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[Display omitted] • Soil N-oxide fluxes showed high spatiotemporal variability in tea plantations. • N-oxide emissions from soils between rows were higher than those under the canopy. • Factors regulating N-oxide emissions were different between tea plantations. • Acidic tea plantations are hotspots of N-oxide emissions in subtropical regions. Subtropical agricultural soils are hotspots of nitrogen(N)-oxide emissions, whereas the spatiotemporal variability and driving factors of their emissions in different cultivation systems are poorly understood. Here, to assess the magnitude and pattern of soil N-oxide emissions, we conducted measurements of nitrous oxide (N 2 O) and nitric oxide (NO) fluxes from the soil between rows and under the canopy of tea plants in two subtropical tea plantations over a one-year period. Results showed that N 2 O and NO emissions from the soil between rows were 32.6 and 9.1 kg N ha−1 for the Yixing (YX) site and 33.9 and 9.9 kg N ha−1 for the Jurong (JR) site, respectively. Across both sites, N 2 O and NO emissions from the soil between rows were 2.8–5.2 and 1.4–4.0 times, respectively, larger than those from the soil under the canopy. We attributed greater N-oxide emissions from the soil between rows mainly to increased soil mineral N and water contents as compared to the soil under the canopy. On average, N 2 O and NO emissions from the soil under the canopy accounted for 36% and 44% of the total losses from the entire field, respectively. For the entire tea field, N 2 O emissions were 12.6 and 15.7 kg N ha−1 for the YX and JR sites, respectively, but the difference was not statistically different. In contrast, NO emissions from the YX and JR sites were 3.8 and 5.7 kg N ha−1 and differed significantly between the two sites, which was due to higher NO emissions from the soil under the canopy in the JR site. The greatest N-oxide fluxes occurred in the spring and summer seasons after topdressing when soil conditions were conducive to microbial N-oxide production. The structural equation modeling analyses suggested that the variables explaining the variances of soil N-oxide emissions were different between the two tea plantations. Our results indicated that microbial nitrification and abiotic chemodenitrification processes were likely the major pathways leading to N-oxide emissions in the soil under the canopy. Our findings highlight the importance of N-oxide fluxes simultaneously taken from the soil between rows and under the canopy and implementing mitigation practices in subtropical tea plantations. [ABSTRACT FROM AUTHOR]

• Synthetic N fully replaced with composted manure reduced N-oxide emissions. • Bio-organic fertilizer application had the lowest yield-scaled N-oxide emission. • Soil N-oxide emissions were relevant during the fallow period. In order to reduce soil and environmental quality degradation associated with the use of synthetic nitrogen (N), substituting chemical fertilizer with organic or bio-organic fertilizer has become an increasingly popular option. However, components of this fertilizer strategy related to mitigation of soil N-oxide emissions and maintenance of crop yield remain uncertain. Here, we evaluated the effects of three different fertilizer strategies, with equal amounts of N, on nitrous oxide (N 2 O) and nitric oxide (NO) emissions, vegetable yield, and yield-scaled N 2 O and NO emissions under three consecutive cucumber growing seasons. The three treatments were chemical fertilizer (NPK, urea), organic fertilizer (O, composted cattle manure), and bio-organic fertilizer (O + T, O combined with Trichoderma.spp). Results showed that the NPK plot had the highest area-scaled emissions of N 2 O (13.1 ± 0.48 kg N ha−1 yr−1) and NO (5.01 ± 0.34 kg N ha−1 yr−1), which were 1.3–1.4 and 3.1–3.7 times greater than the O and O + T plots, respectively. The annual direct emission factors for N 2 O and NO were 2.08% and 0.92% for the NPK plot, which declined to 1.34% and 0.09% in the O plot, and 1.12% and 0.03% in the O + T plot, respectively. The annual vegetable yield was 117 ± 2.9 t ha−1 for NPK plot and 122 ± 2.0 t ha−1 for O + T plot, which was higher than 111 ± 1.7 t ha−1 for O plot. The yield-scaled N 2 O + NO emissions differed significantly with fertilization treatment, with the lowest value observed in the O + T plot. We attributed the lower soil N-oxide emissions following organic fertilizer application to the slow release of available N and enhanced denitrification caused by the increase of soil dissolved organic carbon and pH. Compared with the use of organic fertilizer alone, the addition of Trichoderma.spp significantly increased the potential denitrification rate but decreased N 2 O emissions, which may have promoted the reduction of N 2 O to N 2. Therefore, our results suggest that adopting composted organic fertilizer mixtures with microbial inoculants could be a win-win practice to mitigate gaseous N losses and simultaneously improve crop yield in intensively managed vegetable cropping systems. [ABSTRACT FROM AUTHOR]

Are desert ecosystems a stable sink for atmospheric CO 2 ? Although the uptake of atmospheric CO 2 by soil during the nighttime is detected in deserts and some semi-deserts, the underlying mechanisms remain elusive. In order to determine the factors affecting the CO 2 fluxes into soil and to reveal the relationship between CO 2 fluxes and carbonate formation and recrystallization in saline and alkaline soils, four soils with contrasting salinity from two sites, Aksu and Yingbazar, along the Tarim River were analysed. Soils were incubated in 14 CO 2 labelled atmosphere for 90 days at three CO 2 concentrations: 0.04%, 0.4% and 4%. The 14 C activity was measured in soil water and air, as well as in carbonates after 2, 14 and 90 days. The 14 C incorporation in CaCO 3 increased with corresponding 14 C decrease remaining in the CO 2 . The highest 14 C incorporation into CaCO 3 (54%) was observed in the Yingbazar saline soil. The carbonate recrystallization rates increased logarithmically (r 2 > 0.97) with the CO 2 concentration. The average carbonate recrystallization rate from three sampling times was highest in the Yingbazar saline soil under 4% CO 2 (8.45 × 10 − 6 day − 1 ) and lowest in the Aksu alkaline soil under 0.04% CO 2 (0.03 × 10 − 6 day − 1 ). The average carbonate recrystallization rate increased with electric conductivity (corresponding to soil salinity) but decreased with pH ( R 2 = 0.99 for 4% CO 2 ). The alkaline soils incorporated less 14 C into CaCO 3 than the saline soils. At the highest CO 2 concentration of 4%, the full recrystallization period of the remaining primary carbonates was 10- to 100-fold shorter than at the lower CO 2 concentrations. Therefore, besides soil chemical parameters (e.g. pH, CaCO 3 content), CO 2 concentration (respiration of microorganisms and roots) is an important factor for CaCO 3 recrystallization and formation of pedogenic carbonates in desert soils. It is the most important factor for CaCO 3 recrystallization and so, for the formation of pedogenic carbonates. [ABSTRACT FROM AUTHOR]