| Crop straw represents an abundant, inexpensive and renewable fiber source for papermaking. Use of straw as a papermaking material may reduce deforestation through adopting alternative pulping materials. However, current reliance on Na-based pulping technology often generates black liquor that produces undesirable effects when applied to soil. Pulping of crop straw by substitution of NaOH with KOH should produce black liquor that may be a potential K source and soil amendment while offering an environmentally friendly and economically viable disposal option. Laboratory, growth chamber, and field trials were conducted to examine whether black liquor from wheat and bluegrass straw pulping with KOH could be land applied as a beneficial K and soil amendment. Black liquors generated by bluegrass straw pulping with 100% NaOH, 100% KOH or the 50% NaOH and 50% KOH slightly increased soil pH, indicating that they had potential as mild liming materials. Soil electrical conductivity (EC) increased slightly, but within low levels (<4 dS m-1), suggesting that these three black liquors would have no soil salinity concern when applied at 5 to 20 mL kg-1 soil. Soil exchangeable sodium percentage (ESP) increased with 100% NaOH or 50% KOH and 50% NaOH based black liquor rates, suggesting that Na-based black liquor may potentially increase soil ESP to levels impacting soil physical conditions. Sweet or field corn did not respond to KCl or KOH-based black liquor application under field conditions, which was likely related to high initial available soil K levels. The KOH-based black liquor had the same effect as KCl in increasing available soil K. It also increased soil respiration, soil microbial biomass C, soil dehydrogenase, beta-glucosidase, and arylsulfatase activities, and wet stable macroaggregates compared to non-amended control or comparable KCl rates, suggesting that KOH based-black liquor had potential as a beneficial K source and soil amendment. Polysaccharides and lignin contained in KOH-based black liquor were likely responsible for these beneficial effects. |
