Organic Farming

Organic farming is a method of planting by which synthetic chemicals, including chemical pesticides, bactericides, fertilizers and growth hormones, are not applied. It aims at:

Problems arising from Chemical Fertilizers

Common chemical fertilizers mostly provide three essential elements for plants, namely nitrogen, phosphorus and potassium. However, plants also need many other microelements. Only some chemical fertilizers provide one to a few types of elements other than nitrogen, phosphorus and potassium. Under such circumstances, plants have to absorb the remaining nutrients required from the soil. Therefore, after several years, these microelements will become deficient, damaging the health of plants and stunting their growth. On the contrary, organic fertilizers can provide plants with all the elements required. They are also easily soluble in water, thereby minimizing pollution and damage to ecological balance. The fertilizers applied today will remain in the fields for a few years and the fields cultivated by the organic approach will become more and more fertile.

Problems arising from Chemical Pesticides

The use of chemical pesticides will easily lead to resistance in insects. Whenever chemical pesticides are applied, there will always be a small number of strong insects which survive. Their next generations will develop stronger resistance to the pesticides. In fact, most pesticides are harmful to different types of insects, fish and birds. Not only do chemical pesticides kill the target pests, they also kill other beneficial or harmless living organisms as well. As a result, the balance of the numbers of various types of living organisms will be upset, leading to easier spread of pests. Consumption of vegetables and fruits with excessive pesticides will even cause food poisoning, which is hazardous to the health of human beings.

Organic Fertilizers

Since organic fertilizers provide sufficient and a full range of nutrients, plants will grow healthy and luxuriant, and naturally become less susceptible to disease and pest infestation. Organic fertilizers will also improve the structure of the soil by creating a properly drained, aerated, moisture and fertilizer retenting environment, rendering the soil more suitable for the survival of micro-organisms.

1.Home-made Compost

Compost is the best fertilizer and soil conditioner in organic farming. In nature, micro-organisms decompose organic matters every minute or second for recycling and reuse. Composting is only a simulation of the cycle of nature and accelerates the process. Degradable matters originally considered as refuse are put together for decomposition by various types of living organisms so that the organic matters of useful materials can be recycled and reused. Composting provides a relatively full supplement to the nutrients in the soil. It facilitates better growth of plants which will develop a stronger resistance to diseases and pests accordingly. As a result, the demand for pesticides will naturally drop. Composting also provides food for living organisms in the soil, recycling and reusing organic refuse which will in turn alleviate pollution of the ecological environment.

1.1 Materials

1.1.1 Materials unsuitable for Composting

1.1.2 Materials suitable for Composting

1.2 Methods of Composting

1.2.1 Aerobic Composting : Please refer to Illustrations (1) to (8)

Illustrations (1) to (8) — Note : Home-made Aerobic Composting

(1) Insert four wooden posts into the soil and fix three sides with mesh.		(2) Place branches on the ground for aeration.
(3) Pile up vegetable stalks and fruit peels, etc and then fix the fourth side of the enclosure with mesh.		(4) There will be immediate bacterial activity in the compost to decompose the plants.
(5) The volume of the compost will obviously decrease and the temperature will rise.		(6) Cover the top with cloth or wooden boards to block the rainfall.
(7) Turn the compost pile once every fortnight to allow more aeration.		(8) The compost pile will decompose after approximately two to four months. All the substances will turn deep brown in colour like sawdust. The compost can then be put into the soil to be used as fertilizers.

1.2.2 Anaerobic Composting

All the materials are mixed with water and sealed in a container (a black plastic bin with lid may be used) to be placed under the sun and shaken occasionally. The compost will be ready for use after a few months to a year.

1.2.3 Composting with dead leaves

The dead leaves collected are placed in the mesh enclosure and added with water. Despite the low level of nutrients, composting with dead leaves is a very good soil conditioner.

1.2.4 Earthworm Composting : Please refer to Illustration (9)

Earthworm composting is mainly conducted through earthworms’ digestion of organic matters. After earthworms have eaten and digested organic matters, they will excrete them out of the body. These excreted matters will become smaller and simpler particles to be eaten by the earthworms again. The whole process repeats a number of times and finally the organic matters will become useful manure.

Design of an Earthworm Composting Bin

Illustration (9) : Cross-section of an Earthworm Composting Bin

1.3 Major Factors Affecting the Composting Process

1.3.1 Aeration

Since the micro-organisms in the composting pile need air, the pile has to be turned from time to time. The more frequent it is turned, the more abundant the supply of air will be. If the compost pile can be turned on a daily basis, the time for full decomposition will be shortened. It is preferable to place a layer of twigs or crushed rock below the compost bedding for aeration. Materials such as leaves and grass which stick together when wet will easily cause shortage of oxygen and are difficult to decompose. Therefore, they should be mixed with other materials before being placed in the compost pile.

