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Keeping soil healthy

Keeping soil healthy is an essential part of gardening. The materials, i.e. the types of fertilizer, most often used in most areas where cultivation takes place, to maintain and improve soil fertility may be classified as follows:

  1. The natural, organic fertilizer types in the shape of manures. These are usually the relatively bulky fertilizer types, like animal or green manures. Animal and the green manures are usually added to garden soil to; not only improve the physical condition of the soil, but also to replenish and keep up its humus status, as well as to maintain the optimum conditions for the activities of soil micro-organisms and make up some amelioration to a small part of the plant nutrients removed by crops or otherwise lost through leaching and soil erosion. The plant-nutrition that can be found in manure is released in an available form after it is applied to the soil and is decomposed by soil micro-organisms. Similarly, the green manures add not only substantial amounts of organic matter but also nitrogen.
  2. The chemical, inorganic fertilizers. Fertilizers are inorganic materials of a concentrated nature; they are applied mainly to increase the supply of one or more of the essential nutrients, e.g. nitrogen, phosphorous and potash. Fertilizers contain these basic elements either in soluble or readily available chemical compound form and can usually be purchased from commercial sources such as garden centers, nurseries, and the like.
  3. The concentrated organic manure fertilizer types. This fertilizer type is comprised of concentrated materials, such as oil-cakes, bone-meal, urine and blood. It is important for the home gardener to remember that the use of manures and fertilizers is complimentary and should not be viewed as a substitute for each other.
  4. The bulky organic manure type of fertilizers. the properties and role of organic matter and humus in the soil have been explained already in our organic matter page.

Organic gardening

Organic Gardening has become a real buzz word and it is no surprise since people have become more aware of nature conservation, health and health issues and how interlinked all aspects of human life is. In essence organic gardening is a return to more natural practices without using any refined chemical soil amendments like chemical fertilizer, fungicides, pesticides and herbicides, especially the one that can be harmful to nature. These harmful side effects are manifested as residues in soils, water, on crops and the atmosphere.

The idea with organic gardening is to strive to keep the soil healthy and make use of natural measures such as crop rotation, companion planting and biological control. This means that it becomes important to put as much organic matter as possible back into the soil and control weeds by mulching and removing them physically. The control of weeds is important since these weeds may be harboring pests and diseases. All diseased plant material should also be destroyed to avoid contamination of a compost heap for instance. Weak and stressed plants are also much more susceptible to pests and disease and should as a result be avoided by making the right decisions when choosing plants for the area where you intend making your garden.

To achieve the ideal garden soil structure, we should strive to maintain high levels of organic matter in the garden soil which will encourage micro-organisms to supply nutrients to plants via the plant roots. Organic mulching also becomes important in that regular mulching will prevent bare soil patches where the garden soil will be exposed to sunlight, and do not cultivate the soil too much. Organic matter results in improved soil texture and moisture retention.

Organic fertilizer is also readily available from local nurseries and garden centers. Most organic fertilizer is formulated to target the deficiencies that might occur due to a lack of basic nutrients such as Nitrogen, Phosphorous, Potassium and even some of the micro or trace elements. The Nitrogen rich organic fertilizers usually contain dried blood, hoof-and-horn meal, bone meal and composted chicken, sheep and goat manure. Other organic fertilizer include fish meal to supplement the major macro nutrients; rock phosphate to supplement phosphorous, calcium and micro nutrients; bone meal to supplement phosphorous; wood ash to supplement potassium; gypsum and lime to supplement calcium; and seaweed meal to supplement potassium and micro nutrients.

Pest and disease control

In practicing organic gardening we need to take the concept further than mere soil amendments by means of organic fertilizer. We also need to practice pest and disease control in a manner consistent with organic gardening, which means implementing organic pest control and using organic pesticides.

