Tips on preparing high quality compost on a large scale
In my last blog entitled Organic farming isn’t always easy, I promised to present our experience in preparing compost in large quantities. This is an attempt to do just that. As mentioned earlier, we have been growing over 200 acres of bananas for the past 4 years, relying mostly on compost. Our compost requirement each year has been in excess of 3,000 tons – 12-15 Kg per plant per year (other crops might require much less). It would be prohibitively expensive to purchase that much compost from commercial suppliers; further, we could not rely on their quality. We were motivated by the fact that large quantities of plant material is available within our own farm every year after harvest of bananas (banana plant is cut down after harvest at the end of 12-13 months).
Here below is a cookbook recipe style explanation on how to produce 200 tons of compost. I have used this quantity as a guide as each of our compost pits holds approximately that quantity. However, there is no restriction on the size of the pit, and all the “ingredients” may be adjusted according to the total compost produced.
We start with banana waste collected after harvest. Banana waste is one of the best plant material available as it is rich in NPK (nitrate, phosphate and potassium), especially in potassium which is usually not contained in sufficient amounts in most other plant material. Banana waste also has several micronutrients such as iron, boron, magnesium, manganese, and zinc.
Banana waste is crushed using earth-mover (JCB) bucket and brought to a central location. It is then placed on a 400-500 sq. ft area in layers of approximately 2 ft. Over each layer, a solution containing EM (Effective Micro-organisms) is poured to speed up the decomposition process. Maximum of 3 layers are placed, and the entire pile is covered with 50-60% shade net to avoid too much direct sun. The pile is maintained moist by weekly application of water.
Before we go any further, just a few words about EM, originally developed by Dr. Teruo Higa, professor of horticulture at the University of the Ryukyus in
Many suppliers of composting bacteria claim that full decomposing can take place in 45 days or less. Our experience is that banana waste, especially stem, does not compost sufficiently in less than 75 days. Even then, it needs further decomposing in a large pit along with other compost ingredients for at least another 45 days.
We use some amount of sandy soil in the preparation of compost as our land is slightly clayish. We believe that soil is a necessary media for bacteria to function effectively in producing good compost.
Here below is the list of ingredients in 200 tons of finished compost. I have indicated multiples of 15 tons as a tipper load is around that weight.
30 tons of sandy soil
60 tons of decomposed garbage waste from government-run processing factory
60 tons of banana and plant waste (partly decomposed as described above)
60 tons of cow-dung
10 tons of dry decomposed poultry waste
There will be approximately 10-15% evaporation of moisture, and hence the above quantity yields no more than 200 tons of final output.
All the above are put into a large pit in no less than 4 or 5 installments. Use the bucket of the JCB to thoroughly mix the ingredients. Water well to assure that the material remains moist. It requires 2-3 days of effort to put each installment of ingredients and to mix them. After the entire quantity is put into the pit and mixed, cover it with tarpaulin or plastic sheet. Once a month, mix and spray water to keep it moist.
In our experience, it takes approximately 2 months of decomposing in the pit for the compost to be ready. Practically all the plant material will be totally “digested” by the heat generated in the pit as a result of the composting process. The final material is fairly soft and black in color.
The required quantity of compost is put around each plant at least 6 inches away from the stem. SEM (without cow-dung) as well as nitrogen and phosphate fixing bacteria (azetobacteria and phosphobacteria) solutions are applied and covered with a thin layer of soil.
It is important that no chemical fertilizers (if needed) are applied for at least 45-60 days after the compost is put around the plant to allow healthy multiplication of good bacteria. It takes over 30 days for the compost to become digestible for plant absorption.
The above process is what we have experimented with and found successful for vigorous plant growth. This approach to compost preparation can be applied to smaller farms by using proportionately smaller quantities of ingredients. Also, plant materials other than banana waste may be used, but care must be taken to ensure that they do not create toxicity from acidity or other factors, as is the case with coconut fiber. Similarly, leaves of eucalyptus tree are not suitable for preparing compost.
The all-in cost of finished compost is estimated to be around Rs. 250 ($6.25) per ton assuming that banana waste is free. We have found the above process to be a practical methodology to produce large quantities of high quality compost in our own farm. Other agro-specialists may recommend different techniques for preparing compost; their results should be confirmed by laboratory tests of the finished product. I hope my sharing our experience with readers will help others develop their own relevant methodology.
In a subsequent blog I shall write about processing raw sewage into safe fertilizer and water for irrigation. It is based on our experience in Shanti Bhavan residential school where its sewage processing facility generates over 75,000 litres of residue water for irrigation every day.
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