Rice Straw Decomposition Research Articles

Simulating the effects of soil temperature and moisture in the off-rice season on rice straw decomposition and subsequent CH4 production during the growth season in a paddy soil

To understand the effects of soil temperature and moisture on rice straw decomposition during the off-rice season and subsequent CH4 production in rice growth season, we firstly incubated a paddy soil with 13C-labeled straw addition under four temperature (±5, 5, 15, and 25 °C) and two moisture levels (60 and 100 % water-filled pore space (WFPS)) under aerobic conditions for 24 weeks and subsequently incubated those samples anaerobically at 30 °C and under submerged conditions for 4 weeks. Temperature change at ±5 °C was used to simulate the diurnal variation of soil temperature between night (−5 °C, 12 h) and day (5 °C, 12 h) during the corresponding freeze-thaw cycles. Our results showed that both increased soil temperature and moisture significantly promoted straw aerobic decomposition as observed by carbon dioxide (CO2) production, soil organic carbon (SOC) content, and its δ13C value in this incubation experiment. During the anaerobic incubation, straw-amended soil samples remarkably promoted CH4 production and CH4/total decomposed C. Both CH4 and CO2 productions in straw-amended soil samples were lowest at 25 °C and 100 % WFPS and highest at ±5 °C and 100 % WFPS, which could be attributed to a depletion of labile organic C derived from straw during the 24-week aerobic incubation. Total rates of straw C decomposition calculated from decomposed C production, SOC content, and δ13C value in the whole incubation (aerobic + anaerobic) ranged from 29.8 to 48.1, 45.0 to 64.2, and 25.7 to 35.7 %, respectively. These results imply that increasing soil temperature during the off-rice season promotes the rice straw decomposition and leads to a decrease in CH4 production during the subsequent rice growth season under conditions of northeastern Japan.

Sorption of Cu by organic matter from the decomposition of rice straw

Sorption of heavy metals on soil components plays an important role in reducing their mobility and bioavailability. Organic matter is an important sorbent of heavy metals in soil. Crop residues which are important sources of soil organic matter will undergo decomposition after addition to the soil. However, few studies reported the effect of organic matter decomposition on heavy metal sorption. This study aimed to investigate the effect of straw decomposition on the sorption of Cu. Rice straw was decomposed in aerobic conditions for 1, 3, 6, and 12 months, respectively. Solid organic matter in decomposed rice straw was collected and marked OM-1, OM-3, OM-6, and OM-12, respectively. Sorption isotherms and kinetics of Cu on solid organic matter were studied by batch experiments. The sorption of Cu was calculated by the difference between the amount of Cu added initially and that remained in the supernatant. Sorption thermodynamics of Cu were studied by isothermal titration calorimetry technique. Potential mechanisms of Cu sorption were analyzed by combining the information from sorption thermodynamics, desorption experiments, and Fourier transform infrared spectroscopy observations. All sorption experiments were carried out at pH 5.0. The maximum sorption of Cu was 165.8, 170.5, 186.6, and 226.9 mmol kg−1, and the rate constant of Cu sorption was 0.80, 0.58, 0.50, and 0.32 kg mmol−1 h−1 on OM-1, OM-3, OM-6, and OM-12, respectively, indicating that the maximum sorption of Cu increased while sorption rate of Cu decreased with increasing the duration of straw decomposition from 1 to 12 months. The negative values of Gibbs free energy change and positive values of enthalpy change and entropy change revealed that Cu sorption was spontaneous, endothermic in nature, and the randomness was increased during sorption. Carboxyl and hydroxyl in solid organic matter were involved in Cu sorption. The percentage of Cu desorbed by NH4Ac from OM-1, OM-3, OM-6, and OM-12 was 45.0, 43.5, 42.8, and 37.8 %, respectively. In the current study, the decomposition of straw promoted the sorption capacity but reduced the sorption rate of Cu on solid organic matter. Copper sorption was an endothermic and spontaneous process. The formation of inner-sphere complexes was the main mechanism of Cu sorption, and its role in Cu sorption tended to increase with increasing the duration of straw decomposition. The information will facilitate the understanding of the contamination and remediation of heavy metal in cropland.

