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1.
The effects of compost application on soil carbon sequestration potential and carbon budget of a tropical sandy soil was studied. Greenhouse gas emissions from soil surface and agricultural inputs (fertiliser and fossil fuel uses) were evaluated. The origin of soil organic carbon was identified by using stable carbon isotope. The CO2, CH4 and N2O emissions from soil were estimated in hill evergreen forest (NF) plot as reference, and in the corn cultivation plots with compost application rate at 30 Mg ha−1 y−1 (LC), and at 50 Mg ha−1 y−1 (HC). The total C emissions from soil surface were 8·54, 10·14 and 9·86 Mg C ha−1 y−1 for NF, HC and LC soils, respectively. Total N2O emissions from HC and LC plots (2·56 and 3·47 kg N2O ha−1 y−1) were significantly higher than from the NF plot (1·47 kg N2O ha−1 y−1). Total CO2 emissions from fuel uses of fertiliser, irrigation and machinery were about 10 per cent of total CO2 emissions. For soil carbon storage, since 1983, it has been increased significantly (12 Mg ha−1) under the application of 50 Mg ha−1 y−1 of compost but not with 30 Mg ha−1 y−1. The net C budget when balancing out carbon inputs and outputs from soil for NF, HC and LC soils were +3·24, −2·50 and +2·07 Mg C ha−1 y−1, respectively. Stable isotope of carbon (δ13C value) indicates that most of the increased soil carbon is derived from the compost inputs and/or corn biomass. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

2.
Minesoils are characterized by low soil organic matter and poor soil physicochemical environment. Mine soil reclamation process has potential to restore soil fertility and sequester carbon (C) over time. Soil organic C (SOC) pool and associated soil properties were determined for reclaimed minesoils under grass and forest landuses of varied establishment year. Three grassland sites of 30, 9, and 1 years after reclamation (G30, G9, and G1) and two forest sites, 11 years after reclamation (RF) and undisturbed stand of 40 years (UF), were selected within four counties (Morgan, Muskingum, Noble, and Coshocton) of southeastern Ohio. Soil bulk density (BD) of reclaimed forest (RF) soil was significantly higher than undisturbed forest (UF) soils within 10–40 cm soil depth profile. Reclamation process increased soil pH from slightly acidic to alkaline and decreased the soil EC in both landuses. Among grassland soils, significant changes in SOC and total soil N contents were observed within 0–10 cm soil depth. SOC contents of G30 (29.7 Mg ha−1) and G9 (29.5 Mg ha−1) were significantly higher than G1 soils (9.11 Mg ha−1). Soil N content was increased from G1 (0.95 Mg ha−1) to G9 (2.00 Mg ha−1) site and then the highest value was found under G30 (3.25 Mg ha−1) site within 0–10 cm soil depth. UF soils had significantly higher SOC and total N content than RF soils at 0–10 and 10–20 cm soil depths. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

3.

Purpose

The aim of this study was to understand the effect of nitrogen fertilization on soil respiration and native soil organic carbon (SOC) decomposition and to identify the key factor affecting soil respiration in a cultivated black soil.

Materials and methods

A field experiment was conducted at the Harbin State Key Agroecological Experimental Station, China. The study consisted of four treatments: unplanted and N-unfertilized soil (U0), unplanted soil treated with 225?kg?N?ha?1 (UN), maize planted and N-unfertilized soil (P0), and planted soil fertilized with 225?kg?N?ha?1 (PN). Soil CO2 and N2O fluxes were measured using the static closed chamber method.

