Rice Cluster Research Articles

A Review of Milled Rice Demand and Supply of Some ASEAN Countries and Lesson Learnt for Cambodia

Rice is a vital crop for ASEAN countries, serving as a primary source of food security and playing a significant role in the regional economy. To draw lessons for rice supply and demand in Cambodia, this article will examine and briefly describe the rice markets in different ASEAN nations, including import and export, rice milling technology, government policy, obstacles, and opportunists. In Cambodia, a program utilizing the sustainable rice cluster (SRC) approach has been developed and put into action by the government in order to maintain the rise of rice production. Compared to traditional approaches, SRC has enhanced rice cultivation by about 40%. The key lessons Cambodia can learn are boosting domestic production, diversifying rice varieties, improving storage and distribution, practicing climate-smart practices, strengthening regional cooperation, improving market access, and farmer empowerment. By analyzing rice demand and supply dynamics in ASEAN and applying the lessons learned, Cambodia can strive to achieve self-sufficiency in rice production and reduce reliance on imports, increase the profitability and competitiveness of the rice sector, enhance food security for its population, and contribute to regional food security within ASEAN.

Rationale for the composition, type and quantity of technology for rice clusters

This paper underscores the predominant employment of seedling technology for rice cultivation in rice-growing clusters within the Republic of Uzbekistan. Despite its benefits in terms of minimal water and resource consumption, accelerated maturation, and harvest timing, this technology's widespread adoption remains limited. The study identifies a key factor in this limitation to be the absence of scientifically grounded information concerning the technical rationale required for rice cultivation via the cluster method, particularly among rice farm experts. (Research purpose) To provide the rationale for the composition, types, and quantities of technical equipment necessary to enhance the level of mechanization in the rice seedling technology. (Materials and methods) The research involves a range of methodologies, including monographic observation rules, information analysis and synthesis, normative methods, as well as the fundamental principles governing the operation of the machine and tractor fleet. (Results and discussion) The research focuses on the TCT RICE rice cluster, which encompasses a cropland area of 2700 hectares. The principal technical attributes of the PRO-600V transplanter were provided. In substantiating the composition, type and quantity of technical equipment for executing the production process, the operations delineated in standard flow charts for rice cultivation were employed as the foundational framework. A set of nine assessment criteria is utilized to determine the appropriate composition, type, and quantity of technical equipment necessary for the key agrotechnical activities, including plowing, pre-sowing tillage, seedling, plant cultivation, crop harvesting, and transportation. (Conclusions) Full mechanization of the production process in the cropland of the TCT RICE rice cluster is achieved by using 15 types of technical equipment with a total of 301 units. The results obtained can serve as primary material in the preparation of machine-tractor rice-growing units and the justification of the repair and maintenance base of rice-growing clusters. Complete mechanization of the production process within the cropland of the TCT RICE rice cluster is realized through the deployment of 15 categories of technical equipment, amounting to a total of 301 units. The research outcomes can be utilized as fundamental data for crafting machine-tractor units used for rice cultivation, as well as substantiating the infrastructure for repair and maintenance within rice-growing clusters. Keywords: rice cluster, rice cultivation, technical equipment, transplanter, assessment criteria, mechanization.

JUSTIFICATION OF THE GENERAL MODEL OF RICE-GROWING CLUSTER AND MACHINE PARK COMPOSITION

This article presents the results of a study on the development of a general model of the rice cluster and the determination of the composition, types and quantity of the required machine park. The concept of “General model of a rice-growing cluster” is introduced and its definition is given. The general model for sown area is substantiated by the following sequence: regional rice clusters are grouped according to the values of sown area; clusters with the largest sown areas were selected from the groups and the corresponding variational series of numbers was formed; the upper limit of the mathematical expectation of this series is taken as the rational sowing area of the general model. Using the standard coefficients (numbers) of technical equipment required per 1 000 hectares of rice land, the composition, brands and number of tractors and agricultural machines that perform technological operations on the sowing area of the rice-growing cluster are determined. In ricegrowing clusters with a rational technical park, all agrotechnical operations are carried out at the optimum time and agricultural products adapted for processing are grown.

