Wheat straw pulping by-product mixed with lime may address soil acidification in no-till fields
Pan, William L.
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Soil acidification has become a growing concern for dryland crop production in the Pacific Northwest (PNW). Many no-till (NT) soils have stratified soil pH in the fertilizer application zone due to repeated nitrogen (N) fertilizer applications. The practice of liming to correct low soil pH is less effective for stratified soil acidity in no-till systems because lime is relatively insoluble. Consequently, without tillage, the vertical movement of surface-applied lime to the most acid-affected depths (generally 4–12 inches) can take many years. We conducted a greenhouse study to determine whether mixing lime materials with lignin-containing black liquor, a by-product from the pulp industry, offers a viable solution for soil acidity in no-till systems. Results indicate that the lime-black liquor mixture can expedite downward movement of lime and correct stratified soil pH in a short period of time. At 42 days after liming, the super fine micro lime-black liquor mixture increased soil pH from the soil surface to a depth of 6 inches. After 147 days, this finer mixture increased soil pH in the 10–12 inches depth, and the coarser agricultural lime-black liquor mixture increased soil pH from the surface to a depth of 10 inches.