Results and discussion

Cumulative CO2 emissions during the maize growing season with the U0, UN, P0, and PN treatments were 1.29, 1.04, 2.30 and 2.27?Mg?C?ha?1, respectively, indicating that N fertilization significantly reduced the decomposition of native SOC. However, no marked effect on soil respiration in planted soil was observed because the increase of rhizosphere respiration caused by N addition was counteracted by the reduction of native SOC decomposition. Soil CO2 fluxes were significantly affected by soil temperature but not by soil moisture. The temperature sensitivity (Q 10) of soil respiration was 2.16?C2.47 for unplanted soil but increased to 3.16?C3.44 in planted soil. N addition reduced the Q 10 of native SOC decomposition possibly due to low labile organic C but increased the Q 10 of soil respiration due to the stimulation of maize growth. The estimated annual CO2 emission in N-fertilized soil was 1.28?Mg?C?ha?1 and was replenished by the residual stubble, roots, and exudates. In contrast, the lost C (1.53?Mg?C?ha?1) in N-unfertilized soil was not completely supplemented by maize residues, resulting in a reduction of SOC. Although N fertilization significantly increased N2O emissions, the global warming potential of N2O and CO2 emissions in N-fertilized soil was significantly lower than in N-unfertilized soil.

Conclusions

The stimulatory or inhibitory effect of N fertilization on soil respiration and basal respiration may depend on labile organic C concentration in soil. The inhibitory effect of N fertilization on native SOC decomposition was mainly associated with low labile organic C in tested black soil. N application could reduce the global warming potential of CO2 and N2O emissions in black soil.  相似文献   

4.
Leaching of dissolved organic matter (DOM) from pastoral soils is increasingly seen as an important but poorly understood process. This paper examined the relationship between soil chemical properties, microbial activity and the losses of dissolved organic carbon (DOC) and nitrogen (DON) through leaching from six pasture soils. These soils differed in carbon (C) (4.6–14.9%) and nitrogen (N) (0.4–1.4%) contents and in the amount of organic C and N that had accumulated or been lost in the preceding 20+ years (i.e. −5131 to +1624 kg C ha−1 year−1 and −263 to +220 kg N ha−1 year−1, respectively). The paper also examined whether between‐soil‐type differences in DOC and DON leaching was a major explanatory factor in the observed range of soil organic matter (SOM) changes in these soils. Between 280 and 1690 kg C ha−1 year−1 and 28–117 kg N ha−1 year−1 leached as DOC and DON, respectively, from the six soils in a lysimeter study, with losses being greater from two poorly drained gley soils. Losses of C and N of this magnitude, while at the upper end relative to published data, could not fully explain the losses at Rawerawe, Bruntwood and Lepperton sites reported by Schipper et al. (2007) . The study highlights the leaching of DOM as a significant pathway of loss of C and N in pasture soils that is often ignored or given little attention in predictive models and nutrient budgeting. Leaching losses of DOC and DON alone, or in combination with slightly increased respiration losses of SOM given a 0.2°C increase in the mean annual soil temperature, do not fully explain long‐term changes in the SOM observed at these sites. When soils examined in the present study were separated on the basis of drainage class, the losses of DOC by leaching were correlated with both total and hot‐water extractable C (HWC), the latter being a measure of the labile SOM fraction. Basal microbial CO2 respiration rates, which varied between 1 and 3.5 µg CO2‐C g−1 soil hour−1 in surface soils (0–75‐mm depth), was also linked to HWC and the quantities of C lost as DOC. Adoption of the HWC method as an approach that could be used as a proxy for the direct measurement of the soil organic C lost by leaching as DOC or respired needs to be examined further with a greater number of soils. In comparison, a poor relationship was found between the hot‐water extractable N (HWN) and loss of DON by leaching, despite HWN previously being shown to be a measure of the mineralizable pool of N in soils, possibly reflecting the greater competition for N than C in these soils.  相似文献   

