Drainage, Liming and Fertilization of Organic Soils. I. Long-term Effects on Acid/Base Relations
Long-term changes of the acid/base relations of organic soils after drainage, fertilization and/or liming at three experimental sites—two ombrogenous and one soligenous—in south-central Norway are discussed. These sites were drained, fertilized and/or limed in 1953–1956 and sampled in 1991–1992. Drainage at the ombrogenous sites caused: insignificant shifts of pH, higher bulk densities to 40 cm depth, higher ash percentage, higher contents of N and P to 20 cm depth and reduced concentrations of total Ca, K, Mg, Na, Al and Fe in soil layers deeper than 20 cm. The soligenous site was not effectively drained; despite this, pH dropped about 0.5 unit in the surface and subsurface soil layers of the control plots, while small changes were measured for most other soil variables. The suggested reason for the pH drop is limited sulphide oxidation in the upper 20 cm drained layer. Base saturation at actual soil pH, when all treatments were included, was estimated with good precision by four regressors: pH, extractable Al, extractable Fe and extractable Ca (R2=0.90–0.95) Similar models explained 97–99% of the variation in base saturation at soil pH=7.0. The lime effects at the properly drained oligotrophic sites were proportional to applied doses; for pH to 40 cm, base saturation to 60 cm, and Ca concentration to 60 cm depth. At the less well-drained soligenous site, effects were limited to the upper 30 cm layer. Both drainage and liming caused higher cation exchange capacities and proper drainage seems to be a prerequisite for the liming effect. Estimated recovery of calcium to 60 cm depth was 64–79% at the ombrogenous sites and 42–46% at the soligenous site.