Different microplastics in anaerobic paddy soils: Altering methane emissions by influencing organic matter composition and microbial metabolic pathways

Microplastics are widespread in farmland and threaten soil ecology. However, how different microplastics affect methane emission in paddy soil are still unclear. To address this knowledge gap, three typical microplastics, polyethylene, polypropylene, and polyvinyl chloride were added to paddy soil with different doses (0.01%, 0.1%, and 1%), and a 50-day incubation experiment was conducted. Compared with polyethylene and polypropylene microplastics, 1% of polyvinyl chloride microplastic resulted in the highest increase in methane production. According to the integrated liquid phase analysis, all three microplastics contributed to the accumulation of humus in the soil solution. Differential microbial taxa analysis indicated that some denitrifying bacteria such as Gemmatimonadetes and Omnitrophicaeota were significantly enriched in 1% polyethylene and polypropylene microplastics groups on day 30, and Rice Cluster I methanogens archaea were enriched specially in the 1% polyvinyl chloride microplastic group. The predicted soil metabolic functions suggested that polyethylene and polyvinyl chloride microplastics enhanced oxidative phosphorylation and amino acid reduction pathways. Macromolecular humus induced by microplastics may play a critical role in the dynamic equilibrium of anaerobic systems in paddy soils. These findings highlighted the threat of microplastics in agricultural fields greenhouse gas emissions. The identified quinone reductive metabolic pathways may provide potential strategies to reduce methane emissions.

MODIFICATION OF AN EXISTING HOLD-ON RICE THRESHER

Manual paddy threshing using metal drums with attendant low output and high losses is still being widely used in the Kano-Kura rice cluster. An existing stationary Hold-on thresher designed to address these, was modified and evaluated. The thresher was designed taking all peculiar technical considerations. It was then fabricated using available materials. Paddy Faro 44 variety at a mean moisture content of 13 % (w. b.) was used for evaluation in this study. The independent variables consist of three different speeds 500, 600 and 700 rpm and two feed rates of 200 and 300 kg/h were used. Factorial experiments were conducted in a completely randomized design with three replications. The performance dependent indices used were output capacity, threshing efficiency and cleaning efficiency. The analysis was done using GENSTAT statistical package. It was found out that the effects of variables on the performance indices were highly significant. The mean highest value of the output capacity was 229.09 kg/h at the combination of 700 rpm speed and 300 kg/h feed rate. The mean value obtained for the threshing was 99.99 % and is statistically similar for all the combinations. The cleaning efficiency indicate highest value of 85 % at the combination of 500 rpm speed and 200 kg/h feed rate. T-test for comparison between machine performance and manual threshing showed that the mean value for output capacity, threshing efficiency and cleaning efficiency for the machine are significantly higher than the manual threshing, the, the machine performance has promising prospect.

Activity and abundance of methanotrophic bacteria in a northern mountainous gradient of wetlands.

Methane uptake and diversity of methanotrophic bacteria was investigated across six hydrologically connectedwetlands in a mountainous forest landscape upstream of lake Langtjern, southern Norway. From floodplain through shrubs, forest and sedges to aSphagnum covered site, growing season CH4 production was insufficiently consumed to balance release into the atmosphere. Emission increased by soil moisture ranging 0.6-6.8mg CH4 m-2 h-1 . Top soils of all sites consumed CH4 including at the lowest 78 ppmv CH4 supplied, thus potentially oxidizing 17-51 nmol CH4 g-1 dw h-1 , with highest Vmax 440 nmol g-1 dw h-1 under Sphagnum and lowest Km 559 nM under hummocked Carex. Nine genera and several less understood type I and type II methanotrophs were detected bythe key functional gene pmoA involved in methane oxidation. Microarray signal intensities from all sites revealed Methylococcus, the affiliated Lake Washington cluster, Methylocaldum, a Japanese rice cluster, Methylosinus, Methylocystis and the affiliated Peat264 cluster. Notably enriched by site was a floodplain Methylomonas and a Methylocapsa-affiliated watershed cluster in the Sphagnum site. The climate sensitive water table was shown to be a strong controlling factor highlighting its link with the CH4 cycle in elevated wetlands.

