The second problem arises when substrate pH drifts away from the initial target over the course of production. First, there is difficulty in attaining consistently initial substrate pH targets using standard formulas for limestone additions. Growers who formulate their own soilless substrates and companies that sell ready-mixed soilless substrates face two problems. Keywords: Sphagnum species neutralization requirement pH drift Understanding the species composition in peat-based substrates can alleviate problems of inconsistent initial pH and subsequent pH drift.

Moss peats with high BS should have a low neutralization requirement to achieve a target pH. Moss peats with high CEC have a greater buffering capacity than those with low CEC, resulting in less pH drift. Neither CEC nor BS was influenced by degree of decomposition (r = 0.002 and r = 0.08, respectively). BS was positively correlated to the amount of sedge (r = 0.28). CEC was positively correlated to the amount of Sphagnum fuscum (Schimp.) Klingrr.

Averaged overall samples, BS ranged from 15% to 71% of CEC and calcium accounted for 68%, magnesium for 25%, sodium for 5%, and potassium for 1.4% of BS. CEC and BS were measured in three replications on 64 moss peat samples that were selected from three mires across Alberta, Canada, to represent maximum gradients in plant species composition within six degrees of decomposition acceptable for professional peat-based substrates. This study was conducted to determine the extent of such variation. Variations in moss peat cation exchange capacity (CEC) and base saturation (BS) can result in inconsistent initial pH in moss peat-based substrates created using standard formulas for limestone additions and can lead to subsequent drift from the initial pH in those substrates.

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