Compost: Quality checks

18/04/2015

The processes that explain the composting process are complex and very numerous. A number of biochemical processes come from the organisms that are in it. Fungi, bacteria, yeasts and other organisms (such as worms) are responsible for decomposing and transforming compostable waste into mature compost. Each group of microorganisms "attacks" the compostable waste at different times and phases, depending on the decomposition phase of the material and the conditions (temperature, pH, humidity ...). The process of humification or formation of humus is one of the most complex that is still being studied with profusion. This process is vital for the proper development of plants and occurs in all fertile soil. In fact, valuing a soil as fertile, is synonymous with a good process of humification, among other things.

The humification in 4 words

The process of humification is complex, but we could define it in a very general way as the intermediate step between fresh organic matter and the mineral compounds in which it has ultimately become converted. In a schematic and very general way we could establish:

The result of the complex process of humification can be more or less stable depending on the time spent in the process and above all on the balance achieved between the organic matter rich in nitrogen (young and green parts of the plants) and the organic matter rich in carbon (cellulose and lignified compounds from older parts). In fact, if you are somewhat into the world of compost, you will know that one of the values that tell us if the compost produced is stable, is the C / N ratio.

As a result of the composting process, depending on the time, we can obtain young compost or mature compost. None is better than another. They have different properties and uses from the point of view of the agricultural use of the garden.

It is understood that mature compost is more stable and the elements that compose it can be used directly by the plants. It is what we know as mulch. If our plants need a supply of immediate available nutrients, this will be the best compost, for example, in germination processes or if there is a serious deficit of nutrients in the soil. The problem is that the contribution is so immediate that, in the long term, the soil will be undernourished again (although in a lesser proportion). This type of compost takes approximately one to two years to form.

On the contrary, young compost has a part of its elements degraded and usable by plants and there will be another fraction with complex compounds that must still be decomposed. This compost, in the long run, will cause greater activity in the soil, because in it, there is still material that can be transformed by the organisms that feed on it. Let's say that young compost can become a slow release fertilizer on the ground. The young compost will take to form from 3 to 6 months. All these times are relative. It depends a lot on the conditions of the process (temperature, season, humidity, pH, aeration, balance of raw material ...).

How we recognize a compost in good condition

The theory is the theory and then you have to put it into practice. Composting well is a matter of learning, documentation, time and experience and things do not always go well although we believe that we do everything as we are told or have learned. There are certain conditions specific to each situation and person who compost, which make this not an exact science and sometimes it does not turn out well.

Therefore, to try to know if the composting process has gone as it should we will see certain tests or testing.

Color and smell The first thing to notice

This is the first test to know if the compost is incomplete or not in good condition to be used. The characteristic smell of well-made compost is that of forest, moist earth. Conclusion, it should not be an unpleasant odor. If so (nauseating odors, acids, ammonia, putrefaction), something is going wrong. They can be anaerobic fermentations, excess moisture, lack of aeration, imbalance between primary components. The color must be a dark brown, in which we do not see or it costs us to see recognizable remains of the initially incorporated residues.

Structure of the compost. Another complementary indicator

Another way to check if the result is satisfactory is to check the texture of the compost. Just pick up a compost and press it hard on your fist:

- If when released it crumbles and falls, we will be facing a dry compost.

- If, on the other hand, water sculpts through your hand and drips, we will have an excess of humidity (it may be a lack of aeration).

- If the handful of compost remains with good structure, it does not sculpt water, nor does it decompose, we will be facing a compost in good condition.

Germination tests and the C / N ratio

Analytically, the germination tests together with the C / N ratio are the most objective methods to establish if our compost is of good quality and has been formed as expected. The most accepted method is the Zucconi test. It requires an instrumental minimum of laboratory to be able to do it correctly. With this test we will be able to establish a quantitative value called the germination index. If its value exceeds 80-85% it is enough to affirm that we are facing a balanced and stable compost.

As many of us do not have access to such laboratory material, we can always make a test a bit coarser but that can serve as a guide to know if the compost is as it should be. It is about sowing seeds of watercress in a container and see its evolution. Depending on their adequate or inadequate growth we can establish, although not quantitatively, if the compost we have is of quality.

Source: Agromatica.es