Youths’ Involvement in Rice Production in Bende Local Government Area of Abia State, Nigeria

The study ascertained the level of youths’ involvement in rice production activities in Abia State, Nigeria. A total of 80 respondents from Bende Local Government Area rice cluster was purposively selected because of their high level in rice production in the State. Data were collected using a structured interview schedule and were analysed using mean, standard deviation and regression. The study revealed that youths were into land clearing (𝑥̅=2.00), raising of nursery (𝑥̅=2.00), buying and selling of rice seedling (𝑥̅=2.00)and planting of seedling (𝑥̅=2.00). Access to credit (t=-2.57) and number of extensions visit (t=2.46) significantly influenced youths’ involvement. Youths were constrained mainly by lack of capital to scale up production (𝑥̅=2.98), poor support from government (𝑥̅=2.73), poor access to improved seedlings (𝑥̅=2.49), high cost of production (𝑥̅=2.34), climatic factors (𝑥̅=2.10)and lack of information on agricultural business opportunities (𝑥̅=2.08). Youths were involved in rice production though, occasioned by lack of access to credit and extension visit. Extension should increase the frequency of visit to at least once in a month to allow for more productive engagement and should expose youths to lucrative opportunities in rice production coupled with linking them to available credit options that can meaningfully support their activities.

Maintaining grass coverage increases methane uptake in Amazonian pastures, with a reduction of methanogenic archaea in the rhizosphere

Cattle ranching is the largest driver of deforestation in the Brazilian Amazon. The rainforest-to-pasture conversion affects the methane cycle in upland soils, changing it from sink to source of atmospheric methane. However, it remains unknown if management practices could reduce the impact of land-use on methane cycling. In this work, we evaluated how pasture management can regulate the soil methane cycle either by maintaining continuous grass coverage on pasture soils, or by liming the soil to amend acidity. Methane fluxes from forest and pasture soils were evaluated in moisture-controlled greenhouse experiments with and without grass cover (Urochloa brizantha cv. Marandu) or liming. We also assessed changes in the soil microbial community structure of both bare (bulk) and rhizospheric pasture soils through high throughput sequencing of the 16S rRNA gene, and quantified the methane cycling microbiota by their respective marker genes related to methane generation (mcrA) or oxidation (pmoA). The experiments used soils from eastern and western Amazonia, and concurrent field studies allowed us to confirm greenhouse data. The presence of a grass cover not only increased methane uptake by up to 35% in pasture soils, but also reduced the abundance of the methane-producing community. In the grass rhizosphere this reduction was up to 10-fold. Methane-producing archaea belonged to the genera Methanosarcina sp., Methanocella sp., Methanobacterium sp., and Rice Cluster I. Further, we showed that soil liming to increasing pH compromised the capacity of forest and pasture soils to be a sink for methane, and instead converted formerly methane-consuming forest soils to become methane sources in only 40–80 days. Liming reduced the relative abundance of Beijerinckiacea family in forest soils, which account for many known methanotrophs. Our results demonstrate that pasture management that maintains grass coverage can mitigate soil methane emissions, compared to bare (bulk) pasture soil.

Methanogenic community linked to organic acids fermentation from root exudates are affected by rice intensification in rotational soil systems

Rice paddy soils are an important biogenic source of methane, a relevant greenhouse gas. Rice rotation with upland crops and pastures affects hydrolytic and fermentative bacteria and methanogenic archaea by sequential exposition to oxic and anoxic conditions. There are several ways to reduce methane emissions from rice paddy soils. Here we examine the effect of intensification in rice rotations with upland crops upon the microbial community structure and methanogenesis when dicarboxylic acids exudated by rice root were amended in microcosms assays. Soils under rotations rice-pasture, rice-soybean and continuous rice, with the last two more intensive systems recently installed in the field experiment, were sampled. Amplicon sequencing of 16S rRNA gene analysis showed that the rotation system was a main driver of the microbial community structure, explaining 33%, 38% and 55% of the differences in the structure of Bacteria, Archaea and methanogens, respectively. The density of mcrA gene copies was significantly higher in continuous rice soil than in other soils, and the relative abundance of methanogenic archaea was 33% for rice monoculture, whereas represented 15% and 14% for the rice-pasture and rice-soybean soils, respectively. The incubation of soils with tartrate and succinate confirmed functional differences among soils since rice monoculture showed similar or higher methane production and significantly less acetate and propionate accumulation than other soils. The T-RFLP analysis of mcrA gene in soils and incubated soils revealed that Rice Cluster I increased after incubation in all rotational soils, whereas Methanosarcinaceae and Methanobacteriaceae remained relevant after incubation. Furthermore, a more stable community of methanogenic archaea was established in soil under continuous rice, since T-RF profiles of soils and incubated soils with dicarboxylic acids grouped together with 62% similarity, while communities from other rotational soils experimented a great shift after incubation with these substrates. Altogether, these results showed that the conversion of rice-pasture rotational fields to a more intensive rice crop production strongly impacts the methanogenic community structure and their potential for methane emission.

