Thermophillic Compost Production
The most essential component for any sustainable agriculture enterprise is the production of compost. Well made compost is a biologically active, nutrient rich, weed and pathogen free soil amendment. Compost is similarly superior to just adding fresh FYM or crop residues both in terms of plant and soil nutrition and as a means to add soil organic carbon. It is also an excellent substrate to feed to brandling worms for the production of high quality worm casts suitable for use in potting mixtures.
The 3-2-1 Compost System Installed at ADAOS
Currently we are engaged at ADAOS in building a two stage thermophillic composting operation using horse and cow manure mixed with wood shavings and grass cuttings. Which will then be used as a substrate for worm cast production.
Container and Heap Construction
In the first stage three 2m x 2m bins were constructed and then filled with alternate layers of horse manure, wood shavings, cow manure and grass cuttings. Heaps can be built longer, as windrows but should not be built any wider or higher that 2m as air will not be able to fully peculate within the heap if it is. It is important to both layer the material so that the heap is kept open and air can peculate. This is achieved by building the heap from the outside and working in towards the middle, taking care NOT to compress or ‘pat’ the heap down.
Peculating the air can be further assisted by putting woody branch material as a base layer.
Each layer should be between three inches (7cm) and six inches (15cm) deep.Copious amounts of water should be added using a watering can or a hose fitted with a rose, so as not to compact the heap, and a couple of handfuls of lime (approx 500g/ 1 lbs) should be sprinkled in. If available Gypsum can also be added at every layer as it helps to prevent ‘slimming’ keeping the heap open and reacts with volatile ammonia (converting it to ammonia sulfate) preventing Nitrogen loss without affecting pH. This is particularly relevant if the material contains animal manures with urine. Once built the heap should be covered to prevent rain penetration but left open so that air can freely peculate.
Using a Starter Heap
It is not essential but building a starter heap, to encourage a high proliferation of the thermophillic bacteria will aid the heaps subsequently reaching temperature. This starter heap should be made 2 – 3 weeks earlier and sprinkled on to the layers in each of the subsequent heaps constructed.
Using a starter heap the main heaps should then rapidly rise in temperature (60-70 degrees Celsius) over the next few days. After 3 to 4 weeks the heaps will have cooled to about 50 degrees Celsius and shrunk in volume by about a third. They can then be turned into two more bins leaving about 1/2 to 1/3rd of one compost bin to be used as a starter for the next three heaps.
The compost at this first and only turn should be turned ‘inside out’ with the outer part placed in the middle and the inner material used to build the outside of the two new heaps. This will ensure that all of the material reaches the optimum temperature and weed seeds and pathogens are destroyed. It should again be built in layers and if dry (it shouldn’t be) water added. It will again heat up to 60-70 degrees Celsius and once it has cooled to below 50 degrees Celsius again (about 3 – 4 weeks) it is finished.
The ‘Finished’ Product
Having been ‘cooked’ (reached and maintained a temperature of 70 degrees Celsius) twice for a total period of 6-8 weeks the material will now be weed and pathogen free (including human as well as plant pathogens) and can be safely handled and used as a surface mulch, dug into land , used to make liquid feeds and pathogen suppression sprays or just left to ‘mature’ and dry stored for later use. For more information see the Compost Science pages on https://phasm.co.uk
However in this case the material is destined to be fed to worms in a third process to produce high quality worm worked compost. A bed should be constructed and as there is no longer a need for air to peculate this bed can have any dimension that facilitates both feeding and harvesting the casts. The worms should be placed in the bottom of the bed and then a 6″-8″ (15-25cm) layer of compost should be added. The compost should be covered, ideally with cardboard, hessian sacking or similar organic material. This will encourage the worms to work right up to and through the layer of feed stock. Once the worms have worked through the initial feed layer another 6″-8″ layer should be added. This should be repeated until the volume is at least 2-3 feet (50-100cm).
Once the worms have digested the feed stock (about one month) addition layers of compost can be added. This should be repeated every time the worms have worked they way up and through each layer. When the bed has reached the desired height a final feed of compost should be added and left for a week or two for the worms to migrate in. This top layer, which will contain the majority of worms and eggs, can then be removed and put aside whilst the casts underneath are harvested. The harvested casts will still contain a lot of worms. These can be removed by laying the casts in a line onto some polythene sheeting or similar, or onto a hard surface (i.e concrete). The worms will then move down away from the surface. This surface can then be scrapped off. The worms will then move deeper down and again after sufficient time (30 mins) the surface can be scrapped off. This is continued until the worms are concentrated at and in the bottom and final layer. Once this is achieved the worms can be added back to the vermi beds or used to start more vermi-culture beds or operations.
