Ash content in compost

In many countries the ash content in compost is often too high. Possible causes may include: contaminated raw materials such as sand in chicken manure; too much dust in the straw depending on the way it was harvested; a prolonged fermentation process or too much gypsum.

Things often go wrong when adding gypsum which is added to retain a good compost structure and has a positive influence on the pH values. Frequently too much gypsum and more importantly gypsum with a too high pH value (above pH 60!) is added to the compost. If the structure is good and if ammonium sulphate is used too (this positively influences the pH value and ultimately the N-content) the gypsum dose can be reduced. The ash content towards the end of phase 3 must not exceed 30%. Higher levels will be detrimental to production If chicken manure is contaminated more than thought this may also result in an incorrect nitrogen concentration It’s therefore very important to analyse batches of chicken manure on delivery.

Jos Buth, C point

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