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1.
Aims
A pot study spanning four consecutive crop seasons was conducted to compare the effects of successive rice straw biochar/rice straw amendments on C sequestration and soil fertility in rice/wheat rotated paddy soil.Methods
We adopted 4.5 t ha?1, 9.0 t ha?1 biochar and 3.75 t ha?1 straw for each crop season with an identical dose of NPK fertilizers.Results
We found no major losses of biochar-C over the 2-year experimental period. Obvious reductions in CH4 emission were observed from rice seasons under the biochar application, despite the fact that the biochar brought more C into the soil than the straw. N2O emissions with biochar were similar to the controls without additives over the 2-year experimental period. Biochar application had positive effects on crop growth, along with positive effects on nutrient (N, P, K, Ca and Mg) uptake by crop plants and the availability of soil P, K, Ca and Mg. High levels of biochar application over the course of the crop rotation suppressed NH3 volatilization in the rice season, but stimulated it in the wheat season.Conclusions
Converting straw to biochar followed by successive application to soil is viable for soil C sequestration, CH4 mitigation, improvements of soil and crop productivity. Biochar soil amendment influences NH3 volatilization differently in the flooded rice and upland wheat seasons, respectively. 相似文献2.
Marcus Hardie Brent Clothier Sally Bound Garth Oliver Dugald Close 《Plant and Soil》2014,376(1-2):347-361
Aims
This study aims to (i) determine the effects of incorporating 47 Mg ha?1 acacia green waste biochar on soil physical properties and water relations, and (ii) to explore the different mechanisms by which biochar influences soil porosity.Methods
The pore size distribution of the biochar was determined by scanning electron microscope and mercury porosimetry. Soil physical properties and water relations were determined by in situ tension infiltrometers, desorption and evaporative flux on intact cores, pressure chamber analysis at ?1,500 kPa, and wet aggregate sieving.Results
Thirty months after incorporation, biochar application had no significant effect on soil moisture content, drainable porosity between –1.0 and ?10 kPa, field capacity, plant available water capacity, the van Genuchten soil water retention parameters, aggregate stability, nor the permanent wilting point. However, the biochar-amended soil had significantly higher near-saturated hydraulic conductivity, soil water content at ?0.1 kPa, and significantly lower bulk density than the unamended control. Differences were attributed to the formation of large macropores (>1,200 μm) resulting from greater earthworm burrowing in the biochar-amended soil.Conclusion
We found no evidence to suggest application of biochar influenced soil porosity by either direct pore contribution, creation of accommodation pores, or improved aggregate stability. 相似文献3.
Background and Aims
Understanding the impact of soil rhizobial populations and inoculant rhizobia in supplying sufficient nodulation is crucial to optimising N2 fixation by legume crops. This study explored the impact of different rates of inoculant rhizobia and contrasting soil rhizobia on nodulation and N2 fixation in faba bean (Vicia faba L.).Methods
Faba beans were inoculated with one of seven rates of rhizobial inoculation, from no inoculant to 100 times the normal rate of inoculation, sown at two field sites, with or without soil rhizobia present, and their nodulation and N2 fixation assessed.Results
At the site without soil rhizobia, inoculation increased nodule number and increased N2 fixation from 21 to 129 kg shoot N ha?1, while N2 fixation increased from 132 to 218 kg shoot N ha?1 at the site with high background soil rhizobia. At the site without soil rhizobia, inoculation increased concentrations of shoot N from 14 to 24 mg g?1, grain N from 32 to 45 mg g?1, and grain yields by 1.0 Mg (metric tonne) ha?1. Differences in nodulation influenced the contributions of fixed N to the system, which varied from the net removal of 20 kg N ha?1 from the system in the absence of rhizobia, to a net maximum input of 199 kg N ha?1 from legume shoot and root residues, after accounting for removal of N in grain harvest.Conclusions
The impact of inoculation and soil rhizobia strongly influenced grain yield, grain N concentration and the potential contributions of legume cropping to soil N fertility. In soil with resident rhizobia, N2 fixation was improved only with the highest inoculation rate. 相似文献4.