An evaluation of a microbial inoculum in promoting organic C decomposition in a paddy soil following straw incorporation

Impacts of a commercially available decay-facilitating microbial inoculum on carbon (C) and nitrogen (N) mineralization were evaluated during decomposition of rice straw in a paddy soil. Two incubation experiments were conducted for 105 days with a typical low-yield high-clay soil in central China to monitor effects of straw and the inoculum on CO2 evolution, as well as dissolved organic C (DOC), NH4 +, NO3 −, and pH under conditions of 15 °C 70 %, 25 °C 40 %, 25 °C 70 %, 25 °C 100 %, and 35 °C 70 % of water-holding capacity (WHC) with adequate N, supplied as urea or manure, respectively. Treatments of 25 °C 70 % WHC, 25 °C 100 % WHC, and 35 °C 70 % WHC generally achieved significant higher CO2 evolution while treatment of 25 °C 40 % WHC had least. This was more evident with added manure compared to urea (P < 0.05). The inoculum generally increased the decomposition of C inputs and the largest increases were in the initial 28 day in treatments 25 °C 70 % WHC, 25 °C 100 % WHC, and 35 °C 70 % WHC; only the 25 °C 40 % WHC actually immobilized C. The CO2 release rates were positively correlated with DOC, but with different slopes within treatments. Despite equivalent N application rates, manure treatments had significantly less N (including NO3 −, NH4 +, and total dissolved N) than those with urea. Incubation of 25 °C 40 % WHC decreased soil pH the least, probably due to relative low moisture causing delayed nitrification. The results implied that the inoculum, especially fungi, would adjust to edaphic and N fertilization in regulating organic C mineralization, during which water potential would exhibit a great role in regulating substrate and nutrient availability.

The Effects of UV-A on Dry Rice Straw Decomposition under Controlled Laboratory Conditions

In arid and semi-arid areas, organic matter decomposition is stimulated by ultraviolet radiation. In this paper, the association between straw decomposition and UV-A exposure was evaluated. Oven-dried rice straw samples were chronically exposed to UV-A radiation and examined periodically for up to 90 days at room temperature. Scanning electron microscopy (SEM) showed that noticeable disintegration of the fiber structure occurred on the irradiated sample surface in comparison to the control. At the end of the UV-A treatment period, straw mass had decreased by 5%, and dissolved organic carbon (DOC) increased by 18%. The content of cellulose, hemicellulose, and lignin of the irradiated straw decreased by 29.3%, 14.4% and 49.3%, respectively. The marked loss of nitrogen and potassium in the exposed straw were also observed. Thermogravimetric analysis (TGA) showed that treatment with UV-A radiation tended to decrease the mass loss rate and the thermal degradation temperature of the straw biomass from 220 °C to 208 °C. Infrared spectrometric analysis (ATR-FTIR) showed that functional groups, e.g., C–OH and C–O–C, were disrupted obviously due to UV-A exposure. These results suggest that ultraviolet-A irradiation facilitates straw decomposition by direct photochemical degradation.

H2-Producing Bacterial Community during Rice Straw Decomposition in Paddy Field Soil: Estimation by an Analysis of [FeFe]-Hydrogenase Gene Transcripts.

The transcription patterns of [FeFe]-hydrogenase genes (hydA), which encode the enzymes responsible for H2 production, were investigated during rice straw decomposition in paddy soil using molecular biological techniques. Paddy soil amended with and without rice straw was incubated under anoxic conditions. RNA was extracted from the soil, and three clone libraries of hydA were constructed using RNAs obtained from samples in the initial phase of rice straw decomposition (day 1 with rice straw), methanogenic phase of rice straw decomposition (day 14 with rice straw), and under a non-amended condition (day 14 without rice straw). hydA genes related to Proteobacteria, Firmicutes, Bacteroidetes, Chloroflexi, and Thermotogae were mainly transcribed in paddy soil samples; however, their proportions markedly differed among the libraries. Deltaproteobacteria-related hydA genes were predominantly transcribed on day 1 with rice straw, while various types of hydA genes related to several phyla were transcribed on day 14 with rice straw. Although the diversity of transcribed hydA was significantly higher in the library on day 14 with rice straw than the other two libraries, the composition of hydA transcripts in the library was similar to that in the library on day 14 without rice straw. These results indicate that the composition of active H2 producers and/or H2 metabolic patterns dynamically change during rice straw decomposition in paddy soil.

