Factors affecting the determination of the moisture characteristics of peat by the filter paper method

Abstract The filter paper method of Fawcett and Collis-George (1967) for determining soil moisutre characteristics was modified for use with finely milled peat; a carrier used in the production of legume inoculants. The filter paper method proved to be as accurate as the standard method using pressure plate apparatus. Fungal growth in the peat and on the filter papers was overcome by using fungicides or by sterilising the peat. However, these preventative measures all significantly affected the resultant moisture characteristic curves (mcc's) by underestimating the amount of moisture required to adjust peat to any specified moisture potential. Substituting either sterile yeast mannitol (YM) broth or YM broth containing Rhizobium leguminosarum bv. trifolii strain TAI had a similar effect. Reducing the equilibration time of the filter papers from 7 to as little as 2 days gave consistent results and avoided fungal growth. The mcc of solid-based carriers for bacterial inoculants should be determined after they have been subjected to the same treatments as used in the production process.