Colour of Peat as an Indicator of Chemical, Biological and Physical Properties of Peats

Biodegradability of peats is an important for long term cropping. Lignin content is an important parameter in predicting the susceptibility of peats to biodegradability. However lignin analysis is time consuming and can be expensive. Consequently tests were carried to see if determinations of peat colour using a colour meter could be used to predict lignin content and peat stability. Three trials are reported. In the first trial peats of different degrees of decomposition from three peat producing European countries were incubated for approximately three years. Initial measurements of the samples included colour and lignin. After drying and sieving of the peat material, colour was determined using a Minolta Chrome meter. Shrinkage was measured over the period. There was a strong correlation between colour parameters and shrinkage. In the second trial more than 20 peat samples were taken of different degrees of decomposition from seven peat producing European countries.). Colour was measured as above and other tests on the peats included lignin content E4/E6 measurement, organic matter, respiration activity and bulk density. E4/E6 ratio is an optical property of soil humus A very strong correlation was found between L and b values with lignin content. There was a good relationship between colour and other peat properties on a limited number of samples. In the third trial a much larger sample again from a number of countries was taken and analysed for colour as above and lignin content. There was a strong relationship between colour parameters and lignin content. The results indicate that colour measurements could be used as an indicator of lignin content and susceptibility of peat to shrinkage. It could be of practical value insofar as peats of high degree of structural stability are used for crops of long duration needing a high aeration requirement.