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By Charles Hopkins Published 05/7/2006 | Nutrition

Okay, lets cut out the jokes about piles of you know what and get to the heart of the matter. Manures, as we all know, are a valuable source of nutrients for the soil, whether in your little patch of green or in a commercial vegetable garden. As organic crop production increases, so does the demand for manures. However, few people know how to use manures, which represent a balanced diet for your plants, so here are a few guidelines to point you in the right direction.

Essentially, we use manures because they enhance the nitrogen content of the soil, but it is important to stick to the recommended volumes of manure for different soil types. Too little or too much use of manures can do equal damage to the soil.

As a first step, you should buy the manures as close as possible to the actual time of use, especially if you cant store it in a covered area. If you are using manure in winter, you should do so only after the soil has cooled to less than 50F. And you cant just bung in any old pile of you know what either you have to have the manures tested for nitrogen and phosphorous content to determine whether it will actually enrich the soil.

As we mentioned earlier, avoid using excessive manure because this is akin to overfeeding the soil. This could translate into apparently luxuriant growth but inferior quality. More seriously, there will be large amounts of leftover nutrients that will percolate into the soil after the season. Why do we view this as more serious? Well, the leftover nutrients in manures can easily lead to pollutions, particularly if the organic nitrogen in manure is converted to nitrate in warm soils. This nitrate has the same action as nitrate from synthetic fertilizers, so your organic growths can go for a toss.

This is why it is necessary to apply manures correctly with a calibrated spreader. Also, you should avoid applying manure to the same spot in the garden year after year. As earlier, this can cause a buildup of nutrients that will later leach into surface water.

The best way to use manures correctly is to find out the nutrient requirements of your plants and apply the manures in the required amounts only. For a few plants, you may have to use manures that include hydrating agents, but your local garden center will be able to tell you more on the subject. If you think that the manures that you are using are not supplying the nutrients in required quantities, you may have to supplement the dose with synthetic nutrients, but that is rare in small gardens. This is more likely to be the case in large commercial gardens or orchards.

Whatever manure you use, remember that manures are excellent nutrient resources, particularly for vegetable gardens, but only when used properly. In the wrong hands, manures can pose environmental and health risks of a grave nature.