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1.
Abstract

This study was undertaken to assess the mineralization of nitrogen (N) in rice soils amended with organic residues under flooded condition. A lab incubation study with a 3x3 factorial design (two replications) was conducted with three rice soils (Joydebpur, Faridpur, and Thakurgaon) receiving the following treatments: 1) control, 2) rice straw (Oryza sativa L.), or 3) pea vine (Pisum sativum L.). The organic residue (25 mg straw g‐1 soil) was mixed with soil and glass beads (1:1, soil to beads ratio), and transferred into a Pyrex leaching tube, flooded and then incubated at 35°C for up to 12 weeks. The soils in the leaching tubes were leached (while maintaining flooded condition) at 1,2,4, 8, and 12 weeks with deionized water for determination of NH4‐N, NO3‐N, pH, and Eh. Nitrogen mineralization in soils amended with rice straw was somewhat different than that of soils treated with pea vine. Soil treated with rice straw had a higher N mineralization rate than soils treated with pea vine, which was due to a lower carbon (C):N ratio for rice straw. The potentially mineralizable N pool (No) in soils amended with rice straw and pea vine under flooded conditions, estimated using a 1st order exponential equation, were 7 to 15 times, and 3 to 9 times greater for rice straw No values and pea vine, respectively, than the control. The KN values for unamended soils ranged from 0.35 to 0.52 mg N kg‐1 wk‐1 and rice straw and pea vine treated soils were from 0.75 to 1.22 and 0.46 to 0.58 mgN kg‐1 wk‐1. The lower No and KN values in pea vine treatments suggested there was greater immobilization of N than in rice straw treatments.  相似文献   

2.
Rice‐straw amendment increased methane production by 3‐fold over that of unamended control. Application of P as single superphosphate at 100 μg (g soil)–1 inhibited methane (CH4) production distinctly in flooded alluvial rice soil, in the absence more than in the presence of rice straw. CH4 emission from rice plants (cv. IR72) from alluvial soil treated with single superphosphate as basal application, in the presence and absence of rice straw, and held under non‐flooded and flooded conditions showed distinct variations. CH4 emission from non‐flooded soil amended with rice straw was high and almost similar to that of flooded soil without rice‐straw amendment. The cumulative CH4 efflux was highest (1041 mg pot–1) in rice‐straw‐amended flooded soil. Appreciable methanogenic reactions in rice‐straw‐amended soils were evident under both flooded and non‐flooded conditions. Rice‐straw application substantially altered the balance between total aerobic and anaerobic microorganisms even in non‐flooded soil. The mitigating effects of single‐superphosphate application or low‐moisture regime on CH4 production and emission were almost nullified due to enhanced activities of methanogenic archaea in the presence of rice straw.  相似文献   

3.
The mineralization of sulfur (S) was investigated in a Vertisol and an Inceptisol amended with organic manures, green manures, and crop residues. Field‐moist soils amended with 10 g kg—1 of organic materials were mixed with glass beads, placed in pyrex leaching tubes, leached with 0.01 M CaCl2 to remove the mineral S and incubated at 30 °C. The leachates were collected every fortnight for 16 weeks and analyzed for SO4‐S. The amount of S mineralized in control and in manure‐amended soils was highest in the first week and decreased steadily thereafter. The total S mineralized in amended soils varied considerably depending on the type of organic materials incorporated and soil used. The cumulative amounts of S mineralized in amended soils ranged from 6.98 mg S (kg soil)—1 in Inceptisol amended with wheat straw to 34.38 mg S (kg soil)—1 in Vertisol amended with farmyard manure (FYM). Expressed as a percentage of the S added to soils, the S mineralized was higher in FYM treated soils (63.5 to 67.3 %) as compared to poultry manure amended soils (60.5 to 62.3 %). Similarly the percentage of S mineralization from subabul (Leucaena leucocephala) loppings was higher (53.6 to 55.5 %) than that from gliricidia (Gliricidia sepium) loppings (50.3 to 51.1 %). Regression analysis clearly indicated the dependence of S mineralization on the C : S ratio of the organic materials added to soil. The addition of organic amendments resulted in net immobilization of S when the C : S ratio was above 290:1 in Vertisol and 349:1 in Inceptisol. The mineralizable S pool (So) and first‐order rate constant (k) varied considerably among the different types of organic materials added and soil. The So values of FYM treated soils were higher than in subabul, gliricidia, and poultry manure treated soils.  相似文献   

