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1.
Nitric oxide (NO) and nitrous oxide (N2O) emissions were measured from experimental dung and urine patches placed on boreal pasture soil during two growing seasons and one autumn period until soil freezing. N2O emissions in situ were studied by a static chamber method. NO was measured with a dynamic chamber method using a NO analyser in situ. Mean emissions from the control plots were 47.6±4.5 μg N2ON m−2 h−1 and 12.6±1.6 μg NON m−2 h−1. N2O and NO emissions from urine plots (132±21.2 μg N2ON m−2 h−1 and 51.9±7.6 μg NON m−2 h−1) were higher than those from dung plots (110.0±20.1 μg N2ON m−2 h−1 and 14.7±2.1 μg NON m−2 h−1). There was a large temporal variation in N2O and NO emissions. Maximum N2O emissions were measured a few weeks after dung or urine application, whereas the maximum NO emissions were detected the following year. NO was responsible on average 14% (autumn) and 34% (summer) of total (NO+N2O)N emissions from the pasture soil. NO emissions increased with increasing soil temperature and with decreasing soil moisture. N2O emissions increased with increasing soil moisture, but did not correlate with soil temperature. Therefore we propose that N2O and NO were produced mainly during different microbial processes, i.e., nitrification and denitrification, respectively. The results show that the overall conditions and mechanism especially for emissions of NO are still poorly understood but that there are differences in the mechanisms regulating N2O and NO production.  相似文献   

2.
Carbon dioxide, water vapour and energy fluxes were measured above and within a maritime pine forest during an atypical year with long-lasting reduced soil water availability. Energy balance closure was adequately good at both levels. As compared with what is usually observed at this site the ecosystem dissipated less energy via latent heat flux and more via sensible heat flux. The understorey canopy was responsible for a variable, significant component of the whole canopy fluxes of water vapour and carbon dioxide. The annual contribution of the understorey was 38% (154 mm) of the overall evaporation (399 mm) and 32% (89 mm) of the overall sensible heat flux (274 mm). The participation of the understorey reached 45% of the overall evaporation and 30% of the daytime overall assimilation during significant soil water deficit periods in summertime. Even during winter, understorey photosynthesis was consistent as it compensated soil and understorey respiration. The ecosystem behaved as a sink of carbon, with a negative annual carbon budget (−57 g C m−2). However, due to high soil water deficit, the annual ecosystem GPP was 40% less than usually observed at this site. This budget resulted from a sink of −131 g C m−2 for the overstorey and a source of +74 g C m−2 for the understorey. Moreover, on an annual basis the overstorey layer contributed to almost two-thirds of the ecosystem respiration. Finally, the effect of long-lasting soil water deficit on the maritime pine forest was found more important than the effect of the heat wave and drought of summer 2003.  相似文献   

3.
Abstract

Seedlings of nine different conifers were exposed to 355 and 730 μmol mol-1 CO2, or low (> 15 nmol mol?1) and elevated 03 concentration (70 nmol mol?1) for 81–116 days. The experiments were conducted in growth chambers placed in a greenhouse. Increased CO2 concentration enhanced the mean relative growth rate (RGR) and total plant dry weight by 4 and 33% in Larix leptolepis, by 4 and 38% in Larix sibirica, by 7 and 47% in Picea glauca and by 3 and 16% in Picea sitchensis, respectively. The growth rates and dry weights of Pimis contorta, Pinus mugo and Pseudotsuga menziesii were not significantly affected. Carbon dioxide enrichment enhanced RGR of two provenances of Picea abies by 4 and 6%, respectively, while a third provenance was unaffected. In Pimis sylvestris, only the RGR of one of three provenances was stimulated by CO2 enrichment (4%).

After two growth seasons CO2 enrichment enhanced RGR and total plant dry weight by 11 and 35% in Picea abies and by 12 and 36% in Pinus sylvestris, respectively. Elevated CO2 decreased the shoot:root ratio in Larix leptolepis, and decreased the needlerstem ratio in Picea glauca, but increased it in Pseudotsuga menziesii.