Crop rotation

Marigold for crop rotation
Marigold can be used for crop rotation in the home garden

In some cases problems do occur if the same type of plant is grown in the same soil season after season. The garden soil will then be vulnerable to the pests and diseases that thrive on that particular crop. Furthermore those pests and disease have the opportunity to multiply exponentially. The most fundamental rule of crop rotation is also the simplest: never plant the same thing in the same place twice. The aim of rotation is threefold: to balance nutrient demands, foil insect and disease attacks, and deter weeds. Working out rotations can be fascinating work. With nutrient rotation the aim is to find the balance between the nutrient demands that each crop makes on the garden soil. The strategy here would be to divide the crops into four types, depicting the four different seasonal rotations as follows:

  • Leave crops like lettuce, salad greens, spinach, chard, broccoli, cauliflower, chicory, cabbage, Brussels sprouts, kale and kohlrabi; all the crops that will thrive on Nitrogen.
  • Fruit crops like pumpkins, squash, cucumbers, zucchini, melons, tomatoes, peppers and eggplants; all the crops that thrive on Phosphorous.
  • Root crops like onions, garlic, shallots, carrots, beets, radishes, turnips, leeks and scallions; all the crops that thrive on Potassium.
  • Soil building and cleaning crops like legumes are great for storing Nitrogen from the air and releasing it into the soil. Cleaning crop examples are corn and potatoes, and builder crop examples are beans and peas.
(TIP: In the first season plant the leafy crops, follow this by planting the fruit crops, then the root crops and then the legumes.)

Another aspect of crop rotation is prevention rotation. Crop rotation also serves to break the cycles of pest and disease problem that can build up in garden soil as a result of planting the same crop season after season. Again the golden rule would be to never plant the same thing in the same place twice so that no two crops that are subject to the same type of diseases follow one another within the disease's incubation period. The same argument holds true for the control of insect pests because crop rotation makes it harder for the emerging insects to find their preferred food. Different plant types attract different pests, so by rotating legumes, root crops and leafy crops the pests' life cycle gets interrupted and if they do survive then they do not have enough time to multiply and become a serious problem.

Crop rotation is also a form of organic weed control. If shallow rooted plants like lettuce or cabbages are alternated with deep-rooted plants like tomatoes then the plants' roots are permitted to loosen the soil that would under other circumstances had to be done manually.

This is the generally accepted notion of crop rotation as it is practiced by agriculturalists and commercial farmers; however, since our focus is the home garden, we will need to adapt the generally accepted notion of crop rotation to suit the needs of the home garden. There is one major pest that manages to surpass prevention crop rotation: the dreaded eelworm. The eelworm can overwhelm all other pests in its impact on a vegetable home garden because the home gardener will feel the impact of on eelworm infestation so much more than the large scale commercial farmer since there are fewer commercially available chemicals to control eelworms. On commercial farms certain legumes and grasses are left in the soil for many years to improve the quality of the soil, the fertility of the soil and improved structure of the soil for more valuable crops to follow. This solution may not work for the home garden. In your home vegetable garden you may not always have years to wait for soil to improve, you need a more rapid solution. Adding compost and manures to your garden soil will improve the organic content of your garden soil and thereby improve the garden soil's physical condition and fertility. This is important as eelworm infestations can be stemmed by healthy organic soil. In some cases more than two-thirds of homegrown vegetables can suffer damages caused by eelworms. Eelworms thrive in warm conditions and sandy soil. So if you want to practice crop rotation in your home vegetable garden, you must make sure to base your crop rotation as determined solely by the resistance and susceptibility to eelworms.