4.
The effect of rice straw on parathion degradation in a flooded alluvial soil was investigated. In soils inoculated with an enrichment culture which exhibited an exceptionally high ability to hydrolyze parathion, rice straw amendments inhibited parathion hydrolysis to p-nitrophenol and diethyl thiophosphoric acid. On the other hand, in uninoculated soils, rice straw enhanced the degradation of parathion via nitro reduction. During the enhanced breakdown of parathion in uninoculated soils amended with rice straw, aminoparathion and an unidentified metabolite evidently possessing a PS bond were detected. Thus, the influence of organic matter on the persistence of parathion in flooded soil is governed by the metabolic pathway involved in the degradation.  相似文献   

5.

Purpose

Acid sulfate soils (ASS) are common in wetlands and can pose an environmental threat when they dry because oxidation of pyrite may cause strong acidification. Addition of organic matter can stimulate sulfate reduction during wet periods and minimize acidification during dry periods. However, the effect of the organic amendment may depend on its composition.

Materials and methods

Three wetland acid sulfate (sulfuric, hypersulfidic, and hyposulfidic) soils collected from different depth in one profile were used. The soils, unamended or amended with 10 g C kg?1 as glucose, wheat straw, pea straw, or Phragmites litter, were incubated for 18 weeks under flooded conditions (“wet period”) followed by 10 weeks during which the soils were maintained at 100 % of maximum water-holding capacity (“dry period”).

Results and discussion

During the wet period, the pH decreased in the control and with glucose to pH 3–4, but increased or was maintained in residue-amended soils (pH at the end of the wet period about 7). In the dry period, the pH of the control and glucose-amended soils remained low, whereas the pH in residue-amended soils decreased. However, at end of the dry period, the pH was higher in residue-amended soils than in the control or glucose-amended soils, particularly with pea straw (C/N 50).

Conclusions

Amendment of acid sulfate soils with plant residues (particularly those with low to moderate C/N ratio) can stimulate pH increase during flooding and reduce acidification under oxidizing conditions.
  相似文献   

6.
 CH4 production in an alluvial soil, unamended or amended with rice straw (1% w/w), was examined under nonflooded [–1.5 MPa, –0.01 MPa and 0 MPa (saturated) and flooded (1 : 1.25 soil to water ratio)] conditions during a 40-day incubation in closed Vacutainer tubes. CH4 production was negligible at –1.5 MPa, but increased with an increase in the moisture level. Addition of rice straw distinctly increased CH4 production in the soil at all moisture levels including –1.5 MPa. Evidence, in terms of the drop in redox potential and Fe2+ accumulated, suggested that the addition of rice straw hastened the reduction of the soil, even under nonflooded conditions; thus its addition stimulated even the nonflooded soil to produce CH4 in substantial amounts. Our results indicate that many currently unidentified sources of CH4, possibly including organic-amended nonflooded soils, may make a significant contribution to the global CH4 budget. Received: 10 July 1997  相似文献   

7.
The influence of several carbon sources on heterotrophic N2 fixation in four paddy soils under flooded and nonflooded conditions was investigated by 15N-tracer technique. Greater N2 fixation occurred in submerged soils amended with cellulose and rice straw, the former being superior. Addition of sucrose, glucose and malate in that order stimulated N2 fixation in submerged alluvial soil, while sucrose alone enhanced N3 fixation in laterite soil. In submerged acid soils none of these C sources stimulated N2 fixation. Nonflooded conditions favoured N2 fixation in alluvial and acid saline soils amended with cellulose, sucrose and glucose.  相似文献   