Elevated O3 significantly decreased the plant dry weight in Picea sitchensis, Pseudotsuga menziesii and in one of three provenances of Pinus sylvestris, while the other species and provenances were unaffected. Increased O3 concentration increased the shoot:root dry weight ratio in one of three Picea abies provenances, in all three Pinus sylvestris provenances and in Pinus contorta. The needle:stem ratio was enhanced by O3 in seven of the nine species. The O3 exposure caused chlorosis of needles in all species except Pseudotsuga menziesii.  相似文献   

4.
Soil heterotrophic respiration fluxes at plot scale exhibit substantial spatial and temporal variability. Within this study secondary information was used to spatially predict heterotrophic respiration. Chamber-based measurements of heterotrophic respiration fluxes were repeated for 15 measurement campaigns within a bare 13 × 14 m2 soil plot. Soil water contents and temperatures were measured simultaneously with the same spatial and temporal resolution. Further, we used measurements of soil organic carbon content and apparent electrical conductivity as well as the prior measurement of the target variable. The previous variables were used as co-variates in a stepwise multiple linear regression analysis to spatially predict bare soil respiration. In particular the prior measurement of the target variable, the soil water content and the apparent electrical conductivity, showed a certain, even though limited, predictive power. In the first step we applied external drift kriging and regression kriging to determine the improvement of using co-variates in an estimation procedure in comparison to ordinary kriging. The improvement using co-variates ranged between 40 and 1% for a single measurement campaign. The difference in improving the prediction of respiration fluxes between external drift kriging and regression kriging was marginal. In a second step we applied sequential Gaussian simulations conditioned with external drift kriging to generate more realistic spatial patterns of heterotrophic respiration at plot scale. Compared to the estimation approaches the conditional stochastic simulations revealed a significantly improved reproduction of the probability density function and the semivariogram of the original point data.  相似文献   

5.
Digestates vary in composition and studies regarding their impact on C and N dynamics in soils are scarce. The objective was to analyse the C and N dynamics of digestates originating from various substrates applied to a sandy Cambisol and a silty Anthrosol. In three laboratory experiments (4–6 weeks), the effects of digestate properties, N rate and water content were tested. Averaged over both soils, 21% of the C supplied was emitted as CO2. Potential NH3 emissions during the first week ranged between 6% and 12% of NH4+ present in the digestates. The emission factors in the sandy Cambisol were on average 1.2 and 2 times higher for CO2 and potential NH3, respectively, compared to the silty Anthrosol. Similarly, net nitrogen mineralization in the sandy Cambisol was approximately twice the N mineralized in the silty Anthrosol. Net nitrification was not influenced by soil texture or different digestates, but increased with increasing application rates and had highest values at 75% of water holding capacity. Our results indicate that the type of substrate input for anaerobic digestion influences the properties of the digestate and therefore the dynamics of C and N. However, soil texture can affect these dynamics markedly.  相似文献   

6.
A two-year study in a typical red soil region of Southern China was conducted to determine 1) the dry deposition velocity (Vd) for SO2 and particulate SO4^2- above a broadleaf forest, and 2) atmospheric sulfur fluxes so as to estimate the contribution of various fractions in the total. Using a resistance model based on continuous hourly meteorological data, atmospheric dry sulfur deposition in a forest was estimated according to Va and concentrations of both atmospheric SO2 and particulate SO2^4-. Meanwhile, wet S deposition was estimated based on rainfall and sulfate concentrations in the rainwater. Results showed that about 99% of the dry sulfur deposition flux in the forest resulted from SO2 dry deposition.In addition, the observed dry S deposition was greater in 2002 than in 2000 because of a higher average concentration of SO2 in 2002 than in 2000 and not because of the average dry deposition velocity which was lower for SO2 in 2002. Also,dry SO2 deposition was the dominant fraction of deposited atmospheric sulfur in forests, contributing over 69% of the total annual sulfur deposition. Thus, dry SO2 deposition should be considered when estimating sulfur balance in forest ecological systems.  相似文献   