Modeling aerobic decomposition of rice straw during the off-rice season in an Andisol paddy soil in a cold temperate region of Japan: Effects of soil temperature and moisture

ABSTRACTSubmerged rice paddies are a major source of methane (CH4) which is the second most important greenhouse gas after carbon dioxide (CO2). Accelerating rice straw decomposition during the off-rice season could help to reduce CH4 emission from rice paddies during the single rice-growth season in cold temperate regions. For understanding how both temperature and moisture can affect the rate of rice straw decomposition during the off-rice season in the cold temperate region of Tohoku district, Japan, a modeling incubation experiment was carried out in the laboratory. Bulk soil and soil mixed with 2% of δ13C-labeled rice straw with a full factorial combination of four temperature levels (−5 to 5, 5, 15, 25°C) and two moisture levels (60% and 100% WFPS) were incubated for 24 weeks. The daily change from −5 to 5°C was used to model the freezing–thawing cycles occurring during the winter season. The rates of rice straw decomposition were calculated by (i) CO2 production; (ii) change in the soil organic carbon (SOC) content; and (iii) change in the δ13C value of SOC. The results indicated that both temperature and moisture affected the rate of rice straw decomposition during the 24-week aerobic incubation period. Rates of rice straw decomposition increased not only with high temperature, but also with high moisture conditions. The rates of rice straw decomposition were more accurately calculated by CO2 production compared to those calculated by the change in the SOC content, or in its δ13C value. Under high moisture at 100% WFPS condition, the rates of rice straw decomposition were 14.0, 22.2, 33.5 and 46.2% at −5 to 5, 5, 15 and 25°C temperature treatments, respectively. While under low moisture at 60% WFPS condition, these rates were 12.7, 18.3, 31.2 and 38.4%, respectively. The Q10 of rice straw decomposition was higher between −5 to 5 and 5°C than that between 5 and 15°C and that between 15 and 25°C. Daily freezing–thawing cycles (from −5 to 5°C) did not stimulate rice straw decomposition compared with low temperature at 5°C. This study implies that to reduce CH4 emission from rice paddies during the single rice-growth season in the cold temperate regions, enhancing rice straw decomposition during the high temperature period is very important.

The Efficiency of Some Wild Strain Bacilli on Celluase and Nitrogenase Activities During the Rice Straw Decomposition

&lt;p&gt;This experiment aimed to select new effective bacteria with high ability for cellulose decomposition and nitrogen fixation from various natural materials in order to improve organic fertilizers. CMC, N-free medium were used as culture broth and agar. The procedure determined 60 isolates of bacteria from decomposing rice straw, decomposing wood, cow manure, bagasse organic fertilizers, termite nest and the LDD1 inoculum. After that process, the selected bacteria (6 isolates) were identified for species level. All isolates were rod-shaped, gram-positive and spore forming bacteria that belonged to a bacillus group in species of &lt;em&gt;Geobacillus stearothermophilus&lt;/em&gt; and &lt;em&gt;Bacillus cereus&lt;/em&gt; which some species showed thermophillic character. Then, three sub-experiments were conducted. By considering the testing of the bacterial ability on cellulase activity, CRD with 3 replications were employed. The result showed that 1)&lt;em&gt; G. stearothermophilus&lt;/em&gt;&lt;em&gt; &lt;/em&gt;DW3 had the highest potential of CMCase activity (37.50 mm diameter), 2)&lt;em&gt; G. stearothermophilus&lt;/em&gt; RS6 had the highest potential of FPase activity (4.942 mU/ml), 3)&lt;em&gt; G. stearothermophilus&lt;/em&gt;&lt;em&gt; &lt;/em&gt;RS2 had the highest potential of Avicelase activity (12.680 mU/ml) and 4) &lt;em&gt;G. stearothermophilus&lt;/em&gt;&lt;em&gt; &lt;/em&gt;DW3 had the highest potential of α-cellulase activity (4.289 mU/ml). In addition, regarding the study of bacterial nitrogenase activity, CRD with 3 replications were employed. The result showed that &lt;em&gt;B. cereus &lt;/em&gt;CM6 had the most outstanding nitrogenase activity (278.788 nmolC&lt;sub&gt;2&lt;/sub&gt;H&lt;sub&gt;4&lt;/sub&gt;/ml/hr). In case of the study on the effectiveness of rice straw decomposition, the CRD with 3 replications were conducted. The study based on the standard index of organic fertilizer of Land Development Department (LDD), Thailand Ministry of Agriculture and Cooperatives. The result was found that the decayed rice straw in the inoculated treatment was qualified at 75 days, whereas the control treatment was not. The percentage of N, P and K in the inoculated treatments&lt;em&gt; &lt;/em&gt;at 90 days was better than the previous period. In addition, C/N ratio decreased with times but the amounts of N, P and K increased. On the contrary, the percentages of N, P and K of the control treatment were satisfied while the C/N ratio was not in the standard level. The amounts of bacterial population among the inoculated treatments were not significantly different, but, they were significantly different between the inoculated and the control treatments.&lt;/p&gt;