8.
The degradation of14 C-Carbofuran was studied in sterilized, unsterilized and green manure amended clay soil under moist and flooded conditions overa period of 30 days. The14 C mass balance showed that carbofuran did not undergo any degradation in sterilized moist soil. In sterilized flooded soil bound residues were formed to the extent of about 47% of the applied radioactivity at the end of 30 days. Carbofuran underwent considerable degradation in unsterilized moist and flooded soils. In moist soil about 48% of the applied14 C activity was recovered as bound activity while in flooded soil, about 23% of the activity was bound. Green manure amendment resulted in formation of more bound residues under moist conditions while it enhanced the degradation of carbofuran under flooded conditions. In flooded amended soil about 44% of the appliedl4 C-activity was recovered as against about 54% in the unamended flooded soil. The notable degradation products formed under flooded soil conditions were 3-keto carbofuran and 3-hydroxy carbofuran.  相似文献   

9.
Previous studies have shown that carbon (C) mineralization in saline or sodic soils is affected by various factors including organic C content, salt concentration and water content in saline soils and soil structure in sodic soils, but there is little information about which soil properties control carbon dioxide (CO2) emission from saline-sodic soils. In this study, eight field-collected saline–sodic soils, varying in electrical conductivity (ECe, a measure of salinity, ranging from 3 to 262 dS m−1) and sodium adsorption ratio (SARe, a measure of sodicity, ranging from 11 to 62), were left unamended or amended with mature wheat or vetch residues (2% w/w). Carbon dioxide release was measured over 42 days at constant temperature and soil water content. Cumulative respiration expressed per gram SOC increased in the following order: unamended soil<soil amended with wheat residues (C/N ratio 122)<soil with vetch residue (C/N ratio 18). Cumulative respiration was significantly (p < 0.05) negatively correlated with ECe but not with SARe. Our results show that the response to ECe and SARe of the microbial community activated by addition of organic C does not differ from that of the less active microbial community in unamended soils and that salinity is the main influential factor for C mineralization in saline–sodic soils.  相似文献   

10.
A pot experiment was conducted to study the effects of rice cropping on elemental sulfur (S0) oxidation in three paddy soils under flooded conditions. Unaltered wet samples of paddy soils derived from cinnamon soil, black soil and red soil, respectively, were used. Repacked soils were incubated for 14, 28 and 42 days with or without addition of 2,000 mg kg-1 S0 (particle size of 0.075 cm) and with or without cropping. Substantial amounts of oxidized S0 were found to be immobilized into organic S or taken up by plants. The apparent mass of oxidized S was calculated as the sum of the net increase of the sulfate-S and organic-S pools, and S taken up by plants. Under flooded conditions and in the absence of rice, the oxidation rates in all three soils were the greatest during the initial 14 days and then declined with progressive incubation. Incubation for a 42-day period resulted in oxidation of 5.58-10.15% of applied S0. Meanwhile 3.23-5.60% of the applied S0 was converted into organic S. Cropping with rice could significantly increase S oxidation and conversion of S0 into organic S in soils. Incubation for 42 days resulted in the oxidation of 10.28-14.87% of the applied S0, and conversion of 5.74-8.06% of applied S0 into organic S in the three soils. The results suggest that S0 fertilizers should be applied to the soil horizon rich with rice roots (i.e. the rhizosphere) in flooded paddy soils in order to increase the efficiency of S0 oxidation and plant availability.  相似文献   

11.
There have been few investigations of the possible effects of genetically engineered plants on the microbiota and enzyme activities in flooded soil. We studied the influence of the transgenic rice KeMingDao (KMD) straw on the culturable microbiota and enzymatic activities in a flooded paddy soil under laboratory conditions. KMD contained a synthetic cry1Ab gene from Bacillus thuringiensis under the control of a maize ubiquitin promoter and linked in tandem with the gusA and hpt genes. The results showed that there were only some occasional significant differences (P<0.05) in the number of Colony forming units of aerobic bacteria, actinomycetes and fungi and in the number of anaerobic fermentative bacteria, denitrifying bacteria, hydrogen-producing acetogenic bacteria, and methanogenic bacteria between the paddy soil amended with Bt-transgenic rice straw and with the non-Bt parental rice straw during the early stages of incubation. From d14 to d84 there were significant increases (P<0.05) in soil dehydrogenase and soil neutral phosphatase activity in soils amended with rice straw compared to soil without added straw. The dehydrogenase activity was significantly greatly (almost 1.95-fold) in soil amended with Bt-transgenic straw from d7 to d14 but from d21 to d49 there was significantly greater activity (about 1.47-fold) in the soil amended with non-Bt-straw. There were no apparent differences between the activity of soil neutral phosphatase in the soils to which non-Bt-straw and Bt-straw had been added. However, both soils to which rice straws were added demonstrated significant differences in the number of microorganisms except for aerobic bacteria and enzymatic activities with respect to the control soil throughout the incubation. The above results indicated that the Bt-straw from KMD transgenic rice is not toxic to a variety of culturable microorganisms in the studied flooded paddy soil.  相似文献   

