Some basic information on Plant care and protection.
First a review of the basic requirements for plant growth:-
Water. All plants, like all living things, require water. It sustains life, dissolves nutrients and conveys nutrients to various parts of the plant. It also provides Hydrogen to green plants, for photosynthesis.
Water requirements are different for each type of plants. Water management is one of the most critical factors, of crop management. Over watering is a common mistake. Excess water will, leach out soluble nutrients, away from the plant root zone and alter the soil structure. Controlled watering is most beneficial. Drip irrigation or micro sprinklers are used in commercial horticulture. Some plants do need water stress (dry soil) for flowering. Water requirements, vary at different stages of growth of the same plant.
Sunlight. Required for Photosynthesis by which plants make their own Carbohydrates in the plant, by combining the Carbon and Hydrogen with the help of sunlight and chlorophyll. Some plants are sun loving and others thrive well only under shade. Plants can also grow without sunlight.
Air. Air is essential for plant life. Oxygen is used by plants for metabolic process. During daytime, Carbon dioxide andwater is used, for photosynthesis and the excess oxygen is expelled. It is therefore considered not desirable to keep plants near bedrooms, as they expel carbon dioxide during night. Nitrogen from air is used in nitrate form, as a nutrient.
Soil. Soil is only a medium for plants and provides anchorage. When crops are grown in soil, it also provides nutrients and water.
Soil is not essential for plant growth. Plants can be grown in water (Hydroponics), in peat moss, processed coir pith or in any artificially prepared media. Commercial horticulture is carried out, mostly in artificial media and not in the soil. This is for uniformity of produce, under controlled conditions. Soil does provide some nutrients the plants require, but they can be also provided without soil.
Nutrients. Plants require three main nutrients, namely Nitrogen(N), Phosphates (P)and Pottasium(K). They also require many micro nutrients like calcium, magnesium, iron, copper etc., in small quantities and many trace elements,enzymes and hormones. Absence of some micro nutrients cause physiological problems and have to be identified and supplemented. Plant functions are also influenced by many hormones. All or most of them are naturally available in good soil. Over a period of time, it gets depleted by repeated growth of plants, leaching etc. They have to be supplemented, to the required level and proportions, for proper and healthy growth of plants. In modern commercial Horticulture,all the required nutrients, enzymes and hormones are provided under total controlled conditions, using plant and leaf analysis, on a day to day basis. Nutrients and water supply is often controlled by automatic computers, to meet the exact requirements
Nitrogen is absorbed mainly in soluble nitrate form. Some plants like paddy have the ability to absorb nitrogen in ammoniacal form. Nitrogen provides mainly vegetative growth to plants and is derived in nature from protein decomposition of animal and plant (organic) materials. It is also produced by certain plants (legumes) in their root nodules, by fixing nitrogen from the air, with the help of micro organisms. Nature also provides this as nitrates by lightning, from atmospheric nitrogen. Urea (46% N) and Ammonium Sulphate(16-20% N), Muriate of Potash( 60%K) are the common commercial fertilizers, which provides nutrients, in high concentration. Nitrogen is required more during the growing stage of the plants.
Phosphate mainly helps in root development in plants and is required more in the early part of plant life. Decomposition of bones provide phosphates in nature. Rock phosphate also occurs in nature. But both this forms are not easily available to the plants, except in the presence of acids. Some plants produce their own weak acids at the root tips. Kerala having acid soils by nature, can use these forms of phosphates. The commercial process of making it available to the plants, is to treat them with sulphuric acid, to produce super phosphate (18%P) or Dicalcium Phosphate (36%P). Diammonium Phosphate (DAP) contains both nitrogen (18%N) and phosphate (46%P) both in mostly available soluble form.
Potassium helps plants with flowering, fruit setting, color, sweetness and such qualities. It also provides cell strength and resistance to pests and diseases. Potassium is more required, in the second half of the plant growth. It is available in small quantities in wood ash and also in coconut husk. Potash is mined from nature in large quantities,in concentrated form (60%K) as muriate of potash (MOP) and is commercially used.
Nutrient requirements of each type of plants are different in quantity and proportions. It is important to provide the nutrients in the right quantity, proportion and at the right time. All major and minor nutrients are normally absorbed by plants through their roots, but most plants can also absorb them directly through the leaves and in some cases through aerial roots. Required nutrients are provided to plants in dilute form (as 1% solution), as foliar spray in commercial horticulture.
Fertilisers are better utilized when applied in small quantities at regular intervals of 10 to 15 days. Organic manures being slow acting should be applied in larger quantities, at the time of planting or in early stages of plant growth.