Effects of Residue Management on Decomposition in Irrigated Rice Fields Are Not Related to Changes in the Decomposer Community.

Decomposers provide an essential ecosystem service that contributes to sustainable production in rice ecosystems by driving the release of nutrients from organic crop residues. During a single rice crop cycle we examined the effects of four different crop residue management practices (rice straw or ash of burned straw scattered on the soil surface or incorporated into the soil) on rice straw decomposition and on the abundance of aquatic and soil-dwelling invertebrates. Mass loss of rice straw in litterbags of two different mesh sizes that either prevented or allowed access of meso- and macro-invertebrates was used as a proxy for decomposition rates. Invertebrates significantly increased total loss of litter mass by up to 30%. Initially, the contribution of invertebrates to decomposition was significantly smaller in plots with rice straw scattered on the soil surface; however, this effect disappeared later in the season. We found no significant responses in microbial decomposition rates to management practices. The abundance of aquatic fauna was higher in fields with rice straw amendment, whereas the abundance of soil fauna fluctuated considerably. There was a clear separation between the overall invertebrate community structure in response to the ash and straw treatments. However, we found no correlation between litter mass loss and abundances of various lineages of invertebrates. Our results indicate that invertebrates can contribute to soil fertility in irrigated paddy fields by decomposing rice straw, and that their abundance as well as efficiency in decomposition may be promoted by crop residue management practices.

Decomposition and Carbon Sequestration Potential of Different Rice-Residue-Derived By-products and Farmyard Manure in a Sandy Loam Soil

Large quantities of rice straw are produced annually in India and the majority of it is burnt in the fields, leading to environmental pollution and loss of carbon (C) and essential nutrients. It is imperative to manage rice residues and by-products to derive benefits for soil health and environment conservation. We studied the decomposition of rice straw (RS), rice-straw-derived biochar and compost (RSC), rice husk (RH), rice husk ash (RHA), and farmyard manure (FYM) in laboratory incubation experiments at 30 ºC and field-capacity moisture. The decomposition of organic sources depended on the size of decomposable and recalcitrant C pools. Carbon mineralization was greater from RS and RH compared to FYM, biochar, RSC, and RHA. The initial rate of mineralization was faster for RS and RH, followed by FYM, biochar, and RSC, and the least for RHA. The proportion of antecedent C mineralized from different sources followed the order RS > RH > FYM> RSC = biochar > RHA. The RS and RH showed larger decomposable pools than the other sources. Rice husk ash had decomposable pool and associated rate coefficient similar to the unamended soil. Residence time for recalcitrant pool in FYM, RSC, and biochar applied at 5 g C kg–1 soil ranged between 1020 and 1149 days as opposed to 180 and 254 days for RS and RH, respectively. Increasing the rate of C application (15 g C kg−1) markedly increased the residence time for all the sources, except FYM, and these followed the order RHA (2273 d) > RSC (2000 d) > biochar (1961 d) > RH (529 d) > RS (400 d). It was concluded that RS and RH could result in short-term C accrual in soil, whereas RSC, biochar, and FYM may lead to long-term C sequestration. The disposal of RHA to soil, which is characterized by mainly recalcitrant C, could lead to buildup of soil organic C.

