Efects of peat drainage on labile organic carbon and water repellency in NE Poland

Abstract

Hot and cold water-extractable organic carbon (HWC and CWC, respectively) fractions, as good indicators of organic matterquality, as well as water repellency (WDPT test) and state of secondary humifcation were analyzed in topsoil samples of peatlanddrained for agricultural purposes 160 years ago. Te examined sites (drained and used as grassland) at the peatland had been afectedby the moorsh-forming process. During this process, intense mineralization and secondary humifcation of organic matter took place.Te state of transformation of organic soils varied from weak to complete degradation. Te HWC contents ranged between 2.623and 3.572 g kg 1 in feld-moist samples and 3.999 and 6.074 g kg 1 in air-dried soil samples. Te CWC contents were generally lowerthan HWC and ranged between 0.411 and 0.535 g kg 1 in feld-moist samples and 0.696 and 0.939 g kg 1 in air-dried soil samples. Teexamined soils were extremely water repellent when dried. Te measures of transformation of peat afer drainage and WDPT were notsignifcantly correlated, but a tendency for higher values of water repellency at the site regarded as degraded was noted. Deep drainagecaused an increase of HWC fraction, which in light of the moorsh-forming process should be regarded as negative. Te topsoil of thepeatland became dry and resistant to rewetting. However, when the ground water level is maintained at not deeper than 0.50 m, thechanges in peat matter do not lead to degradation. HWC is a good measure to show diferences occurring within the ecosystem. Givenits correlation with state of transformation (W1 index) and water repellency (WDPT test), HWC is a good measurement of peat quality.HWC and WDPT measurements may be helpful in determining degradation of peat soil afer drainage.