Long-term effects of contrasting tillage on soil organic carbon, nitrous oxide and ammonia emissions in a Mediterranean Vertisol under different crop sequences

• DOI: 10.1016/j.scitotenv.2017.11.116
• Publication Date: 2017-11-14T20:06:11Z
• Authors: Giuseppe Badagliacca; Emilio Benítez; Gaetano Amato; Luigi Badalucco; Dario Giambalvo; Vito Armando Laud...; Paolo Ruisi
• Keywords: 2. Zero hunger; No tillage; Mediterranean environment; 04 agricultural and veterinary sciences; 15. Life on land; 6. Clean water; Carbon stocks; 13. Climate action; nosZ gene; Wheat; Greenhouse gas emissions; 0401 agriculture, forestry, and fisheries

This 2-year study aimed to verify whether the continuous application of no tillage (NT) for over 20years, in comparison with conventional tillage (CT), affects nitrous oxide (N2O) and ammonia (NH3) emissions from a Vertisol and, if so, whether such an effect varies with crop sequence (continuous wheat, WW and wheat after faba bean, FW). To shed light on the mechanisms involved in determining N-gas emissions, soil bulk density, water filled pore space (WFPS), some carbon (C) and nitrogen (N) pools, denitrifying enzyme activity (DEA), and nitrous oxide reductase gene abundance (nosZ gene) were also assessed at 0-15 and 15-30cm soil depth. Tillage system had no significant effect on total NH3 emissions. On average, total N2O emissions were higher under NT (2.45kgN2O-Nha-1) than CT (1.72kgN2O-Nha-1), being the differences between the two tillage systems greater in FW than WW. The higher N2O emissions in NT treatments were ascribed to the increased bulk density, WFPS, and extractable organic C under NT compared to CT, all factors that generally promote the production of N2O. Moreover, compared to CT, NT enhanced the potential DEA (114 vs 16μgNkg-1h-1) and nosZ gene abundance (116 vs 69 copy number mg-1 dry soil) in the topsoil. Finally, NT compared to CT led to an average annual increase in C stock of 0.70MgCha-1year-1. Though NT can increase the amount os soil organic matter so storing CO2 into soil, some criticisms related to the increase of N2O emission arise, thereby suggesting the need for defining management strategies to mitigate such a negative effect.