12.
Nitrate leaching from intermittently flooded rice fields contributes to nitrate pollution in groundwater. In this study, redox conditions and nitrate change in a newly flooded rice soil under the influence of oxidative iron (Fe) and manganese (Mn) were investigated using flooded soil columns under moderate percolation (4.2?mm?d?1). The amendments of α-Fe2O3 and β-MnO2 powder (5 and 2.7?mg?g?1, respectively) delayed the establishment of reducing conditions and lowered the rate of nitrate removal in the soil column, and subsequently increased the percolation of soil indigenous nitrate (8.3?mg nitrogen [N]?kg?1) from 2.0% to 8.0%, and the percolation of externally amended nitrate (250?mg?N?kg?1) from 11.0% to 26.0%. The pool of oxidative iron-centered metal oxidants needs to be jointly considered with the availability of organic carbon and hydrological conditions in evaluating redox conditions and nitrate change in intermittently flooded rice soils.  相似文献   

13.
Net carbon dioxide (CO2) emission from soils is controlled by the input rate of organic material and the rate of decomposition which in turn are affected by temperature, moisture and soil factors. While the relationships between CO2 emission and soil factors are well-studied in non-salt-affected soils, little is known about soil properties controlling CO2 emission from salt-affected soils. To close this knowledge gap, non-salt-affected and salt-affected soils (0-0.30 m) were collected from two agricultural regions: in India (irrigation induced salinity) and in Australia (salinity associated with ground water or non-ground water associated salinity). A subset (50 Indian and 70 Australian soils) covering the range of electrical conductivity (EC) and sodium adsorption ratio (SAR) in each region was used in a laboratory incubation experiment. The soils were left unamended or amended with mature wheat residues (2% w/w) and CO2 release was measured over 120 days at constant temperature and soil water content. Residues were added to overcome carbon limitation for soil respiration. For the unamended soils, separation in multidimensional scaling plots was a function of differences in soil texture (clay, sand), SOC pools (particulate organic carbon (POC) and humus-C) and also EC. Cumulative CO2-C emission from unamended and amended soils was related to soil properties by stepwise regression models. Cumulative CO2-C emission was negatively correlated with EC in saline soils (R2 = 0.50, p < 0.05) from both regions. In the unamended non-salt-affected soils, cumulative CO2-C emission was significantly positively related to the content of POC for the Indian soils and negatively related to clay content for the Australian soils. In the wheat residue amended soils, cumulative CO2-C emission had positive relationship with POC and humus-C but a negative correlation with EC for both Indian and Australian soils. SAR was negatively related (β = −0.66, p < 0.05) with cumulative CO2-C emission only for the unamended saline-sodic soils of Australia. Cumulative CO2-C emission was significantly negatively correlated with bulk density in amended soils from both regions. The study showed that in salt-affected soils, EC was the main factor influencing for soil respiration but the content of POC, humus-C and clay were also influential with the magnitude of influence depending on whether the soils were salt affected or not.  相似文献   

