PEAT COMPRESSIBILITY - A PARAMETER FOR AUTOMATIC DEPTH CONTROL OF MILLING MACHINES

The primary object of the peat milling operation is to mill a layer of peat on the surface of the bog such that all of this layer (throughou t the bog) dries to the required moisture content in the same time int erval, so that it can all be harvested simultaneously. Feat type (and hence drying characteristics) vary considerably throughout a given bog , hence the depth of this milled layer should at any given location in the bog match the drying characteristics of the peat at this location . In order to do this, it is necessary to determine some measurable ch aracteristic,of peat, representative of the drying time, so this can b e used to determine the milling depth. Field and laboratory experiment s revealed that compressibility of milled peat is a good depth control characteristic because of its high correlation with the relative dryi ng time of milled peat. For example a typical high density peat (compr essibility of 12%) has a milling depth requirement of 21 mm compared w ith 9 mm for a low density peat (compressibility of 25%). Results indi cate that the application of this method within the peat industry woul d give a 27% increase in dry matter yields per hectare and the variati on of the moisture content of the harvested milled peat would be reduc ed from a standard deviation of 0.55 kg/kg to one of 0.22 kg/kg. (C) 1 966 Silsoe Research Institute