5.
Under semiarid climatic conditions, intensive tillage increases soil organic matter losses, reduces soil quality, and contributes to climate change due to increased CO2 emissions. There is a need for an agricultural management increasing soil organic matter. This paper presents the organic carbon (OC) and nitrogen (N) stocks, C:N ratio and stratification ratios (SRs) of these properties for olive groves soils under long‐term organic farming (OF), and conventional tillage (CT) in Los Pedroches valley, southern Spain. The results show that OF increased C and N stocks. The soil organic carbon (SOC) stock was 73·6 Mg ha−1 in OF and 54·4 Mg ha−1 in CT; and the total nitrogen (TN) stock was 7·1 Mg ha−1 and 5·8 Mg ha−1 for OF and CT, respectively. In the surface horizon (A: 0–16·9 cm in OF and Ap: 0–21·8 cm in CT) and Bw horizon (16·9–49·6 cm in OF and 21·8–56 cm in CT), SOC and TN concentrations and C:N ratios were higher in OF than in CT. Soil properties stratification in depth, expressed as a ratio, indicates the soil quality under different soil management systems. The SR of SOC ranged from 2·2 to 3·1 in OF and from 2·1 to 2·2 in CT. However, only SR2 (defined by Ap‐A/C) showed significant differences between CT and OF. The SR of TN showed similar trends to that of the SR of SOC. Organic farming contributes to a better soil quality and to increased carbon sequestration. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

6.
Chemical reclamation of sodic and saline-sodic soils has become cost-intensive. Cultivation of plants tolerant of salinity and sodicity may mobilize the CaCO3 present in saline-sodic soils instead of using a chemical approach. Four forage plant species, sesbania (Sesbania aculeata), kallar grass (Leptochloa fusca), millet rice (Echinochloa colona) and finger millet (Eleusine coracana), were planted in a calcareous saline-sodic field (ECe = 9·6–11·0 dS m−1, SAR = 59·4–72·4). Other treatments included gypsum (equivalent to 100 per cent of the gypsum requirement of the 15 cm soil layer) and a control (no gypsum or crop). The crops were grown for 5 months. The performance of the treatments in terms of soil amelioration was in the order: Sesbania aculeata ≅ gypsum > Leptochloa fusca > Echinochloa colona > Elusine coracana > control. Biomass production by the plant species was found to be directly proportional to their reclamation efficiency. Sesbania aculeata produced 32·3 Mg forage ha−1, followed by Leptochloa fusca (24·6 Mg ha−1), Echinochloa colona (22·6 Mg ha−1) and Eleusine coracana (5·4 Mg ha−1). Sesbania aculeata emerged as the most suitable biotic material for cultivation on salt-affected soils to produce good-quality forage, and to reduce soil salination and sodication processes.  相似文献   

7.
Pig slurries are widely used on calcareous soils in European rainfed systems. Here we assess their impact on the amount of soil organic carbon (SOC) and on the composition of humic-type substances (HTS). Seven doses of slurry (five from fattening pigs and two from sows) ranging from 1.0 to 4.8 Mg ha−1 yr−1 of organic matter were evaluated after a period of 12 years and compared with mineral fertilizer treatment. At the end of the last annual cropping season (September), SOC was quantified, and HTS were isolated by alkaline extraction followed by acid precipitation, and studied by visible spectroscopy (800–400 nm) and Fourier-transformed infrared spectroscopy (4000–400 cm−1). Following the trend in the slurry organic matter applied rates, SOC increased from 9.5 g C kg−1 (mineral treatment) to 13.8 g C kg−1. This SOC increase was equivalent to c. 25.4% of the slurry organic carbon applied. The incorporation of aliphatic structures, mainly polyalkyl, from slurries into the HTS tends to modify the composition of the soil organic matter (SOM), which is reflected in a decrease in the intensity of FT-IR peaks related to aromatic structures. Despite the trend of significant increase in SOC with fattening slurries, mainly from the organic matter rate of 1.6 Mg ha−1 yr−1 (c. 185 kg N ha−1), the composition of the HTS showed an important aliphatic enhancement. The FTIR results showed that using exclusively the relative intensities of specific peaks (alkyl, carboxyl, aromatic and amide groups) as variables for the discriminant analysis, it is possible to identify HA between different groups of soils treated with progressive levels of slurry. Although the new aliphatic components could be considered important to improve soil physical quality, after the incorporation of additional SOM, the spectroscopic characteristics of HTS in soils treated with slurries suggested a weak effect in long-term C sequestration, as the newly incorporated OC forms are not qualitatively similar to the presumably stable native SOM. These potential changes in SOC and SOM composition at field level are constrained by the maximum allowed N rates from organic origin in some agricultural systems.  相似文献   