Estimating and evaluating the rice cluster distribution uniformity with UAV-based images

The uniformity of the rice cluster distribution in the field affects population quality and the precise management of pesticides and fertilizers. However, there is no appropriate technical system for estimating and evaluating the uniformity at present. For that reason, a method based on unmanned aerial vehicle (UAV images) is proposed to estimate and evaluate the uniformity in this present study. This method includes rice cluster recognition and location determination based on the RGB color characteristics of the seedlings of aerial images, region segmentation considering the rice clusters based on Voronoi Diagram, and uniformity index definition for evaluating the rice cluster distribution based on the variation coefficient. The results indicate the rice cluster recognition attains a high precision, with the precision, accuracy, recall, and F1-score of rice cluster recognition reaching > 95%, 97%, 97%, 95%, and 96%, respectively. The rice cluster location error is small and obeys the gamma (3.00, 0.54) distribution (mean error, 1.62 cm). The uniformity index is reasonable for evaluating the rice cluster distribution verified via simulation. As a whole process, the estimating method is sufficiently high accuracy with relative error less than 0.01% over the manual labeling method. Therefore, this method based on UAV images is feasible, convenient, technologically advanced, inexpensive, and highly precision for the estimation and evaluation of the rice cluster distribution uniformity. However, the evaluation application indicates that there is much room for improvement in terms of the uniformity of mechanized paddy field transplanting in South China.

Methane emissions may be driven by hydrogenotrophic methanogens inhabiting the stem tissues of poplar.

Living trees in forests emit methane (CH4 ) from their stems. However, the magnitudes, patterns, drivers, origins, and biogeochemical pathways of these emissions remain poorly understood. We measured insitu CH4 fluxes in poplar stems and soils using static chambers and investigated the microbial communities of heartwood and sapwood by sequencing bacterial 16S, archaeal 16S, and fungal ITS rRNA genes. Methane emissions from poplar stems occurred throughout the sampling period. The mean CH4 emission rate was 2.7 mg m-2 stem d-1 . Stem CH4 emission rate increased significantly with air temperature, humidity, soil water content, and soil CH4 fluxes, but decreased with increasing sampling height. The CO2 reduction and methylotrophic methanogenesis were the major methanogenic pathways in wood tissues. The dominant methanogen groups detected in stem tissues were Methanobacterium, Methanobrevibacter, Rice Cluster I, Methanosarcina, Methanomassiliicoccus, Methanoculleus, and Methanomethylophilaceae. In addition, three methanotrophic genera were identified in the heartwood and sapwood - Methylocystis, Methylobacterium, and Paracoccus. Overall, stem CH4 emissions can originate directly from the internal tissues or co-occur from soils and stems. The co-existence of methanogens and methanotrophs within heartwood and sapwood highlights a need for future research in the microbial mechanisms underlying stem CH4 exchange with the atmosphere.

Mitigation of methane emission in a rice paddy field amended with biochar-based slow-release fertilizer