Aims
Effects of different soil amendments were investigated on methane (CH4) emission, soil quality parameters and rice productivity in irrigated paddy field of Bangladesh.Methods
The experiment was laid out in a randomized complete block design with five treatments and three replications. The experimental treatments were urea (220 kg ha?1) + rice straw compost (2 t ha?1) as a control, urea (170 kg ha?1) + rice straw compost (2 t ha?1) + silicate fertilizer, urea (170 kg ha?1) + sesbania biomass (2 t ha?1 ) + silicate fertilizer, urea (170 kg ha?1) + azolla biomass (2 t ha?1) + cyanobacterial mixture 15 kg ha?1 silicate fertilizer, urea (170 kg ha?1) + cattle manure compost (2 t ha?1) + silicate fertilizer.Results
The average of two growing seasons CH4 flux 132 kg ha?1 was recorded from the conventional urea (220 kg ha?1) with rice straw compost incorporated field plot followed by 126.7 (4 % reduction), 130.7 (1.5 % reduction), 116 (12 % reduction) and 126 (5 % reduction) kg CH4 flux ha?1 respectively, with rice straw compost, sesbania biomass, azolla anabaena and cattle manure compost in combination urea and silicate fertilizer applied plots. Rice grain yield was increased by 15 % and 10 % over the control (4.95 Mg ha?1) with silicate plus composted cattle manure and silicate plus azolla anabaena, respectively. Soil quality parameters such as soil organic carbon, total nitrogen, microbial biomass carbon, soil redox status and cations exchange capacity were improved with the added organic materials and azolla biofertilizer amendments with silicate slag and optimum urea application (170 kg ha?1) in paddy field.Conclusion
Integrated application of silicate fertilizer, well composted organic manures and azolla biofertilizer could be an effective strategy to minimize the use of conventional urea fertilizer, reducing CH4 emissions, improving soil quality parameters and increasing rice productivity in subtropical countries like Bangladesh. 相似文献5.
High surface area biochar negatively impacts herbicide efficacy 总被引:2,自引:0,他引:2
Background and Aims
Amendment of soil by biochar may reduce efficacy of soil-applied herbicides due to sorption.Methods
Bioassays with Green Foxtail (Setaria viridis) tested the influence of two biochars on phytoavailability of S-metolachlor and sulfentrazone under biochar amendment of 0, 13, 26 and 52?Mg?ha-1.Results
Adsorption of both herbicides was an order of magnitude greater on a high specific surface area (SSA) biochar (EUC-800; SSA 242?m2?g-1) than on a low SSA biochar (BC-1; SSA 3.6?m2?g-1). Herbicide doses near the lowest recommended label rates controlled the weed at 13 and 26?Mg?ha-1 of BC-1; sulfentrazone was also effective at 52?Mg BC-1?ha-1. These same herbicide doses controlled weed germination and development only at 13?Mg?ha-1 of EUC-800; at herbicide doses near the highest label rates, weed control was also achieved at 26?Mg EUC-800?ha-1, but not at 52?Mg EUC-800?ha-1.Conclusions
Increased doses of soil-applied herbicides cannot necessarily offset decreases in herbicide phytoavailability in biochar-amended soils, particularly if the biochar has a high SSA. Considering the long half-life of biochar in soil, pest control needs will be best served by low SSA biochars. 相似文献6.
Aim
To determine, for arable land in a temperate area, the effect of tree establishment and intercropping treatments, on the distribution of roots and soil organic carbon to a depth of 1.5 m.Methods
A poplar (Populus sp.) silvoarable agroforestry experiment including arable controls was established on arable land in lowland England in 1992. The trees were intercropped with an arable rotation or bare fallow for the first 11 years, thereafter grass was allowed to establish. Coarse and fine root distributions (to depths of up to 1.5 m and up to 5 m from the trees) were measured in 1996, 2003, and 2011. The amount and type of soil carbon to 1.5 m depth was also measured in 2011.Results
The trees, initially surrounded by arable crops rather than fallow, had a deeper coarse root distribution with less lateral expansion. In 2011, the combined length of tree and understorey vegetation roots was greater in the agroforestry treatments than the control, at depths below 0.9 m. Between 0 and 1.5 m depth, the fine root carbon in the agroforestry treatment (2.56 t ha-1) was 79% greater than that in the control (1.43 t ha?1). Although the soil organic carbon in the top 0.6 m under the trees (161 t C ha?1) was greater than in the control (142 t C ha?1), a tendency for smaller soil carbon levels beneath the trees at lower depths, meant that there was no overall tree effect when a 1.5 m soil depth was considered. From a limited sample, there was no tree effect on the proportion of recalcitrant soil organic carbon.Conclusions
The observed decline in soil carbon beneath the trees at soil depths greater than 60 cm, if observed elsewhere, has important implication for assessments of the role of afforestation and agroforestry in sequestering carbon. 相似文献7.
