title: Amelioration of an acidic ultisol by straw-derived biochars combined with dicyandiamide under application of urea.
abstract: The rapid increase in agricultural pollution demands judicious use of inputs and outputs for sustainable crop production. Crop straws were pyrolyzed under oxygen-limited conditions at 400 °C for 2 h to prepare peanut straw biochar (PB), canola straw biochar (CB), and wheat straw biochar (WB). Then, 300-g soils were incubated each with urea nitrogen (UN) and UN + biochars with or without dicyandiamide (DCD) for 60 days. During the incubations, soil acidification induced by urea was somewhat inhibited by biochars, but nitrification of hydrolyzed NH4+produced much more acidity than the neutralization potential of the biochars. In single UN (200 mg/kg) treatment, soil pH decreased drastically and the final pH after incubation was lower than the control. Antagonistic to UN, all three biochars neutralized the soil acidity, which was consistent to their inherent alkalinity. DCD inhibited nitrification which was obvious throughout the incubations, as 30 mg/kg DCD + 200 mg/kg UN combined with 1  % PB, CB, and WB retained 0.94, 0.79, and 1.19 units higher pH, respectively, and significantly reduced exchangeable acidity over the treatments without DCD (P < 0.05). The treatments of UN + biochars with and without DCD had highly significant effects on soil pH, exchangeable Al3+, NH4+-N, (NO3-+NO2-)-N, and available P (P < 0.05). Amplified NH4+-N retentions at higher rates of PB referred increased negatively charged sites for nutrient adsorptions. Applied UN transformations varied among different treatments, and the maximum amounts of total mineral N recovered were 218.3, 218.5, and 223.8 mg/kg in the presence of DCD by PB, CB, and WB, compared to 198.2, 201.6, and 205.2 mg/kg, respectively, in no DCD treatments. Urea induced severe soil acidification and even lowered the ameliorative effects of applied biochars. Thus, ammonium-based fertilizers must include nitrification inhibitor (DCD) and, if used in combination with biochars will offer a suitable choice to reduce the acidity, improve base saturation and fertility of soil for sustainable agriculture.
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P.O. Box 821, Nanjing, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.|Department of Agronomy, The University of Poonch, Rawalakot, Azad Jammu & Kashmir, Pakistan.
authors.forename: Khalid
authors.initials: K
authors.lastname: Mehmood
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P.O. Box 821, Nanjing, China.
authors.forename: Jiu-Yu
authors.initials: JY
authors.lastname: Li
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P.O. Box 821, Nanjing, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P.O. Box 821, Nanjing, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Ren-Yong
authors.initials: RY
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P.O. Box 821, Nanjing, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Zhao-Dong
authors.initials: ZD
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P.O. Box 821, Nanjing, China. rkxu@issas.ac.cn.
authors.forename: Ren-Kou
authors.initials: RK
authors.lastname: Xu
mesh_terms: D000383:Agriculture; D064751:Ammonium Compounds / Q000737:chemistry; D010367:Arachis / Q000737:chemistry; D002606:Charcoal / Q000737:chemistry*; D006146:Guanidines / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D035261:Plant Components, Aerial / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry / Q000302:isolation & purification*; D014908:Triticum / Q000737:chemistry; D014508:Urea / Q000737:chemistry*
chemical_list: D064751:Ammonium Compounds; D006146:Guanidines; D012987:Soil; D012989:Soil Pollutants; C540010:biochar; D002606:Charcoal; D014508:Urea; C004711:dicyandiamido
keywords: Acidity amelioration; Base saturation; Biochar; Dicyandiamide; NH4 + and (NO3 −+NO2 −)-N; Urea nitrogen