In areas where the usual notion of crop rotation does not have the desired effect, in other words the areas where the climate aids pests and diseases, one has to practice the type of crop rotation most appropriate to the circumstances and conditions that are prevailing. First and foremost it would be advantageous to recognize eelworm. There is a wide variety of eelworm infestations that can take place. The most common is the root-knot eelworm. This is a microscopic worm that penetrates the root tips and results in swelling and grossly distorted root systems. A vegetable crop like carrots will show the manifestation of this type of eelworm easily. Any carrots that have forked roots and lumps on the root system will indicate an eelworm infestation. In cases where the eelworm infestation is heavy, the carrot crop will be rendered useless. Eelworms can increase their numbers so rapidly, and in cases where a susceptible crop follows, even with the practice of crop rotation, the results will be disastrous. By selecting a crop rotation that includes a follow-up crop that is eelworm resistant, you can starve the eelworm population. In essence you would be reducing the eelworm food and then their numbers will decline accordingly. By practicing a crop rotation with eelworm resistant crops, you can keep eelworm populations under control and under manageable levels.

Under the usual notion of crop rotation, one would be planting a legume crop (e.g. beans), follow it up with a root crop (e.g. carrots), and then with a leaf crop that is totally unrelated (e.g. spinach). This type of crop rotation would be totally wrong for the home vegetable garden if you have an eelworm infestation. You are bound to end up with a massive infestation that increases exponentially since these crops are all highly susceptible to eelworm. At the end of the rotation of these crops you will end up with a total crop failure. Crop rotation in such a case should rather be carried out using eelworm resistant crops such as garlic, leeks, onions, shallots, cabbage, cauliflower, broccoli and even some tomato and lettuce varieties. Below are a few more tips on crop rotation:

  • Together with the proper crop rotation as you garden soil may dictate, you could also reduce eelworm infestation by making use of compost and manures to increase the organic content of your soil. With healthy soil conditions the bacteria and fungi are able to survive and attack the eelworm.
  • You could also plant marigolds (khakiweed, stinking roger, Tagetes species) in rotation and work the plants into the garden soil when they flower.
  • You could also cover a section of the moist garden soil with a clear plastic sheet during hot weather and after a couple of weeks; you will have managed to sterilize your garden soil. Then the soil would be free of eelworms and ready for your vegetable crops.
  • Remember that the best solution will vary from garden to garden due to the different types of soil, the different types of crops that are cultivated, and the different climatic conditions that are prevalent in those areas. The best advice at this stage is that one must learn to examine the root systems of one's vegetable crops and always be aware of the world's biggest, microscopic pest. I say biggest because the eelworm most often goes unnoticed and when you may start to think that you do not have green fingers, it could in fact only be an eelworm infestation that is thwarting you vegetable crop cultivation.

Companion planting

Petunia as a companion plant
Petunia: a good companion plant in vegatable gardens

Companion planting essentially refers to the planting of different crops in close physical proximity according to Wikipedia. This is another form of organic pest control. By simulating plants in nature in having a variety of different plants growing together the problem of pests and diseases can be avoided. Certain plants attract useful insects such as parasitic wasps and others deter harmful insects. On another level companion planting also means the grouping of plants with different root lengths and light requirements together so that they complement each other and not compete for the same resources. Companion planting is great for the environment in that are also acts as a means to mitigate the decline of biodiversity. The typical cottage garden is an excellent example of companion planting. Organic gardening depends heavily on companion planting for its best performance. Apart from being central to organic gardening, companion plants can benefit each other as follows:

  • Enhancing flavor – some plants, especially herbs, seem to subtly change the flavor of other plants around them.
  • Hedging investment – multiple plants in the same space increase the odds of some yield being given, even if one category encounters catastrophic issues.
  • Interaction between different levels – plants which grow on different levels in the same space, perhaps providing ground cover or working as a trellis for another plant.
  • Fixing Nitrogen – plants which fix nitrogen in the ground, making it available to other plants.
  • Positive hosting – attracts or is inhabited by beneficial insects or other organisms which benefit plants, as with ladybugs or some "good worms".
  • Organic pest control – plants which repel insects, plants, or other pests like nematodes or fungi, without relying chemical pest control.
  • Protective sheltering – one plant type of plant may serve as a wind break, or shade from noonday sun, for another.
  • Trap cropping – plants which attract pests away from others.
  • Pattern disruption – with one type of crop, pests can quickly and easily spread from one plant to the next. Companion plants interrupt this spread.

