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COMPOST


At Laurel Valley in the USA a spinner has been installed on the transport belt that supplies the fil- ling cassette. The result is staggering.


Avoid too high concentrations Reducing the amount of, say, chicken manure, is not always the right solution. Moreover, a professional composter is unlikely to radically alter the dose of e.g. chicken manure from one week to another. So it’s illogical to presume that too much chicken manure has suddenly been added to the compost. Professional composting companies calculate per batch - depen- ding on the nitrogen concentration in the chicken manure - how much of it has to be mixed through the straw and/or horse manure. Generally, fluctuations in the nitrogen content of chicken manure are not that large if the manure is provided by the same supplier. However, if the chicken manure is sourced from various suppliers large differences in the nitrogen content may be seen. It is therefore advisable to investigate this aspect properly and take a critical look at the quality of the chicken manure being supplied. There is a hidden risk though. Adding unlimited volumes of additional chicken manure, if the chicken manure has a very low nitrogen content, is not an option as this will make the compost too greasy and usually increase the ash content too. In this case, urea can be used to compen- sate for the shortage of nitrogen. Another pitfall is that ammonia production and nitrogen content in chicken manure are not always linked. Old chicken manure, for example, may well have the right nitrogen content but still produce less ammonia. This also applies to composted chicken manure, or in other words, chicken manure that has been stored too long. Some chicken farmers add substances to the manure to limit the odour nuisance caused by ammonia. Another feasible option to avoid an excess of ammonia can be to increase aeration for the last few hours in the bunker by setting the frequency controllers of the fan in the bunker to a higher speed for that period. It may even be necessary to increase the fan speed for the last 24 hours in order to expel more ammonia and get rid of more energy. Lengthening the levelling process can also enable the compost to get rid of ammonia. In this case, measuring the ammonia level more frequently is recommended. High nitrogen doses are usually linked to greater activity and linked to higher ammonia production. But an over-composted compost can be less active, yet still contain too much ammonia if too much chicken manure has been added.


Too low ammonia concentrations It can also happen that the ammonia concentrations are too low. This can have grave consequences for the rest of cultivation. Too little ammonia during pasteurisation destroys none, or hardly any, weed mould. Too little ammonia also normally signals inactive compost that in most cases will be a poorer nutrient base. Reason enough to pay due attention to enough compost acti- vity. Even with an optimal mix of the right proportions of raw materials, there are still times when not enough ammonia is measured during pasteurisation. This may have a variety of reasons. Too much air during phase I can be a plausible reason. Another reason may be that the compost has been handled too much after the bunker process. If, after the bunker stage, the compost is placed in a windrow and this pile is turned several times by a manure turner over a few days, more am- monia will be dispelled than when the compost if left for just 8 - 24 hours on the floor after leaving the bunker and is only treated once when water is added. If compost temperatures fail to increase sufficiently during phase I, or if the compost temperature is only high (above 75 degrees Celsius) for a short time, then the compost will be greasy at the end of phase I and will produce too little ammonia. Compost like this often contains nitrogen, but this nitrogen (nutrient) is not easily available enough for the mushroom mycelium later on in cultivation. This type of compost is easy to re- cognise during mycelium growth. You will notice thick threads of mycelium growing in the compost which greatly inhibits the growth of fine mycelium which would otherwise intensively colonise the substrate. The greater the number of thick mycelium threads visible, the poorer the condition of the compost. ◗


A frequency controller linked to the fan in the bunkers is essential for optimal ammonia management.


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