Soil and Crop Response to Wood Ash and Lime Application in Acidic Soils

Wood ash has the properties to be an effective liming material, and research is needed to compare its effectiveness relative to agricultural lime on acidic agricultural soils. Wood ash at a calcium carbonate rate of 6.72 t ha(-1) was compared with an equivalent rate of agricultural lime on a clay loam soil with an initial pH of 4.9. Replicated plots were managed under a barley (Hordeum vulgare L.)-canola (Brassica rapa L.)-pea (Pisum sativum L.) rotation for 4 yr (2002-2005). Soil pH increased in the order of: wood ash = lime > control (without lime or wood ash). Available soil P increased in the order of: wood ash > lime >= control. The effect of wood ash and lime application on pH and available P was greatest in the 0- to 5-cm depth, less but still significant in the 5- to 10-cm depth, and not significant below 10 cm. The effect on soil aggregation was: wood ash > lime > control. Averaged over 4 yr, application of wood ash increased grain yields of barley, canola, and pea by 49, 59, and 55%, respectively, compared to a corresponding increase of 38, 31, and 49% by agricultural lime. The increase in crop yield with wood ash compared with lime is attributed partly to increased P availability in wood ash-amended plots. It is concluded that wood ash applied at rates equivalent to agricultural lime improved some soil chemical and physical properties and increased crop production relative to agricultural lime.