7.
Abstract

Accurate estimates of soybean root productivity are needed to estimate carbon (C) inputs to soil. Soil excavation and coring methods were compared where soybean was subject to ambient, elevated carbon dioxide (CO2) and ozone (O3) treatments. We evaluated within‐season changes in biomass and shoot–root production, labor requirements, and damage to plots. Estimates of root biomass were similar, but excavation‐based estimates required less total time. Core‐based estimates provided similar levels of precision, allowed sampling of deeper depths, and reduced both plot disturbance and the amount of effort devoted to tasks performed in the field. Correlations between root and shoot biomass were weak and varied with time of sampling. Collectively, results suggest caution should be exercised when making predictions about C allocation to roots or soils based on shoot–root ratios or when scaling up field‐based findings to predict larger or longer‐scale trends.  相似文献   

8.
The effects of NO2 and O3 exposure alone or in combination were investigated with respect to the amino acid content and composition in kidney bean. The short-term exposure (up to 8 h) to NO2 at a concentration of 4.0 ppm alone or in combination with O3 at a concentration of 0.4 ppm induced a rapid increase in the total amino acid content among which glutamine accounted for most of the part. Total amino acid content was also increased by O3 exposure at 0.4 ppm after 2 hours’ lag period. Ammonium level became higher in the case of combined exposure to NO2 and O3, while it remained constant in the case of exposure to NO2 and O3 alone.

When the exposure period was extended to 2 to 7 days (long-term exposure), the increase in the content of the total amino acids was observed in most of treatments. Roots of the plants exposed to various concentrations of NO2 and O3 showed the most remarkable increase in the content of total amino acids. Asparagine, in place of glutamine, became a major amino acid. The percentage of asparagine was especially increased by the mixed exposure to NO2 and O3 These results indicate that glutamine which accumulates considerably in the early phase of the gas exposure (short-term exposure) seems to be gradually converted into other amino acids, mainly asparagine.

The correlation between the content of each amino acid, ammonium and total amino acids was calculated using data from the above experiment. Most of the amino acids in the primary and trifoliate leaves showed a high correlation with the total amino acids, suggesting that the changes in the amount of total amino acids caused by the air pollutants may be reflected not only by a particular amino acid, but also by an individual amino acid composing soluble metabolite pool. A high correlation was obtained among amino acids belonging to the serine family such as glYCine, serine, and cysteine.  相似文献   

9.
10.
Most soil respiration measurements are conducted during the growing season. In tundra and boreal forest ecosystems, cumulative winter soil CO2 fluxes are reported to be a significant component of their annual carbon budgets. However, little information on winter soil CO2 efflux is known from mid-latitude ecosystems. Therefore, comparing measurements of soil respiration taken annually versus during the growing season will improve the accuracy of ecosystem carbon budgets and the response of soil CO2 efflux to climate changes. In this study we measured winter soil CO2 efflux and its contribution to annual soil respiration for seven ecosystems (three forests: Pinus sylvestris var. mongolica plantation, Larix principis-rupprechtii plantation and Betula platyphylla forest; two shrubs: Rosa bella and Malus baccata; and two meadow grasslands) in a forest-steppe ecotone, north China. Overall mean winter and growing season soil CO2 effluxes were 0.15-0.26 μmol m−2 s−1 and 2.65-4.61 μmol m−2 s−1, respectively, with significant differences in the growing season among the different ecosystems. Annual Q10 (increased soil respiration rate per 10 °C increase in temperature) was generally higher than the growing season Q10. Soil water content accounted for 84% of the variations in growing season Q10 and soil temperature range explained 88% of the variation in annual Q10. Soil organic carbon density to 30 cm depth was a good surrogate for SR10 (basal soil respiration at a reference temperature of 10 °C). Annual soil CO2 efflux ranged from 394.76 g C m−2 to 973.18 g C m−2 using observed ecosystem-specific response equations between soil respiration and soil temperature. Estimates ranged from 424.90 g C m−2 to 784.73 g C m−2 by interpolating measured soil respiration between sampling dates for every day of the year and then computing the sum to obtain the annual value. The contributions of winter soil CO2 efflux to annual soil respiration were 3.48-7.30% and 4.92-7.83% using interpolated and modeled methods, respectively. Our results indicate that in mid-latitude ecosystems, soil CO2 efflux continues throughout the winter and winter soil respiration is an important component of annual CO2 efflux.  相似文献   

