Impact of Biochar, Black Liquor, and Fly Ash Application to Soil on Productivity of Wheat in Eastern Washington

Soil acidification is a significant issue faced by agriculture in Eastern Washington. Acidification increases concentration of exchangeable aluminum (Al) in soil and reduces nutrient availability leading to reduced plant vigor, greater disease incidence, and reduced yield. Liming is the recommended remedy, but economic feasibility is questionable due to its high cost and limited supply of liming materials in the region. Thus, in this project locally available industry co-products were studied for use as alternatives for agricultural lime (aglime). Two forms of biochar (BC1, BC2), Avista wood ash (AVS), Pelletized (PFA) and flour paper mill fly ash (FFA) were applied individually and in combination to three soils, Rockford Larkin-Southwick complex [Low pH (3.7), high Al (230 ppm)], Pullman Caldwell silt loam [low pH (4.6), low Al (5.6 ppm)] and Naff series soil [low pH (4.6)]. Soil pH data collected from three separate experiments revealed that FFA applied at the same or half-rate as aglime resulted in a comparable or greater increase in soil pH as aglime and at a faster rate. AVS and PFA caused increases in soil pH as well but were not as impactful as FFA. Both aglime and FFA resulted in increased soil concentration of Ca, but concentrations of K, Cu, Cl, and B were increased only by FFA. Furthermore, soil concentrations of Al, Mn, and Fe decreased following both FFA and aglime amendment. Application of FFA resulted in reduced Al concentration in Rockford soil by 97% compared to a 93% reduction with aglime. Uptake of N, P, K, S, Zn, and Mn was reduced in winter wheat plants grown in either aglime- or FFA-amended soils. However, uptake of B was less in plants grown in FFA-amended soils. No traces of Cd, Cr, or Pb were found in plants grown in any amended soils. Winter wheat variety ‘Stephens’ and spring wheat variety ‘Louise’ grown in soils treated with FFA had statistically similar or greater aboveground biomass as aglime. The biochar products used in the study did not have a significant overall impact on soil pH, nutrient availability, plant biomass, or nutrient uptake. Based on these findings, FFA could be an effective replacement for aglime.