Effect of biochar amendment on maize yield and greenhouse gas emissions from a soil organic carbon poor calcareous loamy soil from Central China Plain 总被引:30,自引:0,他引:30
Afeng Zhang Yuming Liu Genxing Pan Qaiser Hussain Lianqing Li Jinwei Zheng Xuhui Zhang 《Plant and Soil》2012,351(1-2):263-275
Aims
A field experiment was conducted to investigate the effect of biochar on maize yield and greenhouse gases (GHGs) in a calcareous loamy soil poor in organic carbon from Henan, central great plain, China.Methods
Biochar was applied at rates of 0, 20 and 40?t?ha?1 with or without N fertilization. With N fertilization, urea was applied at 300?kg?N ha?1, of which 60% was applied as basal fertilizer and 40% as supplementary fertilizer during crop growth. Soil emissions of CO2, CH4 and N2O were monitored using closed chambers at 7?days intervals throughout the whole maize growing season (WMGS).Results
Biochar amendments significantly increased maize production but decreased GHGs. Maize yield was increased by 15.8% and 7.3% without N fertilization, and by 8.8% and 12.1% with N fertilization under biochar amendment at 20?t?ha?1 and 40?t?ha?1, respectively. Total N2O emission was decreased by 10.7% and by 41.8% under biochar amendment at 20?t?ha?1 and 40?t?ha?1 compared to no biochar amendment with N fertilization. The high rate of biochar (40?t?ha?1) increased the total CO2 emission by 12% without N fertilization. Overall, biochar amendments of 20?t?ha?1 and 40?t?ha?1 decreased the total global warming potential (GWP) of CH4 and N2O by 9.8% and by 41.5% without N fertilization, and by 23.8% and 47.6% with N fertilization, respectively. Biochar amendments also decreased soil bulk density and increased soil total N contents but had no effect on soil mineral N.Conclusions
These results suggest that application of biochar to calcareous and infertile dry croplands poor in soil organic carbon will enhance crop productivity and reduce GHGs emissions. 相似文献8.
Effectiveness of low-temperature biochar in controlling the release and leaching of herbicides in soil 总被引:1,自引:0,他引:1
Aims
Biochars, being good sorbents of organic compounds, can reduce the mobility of pesticides in soil and subsequent pollution to groundwater, but may also impact on the efficacy of soil-applied herbicides. The aim of this study is to seek a potential solution to this problem.Methods
We prepared a wood biochar at a relatively low heat treatment temperature (350 °C), and used it as an adsorptive carrier for incorporating the herbicides 2,4-D and acetochlor, and also as a soil amendment. Release experiment through a thin soil layer and leaching experiment through a soil column were used to evaluate the effectiveness of the biochar for controlling the release and leaching of herbicides in soil.Results
The release experiments demonstrated that the low-temperature biochar could control the release of herbicides in soil, and the leaching experiments showed that this biochar significantly reduced the leached amount of herbicides by 1/2?~?3/4, depending on the depth (5?~?15 cm) of biochar-amended topsoil. High retention of herbicides in the biochar-amended topsoil was observed.Conclusions
The results suggest that the low temperature biochar, if applied properly in soil, may be useful for extending the efficacy of herbicides while controlling their potential pollution. 相似文献9.
