Chemical aspects of heather burning.
In laboratory experiments mineral nutrients, particularly K, were readily dissolved from the ash left when heather was burnt but the rate of solution was lower after combustion at a higher temperature. The potential losses through downward drainage of rain water are lessened by retention in the soil of ions from the percolating solution; the effect was most marked in organic and clay soils and least marked in sandy soils. Losses of dissolved nutrients were possible where surface drainage occurred over impervious soils but such losses were reduced on wet moorlands by absorption into Sphagnum. Over half the C, N and S in burnt heather was driven off with the smoke. Where burning causes losses from the plant-soil complex, precipitation appeared to restore the mineral nutrient balance in a short time unless the soil was very porous. Replacement of N by rainfall is slower but microbial action may be important here.