Despite improving soil quality and reducing nitrogen (N) loss in paddy soil, replacing chemical fertilizer with organic fertilizer would significantly accelerate greenhouse gas emission in terms of methane (CH4). The application of slow-release fertilizer has been proposed an effective approach to control CH4 emissions, in addition to reducing N loss. Yet, the understanding of CH4 emissions from paddy fields with the additions of different fertilizers is still less known. Therefore, the effects of different fertilizer treatments, including chemical fertilizer treatment (CF), mixed chemical and organic fertilizer treatment (OF), biochar-based slow-release fertilizer treatment (SF), and no fertilizer control treatment (CK) on CH4 emissions and methanogenic community structure in paddy soils were investigated through a field experiment. Results showed that slow-release fertilizer addition significantly decreased CH4 emissions by 33.4%, during the whole rice growing season compared to those in OF. The cumulative CH4 emissions were in a significantly positive relation to soil NH4+-N. Slow-release fertilizer amendment decreased the relative abundances of Methanosarcina and Methanoregula and increased the relative abundances of hydrogenotrophic Methanocella and Rice Cluster I. Reduced CH4 emissions with slow-release fertilizer amendment might be mainly attributed to the different forms of N in the fertilizer and available potassium (K) in the paddy soil. Our findings produce novel insights into the application of slow-release fertilizer in controlling CH4 emissions from rice fields.

Elemental Characterization of Rice Husk Ash from Local Rice Species in South Eastern Nigeria

Heavy metals such as Cr, Zn, As, Pb and Cu can be hazardous to health and the environment. The focus of this study is to investigate the trace metal constituents of rice husk ash (RHA) from Ikwo and Izzi rice clusters. RHA of Izzi CP, R8 and Ikwo CP rice husk species were sampled. Elemental characterization was done using X-ray fluorescence method. A total of 14 elements (K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Rb, As, Br, Sr and Ga) were detected in the rice husk species except in Izzi CP where Ga was not detected. The concentration of these elements in weight percent (wt. %) were compared with literature. Elements like, K, Ca, Fe, and Mn were found to be in negligible concentrations in all the samples while Ga, Rb, Cu, Cr, Zn, As and Ni were found to be well above the literature values. The X-ray fluorescence analysis of the samples showed that some toxic heavy metals like Cr, As, Ni, and Cu were of high concentrations compared to literature which for health reasons are not advisable to have long term exposure.

Humic Substances Mediate Anaerobic Methane Oxidation Linked to Nitrous Oxide Reduction in Wetland Sediments.

Humic substances are redox-active organic molecules, which play pivotal roles in several biogeochemical cycles due to their electron-transferring capacity involving multiple abiotic and microbial transformations. Based on the redox properties of humic substances, and the metabolic capabilities of microorganisms to reduce and oxidize them, we hypothesized that they could mediate the anaerobic oxidation of methane (AOM) coupled to the reduction of nitrous oxide (N2O) in wetland sediments. This study provides several lines of evidence indicating the coupling between AOM and the reduction of N2O through an extracellular electron transfer mechanism mediated by the redox active functional groups in humic substances (e.g., quinones). We found that the microbiota of a sediment collected from the Sisal wetland (Yucatán Peninsula, southeastern Mexico) was able to reduce N2O (4.6 ± 0.5 μmol N2O g sed.–1 day–1) when reduced humic substances were provided as electron donor in a close stoichiometric relationship. Furthermore, a microbial enrichment derived from the wetland sediment achieved simultaneous 13CH4 oxidation (1.3 ± 0.1 μmol 13CO2 g sed.–1 day–1) and N2O reduction (25.2 ± 0.5 μmol N2O g sed.–1 day–1), which was significantly dependent on the presence of humic substances as an extracellular electron shuttle. Taxonomic characterization based on 16S rRNA gene sequencing revealed Acinetobacter (a ɣ-proteobacterium), the Rice Cluster I from the Methanocellaceae and an uncultured archaeon from the Methanomicrobiaceae family as the microbes potentially involved in AOM linked to N2O reduction mediated by humic substances. The findings reported here suggest that humic substances might play an important role to prevent the emission of greenhouse gases (CH4 and N2O) from wetland sediments. Further efforts to evaluate the feasibility of this novel mechanism under the natural conditions prevailing in ecosystems must be considered in future studies.