Nitrogen dynamics following field application of biochar in a temperate North American maize-based production system 总被引:5,自引:0,他引:5
David Güereña Johannes Lehmann Kelly Hanley Akio Enders Charles Hyland Susan Riha 《Plant and Soil》2013,365(1-2):239-254
Background and aims
Biochar additions to tropical soils have been shown to reduce N leaching and increase N use efficiency. No studies exist verifying reduced N leaching in field experiments on temperate agricultural soils or identifying the mechanism for N retention.Methods
Biochar derived from maize stover was applied to a maize cropping system in central New York State at rates of 0, 1, 3, 12, and 30 t?ha-1 in 2007. Secondary N fertilizer was added at 100, 90, 70, and 50 % of the recommended rate (108 kg N ha-1). Nitrogen fertilizer enriched with 15?N was applied in 2009 to the 0 and 12 t?ha-1 of biochar at 100 and 50 % secondary N application.Results
Maize yield and plant N uptake did not change with biochar additions (p?>?0.05; n?=?3). Less N (by 82 %; p?<?0.05) was lost after biochar application through leaching only at 100 %?N fertilization. The reason for an observed 140 % greater retention of applied 15?N in the topsoil may have been the incorporation of added 15?N into microbial biomass which increased approximately three-fold which warrants further research. The low leaching of applied fertilizer 15?N (0.42 % of applied N; p?<?0.05) and comparatively high recovery of applied 15?N in the soil (39 %) after biochar additions after one cropping season may also indicate greater overall N retention through lower gaseous or erosion N losses with biochar.Conclusions
Addition of biochar to fertile soil in a temperate climate did not improve crop growth or N use efficiency, but increased retention of fertilizer N in the topsoil. 相似文献10.
Arezoo Taghizadeh-Toosi Tim J. Clough Robert R. Sherlock Leo M. Condron 《Plant and Soil》2012,353(1-2):73-84
Aims
Ammonia (NH3) can be volatilised from the soil surface following the surface application of nitrogenous fertilisers or ruminant urine deposition. The volatilisation of NH3 is of agronomic and environmental concern, since NH3-N is a form of reactive nitrogen. Ammonia adsorption onto biochar has the potential to mitigate NH3 losses, but to date no studies have examined the potential for reducing NH3 losses when biochar is present in the soil matrix.Methods
We used 15N-enriched urine to examine the effect of incorporating a wood based low-temperature biochar into soil on NH3 volatilisation. Then, we extracted the urine-treated biochar and compared its potential to act as a plant N source with fresh biochar, while growing ryegrass (Lolium perenne).Results
The NH3 volatilisation from 15N-labelled ruminant urine, applied to soil, was reduced by 45% after incorporating either 15 or 30?t ha?1 of biochar. When the urine-treated biochar particles were transferred into fresh soil, subsequent plant growth was not affected but the uptake of 15N in plant tissues increased, indicating that the adsorbed-N was plant available.Conclusions
Our results show that incorporating biochar into the soil can significantly decrease NH3 volatilisation from ruminant urine and that the NH3-N adsorbed onto the biochar is bioavailable. Further studies are now required to assess the temporal dynamics of the N pools involved. 相似文献11.
Zubin Xie Yanping Xu Gang Liu Qi Liu Jianguo Zhu Cong Tu James E. Amonette Georg Cadisch Jean W. H. Yong Shuijin Hu 《Plant and Soil》2013,370(1-2):527-540
Aims
Two field microcosm experiments and 15N labeling techniques were used to investigate the effects of biochar addition on rice N nutrition and GHG emissions in an Inceptisol and an Ultisol.Methods
Biochar N bioavailability and effect of biochar on fertilizer nitrogen-use efficiency (NUE) were studied by 15N-enriched wheat biochar (7.8803 atom% 15N) and fertilizer urea (5.0026 atom% 15N) (Experiment I). Corn biochar and corn stalks were applied at 12 Mg?ha?1 to study their effects on GHG emissions (Experiment II).Results
Biochar had no significant impact on rice production and less than 2 % of the biochar N was available to plants in the first season. Biochar addition increased soil C and N contents and decreased urea NUE. Seasonal cumulative CH4 emissions with biochar were similar to the controls, but significantly lower than the local practice of straw amendment. N2O emissions with biochar were similar to the control in the acidic Ultisol, but significantly higher in the slightly alkaline Inceptisol. Carbon-balance calculations found no major losses of biochar-C.Conclusion
Low bio-availability of biochar N did not make a significantly impact on rice production or N nutrition during the first year. Replacement of straw amendments with biochar could decrease CH4 emissions and increase SOC stocks. 相似文献12.