Well decomposed compost or cow dung are excellent organic manure and contains many enzymes but only very low levels of major nutrients. Oil cakes contain slightly higher levels of nitrogen and is better to be applied in powder form. Bone meal, leather meal and such other manures of animal origin, contains higher levels of nitrogen and phosphates. Organic manures are slow acting, but provide humic acid and enzymes to the soil, which improves the physical properties of the soil; promote microbial activity and makes nutrients more available to the plants. Much larger quantities of organics are required, if all the nutrient requirements are to be provided, only through organic sources, making it expensive. Pure organic cultivation is more of a fad and may not be commercially viable in most cases. A judicial combination of both forms is the best option.
Plant propagation. This is an important part of plant culture and is done either by using seeds or by vegetative multiplication. Propagation by seeds (sexual), is less reliable as the progeny may not be true to the mother plant. Vegetative propagation (asexual), will ensure same qualities as the mother plant. Tissue culture is mass production of vegetative propagation, using minute parts of tissues from selected mother plants, under controlled conditions to ensure desired qualities. Simple vegetative propagation methods are cuttings, layering, grafting and budding. Hormones like, gybralic acid (GA) and naphthalene acetic acid (NAA) are used, for easier rooting in cuttings and layering. Cloning is the modern version of the same process, by which another plant or even animal is produced as an exact duplicate of the selected mother plants from their stem cells, under controlled conditions of multiplication.
Hybrid seeds are used in commercial planting. The seeds are produced by careful selection of male and female grand parents and parents to ensure desired qualities in the first generation (F1) plants. They have extra hybrid vigor and usually have high productivity. The next generation (F2) will not produce such uniform desired qualities and therefore, each time seeds have to be obtained from the same source. The breeders will not disclose the details of the source materials and the parentage.
The quality and reliability of planting material is the most important factor in plant behavior and therefore should be obtained with care and only from very reliable sources.
Genetic engineering. The genes which controls the various functions are identified and manipulated and transferred to produce desired qualities in plants (and in animals). It could be color of flower, fruits, fragrance, sweetness, size and number of flower or fruits, height of plants, time of flowering etc. This process actually takes place even in nature as result of mutation (change of genes and chromosomes in the cells) and natural selection. Mutation takes place due to natural radiation, exposure to forces of nature and many such conditions. Scientists are able to do this today more precisely under controlled conditions to produce the desired results. Genes from a bacteria producing insecticide(bacillus thuringiencis) is introduced into the cotton plant to control ball worms and is already commercially available in India (GT Cotton).The tomato plant can be made to produce potatoes in the same plant (both are of the same botanical family). The Jack and Mango trees are dwarfed to grow them in green houses. The possibilities are limitless.
Plant protection. This is also an important part of plant culture. There is a vast variety of insect, pests and diseases affecting plant growth, only few of them are discussed here.
Insects. The most commonly encountered ones in our gardens are aphids, thrips, mites, mealy bugs, fruit flies, caterpillars and borers. They can be effectively controlled by frequent inspection, manual removal and destruction in early stages, in home garden situations.
They can also be prevented and controlled to an extent by use of organic pesticides based on neem oil, extracts of tobacco, soap-oil emulsion etc.
Insecticides. There is much misconception about the use of insecticides. Only very large multi national companies with advanced multi million research facilities develop and produce new pesticides. All of them are also large producers of basic drugs with large R & D facilities. Each new product undergoes extensive trials before it is released for use. Each country has elaborate regulatory laws in the production and sale of pesticides and drugs.
If used correctly (right quantity at the right time using correct method and for specific insects) insecticides are good tools for effective control of insects. Inadequate knowledge resulting in wrong usage has led to many problems particularly in our country and is the main reason for biased opinion on the use of insecticides. However, use of commercial insecticides should be restricted in home garden situations, for many reasons.
The common available insecticides are Endosulphan, Monocrotophos, Quinalphos, Carboryl, Furadan, Acephate, Sythetic Parathyroid etc. They vary in their action, origin and also residual toxicity. They have to be chosen and used with much care. Some of them based on chlorinated hydrocarbons and organo phosphorus compounds like Endosulphan etc., are more persistent (longer effect), cheaper and therefore popular among ordinary farmers.. But more modern ones, like Acephate, Pyrithroids etc. are more biodegradable (quickly breakdown on exposure to nature, into harmless or less harmful products), are expensive, but more environment friendly.