Working of Puffed Rice Units

Industrialization is a progressive measure that creates social and economic change by transforming human society from pre-industrialization to industrial era; Industrialization plays a predominant role in the development of the economy, acts as a basic fundamental factor that is influenced by the growth prospects of the economy of a country. The prominence of industrialization creates employment opportunities, balancing the regional development living and poverty eradication, etc. In this context, the unorganized sector acts as a factory for entrepreneurship and self-employment opportunities as well as a tool for poverty eradication. So the present study attempts to analyze the working of puffed rice units in the Davangere region. These industries are providing various employment opportunities to the poor and illiterate people. Because these are labor-intensive industries. The present study is based on the puffed rice workers and their working conditions and environment. In malebennur town there are more than 50 puffed rice industries are working. In the study area, people depend on the making of puffed rice for their livelihood. The main purpose of the study is to know about the current status, growth, and development of the puffed rice units and also discuss the government initiative in the development of an unorganized puffed rice cluster in Davangere. The study is based on primary data with field survey and secondary data, which includes different reference books, journals, research papers, seminar proceedings, articles, and government publications, annual reports, etc.

Determining the efficiency of rice production in the Kadawa rice cluster of Kano State, Nigeria

In an efforts to increase the production of rice for food security and reduced deflation of foreign reserves, the Nigerian government eases access to fertilizer, extension services and improved rice seed. Therefore, the paper examines the effect of access to fertilizer and extension services infrastructures and improved rice seed on the productivity of rice farmers as well as identify their level productivity in the Kadawa rice cluster. A five Likert structured questionnaire randomly administered to a sample of 80 rice farmers in the 2018 crop season. The Cobb-Douglas stochastic frontier production model was used to analyze the data. The descriptive result shows that males (83.3%) dominated rice farming. The economically active age group are 53%, the married group are 65.2%, those with at least six years of experience in rice farming are 74.2%, and 22.7% attained tertiary education. Further, the stochastic frontier result shows that improve rice seed and extension services positively affect rice production, while fertilizer negatively affects rice production. Further, the result shows that years of experience in rice farming reduces technical inefficiency. While qualification, age, and marital status reduce rice production. Therefore, the study recommends the provision of educational facilities for quality education. Expanding extension workers’ services to farmers, since one visit per crop season seems to be not enough to offer the necessary information to farmers. Finally, to attract experienced, educated young married farmers to partake in rice cultivation in the study area.

Data Screening and Preliminary Analysis on the Impact of Rural Infrastructure on Rice Productivity in Kano State, Nigeria

Despite having vast farmland suitable for paddy rice farming, local production in the country is weak, especially in Kano where the state has the most abundant farmland put to rice farming and the most extensive rice farmers in the 36 states of the country. As such, over 4mm/t of milled paddy rice has to be imported annually into Nigeria to supplement home production. The economy cannot sustain rice import because it depends on crude oil revenue; thus, leading to scarcity of rice at an exorbitant price. The study was conducted in the 2018 cropping season for rainfed and irrigated paddy rice, to identify the impact of rural infrastructure on the productivity of rice farmers in Kano State, Nigeria. There are seven local governments with 17 rice clusters in the state that are cultivating rice. A random sample of 768 rice farmers was selected in 9 rice clusters from the population of 135,895 rice farmers using multistage and purposive sampling. Using the Statistical Package for Social Science (SPSS) software version 22, data screening and preliminary analysis was conducted, aimed at satisfying the assumptions of the multivariate analysis. Thus, missing data analysis was performed to identify univariate outliers and multivariate outliers. Likewise, normality skewness and kurtosis, as well as multicollinearity issues, were checked. The preliminary analysis indicates that the data fulfil the conditions of multivariate analysis, thus, suitable for inferences.

Genetics of the signs of rice clusters

From the literature, more than 1000 active rice genes are known, from which chromosomal and genetic maps are drawn. Some of them have specific localization in the gene linkage groups. Knowing the specific gene localization in the chromosome, their interaction, interrelations with other neighboring alleles, it is possible to select the parental pairs to hybridize the models of new genotypes and varieties with the necessary traits. The botanical concept of a rice cluster includes all the quantitative and qualitative characteristics of the panicle. The scientific literature describes more than 20 signs that characterize a panicle. At the same time, panicle signs are divided into cluster and spikelet factors (grains). The article presents the characteristics of the parental individuals and the F 1 and F 3 hybrids of rice, the results of the hybridological analysis, the description of the genes and their manifestation in the hybrid combinations. We recommend using valuable genotypes in the selection of parental pairs for hybridization in the process of developing new varieties. In the genetic formulas of varieties and hybrids, each trait is represented by one symbol, as it is in the diploid state. The dominant genes are designated by uppercase (capital) symbols, the recessive one are written by lowercase letters. There have been determined the values of the dominance coefficients, which indicate the trait inheritance in F 1 . The most traits show the effect of dominance and overdominance, which indicates the possibility of their use in the breeding process when developing the source material and new rice varieties. There was carried out a hybridological analysis, which showed the digenic type of inheritance.

