“…Compared with the spring thaw period in 2011/2012, soil moisture was higher in 2012/2013 and 2013/2014 (Fig. b) due to more snow melting water and the legacy effect of the extreme rainfall in summer 2013 (Chen et al ., ), respectively. Accordingly, Rs and Rh were less responsive to N fertilization during the nongrowing season of 2012/2013 and 2013/2014 than 2011/2012.…”
26Extreme precipitation is predicted to be more frequent and intense accompanying global 27 warming, and may have profound impacts on soil respiration (Rs) and its components, i.e., 28 autotrophic (Ra) and heterotrophic (Rh) respiration. However, how natural extreme rainfall or 29 snowfall events affect these fluxes are still lacking, especially under nitrogen (N) fertilization.
30In this study, extreme rainfall and snowfall events occurred during a 3-year field experiment,
“…Compared with the spring thaw period in 2011/2012, soil moisture was higher in 2012/2013 and 2013/2014 (Fig. b) due to more snow melting water and the legacy effect of the extreme rainfall in summer 2013 (Chen et al ., ), respectively. Accordingly, Rs and Rh were less responsive to N fertilization during the nongrowing season of 2012/2013 and 2013/2014 than 2011/2012.…”
26Extreme precipitation is predicted to be more frequent and intense accompanying global 27 warming, and may have profound impacts on soil respiration (Rs) and its components, i.e., 28 autotrophic (Ra) and heterotrophic (Rh) respiration. However, how natural extreme rainfall or 29 snowfall events affect these fluxes are still lacking, especially under nitrogen (N) fertilization.
30In this study, extreme rainfall and snowfall events occurred during a 3-year field experiment,
“…The harvested tobacco plant was separated into root washed with water, stem, and leaf, and then, the biomass of each part was weighed after drying at 105°C for 30 min, subsequently at 75°C for 72 h. Each dried part was then ground and sieved to < 2 mm. After H 2 SO 4 -H 2 O 2 digestion, the content of plant nitrogen, phosphorus, and potassium was determined by Kjeldahl, vanadium molybdate yellow colorimetric, and flame photometry method, respectively (Chen et al 2016;Lu 2000).…”
Section: Physical-chemical Analysis Of Soils and Plantmentioning
The purpose of this study was to investigate the response of physicochemical properties of tobacco-growing soils and N/P/K accumulation of tobacco plant to tobacco straw biochar. Two contrasting tobacco-growing soils of paddy soil (Ultisol in USDA taxonomy) and brown soil (Alfisol in USDA taxonomy) were selected to conduct the pot experiments. Five addition rates (w/w) of tobacco straw biochar of 0%, 1%, 2%, 4%, and 10% without or with tobacco (Nicotiana tabacum) were applied in a greenhouse. The 7.41-35.90% increase of soil field capacity, 0.71-15.11% increase of total porosity, 3.40-17.55% increase of capillary porosity, 15.98-293.13% increase of organic matter, 6.52-58.75% increase of available phosphorus, 109.07-1789.70% increase of potassium, 3.23-147.71% increase of exchangeable cation, and 12.13-48.48% increase of soil pH were observed after biochar addition. And this improvement increased with the increasing application rate. The same trend was also found in the tobacco N/P/K uptake in the biochar application range of 0-4% and subsequently decreased at 10% rate. Meanwhile, biochar decreased the soil bulk density of 0.68-14.06%. The step regression equation showed that the exchangeable potassium and aluminum for Ultisol as well as the exchangeable potassium and hydrogen for Alfisol were the predominant factors that determined the soil pH. According to the PCA results, exchangeable calcium > exchangeable potassium > exchangeable cation > pH > organic matter > exchangeable magnesium > available potassium > available phosphorus and organic matter > exchangeable potassium > available phosphorus > exchangeable cation > available potassium > pH > exchangeable calcium had a significant impact on soil fertility of Ultisol and Alfisol, respectively. Finally, a comprehensive evaluation of soil fertility by PCA revealed that ST10 (10% rate, w/w) performed best, followed by the ST4 (4% rate, w/w) in both soils. The application of tobacco straw biochar, with appropriate rate, is an effect method to improve physicochemical properties of tobacco-growing soil and N/P/ K uptake of tobacco plant.
“…Laboratory experiment conducted by Chen et al . 41 showed that, after freezing at −25 °C for 7d, water extracts of arable soil at 20% WFPS had a significant higher DOC concentration and lower SUVA 280 value compared to the soil at 80% WFPS. Hence, the amount and bioavailability of DOM released into the soil after frost under low moisture conditions was dependent on soil types, the degree of soil drying and freezing conditions.Figure 6Comparison plots of humification index versus ( a ) fluorescence index and ( b ) biological index for water extracts of forest soils during thaw, together with different DOM data refering to results from Fernández-Romero et al .…”
There are large amounts of dissolved organic matter (DOM) released into the soil during spring thaw, but its bioavailability and components are still unknown. The quantity, composition and stability of DOM in water extracts of forest soils during thaw were studied after two-month freezing with 9 levels of soil moisture ranging from 10% to 90% water-filled pore space (WFPS), by measuring soil carbon dioxide (CO2) flux, biodegradable dissolved organic carbon (BDOC) and nitrogen (BDON), ultraviolet absorbance and parallel factor analysis of fluorescence excitation-emission matrices. Concentrations of BDOC, BDON, DOC and DON were lowest around 30% WFPS and relatively higher and lower soil moisture both increased DOM and BDOM concentrations in thawing soil. With increasing WFPS, the dominant component of soil DOM changed from humic acid-like substances to fulvic acid-like substances and the biological origin of DOM increased gradually. The protein-like component accounted for 8–20% of soil DOM and was affected by vegetation type and WFPS singly and interactively. The results implied that forest soils with more than 50% WFPS before winter freezing could release large amounts of fulvic acid-like DOM, which would be easily biodegraded and emitted as CO2 or run off with ground water during spring snow thaw.
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