title: Short-term alleviation of aluminum phytotoxicity by urea application in acid soils from south China.
abstract: A laboratory experiment was conducted to study effects of urea fertilizer on the chemical composition of soil solutions over time, and to determine Al toxicity as a function of rates of urea application. The experiment revealed that addition of urea fertilizer to soils caused drastic changes in soil pH during the hydrolysis and nitrification stages of urea transformation in the experiment. These pH changes, depending on the N rate of urea application and time courses, had variable effects on soil exchangeable Al, extracted with artificial solutions containing 1 mol l(-1) KCl. The Al mobilization rate could be resolved into two phases: A declining phase for Al was attributed to the urea-induced hydrolysis while a second rising phase was dependent with the nitrification of added N fertilizer. The decreases in exchangeable Al reached the greatest in 4-7 days after fertilization, consistent with soil pH increase. Decreased Al availability had been observed as a consequence of increasing urea addition and soil pH when using Root elongation of maize seedlings as the estimators. Results from the present study demonstrate that urea fertilizer to the surface of soils may lead to a temporary immobilization of Al and, therefore, alleviated Al toxicity to plant seedlings.
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, PR China. qrzeng@163.com
authors.forename: Zeng
authors.initials: Z
authors.lastname: Qing-ru
authors.forename: Liao
authors.initials: L
authors.lastname: Bo-han
authors.forename: Zhang
authors.initials: Z
authors.lastname: Li-tian
authors.forename: Zhou
authors.initials: Z
authors.lastname: Xi-hong
authors.forename: Tang
authors.initials: T
authors.lastname: Hong-xiao
mesh_terms: D000535:Aluminum / Q000037:antagonists & inhibitors / Q000633:toxicity*; D002681:China; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D018517:Plant Roots / Q000187:drug effects* / Q000254:growth & development; D036226:Seedlings / Q000187:drug effects* / Q000254:growth & development; D012989:Soil Pollutants / Q000032:analysis*; D014508:Urea / Q000494:pharmacology*; D003313:Zea mays
chemical_list: D012989:Soil Pollutants; D014508:Urea; D000535:Aluminum