Aims
Low numbers of rhizobia in soil or inoculants delay nodulation and decrease symbiotic legume productivity. This study investigated the effect of co-inoculation with a helper bacterium, Pseudomonas fluorescens WSM3457 on the Medicago truncatula - Ensifer (Sinorhizobium) medicae WSM419 symbiosis challenged by a low inoculum dose.Methods
In a glasshouse experiment the effect of co-inoculation with WSM3457 on the kinetics of nodule initiation and development was assessed 5, 7, 10, 14, 17, 21, and 42 days after inoculation of M. truncatula cv. Caliph with 103 cells/plant of E. medicae WSM419.Results
Co-inoculated plants had enhanced rate of nodule initiation and development, greater numbers of larger crown nodules, and by day 42 accumulated more N than plants inoculated with E. medicae WSM419 alone. Nodule development was altered by co-inoculation. Approximately 25% of nodule initials on co-inoculated plants formed in closely associated pairs, young nodules were larger with multiple meristems and developed into cluster-like multi-lobed nodules compared to those on WSM419 inoculated plants. Molecular typing showed WSM3457 occupied a significant proportion of root nodules on co-inoculated plants.Conclusion
Co-inoculation with P. fluorescens WSM3457 enhanced symbiotic effectiveness of M. truncatula when inoculated with a low inoculum dose of E. medicae WSM419. 相似文献13.
To investigate salt stress and biochar application effects on nodulation and nitrogen metabolism of soybeans (Glycine max cv. M7), an experiment was conducted under the control condition. The treatments comprised three biochar rates (non, 50 and 100 g kg?1 soil) and three salinities (0, 5 and 10 dS m?1 NaCl), with four replications of treatments. Salt stress diminished the number of nodules and their weights in the soybean roots. Nitrogen content and metabolism decreased in nodules, roots and shoots, while reducing the activity of glutamate dehydrogenase (GDH), glutamine synthetase (GS), glutamine oxoglutarate aminotransferase (GOGAT) and nitrate reductase (NR). Also, salinity brought down root and shoot weight, total plant biomass, chlorophyll content, leaf area (LA) and rubisco activity in the soybean. On the other hand, application of biochar improved nodulation, nitrogen content, rubisco activity, GDH, GS, GOGAT and NR activities in different parts of the soybean and nodules under salt stress, and consequently improved chlorophyll content, LA, root and shoot weight. Both the 50 and 100 g kg?1 biochar rates showed similar effects in improving nitrogen metabolism and plant performance under salt stress. Generally, biochar increased nodulation and nitrogen metabolism of the soybean under saline conditions. 相似文献
14.
Summary The effect of exogenous applications of gibberellins (GAs) or the growth retardant -chloroethyltrimethylammonium chloride (CCC) on root nodule formation and activity (C2H2-reduction) in soya was studied. Daily foliar application of GA3 (2.89×10–6
M) delayed the formation of nodule initials and reduced the numbers mass nodule–1 and specific activity of nodules by 43%, 31% and 47% respectively, without affecting plant growth. Similar effects on nodulation were produced by foliar application of GA4 (3.01×10–5
M) or GA7 (3.03×10–5
M), or by the addition of GA3 (2.89×10–6
M) to the rooting medium. GA effectiveness in reducing nodule numbers was decreased by delaying its application until after the initial infection process had occurred, but the nodules formed were smaller and less active than those of the untreated control plants. The GA effect on nodulation and nodule activity was not associated with alterations in root exudate or due to a direct inhibitory effect of the hormone on the nitrogenase system. When the endogenous root content of GA-like substances was reduced (86% decrease) by foliar application of CCC (6.30×10–5
M), nodule numbers were increased by 56%, but nodule size and total nodule activity were similar to those of control plants. The GA and CCC treatments had no effect on rhizobial growth in liquid culture nor on root colonisation by rhizobia.The results suggest that the endogenous content of root GA may have a regulatory role in both the infection process and in subsequent nodule morphogenesis, thus controlling both the number and effectiveness of the root nodules formed. 相似文献
15.