8.
Biochar application can reduce global warming via carbon (C) sequestration in soils. However, there are few studies investigating its effects on greenhouse gases in rice (Oryza sativa L.) paddy fields throughout the year. In this study, a year-round field experiment was performed in rice paddy fields to investigate the effects of biochar application on methane (CH4) and nitrous oxide (N2O) emissions and C budget. The study was conducted on three rice paddy fields in Ehime prefecture, Japan, for 2 years. Control (Co) and biochar (B) treatments, in which 2-cm size bamboo biochar (2 Mg ha?1) was applied, were set up in the first year. CH4 and N2O emissions and heterotrophic respiration (Rh) were measured using a closed-chamber method. In the fallow season, the mean N2O emission during the experimental period was significantly lower in B (67 g N ha?1) than Co (147 g N ha?1). However, the mean CH4 emission was slightly higher in B (2.3 kg C ha?1) than Co (1.2 kg C ha?1) in fallow season. The water-filled pore space increased more during the fallow season in B than Co. In B, soil was reduced more than in Co due to increasing soil moisture, which decreased N2O and increased CH4 emissions in the fallow season. In the rice-growing season, the mean N2O emission tended to be lower in B (?104 g N ha?1) than Co (?13 g N ha?1), while mean CH4 emission was similar between B (183 kg C ha?1) and Co (173 kg C ha?1). Due to the C release from applied biochar and soil organic C in the first year, Rh in B was higher than that in Co. The net greenhouse gas emission for 2 years considering biochar C, plant residue C, CH4 and N2O emissions, and Rh was lower in B (5.53 Mg CO2eq ha?1) than Co (11.1 Mg CO2eq ha?1). Biochar application worked for C accumulation, increasing plant residue C input, and mitigating N2O emission by improving soil environmental conditions. This suggests that bamboo biochar application in paddy fields could aid in mitigating global warming.  相似文献   

9.
During the last few decades, land use changes have largely affected the global warming process through emissions of CO2. However, C sequestration in terrestrial ecosystems could contribute to the decrease of atmospheric CO2 rates. Although Mediterranean areas show a high potential for C sequestration, only a few studies have been carried out in these systems. In this study, we propose a methodology to assess the impact of land use and land cover change dynamics on soil organic C stocks at different depths. Soil C sequestration rates are provided for different land cover changes and soil types in Andalusia (southern Spain). Our research is based on the analysis of detailed soil databases containing data from 1357 soil profiles, the Soil Map of Andalusia and the Land Use and Land Cover Map of Andalusia. Land use and land cover changes between 1956 and 2007 implied soil organic C losses in all soil groups, resulting in a total loss of 16·8 Tg (approximately 0·33 Tg y−1). Afforestation increased soil organic C mostly in the topsoil, and forest contributed to sequestration of 8·62 Mg ha−1 of soil organic C (25·4 per cent). Deforestation processes implied important C losses, particularly in Cambisols, Luvisols and Vertisols. The information generated in this study will be a useful basis for designing management strategies for stabilizing the increasing atmospheric CO2 concentrations by preservation of C stocks and C sequestration. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

10.
This study provides a comparative assessment of greenhouse gas (GHG) emissions when converting a reclaimed minesoil that was previously under meadow to miscanthus (Miscanthus  × giganteus ) and maize (Zea mays L.) land uses in Ohio, USA. Additionally, effluent from an anaerobic digester at rates of 0, 75, 150, and 225 kg N ha−1 rates was also assessed for C and nutrient fertilization. Results from the study show that land use conversion to maize had the highest net release of GHG equivalent of 6·6 Mg CO2equ ha−1 y−1, on average, across effluent application rates. Under miscanthus land use with no and high effluent application rates, net GHG equivalent on average was 4·3 Mg CO2equ ha−1 y−1, which was larger when compared with that under the meadow land use (1·6 Mg CO2equ ha−1 y−1). Miscanthus land use under medium rates of effluent application had similar net GHG equivalent (7·1 Mg CO2equ ha−1 y−1) to the maize land use. The application of effluent did increase CO2–C and N2O–N emissions; but increases in above‐ground–below‐ground biomass production (1·6 Mg C ha−1) in the meadow land use and C input from effluent retained in the soil in the miscanthus and maize land uses offset most of the effluent‐induced GHG equivalent emissions. Contribution of cumulative N2O–N to GHG equivalent emissions in general was 11% when no effluent was applied and 22% when effluent was applied across land uses. Findings from this study show that land use changes from antecedent meadow to maize and miscanthus during the first year of establishment would result in net increase of GHG emissions. Published 2017. This article is a U.S. Government work and is in the public domain in the USA  相似文献   

