Short‐term effects of polyacrylamide and dicyandiamide on C and N mineralization in a sandy loam soil |
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| Authors: | C Watson Y Singh T Iqbal C Knoblauch P Simon F Wichern |
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| Affiliation: | 1. Faculty of Life Sciences, Rhine‐Waal University of Applied Sciences, Kleve, Germany;2. Agricultural and Food Engineering Department, Indian Institute of Technology, Karagphur, West Bengal, India;3. Department of Agronomy and Agricultural Extension, Faculty of Agriculture, University of Rajshahi, Rajshahi, Bangladesh |
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| Abstract: | The soil conditioners anionic polyacrylamide (PAM) and dicyandiamide (DCD) are frequently applied to soils to reduce soil erosion and nitrogen loss, respectively. A 27‐day incubation study was set up to gauge their interactive effects on the microbial biomass, carbon (C) mineralization and nitrification activity of a sandy loam soil in the presence or absence of maize straw. PAM‐amended soils received 308 or 615 mg PAM/kg. Nitrogen (N)‐fertilized soils were amended with 1800 mg/kg ammonium sulphate (NH4)2SO4], with or without 70 mg DCD/kg. Maize straw was added to soil at the rate of 4500 mg/kg. Maize straw application increased soil microbial biomass and respiration. PAM stimulated nitrification and C mineralization, as evidenced by significant increases in extractable nitrate and evolved carbon dioxide (CO2) concentrations. This is likely to have been effected by the PAM improving microbial conditions and partially being utilized as a substrate, with the latter being indicated by a PAM‐induced significant increase in the metabolic quotient. PAM did not reduce the microbial biomass except in one treatment at the highest application rate. Ammonium sulphate stimulated nitrification and reduced microbial biomass; the resultant acidification of the former is likely to have caused these effects. N fertilizer application may also have induced short‐term C‐limitation in the soil with impacts on microbial growth and respiration. The nitrification inhibitor DCD reduced the negative impacts on microbial biomass of (NH4)2SO4 and proved to be an effective soil amendment to reduce nitrification under conditions where mineralization was increased by addition of PAM. |
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| Keywords: | Polyacrylamide dicyandiamide microbial biomass mineralization maize straw soil conditioner |
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