Using The Casts
Fed on a regular basis a worm bin can be filled in under six months and produce a volume of casts relative to the surface area of the vermibed. The bigger the surface area the more casts will be produced. The resulting casts can now be used as a planting and soil amendment or as is the intention here utilized in the manufacture of potting media.
Benefits of Worm Casts
Unlike the raw material or the compost feed stock worm casts are a uniform finished product that are high in both available and stored nutrients as well as a diverse and active micro-flora. They can, as this author has previously demonstrated be used to successfully grow tomato plants to three trusses in 7″ pots using potting media constructed from worm casts, leaf mold and vermiculite without the need for supplementary feeding. The plant on the right here was grown outdoors in the UK and irrigated only with rain water yet produced a full crop of tomatoes .
Historical work done at the University of Reading as part of my undergraduate program in 2001 demonstrated that when correctly handled potting media made from worm worked compost out performed commercial peat based formulas.
Title: The influence of compaction on the emergence and shoot production of Basil (Ocimum basilicum) grown in novel horticultural substrates.
Author: M. J. McEwen
Address: Department of Soil Science, University of Reading, P.O. Box 217, Whiteknights, Reading, Berkshire. RG6 6AH
Keywords: Vermiculture, Compost, Bulk Density, Community composting, container media, soilless.
Studies were conducted to evaluation plant responses to three novel organic substrates. The three substrates, two worm-worked and one allotment were compared to an Irish moss peat with a proprietary seed and cutting compost as a control. Phyto-toxicity was measured using a variation of the direct seed method. To improve the test’s sensitivity the concentration of any potential toxins was encouraged by using more substrate and less water. Phyto toxicity was then assessed by germination over a 72 hour period at 300C. A 20 day bio-assay using Basil (Ocimum basilicum) to evaluate the growth responses was also conducted. In the bio-assay each substrate was subjected to four compaction treatments determined by ratios of 1.25, 1.5., 1.75 and 2.0 times the substrates measured bulk density. Acid washed sand was then used as a casing agent in order to provide a uniform seed covering. Emergence was counted for the first eleven days with a final count on harvesting. Plants were removed intact, shoot and root weights were taken before the roots were preserved for future examination and the shoots dried and weighed. In the phyto-toxicity experiment germination rates for all but one substrate were not significantly different [P = 0.94] however in the bio-assay, compaction ratio had a greater influence on emergence than substrate type. Rates of, and total emergence did not always correspond with shoot bio-mass production. Total shoot bio-mass production for each substrate showed comparatively similar amounts being produced in the three novel substrates whilst the peat produced the least and the control produced the most. Emergence between the control, the peat and one of the worm-worked composts was comparative however bio-mass was 64% lower in the peat and 30% lower in the worm-worked than in the control. At compaction ratio 1.25 bio-mass in the worm-worked composts was 22% and 100% greater than that in the control. Overall the control gained the greatest in bio-mass production whilst the peat the worst. Emergence was greatest at compaction ratio 2.0 and lowest at 1.5 [P = 0.0004] whilst at 1.25 and 1.75 emergence was comparable [P = 0.63]. Generally the performance of the novel substrates was superior to the peat however at different compaction ratios each novel substrates produced greater bio-mass than the control; although in all cases the control had the fastest rate of emergence. Therefore in assessing phyto responses to novel substrates comparison by substrate without regard for compaction effects cannot be relied upon to confidently assess the potential.
UK Government Funded Work
Furthermore I was the principal author of WRAP STA0015: To support the development of standards for compost by investigating the benefits and efficacy of compost use in different applications (2004) and regard my research and recommendations as having been instrumental in helping the UK form a national policy to implement measures and standards that ensured composts made from a broad range of feed stocks were free of contamination and met the minimum standards for use in food production. As a leading expert in the manufacture and use of compost and vermi-compost in agriculture and horticulture I hope to continue this by helping Nepal achieve even higher standards in it’s efforts to become sustainable and self sufficient in food production. A copy of the final document produced for WRAP can be found in the resources page of this site