1.3.2 Moisture

The compost pile cannot be too dry for it is not suitable for microbial activity. Nor can it be too wet as it will result in shortage of oxygen which in turn will lead to slowing down of the decomposition process and generation of odour. The compost pile should maintain a moisture level of a well-wrung sponge. It should be sprayed with water if it is too dry.

1.3.3 Temperature

The temperature of the compost pile can rise to 60¢J-70¢J in five days’ time. Under high temperature conditions, the micro-organisms are active and decomposition is quick. High temperature can also kill pests, pathogenic organisms and weed seeds in the pile. To maintain the decomposition process at full speed, appropriate temperature control is essential and an old carpet, hessian sack or a layer of soil can be laid on top of the pile.

1.3.4 Volume

The larger the volume of the compost pile, the easier is the retention of heat. However, the compost pile is difficult to manage if it is too large in volume. The minimum effective volume is 1 cubic metre.

1.3.5 Micro-organisms

There are a great number of micro-organisms in the materials and the soil.

1.3.6 Duration

It depends on the weather, materials, activators and the method employed. For the local condition, it will take two to eight weeks. Once the compost pile turns dark in colour and the ingredients become indistinguishable, the compost is fully decomposed and ready for use.

1.4 The Uses of Compost

1.4.1 Mixed with the Soil

The compost well-mixed with the soil can improve the soil structure effectively.

1.4.2 Placed on top of the Soil as Mulch

Anything which is placed on top of the soil to slow down loss of moisture and to curb the proliferation of weeds can be called mulch. Examples are compost, sawdust, tree bark, crushed brick and rock, newspaper, carton and plastic sheet.

1.4.3 Making Liquid Fertilizer

Put a bag of fully decomposed compost into a bucket of water. After the mixture turns into the colour of tea in two to three days, it is ready for spraying onto the leaves. If the colour of the compost tea is too dark, it should be diluted to that of a weak tea, otherwise it may burn the plant.

2. Green Manure

Green manure refers to the crops that are specifically grown as fertilizers. It normally includes crops that are fast growing and readily decomposable or leguminous plants which can “fix” atmospheric nitrogen in the soil. Clover, barley and legumes can be used as green manure. It is better to plow the crop into the soil before it grows old since old crops will first consume the nitrogen in the soil in the decomposition process.

3. Other Fertilizers

3.1 Groundnut Cake

Groundnut cake is the residue of groundnut after the extraction of groundnut oil. It has the scent of groundnut and is rich in nitrogen. (Groundnut cake is available for sale in feedstuff or fertilizer stores.)

3.2 Soybean Cake

Soybean Cake is the residue of soybean after the extraction of soybean oil. It is rich in nitrogen. The consumption of nitrogen and the release of heat during the decomposition by micro-organisms is less in comparison with that of groundnut cake. Therefore, it can be used as an alternative to groundnut cake in summer. (Soybean cake is available for sale in feedstuff or fertilizer stores.)
Usage: 0.5-2.5kg per 10 square meters or a handful per pot.

3.3 Cow-horn slices

Cow-horn slices are rich in phosphate. As cow-horns are difficult to decompose, they are normally used as a base fertilizer. (Cow-horn slices are available for sale in feedstuff or fertilizer stores.)
Usage: 0.5-1.5kg per 10 square meters or a handful of slices per pot.

3.4 Bone Meal

Bone meal is the crushed bone of a cow. It is rich in phosphate and calcium. (Bone meal is available for sale in feedstuff or fertilizer stores.)
Usage: 0.5-1.5kg per 10 square meters or a handful per pot.

3.5 Grass and Wood Ashes

As the ashes burnt from grass and wood, these materials are rich in potash fertilizer.
Usage: 50-160 grams per 10 square metres or a handful per pot.

3.6 Algae

Algae are rich in nitrogen, potassium, 69 microelements, plant hormones and the enzymes that stimulate plants to absorb phosphorus in a more effective manner. Algae can also resist bacteria and diseases and improve the quality of the soil. They can be directly put into the soil, or placed in composting bins to be added with water to form algae mixture, or placed on top of the soil as mulch. (Algae are available for sale in Chinese herbs shops and can be picked up at seaside.)

3.7 Gromwell

Gromwell is a fast-growing herbaceous perennial. Its roots can stretch deep intothe soil, bringing nutrients from the inner layer to the surface. Gromwell is rich in nitrogen and potassium. As its leaves have very little fibre, it is easily decomposable. (Gromwell can be ordered by mail with overseas seed suppliers.)
Usage: Gromwell can be directly put into the soil or the compost, or placed on top of the soil as mulch. Gromwell mixture can also be made with the addition of 12 litres of water into 250 grams of gromwell leaves. It can be diluted and used after being sealed for 4 to 5 weeks.

3.8 Lime

Lime can be used to adjust the pH value of the soil. Since lime contains magnesium carbonate and excessive application may turn the soil to alkaline, pH test paper should be used to test the pH value of the soil prior to application. (Lime is available for sale in hardware stores.)
Usage: 0.5-1.5 kg per 10 square metres, and not exceeding 3 kg per 10 square metres per annum.