Biochar’s effect on crop productivity and the dependence on experimental conditions—a meta-analysis of literature data 总被引:19,自引:0,他引:19
Xiaoyu Liu Afeng Zhang Chunying Ji Stephen Joseph Rongjun Bian Lianqing Li Genxing Pan Jorge Paz-Ferreiro 《Plant and Soil》2013,373(1-2):583-594
Background and aims
For the last decade, there has been an increasing global interest in using biochar to mitigate climate change by storing carbon in soil. However, there is a lack of detailed knowledge on the impact of biochar on the crop productivity in different agricultural systems. The objective of this study was to quantify the effect of biochar soil amendment (BSA) on crop productivity and to analyze the dependence of responses on experimental conditions.Methods
A weighted meta-analysis was conducted based on data from 103 studies published up to April, 2013. The effect of BSA on crop productivity was quantified by characterizing experimental conditions.Results
In the published experiments, with biochar amendment rates generally <30 t ha?1, BSA increased crop productivity by 11.0 % on average, while the responses varied with experimental conditions. Greater responses were found in pot experiments than in field, in acid than in neutral soils, in sandy textured than in loam and silt soils. Crop response in field experiments was greater for dry land crops (10.6 % on average) than for paddy rice (5.6 % on average). This result, associated with the higher response in acid and sandy textured soils, suggests both a liming and an aggregating/moistening effect of BSA.Conclusions
The analysis suggests a promising role for BSA in improving crop productivity especially for dry land crops, and in acid, poor-structured soils though there was wide variation with soil, crop and biochar properties. Long-term field studies are needed to elucidate the persistence of BSA’s effect and the mechanisms for improving crop production in a wide range of agricultural conditions. At current prices and C-trading schemes, however, BSA would not be cost-effective unless persistent soil improvement and crop response can be demonstrated. 相似文献16.
Neil A. Hipps Michael J. Davies Joel M. Dunn Howard Griffiths Christopher J. Atkinson 《Plant and Soil》2014,375(1-2):61-74
Aims
The objectives were to investigate (i) the forms and release pattern of P from an ash-rich biochar-amended sandy soil; (ii) the transformation of biochar P in a soil-plant system.Methods
Several methodologies (a bioassay test, soluble P extractions, a sequential P fractionation and successive P extractions via resin strips) were used to study the bioavailability and transformation of P in a sandy soil fertilised with either conventional P fertilisers [Ca(H2PO4)2 (CaP) and Sechura phosphate rock (SPR)] or biochars produced from cattle manure (MAe) and alum-treated biosolids (BSe) at four temperatures (250, 350, 450, and 550 °C).Results
Biochar P mainly contributed to increase soil resin-extractable P- and inorganic NaOH-extractable P-fractions, and thus to plant available P. The decrease in P concentrations of those fractions was caused by the uptake of P by plants rather than their transformations into more stable forms. P release rates diminished following the order: CaP > MAe > BSe > SPR, which indicates a decline in P availability from these P sources.Conclusions
Phosphorus-rich biochar can be used as a slow-release fertiliser. It is necessary to determine available P (either soil or fertiliser tests) in biochars prior to its application to soil, so that dose, frequency and timing of application are correctly established. 相似文献17.
Dipa Paul Chowdhury Knut Asbjørn Solhaug Yngvar Gauslaa 《Symbiosis (Philadelphia, Pa.)》2017,71(1):27-34
The symbiosis of Leguminosae with arbuscular mycorrhizal fungi (AMF) and N2-fixing nodulating bacteria (NFNB) can occur simultaneously, forming a tripartite symbiosis. In particular, AMF can colonize root nodules, although this interaction is not yet well elucidated, especially with regard to nodule activity and to the influence of external factors, such as biostimulants. In this study, we hypothesized that the application of the flavonoid formononetin, used to stimulate root colonization by native AMF, increases the AMF colonization of soybean (Glycine max) root nodules, especially under low availability of phosphorus (P). To test this hypothesis, we performed a field experiment in randomized blocks in a 4 × 3 factorial design, with 4 treatments of formononetin (0, 0.46, 0.92 and 1.84 g per kg seed) and 3 of P (0, 60 and 120 kg ha?1) with 5 replicates. Nodules and roots were collected during the R2 stage (full flowering) and evaluated with respect to AMF colonization. Formononetin stimulated mycorrhizal fungi colonization of active nodules, especially when no P was applied, as also observed for AMF root colonization; however, it had no effect with 60 and 120 kg P ha?1. Thus, the application of formononetin increases surface AMF colonization of active nodules and roots, but its effect disappears with an increase in P and the inactivity of the nodule. 相似文献
18.