14.
Sulfur (S) deficiency in soils is increasingly recognized in agricultural systems. The quantification of S mineralization/immobilization processes after incorporation of organic materials into soils is a key factor to predict the availability of S to growing plants. However, immobilization and mineralization occur simultaneously making the quantification of the magnitude of each process difficult. We used the inverse isotope (35SO4) dilution technique to quantify immobilization and mineralization fluxes after incorporation of two organic residues with contrasting C/S ratio's (cabbage or wheat straw) into a sandy soil in planted and unplanted soils (pot trial with ryegrass and incubation). The soil was labeled with 35SO4 and incubated for 63 days prior to the application of residues. The specific activity (SA) of soil-extractable SO4 did not change significantly in the control soil during the subsequent experimental period despite significant net mineralization, illustrating that labile-S in soil was homogenously labeled. Application of residues decreased the SAs during the incubation due to the dilution with unlabeled-S from the residues. A three-compartment dynamic model was fitted to the SA data predicting that gross mineralization of residue-S was almost complete over 43 days incubation although this release was not matched by the increase in soil SO4 due to immobilization reactions. Soil-extractable SO4 was significantly increased in the cabbage-treated soil while the reverse was true in the wheat straw amended soil in which the S-immobilization was almost twice the gross mineralization of residue-S. The SA of S in ryegrass were maximally 15% lower than in corresponding soil extracts suggesting that residue mineralization was similar in planted and unplanted soils. The inverse isotope dilution method offers potential for screening S release of different residues; however the details of the dynamics of soil-S isotopes show that the individual fluxes are not constant during the incubation.  相似文献   

15.
Subtropical recent alluvial soils are low in organic carbon (C). Thus, increasing organic C is a major challenge to sustain soil fertility. Biochar amendment could be an option as biochar is a C-rich pyrolyzed material, which is slowly decomposed in soil. We investigated C mineralization (CO2-C evolution) in two types of soils (recent and old alluvial soils) amended with two feedstocks (sugarcane bagasse and rice husk) (1%, weight/weight), as well as their biochars and aged biochars under a controlled environment (25 ±2 ℃) over 85 d. For the recent alluvial soil (charland soil), the highest absolute cumulative CO2-C evolution was observed in the sugarcane bagasse treatment (1 140 mg CO2-C kg-1 soil) followed by the rice husk treatment (1 090 mg CO2-C kg-1 soil); the lowest amount (150 mg CO2-C kg-1 soil) was observed in the aged rice husk biochar treatment. Similarly, for the old alluvial soil (farmland soil), the highest absolute cumulative CO2-C evolution (1 290 mg CO2-C kg-1 soil) was observed in the sugarcane bagasse treatment and then in the rice husk treatment (1 270 mg CO2-C kg-1 soil); the lowest amount (200 mg CO2-C kg-1 soil) was in the aged rice husk biochar treatment. Aged sugarcane bagasse and rice husk biochar treatments reduced absolute cumulative CO2-C evolution by 10% and 36%, respectively, compared with unamended recent alluvial soil, and by 10% and 18%, respectively, compared with unamended old alluvial soil. Both absolute and normalized C mineralization were similar between the sugarcane bagasse and rice husk treatments, between the biochar treatments, and between the aged biochar treatments. In both soils, the feedstock treatments resulted in the highest cumulative CO2-C evolution, followed by the biochar treatments and then the aged biochar treatments. The absolute and normalized CO2-C evolution and the mineralization rate constant of the stable C pool (Ks) were lower in the recent alluvial soil compared with those in the old alluvial soil. The biochars and aged biochars had a negative priming effect in both soils, but the effect was more prominent in the recent alluvial soil. These results would have good implications for improving organic matter content in organic C-poor alluvial soils.  相似文献   

16.
The effect of various carbon sources on asymbiotic N2 fixation in a paddy soil was studied by C2H2 reduction and 15N tracer techniques. N2 fixation increased with increasing concentrations of cellulose and rice straw, but the former was more effective. N2 fixation was considerably enhanced in soils amended with glucose, sucrose, succinate, acetate, butyrate, pyruvate or n-propanol, while n-butanol, ethanol, lignin or paraffin were ineffective. Succinate at low moisture content and butyrate under flooded conditions stimulated N2 fixation during a 15-day incubation.  相似文献   

