Plant material addition affects soil nitrous oxide production differently between aerobic and oxygen-limited conditions |
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| Institution: | 1. Laboratory of Soil Ecology, College of Resources and Environmental Sciences, Nanjing Agricultural University, Jiangsu 210095, China;2. Department of Soil Science, College of Agriculture and Life Science, North Carolina State University, NC 27695, USA;1. Department of Agricultural Technology and System Analysis, Norwegian Institute of Bioeconomy Research, Box 115, N-1431 Aas, Norway;2. Department of Environmental Science, Norwegian University of Life Science, Box 5003, N-1432 Aas, Norway;1. Landcare Research, Palmerston North, New Zealand;2. Landcare Research, Lincoln, New Zealand;3. AgResearch, Hamilton, New Zealand;1. Hainan Key Laboratory of Tropical Eco-circular Agriculture, National Agricultural Experimental Station for Agricultural Environment, Institute of Environmental and Plant Protection, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China;2. College of Tropical Crops, Hainan University, Haikou 570228, China;3. College of Agriculture, Heilongjiang August First Land Reclamation University, Daqing, Heilongjiang 163319, China;4. Key Laboratory of Cause and Control of Atmospheric Pollution, State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China;5. Institute of Karst Geology, CAGS, Karst Dynamics Laboratory, MLR and Guangxi, Guilin 541004, China;6. International Research Centre on Karst, Under the Auspices of UNESCO, Guilin 541004, China;1. Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing, Jiangsu 210014, People''s Republic of China;2. Laboratory for Agricultural Wastes Treatment and Recycling, Circular Agriculture Research Center, Jiangsu Academy of Agricultural Sciences, Nanjing, Jiangsu 210014, People''s Republic of China;3. State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210023, People''s Republic of China;4. Soil and Water Science Department, University of Florida, Gainesville, FL 32611, United States;1. University of Rostock, Agricultural and Environmental Faculty, Grassland and Fodder Sciences, Justus-von-Liebig-Weg 6, Rostock, Germany;2. University of Hannover, Institute of Microbiology, Herrenhäuser Str. 2, 30419 Hannover, Germany;3. Thuenen Institute of Climate-Smart Agriculture, Bundesallee 65, 38116 Braunschweig, Germany;4. Department of Plant Ecology (IFZ), Justus Liebig University Giessen, Heinrich-Buff-Ring 26, Germany;5. School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland;6. Wageningen University & Research, Environmental Research, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands |
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| Abstract: | It is a common agricultural practice for crop residues to be plowed into the soil or left on the soil surface. Soil addition of crop residues can considerably modify soil microbial activity and net N mineralization, and in general such modifications are negatively related to the C:N ratios of crop residues. Yet, little is known on the impacts of crop residues of different C:N ratios on soil nitrous oxide (N2O) production under different aeration conditions via nitrification and denitrification. In this study, an 84-day laboratory incubation was conducted under aerobic and O2-limited conditions and soil N2O production was measured every 3 days after the addition of plant materials with a wide range of C:N ratios from 14 to 297. Two aerobic conditions were created by adjusting the water content of soil at a bulk density of 1.1 g cm?3 to 30% water-filled pore space (WFPS) and 60% WFPS, and two O2-limited conditions were made by 90% WFPS and fluctuation between 90% and 30% WFPS. Each fluctuation cycle lasted 9 days and soil water content was readjusted to 90% WFPS at the end of each cycle. We also measured microbial respiration activity and net N mineralization periodically (i.e., 3, 7, 14, 28, 42, 56, 70, and 84 days) during the incubation and microbial biomass C at the end of incubation. At aerobic conditions, soil amendments of plant materials, regardless of their C:N ratios, all enhanced soil N2O production. However, net N mineralization was dependent on plant material C:N ratios, being significantly higher or lower than the control for C:N ratios ～15 and C:N ratios ≥44, respectively. Such inconsistent responses indicated that nitrifiers mediating nitrification and therefore byproduct N2O production could strongly compete with heterotrophic microbes for NH4+ and therefore net N mineralization was not a good predictor for nitrification-associated N2O production. Interestingly, plant material additions reduced soil N2O production by up to ～95% at O2-limited conditions, perhaps due to NO3? limitation. Soil NO3? production via nitrification could be low at O2-limited conditions, and soil NO3? availability could be further reduced due to increases in microbial biomass and thus microbial N assimilation after plant material additions. This NO3? limitation might enhance N2O reduction to N2, by which denitrifiers could harvest more energy from the consumption of limited NO3?. Nonetheless, our results revealed contrasting differences in N2O production between aerobic and O2-limited conditions following soil amendments of plant materials. |
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