen to last several months. The added bonus is that it is also a natural soil insecticide.

Phosphorus is an essential element for healthy development of the roots and flowers. It is also important for the setting of fruits. If leaves are stunted, have a purple or red discolouration they are signs of deficiency. It is useful to mix this element near the root zone, at the time of planting, sowing and before flowering. Since the commonly available sources of phosphorus are not soluble in water, it will not suffice to sprinkle it on top. A few holes, about three inches deep, can be made with a stick, and the phosphorus put in the holes. This is especially good for potted plants.                         

Sources: The natural sources are the bones of dead animals, and bone-meal is often used to supplement phosphorous in the soil. Bone-meal releases phosphorus rather slowly, and so must be blended into the soil well before it is needed, that is, before the root or flower formation. Superphosphate is a rich and semi-synthetic source of phosphorus, containing 16 per cent of it. It comes in the form of small globules, and should not be crushed, as then some of it may be lost by chemical action of the soil before it is absorbed. Being concentrated, it may cause harm if it comes in direct contact with tender roots, so it is best if it is placed at a little distance (five cm) away from the germinating seeds. Cowdung manure contains only one per cent of phosphorus, but is quicker in acting as compared to bone-meal.

Potassium is abundant in clay soils and should be added to other soils. It is especially important for ripening of fruits and vegetables', and deepens the color of flowers. It also toughens the plants, making them better able to withstand pests, diseases and extreme weather conditions. It is crucial for water distribution within the plant. Potash deficiency can be noticed when leaves turn yellowish and brownish at tips and margins. Leaves may turn under at the edge.

Sources: Cowdung manure-one per cent, wood ash-five per cent, murate of potash-68 per cent.

Secondary nutrients are calcium, magnesium, sulphur, etc. These elements are taken by plants from the soil, and used for their growing functions. Generally they are present in sufficient quantities in most soils, and seldom need to be added to the home garden.

Micronutrients are essential for plant functions, even though in very small amounts. They are found in salts of boron, copper, zinc and, manganese, among others. The presence of these nutrients ensures good photosynthesis and assimilation process, as well as metabolism of carbohydrates and proteins. These are found mainly in organic manure, and commercially available plant foods.

Fertilizers can be natural or synthetic, or a combination of both. The fertilizing value of either is usually reckoned with in terms of nitrogen, phosphorous and potassium (NPK,where N is Nitrogen, P is Phosphorous and K is Kalium, another name for Potassium). These are the elements that give the most conspicuous improvement in plants, and are needed for their healthy growth and development.

Manure contains humus, which is very useful. When it is mixed with soil it conditions the soil to hold more air and water, which is necessary for the roots and useful for soil bacteria. Humus also absorbs and stores nutrients. A fair amount of micronutrients are also found in humus, which are essential for healthy development of plants, even though they are absorbed in small amounts.

Manure should be blended into the top six inches of soil, while preparing beds or lawns. While planting trees, shrubs or potted plants, it should be mixed thoroughly with the soil.

To prepare compost at home, kitchen waste (peels, leftovers, etc.) and leaves should be mixed with some cowdung (or its manure) as a source of fermenting bacteria, in a ditch. If a ditch is not feasible use bricks to build a tank like structure in the corner of two walls. It should have an inside space of about one cubic metre (9 cubic ft.) for effective compost production.

It needs to be turned every week to ensure exposure to the air. It should also be watered occasionally to keep it moist. In the warm months, it results in an odourless, crumbly, black mass, which is good for. plants. Leftover daIs, meat, flour, etc, when added to the compost, fortifies its nitrogen content. Eggshells and bones enrich it with calcium and phosphorous. Dry, burnt leaves or woodash is a good source of potassium. Some slaked lime can also be added, which will help balance any excess acidity in the compost. For slaked lime, it needs to be wetted with water for a few days.

The home gardener is better off using more of organic manure or composts, because they are safer than inorganic fertilizers, which should be used judiciously especially in case of nitrogenous fertilizers. Sterameal is a complete fertilizer, being a mixture of blood, bones and neem cake and other nutrients. There are many ready,made mixtures of organic and inorganic nutrients available at most garden shops that can be used according to the plant requirements. The labels should be read for the contents of these mixtures.

Feeding the Plants

Fertilizing is generally done in two stages-basal feed and top dressing.

As Basal Feed the plants require all three elements-nitrogen, phosphorous and potassium (NPK), for initial growth. Good manure, chemical fertilizer or a blend of both should be incorporated into the soil before planting. If synthetic fertilizers are being used, one tbsp. of DAP (diammonium phosphate) plus one tbsp. of potassium murate should be added for every sq. m. of land. An extra addition of two to three mugs full of organic manure is also recommended. Both these fertilizers should be blended well into the soil.

Top Dressing is feeding the plants after growth has progressed. It is done to maintain a healthy growth, or to provide nutrients for the flowers and food yields. The requirement of top dressing will differ according to what is being grown.

Vegetables require more fertilizer, and a tsp. of urea per sq. metre may be given a month after transplanting, once or twice. For seasonal flowers, two tsp. per sq. metre of superphosphate is given just before flowering, and nitrogen is to be avoided. Ground planted flowering shrubs could be given one tsp. of DAP + 1/2 tsp. potash once or twice during the growth period. Plants in pots being smaller. will require much less fertilizer; usually a pinch or two per plant is suffice.

For ordinary purposes, both basal feed and top dressing can be given, using homemade compost or dung manure. Top dressing can be given every month, since this natural manure releases nutrients slowly; they are sustained for a longer period of time.

Caution needs to be taken that plants are not given synthetic fertilizers during their dormant periods, i.e. when growth is temporarily suspended as in winter. Unused fertilizers can harm the plant, and special care should be taken with urea. It is highly concentrated and can burn the leaves of house plants, even if .it is slightly in excess. A pinch of it is usually sufficient.

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