Study of slash pine response to wood fired boiler ash and fertilizer in a wood fired boiler ash amended soil

Abstract

Application of large quantities of wood boiler ash to soil increases soil pH and salinity, and may affect plant water and nutrient relations. This study determined the effect of boiler ash application rate, with a liming equivalent of 20% and pH of 11.6, on tree growth, moisture retention, plant nutrient and metal uptake, and biomass accumulation under both field and greenhouse conditions. Three fertilizer regimes (0 fertilizer, NPK, and NPK + Fe, Mn and Cu) were used to study the response of (slash pine) Pinus elliottii (L.) to two levels of boiler ash application (0, 896 and 1792 mt ha(-1)) in the greenhouse. Slash pine trees were grown from seedlings for 10 months, harvested in three separate fractions (roots, stems and needles), dried, ground and digested for analyses of N, P, Ca, Mg, K, Cu, Mn, Fe and Zn. Plant mortality was monitored in field plots consisting of the similar ash application rates with two application methods, surface and subsurface application with incorporation. Tree mortality was higher in the surface treatments where there was no buffer between newly planted tree roots and ash in the field. Both total and plant available Ca, Mg, K, Na, and Mn and pH increased significantly under the two experimental conditions. There was significant reduction in Fe due to the high pH. High application rates of ash reduced above-ground biomass in the unfertilized pots by similar to 40% and addition of fertilizer decreased the reduction to 15%. Therefore boiler ash may be successfully used as a soil amendment in forest soils when applied at agronomic rates (below 60 mt ha(-1)).