As mentioned, an aspect to companion planting in that it not only serves as companion plants, it also acts as organic pest control. Since some plants have the ability to repel harmful insects and even attract useful insects by giving off scent. An example is citric companion planting. By growing citrustrees such as lemon, lime, grapefruit, kumquat or tangerine in full sun will protect them from frost. If you are to plant comfrey nearby as companion plants you will ensure that the citrus trees thrive as the comfrey will fix nitrogen in the soil. On the other hand you can also plant lavender as companion plants to citrus trees as the lavender will keep aphids and whitefly away. As a bonus the citrus peels, skins and leaves can be rubbed onto window sills to deter flies and mosquitoes.

With trap copping the Nasturtium proves to be an excellent example. Nasturtiums has all the properties of being the perfect companion plant for crops like broad beans, broccoli, cabbage, cucumber, corn, pomegranate, quince, radish, and tomato as it will trap whitefly, aphids and red spider mite. The added bonus with Nasturtiums is that the fresh leaves, flowers and seeds can be added to the diet to help treat chest ailments, nasal congestion and even emphysema. Try pickled seeds and leaves to fight colds and flu (influenza).

Another example of excellent companion plants are Rosemary and Parsley. Rosemary is a strong perennial that benefits plants like cabbage, beans and carrots as companions since it has discourages snails, slugs, caterpillars and cutworms. Rosemary is full of surprises and also acts as an organic insecticide if one brushes and rub the branches of rosemary on windowsills, countertops, wooden tables and legs of chairs it releases its powerful oils that chases away flies, fleas, mosquitoes, ants and weevils as well as moths. Rosemary and parsley will also be a great companion for roses as it repels aphids as well. (TIP: Do not plant carrots with dill or cabbage with tomatoes, or runner beans or strawberries as they do not make good companions.) Planting parsley under rose bushes in a circle around the base of the rose bush will decrease garden pests such as aphids and even black spot. Parsley also have the added bonus of boosting growth and enhancing flavors and fragrant in the roses and vegetables crops such as asparagus, beans, broccoli, carrots, celery, kale, lettuce, spinach, strawberries and tomatoes.

The Petunia, a very popular flower in many home gardens, also makes for a beautiful and very showy companion plant in many vegetable gardens. Petunias will be beneficial to vegetable crop cultivation such as broccoli, broad bean, cauliflower and lettuce. You will notice the decreased numbers of pests such as whitefly, aphids, cutworms and beetles when using Petunias as a companion plant to these vegetable crops. As an alternative, another companion plant that will have the same effect is the Nicotiana flowers. Nicotiana flowers are after all a close cousin to Petunias.

With companion planting you will most definitely not require so many harmful and toxic sprays, dangerous chemical compounds and chemical fertilizers. It makes economic and ecological and pet-friendly sense to make use of companion planting. The natural, organic way always proves to be the safest and most effective solution.

Biological / organic pest control

Thoughts of garden pests conjures of images of Aphids, worms and caterpillars, spider mites, thrips, greenhouse whiteflies, flies, mealybugs, sweet potato whiteflies, mosquitoes, fire ants, grasshoppers, broadmites, and so on. Organic pest control of insects and mites can be accomplished by using their natural enemies against them. This is one of the oldest and most successful methods of pest control. Beneficial insects are harmless to people, plants, and animals. They are born to hunt, capture, and consume your pest insects. For us organic pest control is the introduction and encouragement of natural predators and pathogens to suppress certain insect pests. The ladybird beetle is probably the most common example of the predatory control of aphids. The praying mantis is also quite a useful insect. We need to be able to identify insects and their various stages in their different life cycles in which they come due to their metamorphosis. This will help to distinguish them from the enemy pests. Furthermore, if we want these useful insects to patrol our gardens, then we better make sure that we provide shelter and food for them.