Long-term effects on soil-water chemistry of wood ash and nitrogen application in a conifer forest

Abstract

Wood-ash application to forestland has been proposed as a means to compensate for increased nutrient removal when harvesting logging residue in addition to stems. A study-plot experiment was established on a mineral soil site in Sweden to investigate how this measure affects soil-water chemistry. In 1995, 10 treatments were applied. Here, we present results from 9 to 17 years after application for eight of the treatments: control; 3 × 103, 6 × 103, and 9 × 103 kg·ha−1 of self-hardened and crushed wood ash (WA); 150 kg N·ha−1 supplied as ammonium nitrate; 3 × 103 kg WA and 150 kg N·ha−1 applied simultaneously; 3 × 103 kg WA with 150 kg N·ha−1 applied 1 month before the ash; and 3 × 103 kg·ha−1 of pelleted ash. Soil-water samples were collected from a depth of 50 cm. Treatment effects (p < 0.05) were detected in the electrical conductivity, pH, and concentrations of K+, Mg2+, Ca2+, Al, SO42−-S, and B. Elevation of K+ and SO42−-S concentrations tended to cease toward the end of the study period. Effects were generally more pronounced with increasing ash dosage. No difference was detected between the 150 kg N·ha−1 treatment and the control. Despite the high solubility of the ash, its effects on soil-water chemistry could still be detected 9–17 years after application.