Influence of Height Waterlogging on Soil Physical Properties of Potential and Actual Acid Sulphate Soils

Water management is main factor that determines the successful of rice cultivation in acid sulphate soil. Soil waterlogging determines the direction and rate of chemical, geochemical and biological reaction in the soil, indirectly these reactions may influence to the changes of soil psycal properties during soil waterlogging process. The experiment was aimed to study the changes of two type of acid sulphate soils physical properties during rice straw decomposition processes. The research was conducted in the greenhouse consisting of the three treatment factors using the completely randomized design with three replications. The first factor was soil type: potential acid sulphate soil (PASS) and actual acid sulphate soil (AASS). The second factor was height of water waterlogging: 0.5-1.0 cm (muddy water–level condition) and 4.0 cm from above the soil surface (waterlogged). The third factor was organic matter type: rice straw (RS), purun tikus (Eleocharis dulcis) (PT) and mixed of RS and PT (MX). Soil physical properties such as aggregate stability, total soil porosity, soil permeability, soil particle density and bulk density were observed at the end of experiment (vegetative maximum stage). The results showed that acid sulphate soil type had large effect on soil physicl properties, soil waterlogging decreased aggregate stability, soil particle density and bulk density both of soil type.Keywords : Acid sulphate soils, soil physical properties, and waterlogging [How to Cite: Arifin F, A Susilawati and A Rachman. 2014. Influence of Height Waterlogging on Soil Physical Properties of Potential and Actual Acid Sulphate Soils. J Trop Soils 19(2): 77-83. Doi: 10.5400/jts.2014.19.2.77]

Microbial community dynamics during the early stages of plant polymer breakdown in paddy soil.

We used paddy soil slurries amended with rice straw to identify the microbial populations involved in the methanogenic breakdown of plant polymers. Rice straw greatly stimulated microbial activity over the 28-day incubation period. On day 7, the transient peak concentration of acetate (24 mM) coincided with the onset of increased methane production. Microbial 16S rRNA transcript numbers increased by one to two orders of magnitude, but not the 16S rRNA gene copy numbers. Using metatranscriptomic rRNA, Clostridiaceae, Lachnospiraceae, Ruminococcaceae, Veillonellaceae and Pseudomonadaceae were identified to be the most abundant and the most dynamic bacterial groups. Changes in methanogen rRNA and mRNA abundances corresponded well with methanogenic activity. Acetate determined the abundance ratio between Methanosarcinaceae and Methanosaetaceae. Methanocellaceae dominated hydrogenotrophic methanogenesis. Transcript levels of mRNA families involved in plant polymer breakdown increased slightly with time. Glycosyl hydrolase (GH) transcripts involved in cellulose and chitin breakdown were predominantly expressed by the Firmicutes, whereas those involved in hemicellulose breakdown exhibited more diverse taxonomic sources, including Acidobacteria, Bacteriodetes and Chloroflexi. Taken together, we observed strong population dynamics and the expression of taxonomically diverse GH families, suggesting that not only Firmicutes, but also less abundant groups play a major functional role in the decomposition of rice straw.

Small-scale variability in the contribution of invertebrates to litter decomposition in tropical rice fields

Sustainable management of agricultural systems includes promoting nutrient cycles, which can reduce the need for application of fertilizer. As rice is one of the most important food resources in the world, sustainable management of rice paddies is increasingly in demand. However, little is known about the influence of invertebrates on decomposition processes in these ecosystems. We hypothesized that invertebrates contribute significantly to the decomposition of rice straw in paddies and that their relative contribution is affected by the distance to other landscape structures within fields. We placed rice straw in litterbags of two different mesh sizes which prevent (20μm×20μm) or allow (5mm×5mm) access of invertebrates in six irrigated rice fields for 84 days. In each field, bags were set on three transects running from the bund to the center of the field. Invertebrates significantly increased total rice straw litter mass loss by up to 45% (total decomposition: fine-meshed bags 64%; coarse-meshed bags 83%). Litter mass loss in bags accessed by invertebrates decreased with increasing distance from the bund. Such a spatial trend in litter mass loss was not observed in bags accessed only by microbes. Our results indicated that invertebrates can contribute to soil fertility in irrigated rice fields by decomposing rice straw, and that the efficiency of decomposition may be promoted by landscape structures around rice fields.