Background and aims
Rhizodeposition of plants is the most uncertain component of the carbon (C) cycle. By existing approaches the amount of rhizodeposition can only roughly be estimated since its persistence in soil is very short compared to other organic C pools. We suggest an approach to quantify rhizodeposition at the field scale by assuming a constant ratio between rhizodeposited-C to root-C.Methods
Maize plants were pulse-labeled with 14CO2 under controlled conditions and the soil 14CO2 efflux was separated into root and rhizomicrobial respiration. The latter and the 14C activity remaining in the soil corresponded to total rhizodeposition. By relating rhizodeposited-14C to root-14C a rhizodeposition-to-root ratio of 0.56 was calculated. This ratio was applied to the root biomass C measured in the field to estimate rhizodeposition under field conditions.Results
Maize allocated 298 kg C ha?1 as root-C and 166 kg C ha?1 as rhizodeposited-C belowground, 50 % of which were recovered in the upper 10 cm. The fate of rhizodeposits was estimated based on the 14C data, which showed that 62 % of total rhizodeposition was mineralized within 16 days, 7 % and 0.3 % was incorporated into microbial biomass and DOC, respectively, and 31 % was recovered in the soil.Conclusions
We conclude that the present approach allows for an improved estimation of total rhizodeposition, since it accounts not only for the fraction of rhizodeposits remaining in soil, but also for that decomposed by microorganisms and released from the soil as CO2. 相似文献19.
Nitrous oxide emissions and nitrate leaching from a rain-fed wheat-maize rotation in the Sichuan Basin, China 总被引:3,自引:0,他引:3
Minghua Zhou Bo Zhu Klaus Butterbach-Bahl Xunhua Zheng Tao Wang Yanqiang Wang 《Plant and Soil》2013,362(1-2):149-159
Aims
A 3-year field experiment (October 2004–October 2007) was conducted to quantify N2O fluxes and determine the regulating factors from rain-fed, N fertilized wheat-maize rotation in the Sichuan Basin, China.Methods
Static chamber-GC techniques were used to measure soil N2O fluxes in three treatments (three replicates per treatment): CK (no fertilizer); N150 (300 kg N fertilizer ha?1 yr?1 or 150 kg N?ha?1 per crop); N250 (500 kg N fertilizer ha?1 yr?1 kg or 250 kg N?ha?1 per crop). Nitrate (NO 3 ? ) leaching losses were measured at nearby sites using free-drained lysimeters.Results
The annual N2O fluxes from the N fertilized treatments were in the range of 1.9 to 6.7 kg N?ha?1 yr?1 corresponding to an N2O emission factor ranging from 0.12 % to 1.06 % (mean value: 0.61 %). The relationship between monthly soil N2O fluxes and NO 3 - leaching losses can be described by a significant exponential decaying function.Conclusions
The N2O emission factor obtained in our study was somewhat lower than the current IPCC default emission factor (1 %). Nitrate leaching, through removal of topsoil NO 3 ? , is an underrated regulating factor of soil N2O fluxes from cropland, especially in the regions where high NO 3 - leaching losses occur. 相似文献20.
Woody legumes can play an important role in forest restoration on degraded land but the knowledge of woody legumes has lagged behind their uses. This study is a pioneer investigation to explore the ability of native woody legumes to form root nodules and fix nitrogen in Hong Kong. Nine sites of different habitat types were surveyed during both wet and dry seasons for two years. Young plants of woody legumes along studied transects were excavated. The patterns of nodulation and nodule morphology were recorded and the nitrogen fixing ability was tested by acetylene-reduction-assay. Twenty-eight species in 16 genera were examined, of which 20 species were nodulating and eight non-nodulating, including all six species in the Caesalpinioideae. Five species were new records to the world’s nodulation inventory. Bowringia callicarpa was a new species and genus examined, which was non-nodulating. The overall nodulation pattern was consistent with previous studies. Nodulation was more profuse in some shrub species while inconsistent in most tree species. Species with higher proportion of nodulated individual plants also tended to have more nodules in each plant. Spherical nodules were common in shrub and woody climber species whilst tree species usually had woody indeterminate nodules. Seasonal difference in the amount of senescent nodules was noted in most species. All the nodules tested by acetylene-reduction-assay were effectively nitrogen-fixing, with nitrogenase activity ranging from 4 μmol C2H4 g?1 h?1 to 20 μmol C2H4 g?1 h?1, which was comparable to other tropical tree species. The findings in nodulation pattern and nitrogen fixing ability of these species are essential in their application in forest restoration on degraded lands. 相似文献