Effects of nickel and cobalt on methane production and methanogen abundance and diversity in paddy soil.

BackgroundPaddies are an important anthropogenic source of methane emissions to the atmosphere, and they are impacted by heavy metal pollution. Nickel (Ni) and cobalt (Co) pollution might either enhance or mitigate CH4 emission from paddy soils due to the total amounts of metals, bioavailability and functional microbial activity and composition.MethodsAn incubation experiment was conducted, and different Ni and Co concentrations were added to test the effects of trace metals on methane production in paddy soil. The archaea community structure and the abundance of methanogen functional groups in the paddy soil with added Ni and Co were detected using high-throughput sequencing and quantitative PCR based on the 16S rRNA and mcrA (methyl coenzyme M reductase) genes, respectively.ResultsThe highest methane production rate was 561 mg CH4 kg−1 dry soil d−1 with the addition of 50 mg kg−1 Ni and 684 mg CH4 kg−1 dry soil d−1 with the addition of 25 mg kg−1 Co. Accordingly, the mcrA gene was most abundant in the 50 mg kg−1 Ni addition (3.1 × 106 ± 0.5 × 106 copies g−1 dry soil). The lowest mcrA gene abundance was detected in the 500 mg kg−1 Co addition (9.2× 105 ± 0.4 × 105 copies g−1 dry soil). The dominant methanogens were Methanobacterium, Methanosarcina, Methanocella, Methanomassiliicoccus, Bathyarchaeota, and Rice Cluster I (RC-I), and the relative abundances of these groups were higher than 1% in the Ni and Co treatments. Additionally, the archaeal compositions differed significantly in the soils with various Ni and Co additions. The most abundant Methanococcus spp. represented 51.3% of the composition in the 50 mg kg−1 Ni addition, which was significantly higher than that of the control (12.9% to 17.5%).DiscussionOur results indicated that the contamination of soil by Ni and Co significantly affected total methanogens abundance and specific methanogen functional groups. Ni and Co additions to paddy soil promoted methanogenic activity at low concentrations, while they had inhibitory effects at high concentrations. Because paddy soils largely contribute to methane emissions and are increasingly exposed to heavy metal pollution, our results show that future assessments of greenhouse gas flux from paddy soils should take into account the effects of pollution by Ni and Co.

ОЦЕНКА ПОТЕНЦИАЛА КЛАСТЕРИЗАЦИИ РИСОВОДЧЕСКОЙ ОТРАСЛИ В КАЗАХСТАНЕ

In the modern economy a special attention is paid to clusters as the optimum form of the organization of production promoting innovative activities and increasing competitiveness of the region. In this connection, cluster potential assessment acquires a great relevance. Methods of clusters identifying are subdivided into the quantitative, qualitative and combined methods. The most interesting methods are the combined methods, in particular, Ermishina’s assessment technique. The main stages of competitive stability are the quantitative analysis of competitive stability (determination of a market position of regional branches); qualitative analysis of existence and structure of resource base and, finally, identification of economy’s specific sectors, in which achievement of competitive advantages of the regional enterprises is possible (using A.V. Ermishina's technique). SWOT analysis of rice-growing branch assessed possibilities for creating a rice cluster in Kazakhstan as favorable on the basis of the analysis of economic, organizational and resource premises. The calculated coefficients of localization and per capita production for rice-growing branch are greater than one, which allows to make an assertion about a possibility of creating a rice cluster. Kazakhstan has significant advantages for creating a cluster in rice growing industry: a large number of the educational centers for training qualified specialists; a strong scientific and research basis; support and assistance of the government in cluster development. In the republic there are a number of the enterprises which can become a basis of a rice-growing cluster ("Abzal and Co", GP; "Nai-Mir", LLC; the Aral region research institute of rice, "Zhalagashsky elevator", LLC; "AgroHolding "Baikonur", LLC, etc.