11.
Abstract

The availability of soil Mn to corn in relation to extractability of soil Mn by EDTA, Mg(NO3)2, CH3COONH4, hydroquinone, H3PO4, and NH4H2PO4 as affected by liming was evaluated under field conditions on a single soil type. EDTA, Mg(NO3)2 and CH3COONH4‐extractable Mn were related inversely to available Mn. No useful relationships were found between hydroquinone, H3PO4, and NH4H2PO4‐extractable soil Mn and Mn uptake by sweet corn.  相似文献   

12.
Open-path gas analyzers are popular in eddy covariance flux measurements of trace gasses (i.e. CO2). The quality of the data, however, may be influenced by several factors. Exposure in an outdoor environment invariably causes the instrument to become colder or warmer than the air temperature. Instruments with internal temperature regulation and/or from heat generated by active electrical components can also influence the sensor temperature. In addition, sensors can have condensation problems on their optical windows thus affecting the quality of the measurement. Unreasonable measurements have been widely discussed, especially in moist, high-latitude regions. As this is a very important research problem facing flux studies, we examined how wetness (dew and raindrops) on the surface of the focus lens of the popular LI-COR LI-7500 infrared gas analyzer may affect flux measurements from the open-path eddy-covariance system. Field experiments showed that additional sensor heating may inhibit dew formation yet greatly improve the quality of flux measurements. A detailed energy balance approach was used to model the gas analyzer window temperature under environmental conditions and dew effect through a pair of LI-COR LI-7500, with and without heat treatment, in a grassland ecosystem in the Netherlands. With the proposed model, existing datasets can be filtered for dew events. Data from three different flux measurement sites were then used to assess the magnitude of dew effects on longer time-scales; 2 years from the Netherlands and 3 weeks of data from an arid coastal desert. About 30% of the measurements were affected by dew in the grassland area versus 4% in the arid region during the dry season. Sensor heating suppresses dew formation but might lead to errors in trace gas fluxes evaluated over long periods, thus we analyzed how sensor heating or cooling affects trace gas flux measurements. Additions to a recent (2006) correction and application to a horizontally and vertically oriented LI-COR LI-7500 are presented as they deal with sensor heating problems in eddy-covariance systems. The sensor energy balance model, together with the proposed modified sensor heating corrections, were used to estimate sensor temperature effects on long-term scale CO2 flux measurements and showed that additional heating does affect the turbulent trace gas CO2 fluxes but is very minor, especially for a horizontally mounted LI-COR LI-7500 gas analyzer. Further efforts are urgently needed to improve the data quality and quality of flux measurements.  相似文献   

