Effects of peat source and length of storage time in bales on selected properties of Sphagnum peat

Abstract

Peat is a common ingredient of growing media used in the horticultural industry in North America and Europe, yet Canada does not have formal standards for peat quality assessment. This study evaluated selected properties of baled peat as affected by peat source and length of storage time under conditions typically occurring at a commercial growing media firm. Nine bales of peat (dominated by fibric white peat) fromthe upper, less-decomposed layers of a Sphagnum bog in Manitoba in the early stage of exploitation (ESE) and nine bales of peat (dominated by hemic brown peat) from the lower, more-decomposed layers of a Sphagnum bog in Alberta in the late stage of exploitation (LSE), were sampled after 1, 3, and 10 mo of storage. The ESE peat had a larger particle size (determined by both dry and wet sieving), and a higher content of total elements (Fe, Mn, Cu, Zn, Mo, Al, As, Cd, Co, Na, Ni, Pb, and Si), water content, and NH4-N than the LSE peat. The LSE peat had higher pH and NH3-N content. Plant-available water, air-filled porosity, and the number of germinated weeds were similar in ESE and LSE peat. In both sources of peat, organic particle size (determined by wet sieving) was lower after 10 mo of storage relative to 1 and 3 mo of storage. Similarly, the NH4-N content decreased from120 mg kg-1 after 1 mo of storage to 90 mg kg-1 after 10 mo of storage. Hence, the growing media industry should monitor particle size distribution and available N at the time when peat is incorporated into growing mixes.