To safeguard against pesticide residues in fruits and vegetables, bought from the market, wash them in luke-warm salt water before use.
Some of the common insects in home gardens are.
Aphids. They are very small and suck the juice from the tender parts of the plant. They are stationary and are dependent on ants for mobility. Presence of many ants, which feed on the secretion of these insects are indicative of the presence of aphids. Controlling the ants will help reduce the infestation. If the intensity is high, even after use of organic pesticides, use of systemic insecticides like Dimetheoate or Monocrotophos will be required.
Thrips. They are mobile and found on the lover surface of the leaves and cause the leaves to curl. They also suck the juice from the leaves. They do not cause much damage in home gardens. The remedial measures are use of Dimetheoate, Monocrotophos or contact insecticides like Quinalphos.
Leaf eating caterpillars and leaf rollers. They are more effectively controlled by daily inspection and physical destruction, in the home situation.
Mealy bugs. They appear as white wooly clusters on the plants. They are common on
Crotons. They also suck plant juices. They could be physically removed and destroyed in early stages itself, by daily inspection. They have a waxy coating and are difficult to control with insecticides. Soap-oil emulsion is effective to control them.
Fruit flies. Providing protective paper or plastic bags or preventive protective sprays with organic insecticides, soon after fruit setting will reduce infestation. Application of organic pesticides as repellant or specific insecticides could be used during flowering stage, immediately after seed setting. Spraying tall mango trees are difficult without proper equipments. Smoking the trees at this stage is helpful to some extent to reduce infestation. Pheromone traps are available now for many fruit flies but they are very specific for each species..
Cut worms and rhizome borers. They usually live under ground. Hey can cause much damage to lawns, most young plants and bananas. Application of wood ash, neem cake powder in the soil around the plants early as a prevention can help reduce the damage. In places where the damage is more, application of 2% Furadan or Carboryl granules or their replacement products, in the soil is recommended early in the growth cycle. They are very toxic chemicals and has to be handled with much care.
Mites are common in summer and are different from other insects (6 legs) and are from spider family (8 legs). Coconut Mandari, Browning of leaves due to mite infestation are common on Roses, Ladies Fingers and Brinjal plants. They increase with dry hot weather. They are mobile and are found in large number on the lower surface of leaves. They are not controlled by normal insecticides. Sulphur in any form is very effective to control them. Specific chemicals like Ethion or Kelthane are used in larger Tea gardens/estates to control infestation of mites.
Other pests. Slugs , Snails and Rodents are other garden pests. Physical inspection for slugs and snails at night (when they are active) and destruction is the solution in home gardens. Poison baits and traps are available and can be used to control the above pests.
Plant Diseases.
During wet season under high humidity level, many fungal diseases cause damage. Bud rot, leaf spots, collar rot, root wilt and powdery mildew are common problems. Powdery mildews (powdery coating on leaf tops) are more effectively controlled by Sulphur, in any form. Most other fungal infections are controlled, with ready to use copper fungicides. Organic based fungicides like Dithane, Bavastine etc are more effective, but are somewhat selective and expensive. They have to be used alternating with copper fungicides, to reduce risk of developing resistance. Fruit rot during ripening, could be prevented by dipping them in dilute solution (1%) of one of these fungicides. They should be washed properly before use.
Bacterial infections are rare in home gardens. If virus infection (shriveled or curly white leaves) is noticed, the plant should be immediately be destroyed by removal and burning. Insects are vectors for virus and therefore should be controlled. Same tools like knives etc. should not be used for tending to healthy plants, after use on infected plants,to prevent further spread of virus infection.
Weed control. In home gardens, manual removal with their roots, at regular intervals, before application of fertilizer, is best solution. In larger areas chemical weed control, using correct herbicide, at the right dose and time, is not only very effective, but also more economical. Glyphoside (Roundup etc) at 120 ml in 10 liters of water, will control most of the common weeds and grasses, including difficult to control nut grass. Flood-jet nozzle (fan spray) and low pressure back pack type sprayer, is recommended for better results. Some of the modern herbicides are very selective and can be used, to control weeds, even in fields with standing crops, with no harm to them. Most of them are absorbed by the plant tissues of weeds and will break down on contact with soil or exposure to weather, into harmless byproducts (most of them are Biodegradable).The plants with fresh growing leaves, will absorb weedicides better and a few hours of sunlight will ensure good results.
Above everything else, personal involvement and care on a daily basis, is the key to growing any plants in the home gardens. Most other requirements are basic knowledge, which can easily be learned using some common sense.
K.George John.
Edited 10/2018.
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