13.
Soil respiration represents the integrated response of plant roots and soil organisms to environmental conditions and the availability of C in the soil. A multi-year study was conducted in outdoor sun-lit controlled-environment chambers containing a reconstructed ponderosa pine/soil-litter system. The study used a 2×2 factorial design with two levels of CO2 and two levels of O3 and three replicates of each treatment. The objectives of our study were to assess the effects of long-term exposure to elevated CO2 and O3, singly and in combination, on soil respiration, fine root growth and soil organisms. Fine root growth and soil organisms were included in the study as indicators of the autotrophic and heterotrophic components of soil respiration. The study evaluated three hypotheses: (1) elevated CO2 will increase C assimilation and allocation belowground increasing soil respiration; (2) elevated O3 will decrease C assimilation and allocation belowground decreasing soil respiration and (3) as elevated CO2 and O3 have opposing effects on C assimilation and allocation, elevated CO2 will eliminate or reduce the negative effects of elevated O3 on soil respiration. A mixed-model covariance analysis was used to remove the influences of soil temperature, soil moisture and days from planting when testing for the effects of CO2 and O3 on soil respiration. The covariance analysis showed that elevated CO2 significantly reduced the soil respiration while elevated O3 had no significant effect. Despite the lack of a direct CO2 stimulation of soil respiration, there were significant interactions between CO2 and soil temperature, soil moisture and days from planting indicating that elevated CO2 altered soil respiration indirectly. In elevated CO2, soil respiration was more sensitive to soil temperature changes and less sensitive to soil moisture changes than in ambient CO2. Soil respiration increased more with days from planting in elevated than in ambient CO2. Elevated CO2 had no effect on fine root biomass but increased abundance of culturable bacteria and fungi suggesting that these increases were associated with increased C allocation belowground. Elevated CO2 had no significant effect on microarthropod and nematode abundance. Elevated O3 had no significant effects on any parameter except it reduced the sensitivity of soil respiration to changes in temperature.  相似文献   

14.
A new principle for measuring soil CO2 efflux at constant ambient concentration is introduced. The measuring principle relies on the continuous absorption of CO2 within the system to achieve a constant CO2 concentration inside the soil chamber at ambient level, thus balancing the amount of CO2 entering the soil chamber by diffusion from the soil. We report results that show reliable soil CO2 efflux measurements with the new system. The novel measuring principle does not disturb the natural gradient of CO2 within the soil, while allowing for continuous capture of the CO2 released from the soil. It therefore holds great potential for application in simultaneous measurements of soil CO2 efflux and its δ13C, since both variables show sensitivity to a distortion of the soil CO2 profile commonly found in conventional chamber techniques.  相似文献   

15.
After implementation of legislative measures for the reduction of environmental hazards from nitrate leaching and ammonia volatilisation when using organic manures and fertilizers in Europe, much attention is now paid to the specific effects of these fertilizers on the dynamics of global warming-relevant trace gases in soil. Particularly nitrogen fertilizers and slurry from animal husbandry are known to play a key role for the CH4 and N2O fluxes from soils. Here we report on a short-term evaluation of trace gas fluxes in grassland as affected by single or combined application of mineral fertilizer and organic manure in early spring. Methane fluxes were characterised by a short methane emission event immediately after application of cattle slurry. Within the same day methane fluxes returned to negative, and on average over the 4-day period after slurry application, only a small but insignificant trend to reduced methane oxidation was found. Nitrous oxide emissions showed a pronounced effect of combined slurry and mineral fertilizer application. In particular fresh cattle slurry combined with calcium ammonium nitrate (CAN) mineral fertilizer induced an increase in mean N2O flux during the first 4 days after application from 10 to 300 μg N2O-N m−2 h−1. 15N analysis of emitted N2O from 15N-labelled fertilizer or manure indicated that easily decomposable slurry C compounds induced a pronounced promotion of N2O-N emission derived from mineral CAN fertilizer. Fluxes after application of either mineral fertilizer or slurry alone showed an increase of less than 5-fold. The NOx sink strength of the soil was in the range of −6 to −10 μg NOx-N m−2 h−1 and after fertilization it showed a tendency to be reduced by no more than 2 μg NOx-N m−2 h−1, which was a result of both, increased NO emission and slightly increased NO2 deposition. Associated determination of the N2O:N2 emission ratio revealed that after mineral N application (CAN) a large proportion (c. 50%) was emitted as N2O, while after application of slurry with easily decomposable C and predominantly -N serving as N-source, the N2O:N2 emission ratio was 1:14, i.e. was changed in favour of N2. Our work provides evidence that particularly the combination of slurry and nitrate-containing N fertilizers gives rise to considerable N2O emissions from mineral fertilizer N pool.  相似文献   

