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Seasonal N2O emissions respond differently to environmental and microbial factors after fertilization in wheat–maize agroecosystem

Author:
Dong, Zhixin, Zhu, Bo, Jiang, Yan, Tang, Jialiang, Liu, Wenli, Hu, Lei
Source:
Nutrient cycling in agroecosystems 2018 v.112 no.2 pp. 215-229
ISSN:
1385-1314
Subject:
Archaea, agroecosystems, ammonia monooxygenase, ammonium, biogeochemistry, cropland, denitrification, gene dosage, genes, greenhouse gas emissions, least squares, microorganisms, models, nitrate reductase, nitrates, nitrite reductase, nitrous oxide, nitrous-oxide reductase, oxidants, seasonal variation, soil, swine, temperature
Abstract:
Biogeochemical processes regulating cropland soil nitrous oxide (N₂O) emissions are complex, and the controlling factors need to be better understood, especially for seasonal variation after fertilization. Seasonal patterns of N₂O emissions and abundances of archaeal ammonia monooxygenase (amoA), bacterial amoA, nitrate reductase (narG), nitrite reductase (nirS/nirK), and nitrous oxide reductase (nosZ) genes in long-term fertilized wheat–maize soils have been studied to understand the roles of microbes in N₂O emissions. The results showed that fertilization greatly stimulated N₂O emission with higher values in pig manure-treated soil (OM, 2.88 kg N ha⁻¹ year⁻¹) than in straw-returned (CRNPK, 0.79 kg N ha⁻¹ year⁻¹) and mineral fertilizer-treated (NPK, 0.90 kg N ha⁻¹ year⁻¹) soils. Most (52.2–88.9%) cumulative N₂O emissions occurred within 3 weeks after fertilization. Meanwhile, N₂O emissions within 3 weeks after fertilization showed a positive correlation with narG gene copy number and a negative correlation with soil NO₃⁻ contents. The abundances of narG and nosZ genes had larger direct effects (1.06) than ammonium oxidizers (0.42) on N₂O emissions according to partial least squares path modeling. Stepwise multiple regression also showed that log narG was a predictor variable for N₂O emissions. This study suggested that denitrification was the major process responsible for N₂O emissions within 3 weeks after fertilization. During the remaining period of crop growth, insufficient N substrate and low temperature became the primary limiting factors for N₂O emission according to the results of the regression models.
Agid:
6163718