title: Lignin from rice straw Kraft pulping: effects on soil aggregation and chemical properties.
abstract: Lignin contained in pulping liquor that is generated during the pulping process for papermaking is a disposal problem for the pulp and paper industry. Separating lignin and other organic components from pulping liquor with inorganic acids may improve its applicability to fields as a beneficial soil amendment while offering a potential disposal alternative. Sulfuric acid-precipitated lignin from rice straw pulping liquor applied at rates of 1.67 and 3.34 g C kg(-1) soil was incubated to evaluate its effects on soil properties over 8 weeks of incubation. Addition of this acid-precipitated lignin at these rates decreased soil pH by 0.24-0.53 units over 8 weeks of incubation, suggesting that this sulfuric acid-precipitated lignin from pulping liquor may have potential as a soil acidifying agent. Soil electrical conductivity (EC) only increased by up to 0.36 d Sm(-1), but highest EC levels were less than 4 d Sm(-1), indicating that lignin applied at both rates would not cause salinity problems. Application of this lignin increased soil organic C by 1.46 and 3.13 g C kg(-1), and total soil N by 0.07 and 0.17 g N kg(-1) over the incubation period. Lignin improved the macroaggregation of >2mm size fraction, and increased wet microaggregate stability of >2mm and 0.5-0.25 mm aggregates compared to a nonamended control. The results of this study suggest that this acid-precipitated lignin from pulping liquor may have potential as a beneficial soil amendment.
authors.affiliation: Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164-6420, United States.
authors.forename: C
authors.initials: C
authors.lastname: Xiao
authors.forename: R
authors.initials: R
authors.lastname: Bolton
authors.forename: W L
authors.initials: WL
authors.lastname: Pan
mesh_terms: D000383:Agriculture / Q000379:methods*; D000704:Analysis of Variance; D002244:Carbon / Q000032:analysis; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D008031:Lignin / Q000737:chemistry / Q000302:isolation & purification*; D012275:Oryza / Q000737:chemistry*; D010209:Paper; D012987:Soil / Q000032:analysis*; D013464:Sulfuric Acids / Q000737:chemistry; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012987:Soil; D013464:Sulfuric Acids; D002244:Carbon; C076151:Kraft lignin; D008031:Lignin; C033158:sulfuric acid