16.
Soil respiration is an important component of terrestrial carbon cycling and can be influenced by many factors that vary spatially. This research aims to determine the extent and causes of spatial variation of soil respiration, and to quantify the importance of scale on measuring and modeling soil respiration within and among common forests of Northern Wisconsin. The potential sources of variation were examined at three scales: [1] variation among the litter, root, and bulk soil respiration components within individual 0.1 m measurement collars, [2] variation between individual soil respiration measurements within a site (<1 m to 10 m), and [3] variation on the landscape caused by topographic influence (100 m to 1000 m). Soil respiration was measured over a two-year period at 12 plots that included four forest types. Root exclusion collars were installed at a subset of the sites, and periodic removal of the litter layer allowed litter and bulk soil contributions to be estimated by subtraction. Soil respiration was also measured at fixed locations in six northern hardwood sites and two aspen sites to examine the stability of variation between individual measurements. These study sites were added to an existing data set where soil respiration was measured in a random, rotating, systematic clustering which allowed the examination of spatial variability from scales of <1 m to 100+ m. The combined data set for this area was also used to examine the influence of topography on soil respiration at scales of over 1000 m by using a temperature and moisture driven soil respiration model and a 4 km2 digital elevation model (DEM) to model soil moisture. Results indicate that, although variation of soil respiration and soil moisture is greatest at scales of 100 m or more, variation from locations 1 m or less can be large (standard deviation during summer period of 1.58 and 1.28 μmol CO2 m−2 s−1, respectively). At the smallest of scales, the individual contributions of the bulk soil, the roots, and the litter mat changed greatly throughout the season and between forest types, although the data were highly variable within any given site. For scales of 1-10 m, variation between individual measurements could be explained by positive relationships between forest floor mass, root mass, carbon and nitrogen pools, or root nitrogen concentration. Lastly, topography strongly influenced soil moisture and soil properties, and created spatial patterns of soil respiration which changed greatly during a drought event. Integrating soil fluxes over a 4 km2 region using an elevation dependent soil respiration model resulted in a drought induced reduction of peak summer flux rates by 37.5%, versus a 31.3% when only plot level data was used. The trends at these important scales may help explain some inter-annual and spatial variability of the net ecosystem exchange of carbon.  相似文献   

17.
The aim of this study was to investigate the effects of increased N deposition on new and old pools of soil organic matter (SOM). We made use of a 4-yr experiment, where spruce and beech growing on an acidic loam and a calcareous sand were exposed to increased N deposition (7 vs. 70 kg N ha−1 yr−1) and to elevated atmospheric CO2. The added CO2 was depleted in 13C, which enabled us to distinguish between old and new C in SOM-pools fractionated into particle sizes. Elevated N deposition for 4 yr increased significantly the contents of total SOM in 0-10 cm depth of the acidic loam (+9%), but not in the calcareous sand. Down to 25 cm soil depth, C storage in the acidic loam was between 100 and 300 g C m−2 larger under high than under low N additions. However, this increase was small as compared with the SOM losses of 600-700 g C g C 0.25 m−1 m−2 from the calcareous sand resulting from the disturbance of soils during setting up of the experiment. The amounts of new, less than 4 yr old SOM in the sand fractions of both soils were greater under high N deposition, showing that C inputs from trees into soils increased. Root biomass in the acidic loam was larger under N additions (+25%). Contents of old, more than 4 yr old C in the clay and silt fractions of both soils were significantly greater under high than under low N deposition. Since clay- and silt-bound SOM consists of humified compounds, this indicates that N additions retarded mineralization of old and humified SOM. The retardation of C mineralization in the clay and silt fraction accounted for 60-80 g C m−2 4 yr−1, which corresponds to about 40% of the old SOM mineralized in these fraction. As a consequence, preservation of old and humified SOM under elevated N deposition might be a process that could lead to an increased soil C storage in the long-term.  相似文献   