17.
Adding easily decomposable organic materials into flooded nitrate-rich soils can effectively decrease the soil nitrate concentration and repair nitrate-rich soil. However, nitrate reduction is usually accompanied with an increase in N2O emission. This study was conducted to reduce N2O emission in a nitrate-rich vegetable soil flooded for remediation and amended with biochar. Nitrate-rich vegetable soil was placed in five treatment groups: flooding (F); flooding with rice straw (F?+?RS); flooding with rice straw and 1% biochar (F?+?RS?+?1% biochar); flooding with rice straw and 3% biochar (F?+?RS?+?3% biochar); flooding with rice straw and CaO (F?+?RS?+?CaO). Biochar and CaO reduced the N2O emission levels relative to the F?+?RS group, with the former being more effective than the latter, achieving reduction of 40.70% (3% biochar) and 17.35% (CaO) of cumulative N2O emission. The 3% biochar was more effective than the 1% biochar. Regression analysis showed a positive correlation between the abundance of NO reductase gene (norB) and soil N2O emission flux. In general, biochar and CaO could effectively reduce N2O emissions from a nitrate-rich vegetable soil during flooding remediation, duo to elevating soil pH and altering denitrifying activity. The norB gene was the most important denitrifying gene driving soil N2O emission in the remediation.  相似文献   

18.
Addition of rice straw, which is a common practice in rice agriculture, generally results in enhanced production and emission of the greenhouse gas methane (CH4). However, it is unclear whether straw addition affects only the activity or also the composition of the methanogenic microbial community. It is also unclear to what extent methanogenic archaea would be able to proliferate in the soil. Anoxic slurries of Italian rice‐field soil produced CH4 after a lag, during which ferric iron and sulfate were reduced. Addition of rice straw slightly decreased this lag and greatly enhanced the subsequent production of CH4. At the same time, addition of rice straw enhanced the intermediate production of H2 and acetate that served as the methanogenic substrates. Compared with the unamended control, the addition of rice straw resulted in an increased concentration of phospholipid fatty acids in the soil. Quantitative ‘real‐time’ PCR targeting the 16S rRNA gene also showed increased copy numbers of both Bacteria and Archaea in the straw‐amended soil at the end of the experiment. The composition of the archaeal community was followed over time by terminal restriction length polymorphism (T‐RFLP) analysis of the archaeal 16S rRNA genes extracted from straw‐amended soil and the control. Rice Cluster‐I (RC‐I) methanogens and Methanosarcinaceae were the most abundant methanogenic populations, followed by Methanobacteriales, Methanomicrobiales and Methanosaetaceae. Addition of rice straw resulted in a relative increase of Methanosarcinaceae and Methanobacteriales and a relative decrease of RC‐I methanogens and Methanomicrobiales. Our results revealed a dynamic methanogenic community in anoxic rice‐field soil and showed that addition of organic matter selectively enhanced the growth of particular methanogenic populations, which were apparently better adapted to the presence of straw than the others. The extent of archaeal growth was consistent with that expected theoretically from the ambient Gibbs free energies of hydrogenotrophic and acetoclastic methanogenesis.  相似文献   

19.
Phenol oxidase (Pox) plays a key role in soil C cycle and its presence may affect soil C mineralization during crop residue decomposition. To examine soil dynamics and relationships between Pox, phenols, Fe2+, and C mineralization, we designed a 53‐d laboratory experiment conducted with and without rice straw addition and under non‐flooded and flooded conditions. The results demonstrate that rice straw can indeed decompose faster under flooded conditions. The addition of rice straw significantly increased soil Pox activity (up to 15‐fold), but only under flooded conditions. Rice straw application increased alkali extractable phenol (AEP) concentration by 129% at day 4. However, flooded conditions reduced soil AEP by 61% and 49% at day 53 with and without rice straw application, respectively. Phenol oxidase activity was positively correlated with dissolved organic C and Fe2+, while negatively related to AEP, which itself was positively correlated with C mineralization (i.e., CO2 emission rates). Also, all relationships between soil Pox, AEP, Fe2+, and C were stronger under flooded conditions. We therefore conclude that flooded conditions in paddy soil may promote straw decomposition as a result of the stimulation of Pox activity and phenol decomposition.  相似文献   

20.
Fusarium solani oxidized So to S2O32?; S4O62? and SO42? in culture and when grown in autoclaved soils amended with the element. The intermediates were also oxidized to SO42?, suggesting involvement of the polythionate pathway in fungal S-oxidation. Indigenous F. solani was shown to oxidize S in non-sterile soil.  相似文献   

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