11.
Grassland management aimed at enhancing carbon (C) in soil is an important tool in mitigation of rising atmospheric CO2, yet little is known of how grassland soil C changes with livestock stocking rate (SR). We relate soil organic and inorganic C mass (t ha−1 to 60 cm depth) with cattle stocking over periods of 7–27 year for 32 paddocks distributed across nine community pastures in the mixed-grass prairie of Saskatchewan, Canada. Initial analysis comparing Akaike information criterion models showed that cattle SR explained a greater proportion of variance in soil C, particularly soil organic C, than rainfall. Soil organic C mass increased with cattle SR (R2 = .293; p = .001), even when the latter was normalized to account for differences in vegetation composition and growing conditions among pastures. Normalized SR varied from 0.49 to 2.30 times recommended levels, over which SOC increased from 24.7 to 57.4 t ha−1. Increases in soil organic C under greater stocking coincided with increased abundance of introduced vegetation, particularly the rhizomatous grass Poa pratensis. Inorganic soil C accounted for 34.6% of total soil C, being particularly large below 30 cm soil depth, but did not vary with stocking rate. These findings indicate that both organic and inorganic C are important pools of C in northern temperate grassland soils, with soil organic C positively associated with long-term cattle SR. Further studies are recommended to understand more fully the mechanisms regulating grazing impacts on soil C mass in northern temperate grasslands.  相似文献   

12.
We used a continuous labeling method of naturally 13C-depleted CO2 in a growth chamber to test for rhizosphere effects on soil organic matter (SOM) decomposition. Two C3 plant species, soybean (Glycine max) and sunflower (Helianthus annus), were grown in two previously differently managed soils, an organically farmed soil and a soil from an annual grassland. We maintained a constant atmospheric CO2 concentration at 400±5 ppm and δ13C signature at −24.4‰ by regulating the flow of naturally 13C-depleted CO2 and CO2-free air into the growth chamber, which allowed us to separate new plant-derived CO2-C from original soil-derived CO2-C in soil respiration. Rhizosphere priming effects on SOM decomposition, i.e., differences in soil-derived CO2-C between planted and non-planted treatments, were significantly different between the two soils, but not between the two plant species. Soil-derived CO2-C efflux in the organically farmed soil increased up to 61% compared to the no-plant control, while the annual grassland soil showed a negligible increase (up to 5% increase), despite an overall larger efflux of soil-derived CO2-C and total soil C content. Differences in rhizosphere priming effects on SOM decomposition between the two soils could be largely explained by differences in plant biomass, and in particular leaf biomass, explaining 49% and 74% of the variation in primed soil C among soils and plant species, respectively. Nitrogen uptake rates by soybean and sunflower was relatively high compared to soil C respiration and associated N mineralization, while inorganic N pools were significantly depleted in the organic farm soil by the end of the experiment. Despite relatively large increases in SOM decomposition caused by rhizosphere effects in the organic farm soil, the fast-growing soybean and sunflower plants gained little extra N from the increase in SOM decomposition caused by rhizosphere effects. We conclude that rhizosphere priming effects of annual plants on SOM decomposition are largely driven by plant biomass, especially in soils of high fertility that can sustain high plant productivity.  相似文献   