18.
Understanding the spatial variation of temperature sensitivity (i.e. Q10) of soil respiration (Rs) and its controlling factors, is critical to improve the precision of carbon budget estimations at regional scales. In this study, data from 2-3 continuous years of Rs measurements over 15 ecosystems of ChinaFLUX were summarized to analyze the response of Rs to soil temperature. Moreover, we improved our dataset by collecting previously published Q10 values from 34 ecosystems in China. The ecosystems studied were located in the main climatic zones of China, spanning from alpine via temperate to tropical. Spatial variations of Q10 and its controlling factors were analyzed. The results showed that soil temperature at a 5 cm depth satisfactorily explained the seasonal variations in Rs of the 15 ChinaFLUX ecosystems (R2 varying from 0.37 to 0.83). Based on the overall data, the Q10 values of Rs in China ranged from 1.28 to 4.75. The spatial variations in Q10 were primarily determined by soil temperature during measurement periods, soil organic carbon (SOC) content, and ecosystem type. Ecosystems in colder regions and with higher SOC content had relatively higher Q10 values. Moreover, ecosystems of different vegetation types showed different Q10 values. A temperature- and SOC-dependent function for Q10 is suggested, which could be a valuable reference for improving the regional-scale models of Rs and ecosystem carbon cycles.  相似文献   

19.
The closed-jar incubation method is widely used to estimate the mineralization of soil organic C. There are two C pools (i.e., organic and inorganic C) in calcareous soil. To evaluate the effect of additional carbonates on CO2 emission from calcareous soil during closed-jar incubation, three incubation experiments were conducted by adding different types (CaCO3 and MgCO3 ) and amounts of carbonate to the soil. The addition of carbonates significantly increased CO2 emission from the soil; the increase ranged from 12.0% in the CaCO3 amended soil to 460% in the MgCO3 amended soil during a 100-d incubation. Cumulative CO2 production at the end of the incubation was three times greater in the MgCO3 amended soil compared to the CaCO3 amended one. The CO2 emission increased with the amount of CaCO3 added to the soil. In contrast, CO2 emission decreased as the amount of MgCO3 added to the soil increased. Our results confirmed that the closed-jar incubation method could lead to an overestimate of organic C mineralization in calcareous soils. Because of its effect on soil pH and the dissolution of carbonates, HgCl2 should not be used to sterilize calcareous soil if the experiment includes the measurement of soil CO2 production.  相似文献   

20.
ABSTRACT

Amelioration of saline soil is a requisite in order to increase crop productivity. A soil incubation study was performed for 60 days using digestate, humic acid, calcium humate and their combinations to investigate the influence on physical, chemical, microbial and enzyme activities of saline soil. Overall, digestate combined with calcium humate followed by humic acid treatments have shown their potency in decreasing the soil pH, electrical conductivity (EC), and sodium ion (Na+) concentration, and increase in potassium ion (K +), calcium ion (Ca 2+), magnesium ion (Mg 2+), mean weight diameter (MWD), soil enzyme activities, microbial biomass carbon (MBC), MBC: microbial biomass nitrogen (MBN) and soil respiration than control. The digestate, humic acid individually and their amalgamation evidenced greater MBN among all the treatments. The digestate alone efficiently improved the soil properties than humic acid and calcium humate individual groups except for the MWD where it is pronounced more in the latter groups. The greater metabolic quotient (qCO2) was observed in control than organic matter amended treatments indicating the stress conditions. The increase in water-extractable organic matter (WEOM) with minimal aromaticity (specific ultraviolet absorbance at 254 nm-Suva 254) in integrated amendments comprising groups, laid the ground reason to improve the properties of saline soil. Therefore, this study concludes that the fusion of fresh and humified substrates could facilitate reclamation.  相似文献   

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