Effect of wood ash and crushed rock soil amendments on red clover growth and dinitrogen fixation

Authors

• A Sigrun Dahlin Swedish University of Agricultural Sciences
• Maria Stenberg Swedish University of Agricultural Sciences

DOI: https://doi.org/10.23986/afsci.63739

Keywords:

circular economy, nitrogen translocation, recycling products, soil amendment

Abstract

The fertiliser effect of adding wood ash or crushed rock to a low-fertility soil, compared with an unamended control, was assessed in a pot experiment with a perennial ryegrass-red clover mixture. Dinitrogen (N₂) fixation by the clover and translocation of fixed N to the grass were determined using ¹⁵N natural abundance. The wood ash produced the highest accumulated clover biomass over two cuts, followed by the crushed rock. Chemical analyses suggested that the increase was due to K supply by the amendments. The wood ash also led to larger amounts of fixed N compared with the control. However, N₂ fixation was not increased as much as biomass amount, leading to dilution of plant N. There were minor or no treatment effects on mineralisation from soil N pools. This indicates that good-quality wood ash can be successfully used as a multi-element soil amendment to enhance clover growth on low-fertility soils.