13.
Soil organic carbon (SOC) pools are important for maintaining soil productivity and reducing the net CO2 loading of the atmosphere. An 18‐year old long‐term field experiment involving pearl millet‐cluster bean‐castor sequence was conducted on an Entisol in western India to examine the effects of chemical fertilizers and manuring on carbon pools in relation to crop productivity and C sequestration. The data showed that even the addition of 33.5 Mg ha−1 C inputs through crop residues as well as farm yard manure could not compensate the SOC depletion by oxidation and resulted in the net loss of 4.4 Mg C ha−1 in 18 years. The loss of SOC stock in the control was 12 Mg C ha−1. Conjunctive use of chemical fertilizers along with farm yard manure produced higher agronomic yields and reduced the rate of SOC depletion. The higher average seed yields of pearl millet (809 kg ha−1), cluster bean (576), and castor (827) over six cropping seasons were obtained through integrated use of fertilizers and manure. For every Mg increase in profile SOC stock, there was an overall increase of 0.46 Mg of crop yield, comprising increase in individual yield of pearl millet (0.17 Mg ha−1 y−1 Mg−1 SOC), cluster bean (0.14) and castor (0.15). The magnitude of SOC build up was proportional to the C inputs. Carbon pools were significantly correlated with SOC, which increased with application of organic amendments. Threshold C input of 3.3 Mg C ha−1 y−1 was needed to maintain the SOC stock even at the low antecedent level. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

14.
An hypothesis about the different temperature dependences of the decomposition of the labile and stable organic carbon pools has been tested using an agrochernozem sampled from an experimental plot of 42-year-old continuous corn in Voronezh oblast. The partitioning of the CO2 loss during the decomposition of the labile and stable soil organic matter (SOM) at 2, 12, and 22°C in a long-term incubation experiment was performed using the method of 13C natural abundance by C3–C4 transition. On the basis of the determined decomposition constants, the SOM pools have been arranged in an order according to their increasing stability: plant residues < new (C4) SOM < old (C3) SOM. The tested hypothesis has been found valid only for a limited temperature interval. The temperature coefficient Q 10 increases in the stability order from 1.2 to 4.3 in the interval of 12–22°C. At low temperatures (2–12°C), the values of Q 10 insignificantly vary among the SOM pools and lie in the range of 2.2–2.8. Along with the decomposition constants of the SOM, the new-to-old carbon ratio in the CO2 efflux from the soil and the magnitude of the negative priming effect for the old SOM caused by the input of new organic matter depend on the temperature. In the soil under continuous corn fertilized with NPK, the increased decomposition of C3 SOM is observed compared to the unfertilized control; the temperature dependences of the SOM decomposition are similar in both agrochernozem treatments.  相似文献   

15.
As global warming intensifies, the soil environment in middle to high latitudes will undergo more extensive and frequent freeze–thaw cycles (FTCs), which will significantly affect the carbon and nitrogen cycles of soil ecosystems and aggravate greenhouse gas (GHG) emissions. Biochar can increase soil organic carbon storage and mitigate climate change. To effectively control GHG emissions, soil supplemented with biochar at different application rates (0%, 2%, 4% and 6% [w/w]) under different numbers of FTCs (0, 3, 6, 9, and 12) was selected as the research object. The soil GHG emission characteristics in different experimental treatments and their relationships with soil physical and chemical properties were determined. Our results showed that N2O and CO2 emissions were promoted during FTCs, with values of 3.13–50.37 and 16.22–135.50 μg m−2 h−1, respectively. The order of N2O and CO2 emissions with respect to biochar application rate was as follows: 2% > 0% > 4% > 6%. CH4 emissions were negative during FTCs, varying from −1.62 to −10.59 μg m−2 h−1, and negative CH4 emissions were promoted by biochar. Correlation analysis showed that N2O, CO2 and CH4 emissions were significantly correlated with pH, soil moisture and soil organic matter (SOM), total nitrogen (TN) and NH 4 + –N contents (p < .01). The conceptual path model demonstrated that GHG emissions were significantly influenced by FTCs, moisture, SOM and biochar application rate. Our results indicate that the effects of FTCs on GHG emissions were greater than those of biochar application. Biochar application rates of 4% or 6% should be considered in the future to reduce soil GHG emissions in the black soil region of Northeast China. Our results can help provide a theoretical basis and effective strategy to reduce soil GHG emissions during FTCs in seasonally frozen regions.  相似文献   

