Paddy Ecosystem Research Articles

The effect of periphyton on seed germination and seedling growth of rice (Oryza sativa) in paddy area

Periphyton is widely distributed in paddy fields and its interactions with paddy soil and rice growth have been reported rarely. In this study, model paddy ecosystems with different additional soil substrates were simulated under controlled conditions to investigate the effects of periphyton on rice seed germination and seedling growth. Results show that the selected soil substrates had significant effects on the metabolic activities and growth of periphyton in paddy fields. The addition of straw to soil enhances but the addition of biochar leads to attenuation of periphyton growth. The presence of periphyton in the paddy system, especially with straw in soil greatly increased the germination index of rice seed (by maximally 21%). However, the biochar treatment in the presence of periphyton was detrimental for the seed vitality with a decrease of 30%. As a result, the periphyton cover on paddy soil surface significantly inhibited the growth of rice seedling, including rice height, leaf width and biomass. To summarize, this study indicates that the presence of periphyton during seed germination period was detrimental for rice growth, but could be used to control the weed growth. Thus, this study provided insight into understanding the periphyton-plant relationships with different soil-substrates and also new approaches to controlling weeds in paddy fields by regulating the growth of periphyton.

Carbon isotope fractionation reveals distinct process of CH4 emission from different compartments of paddy ecosystem.

Carbon isotopic fractionations in the processes of CH4 emission from paddy field remain poorly understood. The δ13C-values of CH4 in association with production, oxidation and transport of CH4 in different pools of a paddy field were determined, and the stable carbon isotope fractionations were calibrated to assess relative contribution of acetate to CH4 production (fac) and fraction of CH4 oxidized (fox) by different pathways. The apparent isotope fractionation for CO2 conversion to CH4 (αapp) was 1.041–1.056 in the soil and 1.046–1.080 on the roots, indicating that fac was 10–60% and 0–50%, respectively. Isotope fractionation associated with CH4 oxidation (αox) was 1.021 ± 0.007 in the soil and 1.013 ± 0.005 on the roots, and the transport fractionation (εtransport) by rice plants was estimated to be −16.7‰ ~ −11.1‰. Rhizospheric fox was about 30–100%, and it was more important at the beginning but decreased fast towards the end of season. Large value of fox was also observed at the soil-water interface and soil and roots surfaces, respectively. The results demonstrate that carbon isotopic fractionations which might be different in different conditions were sensitive to the estimations of fac and fox in paddy field.

Mercury methylation in rice paddies and its possible controlling factors in the Hg mining area, Guizhou province, Southwest China

Understanding mercury (Hg) methylation/demethylation processes and the factors controlling methylmercury (MeHg) production within the rice paddy ecosystem of Hg mining areas is critical to assess the risk of MeHg contamination in rice grain. Two typical Hg-contaminated mining sites, a current-day artisanal site (Gouxi) and an abandoned site (Wukeng), were chosen in this study. We qualified the in situ specific methylation/demethylation rate constants in rice paddy soil during a complete rice-growing season. Our results demonstrate that MeHg levels in rice paddy soil were a function of both methylation and demethylation processes and the net methylation potential in the rice paddy soil reflected the measured MeHg production at any time point. Sulfate stimulating the activity of sulfate-reducing bacteria was a potentially important metabolic pathway for Hg methylation in rice paddies. We suggest that bioavailable Hg derived from new atmospheric deposition appears to be the primary factor regulating net MeHg production in rice paddies.

Transcriptome response to temperature stress in the wolf spider Pardosa pseudoannulata (Araneae: Lycosidae).

The wolf spider Pardosa pseudoannulata is a dominant predator in paddy ecosystem and an important biological control agent of rice pests. Temperature represents a primary factor influencing its biology and behavior, although the underlying molecular mechanisms remain unknown. To understand the response of P. pseudoannulata to temperature stress, we performed comparative transcriptome analyses of spider adults exposed to 10°C and 40°C for 12 h. We obtained 67,725 assembled unigenes, 21,765 of which were annotated in P. pseudoannulata transcriptome libraries, and identified 905 and 834 genes significantly up‐ or down‐regulated by temperature stress. Functional categorization revealed the differential regulation of transcription, signal transduction, and metabolism processes. Calcium signaling pathway and metabolic pathway involving respiratory chain components played important roles in adapting to low temperature, whereas at high temperature, oxidative phosphorylation and amino acid metabolism were critical. Differentially expressed ribosomal protein genes contributed to temperature stress adaptation, and heat shock genes were significantly up‐regulated. This study represents the first report of transcriptome identification related to the Araneae species in response to temperature stress. These results will greatly facilitate our understanding of the physiological and biochemical mechanisms of spiders in response to temperature stress.

