Thursday, October 16, 2008

Microbes - Our Friendly Allies

by Richard Chew

I've read some materials on rose growing and I learned that we are blessed with God's micro creation that we cannot take them for granted. They are essentials for cultivating healthy plants. They are our friendly allies.
It is not necessary to know the details of what microbes do. But more importantly what is necessary to get these friendly allies to work favourably for your plants.

These are some few suggestions you can use.

1. Keep your soil aerated. If earthworms are numerous in your soil, it should provide sufficient aeration. If the soil becomes compacted due to continuous pouring rain, then it is necessary to fork it to improve water drainage. Best indication of good soil aeration, is that bubble surfaces when watering. Aeration is important because Bacteria utilises Nitrogen (N2) from atmospheric air and convert them into "food" for other micro-organism in the soil.

2. Keep soil fertilised with organic manure. As the organic manure decomposes, these microbes will gain the energy to convert Nitrogen gas (N2) from the air into the form that the plant can use.

However there are some special situations that we need to take some pre-cautions. If we understand how these microbes function and apply some counter measures, then it is highly likely we can help sustain high nitrogen production cycle that benefits your plant.

The following are some situations that may limit the cycle of Nitrogen production.

1. Excessive rain - that clogs aeration in soil, thus lack of Nitrogen gas in the soil impedes the rate of decomposition (lower rate of bacteria activity)

2. Lack of sunlight - Lack of sun light will lower photosynthesis activity, thus cause an imbalance of the symbiotic activity of Nitrogen Fixing Bacteria that resides at the roots nodules. The bacteria continue to consume "food" stored at the roots that is supposedly supplied from the photosynthesis process. This cause a depletion in carbon component in the plant. If left unattended the plant condition may deteriorate.

3. Low Nitrogen ratio fertiliser - If low nitrogen material is used for fertilisation (example tree leaves, eggshells or any materials that decompose slowly), it may cause temporary shortage of nitrogen as the microbes draw too much nitrogen from the soil to digest the low-nitrogen material (decompose).

The above diagram illustrate the complete nitrogen cycle. The plant cannot take in nitrogen from the atmosphere directly. It relies on bacteria to convert them (through multiple stages) into a form that can be absorb into the plant. As illustrated above, the end cycle is Nitrates (NO3-) that is assimilated into the plant roots.

Ammonification Phase

N2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi

Although ammonia (NH3) is the direct product of this reaction, it is quickly protonated into ammonium (NH4+).

Nitrification Phase

NH3 + CO2 + 1.5 O2 + Nitrosomonas → NO2- + H2O + H+

NO2- + CO2 + 0.5 O2 + Nitrobacter → NO3-

Nitrifying bacteria converts ammonia to nitrite (NO2-) and subsequently converts nitrite to nitrate (NO3-) which shall be assimilated by the plant as nutrient. To accomplish this task, the bacteria needs CO2 and O2 from the atmospheric air. This explains the importantance of having good soil aeration to ensure higher nitrogen production for the plant roots.

This is why I like to water plants in the morning and also in the evening, always twice daily. Obviously apart from the main purpose for moisting the soil, the other important purpose is to flushed out the "burned" air so that more fresh CO2 and O2 replaces the pores in the soil.

The presence of earthworms in soil helps keep the soil aerated and its worm casting contains Nitrate (NO2-) and bacteria too, thus increase the nitrifying acitivities in the soil.

Another important information is that these bacteria also involved in the formation of soil aggregation. They produce organic compounds called polysaccharides (complex carbohydrates ; Cn (H2O)n-1 where n is usually large number between 200 and 2500), that binds soil particles together in aggregates. These aggregates can vary in size, and they do not necessary fit together thus creating spaces and pores within and between the soil. These spaces and pores are essential for storing air and water, microbes and nutrients in the soil.

I hope by now you will appreciate these lowly creatures. Though they may seemed insignificant, they largely contributes to our food chain.

In case you wish to understand a little bit more, please refer to the useful links below that explains what Bacterias do in the soil. I have extracted this piece of information from the US Department of Agriculture and posted it in this blog.

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