Saturday, May 2, 2009

Soil Secretes

Gardeners add fertilizers to the soil to feed the soil microbes, which control the flow of sulfur, nitrogen and other nutrients to the plants.

Soil isn’t just dirt. It is alive, teeming with tons of organisms per acre. Earthworms come to mind first, but in spite of the fact that we cannot see them, microorganisms comprise a greater weight per acre than worms! Without these microbes, life as we know it would not exist.

Soil microbes control the flow of carbon, nitrogen, phosphorus, sulfur and other soil nutrients. Microbes flourish when the soil nutrients are in balance. Essentially, when we add fertilizer to our soils, we are feeding the microbes, which then release nutrients to, or “feed”, plants. Some soil microbes even produce substances, which help to control plant diseases. Provide the microbes in your soil with a balanced diet of nutrients, and they will feed your plants with a balanced diet of available nutrients. Strangely, it possible to apply too much compost!

Soil science is extremely complex. For every action there is a reaction. For example, for every 1% increase in the base saturation of calcium, there is a 1% decrease in the base saturation of magnesium. The levels of other nutrients impact each nutrient’s availability. By adding too much of one nutrient, you are almost certain to reduce the availability of one or more other nutrients.

Even compost, revered by gardeners as a super soil builder, can be over-applied! Too much compost can make potassium so high that boron and manganese are less readily available to plants.

How pH affects nutrient availability

In low pH soils, aluminum reaches toxic levels and reduces plant uptake of the essential nutrients – calcium, magnesium, potassium and phosphorus. Iron and manganese toxicities can also occur.

In high pH soils (7.5 pH or higher), iron, manganese, zinc and boron are less available to plants.

The pH is essentially a measurement of how well nutrients are balanced. When nutrients are balanced to a pH of 6.5, phosphorus (the “P” in N-P-K) is most available to plants. As you move in either direction from 6.5, phosphorus becomes less available. As a practical matter, soil pH will be impossible to maintain at exactly 6.5. However, with proper soil management, soil pH can be kept between 6.0 and 6.5, a range that is optimal for most nutrients, and, as a result, for most plants.

Healthy plants start with fertile, nutrient-balanced soil

*High yields. The level of yield can be no greater than that allowed by the poorest of the essential plant nutrients
*Better nutritional content of crops. Studies have shown that fresh-grown produce can be much higher in vitamins and minerals that store-bought produce.
*Crops that grow vigorously are less vulnerable to insect attack. Weak plants are always the first to be attacked by pests.

Soil Composition has a major impact on fertilizer requirements

It is no surprise that the “inert” or mineral composition of soils varies widely from region to region. However, it is surprising to discover how much difference can exist in soils from one end of your property to another.
Farmers recognize this and are now using satellite technology to allow them to make adjustments in the amount of nutrients applied to different areas of the same field.

There is no single fertilizer, whether it is organic or chemically derived, which can provide optimal results in all soil types.

While an N-P-K fertilizer will generally improve results, depending on the soil type, it will only proved one portion of the nutrients needed to produce truly healthy plants and bountiful yields.

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