Planning Your Garden

By Steve Aegerter, Master Gardener, Colorado State University Cooperative Extension, Denver County

Before you do anything in the garden, create a plan.  It's the best way to avoid past mistakes you may have made in your garden. List all the plants you'd like to grow. Divide your list into columns of "Must", "Very much would like" and New and experimental" and "If I have room". Use a piece of graph paper, or any other system that will help you scale your garden. Utilizing the spacing requirements on your seed packets, carefully fill in your beds. If you are a raised-bed gardener, you likely can space plants closer together but only an inch or two closer.Consider keeping similar plants together: A salad garden, a pepper garden or legumes, for example.

Think vertical

If your gardening space is limited, think about garden plants that will grow up, rather than out.  By using trellises, available fences, cages, netting, bean towers or anything else that will allow you to grow plants up, you can significantly increase your vegetable harvest.  In addition, planting a vertical garden adds character because of the different height and growing structures you'll use.

Inter-cropping and succession planting

Follow these suggestions to enlarge the productivity of a smaller garden and increase the harvest of  a larger plot. Examples of inter-cropping would be to plant and allow cantaloupe vines to grow beneath corn.  Or, plant vegetables that mature early between rows of vegetables that mature later.  For instance, sow radishes along with carrots.  The radishes will have been harvested before the carrots are 2 to 3 inches high. Utilize the 16 inches between broccoli plants by planting some leaf lettuce, which will mature much sooner than the broccoli.  Other combinations will work as well; your imagination and information on seed packets can be your guide. Succession planting makes common sense.  When you've finished a harvest of one particular crop, sow something else in its place.  Usually that "something" will be quick to mature, such as radishes or lettuce.  You can get a head start by growing seedlings, and transplanting them into areas that have been vacated by a previous harvest.

Along with a grid plan, another useful tool is the garden calendar--your own.   Before the weather will allow you to do much digging in the garden, outline what you want to plant and when.  What do you want to grow from seed?  When do you need to get that seed growing if transplants are to be ready on time? Once your garden is on paper, you are ready to begin.  And, about that time, Mother Nature will be ready for the gardening season.

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Feasible alternative to synthetic pesticides

Insect-pests cause considerable damage to agricultural crops. A number of chemical insecticides have been developed and are being effectively used to control noxious insect populations. The continuous use of these synthetic insecticides causes increasing problems for human health and to the environment. Now, it is widely realized that insecticides thus developed exert immediate side-effects and sometimes long-term indirect effects on living organisms and environment. Potential insecticide e.g. DDT that once proved effective in controlling many species of pests was found to persist in the environment for 15 to 20 years and accumulate at an alarming concentration through food chains. As a consequence in North America, many species of birds were severely depopulated. Further, many of the targeted insects have become resistant to a majority of insecticides. As a result, more number of sprays with higher concentrations had to be applied to control the insect-pests of different crops. In addition, due to non-selectivity beneficial species are also killed.

In view of above abuses of insecticide use, alternative means of controlling harmful insects have been felt. Naturally produced insecticides by plants or micro-organisms could prove effective substitutes which are feasible and economical also. In addition, these compounds are highly specific for a target insect species, biodegradable and slow to select for resistance. Mention can be made of bacterium Baccillus thuringiensis (Bt). At present, 90 per cent of bio-insecticides used, take the advantage of the insecticidal properties of Bt. This bacterium comprises a number of strains, each of which produces different toxin that can kill certain specific insects. For instance one of the strains being toxic to American bollworm and another control mosquitoes and black flies.

Btís mode of action: Unlike most of synthetic chemical insecticides, Bt toxins are not contact poisons, they must be eaten to be toxic. These are consumed by the insects while feeding on the leaves. Toxin binds itself to the receptors present in insectís mid gut, thereby leading to paralysis followed by death of the insect. This happens only in an alkaline medium. So we, with our acidic guts, do not need to worry. Bt toxins can be used for protecting crop plants by two ways ó insecticidal sprays and transgenic (Bt) plants.

Insecticidal sprays: The Bt has been used to produce biological insecticides for foliar application for over 50 years. These products were, and are still, produced by fermentation of single Bt strains in crude, inexpensive media. The most common formulations include wettable powders, or dispersible granules but oil and aqueous-flowable preparations have also been produced. Despite numerous merits of biological insecticides, their use is still limited due to their low field remanence. Indeed, the toxins are rapidly degraded by solar UV conferring short-term protection and requiring frequent sprayings. However, these inherent disadvantages can be overcome by developing plants with inbuilt Bt gene (Transgenic plants).

Transgenic (Bt) plants: To make plants resistant to insects, take the Bt gene and put it in the plant. Plants expressing these toxic genes (which could as such be considered "plant pesticides" have several advantages over classical chemical means in plant protection. Borers, for example, are difficult to reach by conventional means once they have penetrated plant tissues. Since, toxin expression can be achieved throughout the whole plant during the entire lifecycle, the deployment of transgenic plants would allow the control of major insect-pests. Furthermore, pests are exposed to the toxins at their most sensitive stages (early larval instars) and conversely, plants can be protected when they are most sensitive to insect attack. Such transgenic plants have proved more effective to control insects that have developed resistance to chemical insecticides such as American bollworm, the most destructive pest of cotton. The active compound is maintained in the plant tissues and has the potential of lowering cost of sprays. Finally, due to their selectivity and other advantages, transgenic plants expressing Bt toxin genes can easily be integrated in an integrated pest management (IPM) scheme.

The Bt gene has been transferred to impart resistance in several major crops like cotton, maize, rice, potato, tomato, tobacco, etc. Bt cotton and Bt corn have been commercialized in the USA, Canada and Australia. Bt cotton in the USA resulted in insecticide savings as high as $ 60 to $ 120 per acre. In the USA, more than 10 million acres of transgenic-insect resistant crops, including cotton, corn and potatoes, were planted in 1999 and are on the verge of extensive plantings. however, at present, insect-resistant transgenic crops have not been released in India. It is now a established fact that Bt crops are environmental friendly, non-toxic for mammals and effective in controlling the specific insect-pests unlike hazardous synthetic pesticides. In view of this discussion, it is, therefore, imperative to test their efficiency against pest which are otherwise difficult to control. Recently, the Indian Government has given "bio-safety clearance" to the controversial genetically engineered cotton developed by multinational Monsanto for large-scale cultivation and marketing. Bt cotton would help farmers save money they currently spend on chemical pesticides


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