16.
Problems of frequent drought stress, low soil organic carbon (SOC) concentration, low aggregation, susceptibility to compaction, salinization and accelerated soil erosion in dry regions are accentuated by removal of crop residues, mechanical methods of seedbed preparation, summer clean fallowing and overgrazing, and excessive irrigation. The attendant soil degradation and desertification lead to depletion of SOC, decline in biomass production, eutrophication/pollution of waters and emission of greenhouse gases. Adoption of conservation agriculture, based on the use of crop residue mulch and no till farming, can conserve water, reduce soil erosion, improve soil structure, enhance SOC concentration, and reduce the rate of enrichment of atmospheric CO2. The rate of SOC sequestration with conversion to conservation agriculture, elimination of summer fallowing and growing forages/cover crops may be 100 to 200 kg ha−1 y−1 in coarse‐textured soils of semiarid regions and 150 to 300 kg ha−1 y−1 in heavy‐textured soils of the subhumid regions. The potential of soil C sequestration in central Asia is 10 to 22 Tg C y−1 (16±8 Tg C y−1) for about 50 years, and it represents 20 per cent of the CO2 emissions by fossil fuel combustion. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

17.
Studies of rice-based systems in the Indo-Gangetic Plain (IGP) have demonstrated the beneficial effects of Conservation Agriculture on soil organic carbon (SOC) status, along with increased soil health and crop productivity. However, it remains unclear as to the time for such treatments to have a positive effect. In this study of lentil-mung bean-rice and wheat-mung-rice rotations in Bangladesh positive effects of strip planting or bed planting, along with residue return, on SOC pools were apparent after 1.5 years, compared with intensive conventional tillage and limited residue return. Conventional tillage resulted in higher CO2 emission compared with strip planting or bed planting as did high residue return. In the cereal-dominated rotation, the strip planting system sequestered carbon at a rate of 0.24–0.53 Mg C ha−1 year−1 (at 0–0.15 m depth) while conventional tillage was associated with a carbon loss of 0.52–0.82 Mg C ha−1 year−1. In the legume-dominated rotation, neither practice sequestered SOC. Under strip planting, a minimum annual crop residue input of 1.7 Mg C ha−1 for the cereal-dominated system and 5.2 Mg C ha−1 for the legume-dominated system was required to maintain SOC at equilibrium. We conclude that strip planting with high levels of crop residue return can be an effective and quick strategy in either slowing the loss of SOC or improving C sequestration in the intensive rice-based systems of the Eastern IGP.  相似文献   

18.

Background

Riparian buffers are primarily implemented for their water quality functions in agroecosystems. Their location in the agricultural landscape allows them to intercept and process pollutants from immediately adjacent agricultural land. Vegetated riparian buffers recycle soil organic matter, which elevates soil carbon (C), which upon processing, processes and releases carbon dioxide (CO2). The elevated soil C and seasonally anoxic environments associated with riparian buffers promote denitrification and fermentation, further increasing soil CO2 production.

Aim

Against this context, a replicated plot-scale experiment was established at North Wyke, UK, to measure the extent of soil CO2 emissions in permanent pasture served by grass, willow, and woodland riparian buffers, as well as a no-buffer control.

Methods

Soil CO2 was measured using the static chamber technique in conjunction with soil and environmental variables between June 2018 and February 2019.

Results

Cumulative soil CO2 fluxes were in the descending order: woodland riparian buffer; 11,927.8 ± 1987.9 kg CO2 ha–1 > no-buffer control; 11,101.3 ± 3700.4 kg CO2 ha–1 > grass riparian buffer; 10,826.4 ± 2551.8 kg CO2 ha–1 > upslope pasture; 10,554.6 ± 879.5 kg CO2 ha–1 > willow riparian buffer; 9294.9 ± 1549.2 5 kg CO2 ha–1. There was, however, no evidence of significant differences among all treatments of the current study.