Metatranscriptomic analysis of lignocellulolytic microbial communities involved in high-solids decomposition of rice straw.

BackgroundNew lignocellulolytic enzymes are needed that maintain optimal activity under the harsh conditions present during industrial enzymatic deconstruction of biomass, including high temperatures, the absence of free water, and the presence of inhibitors from the biomass. Enriching lignocellulolytic microbial communities under these conditions provides a source of microorganisms that may yield robust lignocellulolytic enzymes tolerant to the extreme conditions needed to improve the throughput and efficiency of biomass enzymatic deconstruction. Identification of promising enzymes from these systems is challenging due to complex substrate-enzyme interactions and requirements to assay for activity. In this study, metatranscriptomes from compost-derived microbial communities enriched on rice straw under thermophilic and mesophilic conditions were sequenced and analyzed to identify lignocellulolytic enzymes overexpressed under thermophilic conditions. To determine differential gene expression across mesophilic and thermophilic treatments, a method was developed which pooled gene expression by functional category, as indicated by Pfam annotations, since microbial communities performing similar tasks are likely to have overlapping functions even if they share no specific genes.ResultsDifferential expression analysis identified enzymes from glycoside hydrolase family 48, carbohydrate binding module family 2, and carbohydrate binding module family 33 domains as significantly overexpressed in the thermophilic community. Overexpression of these protein families in the thermophilic community resulted from expression of a small number of genes not currently represented in any protein database. Genes in overexpressed protein families were predominantly expressed by a single Actinobacteria genus, Micromonospora.ConclusionsCoupling measurements of deconstructive activity with comparative analyses to identify overexpressed enzymes in lignocellulolytic communities provides a targeted approach for discovery of candidate enzymes for more efficient biomass deconstruction. Glycoside hydrolase family 48 cellulases and carbohydrate binding module family 33 polysaccharide monooxygenases with carbohydrate binding module family 2 domains may improve saccharification of lignocellulosic biomass under high-temperature and low moisture conditions relevant to industrial biofuel production.

Effect of temperature on the structure and activity of a methanogenic archaeal community during rice straw decomposition

In recent years, the rice fields in Sanjiang Plain of Northeast China have drawn more and more attention because of the unique high-latitude location and the important contributions to rice production and methane emission. In the present study, a rice field soil in Sanjiang Plain was anaerobically incubated in presence and absence of rice straw at three temperatures (10 °C, 30 °C and 45 °C). The community structure and activity dynamics of methanogenic archaea were investigated by the terminal restriction fragment length polymorphism analyses in combination with cloning and sequencing of mcrA genes and transcripts and archaeal 16S rRNA genes. We found rice straw addition significantly shortened the lag phase of methanogenesis and enhanced the production of CH4 and the accumulation of methanogenic precursors (CO2, H2 and acetate). The T-RFLP analysis of mcrA gene revealed that structure of methanogenic archaeal community was relatively stable during the anoxic incubation. By contrast, analysis at the transcript level showed a highly dynamic composition of the active methanogens. In the beginning and early stages of incubation, Methanosarcinaceae actively utilized the accumulated acetate and H2/CO2 for CH4 production. Then the different methanogenic community developed along with the incubation time, and each representative methanogen group became predominant in different temperatures and treatments. At 10 °C, Methanobacteriales became more abundant in the soil without straw, while Methanosarcinaceae dominated in the soil with straw. The acetoclastic Methanosaetaceae, in particular, appeared to be active at 30 °C, probably due to the low concentration of acetate. High temperature of 45 °C significantly favored the hydrogenotrophic methanogens, with the increasing abundance of Methanobacteriales early and then the Methanocellales in the later stages.