3.9 Eggshells

Eggshells are rich in calcium.
Usage: 1-5 kg per 10 square metres per annum or directly put into the pots.

4. Organic Pest Control

4.1 Prevention Measures

4.1.1 Healthy Growth of Plants

Balanced nutrients, adequate water and appropriate planting density can foster a healthy growth of plants, which will curb the reproduction of pests and alleviate pest infestation directly or indirectly.

4.1.2 Timely Planting

Planting in an appropriate climate may help the plants grow healthier and avoid the period in which pests are most active, thus minimizing pest infestation.

4.1.3 Keeping the Environment Clean

Field weeds, remaining parts after harvesting as well as rotten plants and fruits should be cleared in order to minimize the possibility of pests living on plants.

4.1.4 Rotation/ Alternate Planting

Rotation planting means growing various types of plants by rotation, while alternate planting means growing a particular plant in an extensive area and mix it with other species. It is difficult for pests to find adequate food and massive reproduction is not easy with these planting methods. A special smell from the plants in alternate planting, such as onion, garlic and other scented herbs, can even achieve the effect of repelling pests.

4.2 Biological Control

Pests can be controlled by other living species, including plants that attract the natural enemies of pests, insects that feed on pests, parasites of pests or the organisms that cause diseases in pests.

4.2.1 Use of Natural Enemies in the Local Environment

Animals that feed on pests (including spiders, Chinese porcupines, centipedes, frogs, toads and bats), ladybirds, parasites that are hardly observable and various micro-organisms that cause diseases in pests are made to stay in the local environment. Instead of disturbing them, it is better to avoid as far as possible spraying any toxic substances, even natural pesticides such as derris, on them.

4.2.2 Purchase of Natural Enemies

BT

The natural enemy that can be purchased in Hong Kong is mainly a micro-organism called BT. The spores of BT can live in the natural environment for two to three days, but they will die under sunlight in less than 24 hours. BT can produce a kind of toxic crystals. After being eaten by a pest, the toxic crystals will break down in the insect's stomach and release toxins to paralyze its intestines immediately, making the insect stop eating. At the same time, the spores will also sprout and reproduce in the insect's blood, leading to the death of the insect. BT is effective to the larvae of a number of insects. Before application, one should ensure that the pests are the targets of BT and must be careful about its usage and frequency. Abuse of BT will create resistance in pests. (BT is available for sale in pesticide or seed stores.)
Usage: BT can be added with water to form a mixture (please refer to the package directions for the required amount), which can be sprayed on the surface and bottom of leaves. Since BT will lose its effect quickly in an environment of 32¢J and under strong sunlight, it should be used in evening hours and sprayed mainly on the bottoms of leaves.

4.2.3 Pheromone

Insects are very sensitive to the smell of their opposite sex. Male insects may tell the direction and location of female insects even though they are miles away. A trap with the hexoestrol of a certain insect can be used to catch the male insects of that particular species.

Pheromone for Diamond-back Moth: Please refer to Illustration (10)

The pheromone for Diamond-back Moth can be used to catch the adults of male Diamond-back Moth or Plutella Xylostella(Linnaeus). A plastic basin (preferably yellow in colour) with a height of 10cm and a diameter of approximately 25cm can be used as a trap when filled with clear water. The pheromone should be hung with an iron wire at the centre of the basin and 5 cm above the water level (please refer to the package directions for the required amount). The effect of pheromone will usually last no less than 30 days and will not be reduced by rainwater. Generally speaking, the pheromone should be replaced once a month. It is more desirable to add a small amount of soap or detergent in the basin to reduce the surface tension of water. The pests cannot fly again once having fallen into the water. (Pheromone for Diamond-back Moth is available for sale at the Federation of Vegetable Marketing Cooperative Society in Cheung Sha Wan.)

Illustration (10) : Pheromone Trap for Diamond-back Moth

4.2.4 Attractant

Insects have special preference for certain smell such as sweet soup or rotten melons and fruits. Attractants with these kinds of smell can be placed in a trap to lure the pests.

Melon Fly Attractant (Cuelure): Please refer to Illustration (11)

Melon fly attractant can be used for luring male melon flies. The trap is made of plastic cups, iron wire and a cotton wick impregnated with an attractant (please refer to the package directions for the required amount). In a good weather condition, it is desirable to apply the attractant once every 2 or 3 weeks, otherwise it is necessary to apply once a week. (Melon fly attractant is available for sale at the Federation of Vegetable Marketing Cooperative Society in Cheung Sha Wan.)

Illustration (11) : Melon Fly Trap

Bury the dish or flat can in the soil so that the rim is level with the ground. Bait the dish or flat can with beer, stale cheese, yeast solution or milk solution. A lid can be placed on the top to prevent other animals from drinking the bait or the bait being diluted with rainwater. Make sure that enough space is left for the pests to crawl in. Snails and slugs are attracted to the smell of fermentation and they will be drowned when trapped. Check the trap in the morning every day or every other day. Clean the dish and refill it with bait.