Conclusions

Despite the lack of significant differences, the results from our short-term study show that the woodland riparian buffer had relatively larger soil CO2 emissions than the remainder of the other riparian buffers and the upslope pasture it serves. Our short-term findings may be useful in developing soil CO2 mitigation strategies through careful selection of riparian buffer vegetation and may be useful in calibrating mechanistic models for simulating such emissions from similar agro systems.  相似文献   

19.
Sustainable agricultural land use requires an assessment of degradable soil organic matter (SOM) because of its key function for soil fertility and plant nutrition. Such an assessment for practical land use should consider transformation processes of SOM and its sources of different origin. In this study, we combined a 120‐day incubation experiment with thermal decay dynamics of agricultural soils altered by added organic amendments. The aim was to determine the abilities and limits of thermal analysis as a rapid approach revealing differences in the degradability of SOM. The carried out experiments based on two independent sampling sets. The first sample set consisted of soil samples taken from non‐fertilized plots of three German long‐term agricultural field experiments (LTAEs), then artificially mixed with straw, farmyard manure, sheep faeces, and charcoal equal to 60 Mg ha?1 under laboratory conditions. The second sample set based on soil samples of different treatments (e.g., crop type, fertilization, cultivation) in LTAEs at Bad Lauchstädt and Müncheberg, Germany. Before and after the incubation experiment, thermal mass losses (TML) at selected temperatures were determined by thermogravimetry indicating the degradability of organic amendments mixed in soils. The results confirmed different microbial degradability of organic amendments and SOM under laboratory conditions. Thermal decay dynamics revealed incubation‐induced changes in the artificial soil mixtures primarily at TML around 300°C in the case of applied straw and sheep faeces, whereas farmyard manure showed mainly changes in TML around 450°C. Charcoal did not show significant degradation during incubation, which was confirmed by TML. Detailed analyses of the artificial soil mixtures revealed close correlations between CO2‐C evolution during incubation and changes in TML at 300°C with R2 > 0.96. Results of the soils from LTAEs showed similar incubation‐induced changes in thermal decay dynamics for fresh plant residues and farmyard manure. We conclude that the practical assessment of SOM could be facilitated by thermal decay dynamics if modified sample preparation and evaluation algorithms are used beyond traditional peak analysis.  相似文献   

20.
The application of biochar produced from wood and crop residues, such as sawdust, straw, sugar bagasse and rice hulls, to highly weathered soils under tropical conditions has been shown to influence soil greenhouse gas (GHG) emissions. However, there is a lack of data concerning GHG emissions from soils amended with biochar derived from manure, and from soils outside tropical and subtropical regions. The objective of this study was to quantify the effect on emissions of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) following the addition, at a rate of 18 t ha−1, of two different types of biochar to an Irish tillage soil. A soil column experiment was designed to compare three treatments (n = 8): (1) non-amended soil (2) soil mixed with biochar derived from the separated solid fraction of anaerobically digested pig manure and (3) soil mixed with biochar derived from Sitka Spruce (Picea sitchensis). The soil columns were incubated at 10 °C and 75% relative humidity, and leached with 80 mL distilled water, twice per week. Following 10 weeks of incubation, pig manure, equivalent to 170 kg nitrogen ha−1 and 36 kg phosphorus ha−1, was applied to half of the columns in each treatment (n = 4). Gaseous emissions were analysed for 28 days following manure application. Biochar addition to the soil increased N2O emissions in the pig manure-amended column, most likely as a result of increased denitrification caused by higher water filled pore space and organic carbon (C) contents. Biochar addition to soil also increased CO2 emissions. This was caused by increased rates of C mineralisation in these columns, either due to mineralisation of the labile C added with the biochar, or through increased mineralisation of the soil organic matter.  相似文献   

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