Non isothermal model free kinetics for pyrolysis of rice straw

The kinetics of thermal decomposition of rice straw was studied by thermogravimetry.Non-isothermal thermogravimetric data of rice straw decomposition in nitrogen atmosphere at six different heating rates of 5–40°C/min was used for evaluating kinetics using several model free kinetic methods. The results showed that the decomposition process exhibited two zones of constant apparent activation energies. The values ranged from 142 to 170kJ/mol (Eavg=155.787kJ/mol), and 170 to 270kJ/mol (Eavg=236.743kJ/mol) in the conversion range of 5–60% and 61–90% respectively. These values were used to determine the reaction mechanism of process using master plots and compensation parameters. The results show that the reaction mechanism of whole process can be kinetically characterized by two successive reactions, a diffusion reaction followed by a third order rate equation. The kinetic results were validated using isothermal predictions. The results derived are useful for development and optimization of biomass thermochemical conversion systems.

Flooding effects on soil phenol oxidase activity and phenol release during rice straw decomposition

AbstractPhenol 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.

Straw application in paddy soil enhances methane production also from other carbon sources

Abstract. Flooded rice fields are an important source of the greenhouse gas methane. Methane is produced from rice straw (RS), soil organic matter (SOM), and rice root organic carbon (ROC). Addition of RS is widely used for ameliorating soil fertility. However, this practice provides additional substrate for CH4 production and results in increased CH4 emission. Here, we found that decomposing RS is not only a substrate of CH4 production, but in addition stimulates CH4 production from SOM and ROC. Apart from accelerating the creation of reduced conditions in the soil environment, RS decomposition resulted in enhancement of SOM-derived CH4 production. In particular, hydrogenotrophic methanogenesis from SOM-derived CO2 was stimulated, presumably by H2 released from RS decomposition. On the other hand, the enhancement of ROC-derived CH4 production after RS application was probably caused by the significant increase of the abundance of methanogenic Archaea in the RS treatment compared with the untreated control. Our results show that traditional management of rice residues exerts a positive feedback on CH4 production from rice fields, thus exacerbating its effect on the global CH4 budget.

Discovery of Microorganisms and Enzymes Involved in High-Solids Decomposition of Rice Straw Using Metagenomic Analyses

High-solids incubations were performed to enrich for microbial communities and enzymes that decompose rice straw under mesophilic (35°C) and thermophilic (55°C) conditions. Thermophilic enrichments yielded a community that was 7.5 times more metabolically active on rice straw than mesophilic enrichments. Extracted xylanase and endoglucanse activities were also 2.6 and 13.4 times greater, respectively, for thermophilic enrichments. Metagenome sequencing was performed on enriched communities to determine community composition and mine for genes encoding lignocellulolytic enzymes. Proteobacteria were found to dominate the mesophilic community while Actinobacteria were most abundant in the thermophilic community. Analysis of protein family representation in each metagenome indicated that cellobiohydrolases containing carbohydrate binding module 2 (CBM2) were significantly overrepresented in the thermophilic community. Micromonospora, a member of Actinobacteria, primarily housed these genes in the thermophilic community. In light of these findings, Micromonospora and other closely related Actinobacteria genera appear to be promising sources of thermophilic lignocellulolytic enzymes for rice straw deconstruction under high-solids conditions. Furthermore, these discoveries warrant future research to determine if exoglucanases with CBM2 represent thermostable enzymes tolerant to the process conditions expected to be encountered during industrial biofuel production.

Changes of Soil Chemical Properties During Rice Straw Decomposition in Different Types of Acid Sulphate Soils

Changes of Soil Chemical Properties During Rice Straw Decomposition in Different Types of Acid Sulphate Soils

