Saturday, November 22, 2008

Feeding the Soil - Part 4

by Richard Chew

After my previous improvements as posted in Feeding the Soil - Part 3, there is marked improvement, but I was still not very satisfied with the rate of decomposition.

Upon learning that peat moss helps decrease pH of soil and also increase rate of decomposition of organic matter, I decided to add peat moss as top soil. Peat moss has carbon nitrogen ratio of 50:1. And it has higher population of actinomycete bacteria that is responsible to decompose organic matter. This decomposition process is also known as mineralization of organic matter that converts organic matter into non-organic ammonia mineral. Subsequently ammonia is used by other bacterias for their metabolic activities, also known as nitrogen fixing. During the metabolic activities, these bacteria will respire nitrogen into a form that can be taken in by plant roots as nutrients.

The peat moss also aids in decomposing dry fertilizer (pellets form - chicken and sheep manure), including those that are highly processed which are harder to decompose. Mixing dry fertilizer with the peat moss, will help to break down the fertilizer more easily thus faster release of needed nutrients into the soil. Without peat moss (or any substance that aids decomposition), the bacteria may draw nitrogen from the soil to break down the fertilizer. This is the reason why the dosage of fertilizer must correspond with the size and health of the plant. Otherwise both the fertilizer and the plant roots would be competing for the same source of nitrogen. To build on that, if the plant roots are not healthy, the same bacteria that decompose the organic matter may choose to 'attack' the roots instead because the unhealthy roots become easier to break down.

However peat moss need to be mixed with other low carbon nitrogen ratio matter to create a better soil metabolic effect. Peat moss by itself, tends to retain too much moisture and may invite more fungal decomposition. Its surface tends to be grayish (sign of fungal). Of course retaining moisture has it benefits, but if too much may tightened the top soil that impedes aeration especially after heavy rain fall. Too high moisture content will lead to anaerobic fermentation, because the soil structure lacks access to O2 thus will increase the soil pH (alkaline soil). This probably explains the cause of chlorosis at my Nozomi rose which is sign of suffering from the inability to absorb iron. More about my experience in countering chlorosis in my next posting.

Having mentioned the above I need to clarify that the grayish texture at the peat moss surface is not a bad sign. It actually confirms the presence of actinomycete, a kind of fungal bacteria (because it is fillimous, and has spores) for decomposing organic matter. If its high with actinomycete, don't be surprise a mushroom may suddenly spring up from the soil in the early morning.

To prevent or to minimise anaerobic fermentation (that will increase soil pH), we need to add material that provide good top soil structure for better aeration to aid aerobic decomposition. And it should contain low carbon so that metabolic activities can be raised without depleting nitrogen at the top soil.

I used grass cuttings. It is inexpensive. It cost about RM2.60 per pack. It has the right carbon nitrogen ratio (20:1), that utilises nitrogen from its own source when decomposing. And its structure goes well with peat moss to improve top soil aeration. I would mix about 50% (of volume, not weight) with the peat moss. I noticed a dramatic difference in the soil structure after mixing it with grass cuttings.

The top soil becomes less tight, much softer and more fluffier (better aeration). I noticed it becomes brownier (and less grayish) when I turn over the top soil on the following day This is good sign of good compost soil.

I have just pruned my Portmeirion rose. I did the top soil as mentioned above. Hopefully by Dec I will get good display of flower. The rose is responding well with some buds at the main stem. Hope to get about 10 strong shoots for flowering.

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