雷竹覆盖物分解速率及其硅含量的变化

PDF HTML阅读 XML下载 导出引用 引用提醒 雷竹覆盖物分解速率及其硅含量的变化 DOI: 10.5846/stxb201208191165 作者: 作者单位: 浙江农林大学 环境与资源学院,浙江农林大学 环境与资源学院,浙江农林大学 环境与资源学院,浙江农林大学 环境与资源学院,浙江农林大学 环境与资源学院 作者简介: 通讯作者: 中图分类号: 基金项目: 浙江省自然科学基金重点基金资助项目（LZ12C16003） Decomposition rate and silicon dynamic of mulching residue under Phyllostachys praecox stands Author: Affiliation: School of Environmental and Resource Sciences, Zhejiang A,,,School of Environmental and Resource Sciences, Zhejiang A, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以冬季地表覆盖增温为核心的雷竹早产高效栽培技术被广泛应用于我国亚热带地区的雷竹（Phyllostachys praecox）产区。为探明雷竹覆盖物（稻草和竹叶）的分解速率及在分解残余物中硅含量的年动态变化规律，在浙江临安市雷竹主产区采用分解管法进行了覆盖物分解试验。试验结果表明，稻草、竹叶的月平均分解速率分别为8.5%和11.9%，在1a内分别分解了67.5%和79.3%。分解过程中，稻草和竹叶C含量随时间的推移而下降，而N含量则随时间的推移而增加，两者的C/N比总体都呈现下降的趋势，但在试验初期前者的下降幅度显著大于后者。稻草、竹叶覆盖残余物中的Si含量随着分解时间的增加而增加，并都在12月达到最大值81.8 g/kg和80.0 g/kg。稻草、竹叶的分解残余物中硅含量与铝含量或铁含量之间均呈极显著正相关（P < 0.01），但与磷含量无显著相关性（P > 0.05）。 Abstract:Phytolith-occluded organic carbon (PhytOC) in the soils is an important long-term carbon pool in terrestrial and plays an important role in regulation of global carbon cycle and mitigation of global climate warming. Intensive management technique including winter mulching has been widely used in the cultivation area of Phyllostachys praecox in the subtropical regions of China. The decomposition of mulching materials with high silicon content (bamboo leaves and rice straw) provides large amounts of silicon for Phyllostachys praecox ecosystem, thus affecting the formation of PhytOC in the ecosystem. To ascertain decomposition rate of mulching materials and silicon dynamic change of mulching residue on the land of Phyllostachys praecox stand, a decomposition experiment of mulching materials was conducted in the main typical production area of Phyllostachys praecox of Lin'an city, Zhejiang province by using decomposition tube method. The experiment results showed that the decomposition of rice straw and bamboo leaves mainly occurred between March and October.The decomposition peak of rice straw and bamboo leaves happened in July and August and the decomposition rates were 16.3% and 19.1%, respectively. The decomposition half-life of rice straw and bamboo leaves was 228 d and 166 d, respectively. Rice straw and bamboo leaves were decomposed by 67.5% and 79.3% during one year decay, respectively. During one-year decomposition process, C contents in rice straw and bamboo leaves decreased with time,whereas N contents in those increased with time. Carbon contents in bamboo leaves and rice straw and were decreased by 14.8% and 15.3%, respectively. Nitrogen contents in bamboo leaves and rice straw were increased by 15.8 and 174.4%, respectively. The ratios of C/N in bamboo leaves and rice straw were a decrease tendency with time. Decline ranges of the C/N ratios in bamboo leaves and rice straw were 26.4% and 67.5%, respectively. During the experiment period, Si contents in the mulching residues of rice straw and bamboo leaves increased with time. The maximum Si contents in the mulching residues occurred in December. Silicon contents in the mulching residues of rice straw and bamboo leaves were 81.8g/kg and 80.0 g/kg at the end of the experiment, respectively, which were 3.9 and 3.1 times greater than before the decomposition. The contents of Al and Fe in the mulching residues of rice straw and bamboo leaves increased with time. The contents of Al and Fe in the mulching residues of rice straw and bamboo leaves ranged 0.2-8.4 g/kg and 0.3-5.4 g/kg, respectively. The changes trends of P contents in the mulching residues of rice straw and bamboo leaves were the two-peaked curves. The P content in the mulching residues of rice straw ranged from 0.7 g/kg to 1.4 g/kg. The P contents in the mulching residues of bamboo leaves ranged from 1.0 g/kg to 1.7 g/kg. Silicon contents in the mulching residues of rice straw and bamboo leaves was positively correlated with Al or Fe contents (P < 0.01), but where was no relationship between Si contents and P contents (P > 0.05). 参考文献 相似文献 引证文献