Investigation of biogeochemical controls on the formation, uptake and accumulation of methylmercury in rice paddies in the vicinity of a coal-fired power plant and a municipal solid waste incinerator in Taiwan

Recent studies have shown that rice consumption is another critical route of human exposure to methylmercury (MeHg), the most toxic and accumulative form of mercury (Hg) in the food web. Yet, the mechanisms that underlie the production and accumulation of MeHg in the paddy ecosystem are still poorly understood. In 2013 and 2014, we conducted field campaigns and laboratory experiments over a rice growing season to examine Hg and MeHg cycling, as well as associated biogeochemistry in a suite of paddies close to a municipal solid waste incinerator and a coal-fired power plant station in Taiwan. Concentrations of total Hg and MeHg in paddy soil and rice grain at both sites were low and found not to exceed the control standards for farmland soil and edible rice in Taiwan. However, seasonal variations of MeHg concentrations observed in pore water samples indicate that the in situ bioavailability of inorganic Hg and activity of Hg-methylating microbes in the rhizosphere increased from the early-season and peaked at the mid-season, presumably due to the anoxia created under flooded conditions and root exudation of organic compounds. The presence of Hg-methylators was also confirmed by the hgcA gene detected in all root soil samples. Subsequent methylation tests performed by incubating the root soil with inorganic Hg and an inhibitor or stimulant specific for certain microbes further revealed that sulfate-reducers might have been the principal Hg-methylting guild at the study sites. Interestingly, results of hydroponic experiments conducted by cultivating rice in a defined nutrient solution amended with fixed MeHg and varying levels of MeHg-binding ligands suggested that chemical speciation in soil pore water may play a key role in controlling MeHg accumulation in rice, and both passive and active transport pathways seem to take place in the uptake of MeHg in rice roots.

Exposure to butachlor causes thyroid endocrine disruption and promotion of metamorphosis in Xenopus laevis

Butachlor is extensively applied in rice paddy ecosystem in china, and has been widespread contaminant in the aquatic environment. Here, Xenopus laevis was used for the evaluation of teratogenesis developmental toxicity, and disruption of thyroid system when exposure to different concentrations of butachlor by window phase exposure. Acute toxicity investigation shown that 96 h-LC50 value of butachlor was 1.424 mg L−1 and 0.962 mg L−1 for tadpoles (starting from stages 46/47) and embryos (starting from stages 8/9), respectively. Exposure to butachlor caused malformation, including abnormal eye, pericardial edema, enlarged proctodaeum and bent tail. Window phase exposure test indicated that butachlor significantly promote the contents of whole-body thyroid hormones (THs, T3 and T4) at higher levels, indicating thyroid endocrine disruption. At 7 days, exposure to butachlor up-regulated the mRNA expression of genes involved in THs synthesis and metabolism (tshα, tg, tpo and dio1) and THs receptors (trα and trβ). At 14 days, up-regulation of the mRNA expression of genes related to THs synthesis and metabolism (tshα, tshβ, tg, tpo, dio1, dio2 and ttr) and THs receptors (trβ) were also observed after the exposure to butachlor. At 21 days, butachlor up-regulated the mRNA expression of tshα, tg, tpo genes and down-regulated the mRNA expression of tshβ, tg, dio1, ttr and trα genes. These results showed that butachlor could change the mRNA expression of genes involved in the HPT axis and increase whole-body thyroid hormones levels of X. laevis tadpoles in a dose- and time-dependent manner, causing thyroid endocrine disruption and developmental toxicity.

Effect of chemical vis-a-vis non-chemical pest management on predatory spiders in paddy-ecosystem

Spiders act as one of the most important defenders in paddy ecosystem and there are several families of those with different habits. The question on the effect of chemical application in comparison to the non chemical option on different spider families in the zone under study was attempted for getting answer. For that purpose, the field experiment was conducted during kharif, 2014 for studying spider abundance in chemical versus non-chemical treatments. Chemical based treatment consisted of the application of Phorate 10G at 10 days after transplanting (DAT), followed by spraying with Imidacloprid 17.8 SL at 45 DAT, and dusting of Methyl Parathion 2D at 80 DAT. Transplanting of rice following skip row technique, sowing of okra, cowpea, sesame & balsam on the surrounding bunds, retention of weeds on the bunds, single inoculative release of Trichogramma chilonis @ 1,00,000 at 35 DAT, and use of pheromone (Scirpophaga incertulus lure)-cum -light trap @ 10 traps ha-1 were integrated together in nonchemical based treatment. The results revealed that the population of wolf spiders and long jawed spiders were statistically higher during all the seven dates of observation in non-chemical based approach. Amongst Araneid spiders, non-chemical based approach recorded significantly higher population at 60, 75 and 90 DAT. On the basis of overall mean, the non-chemical treatment had significantly higher population of spiders belonging to most of the families except Thomisidae. The mean population of spiders across the families varied from 1.06 to 12.0 and 0.54 to 6.66 per double sweep per sub plot in non-chemical based and chemical based treatment, respectively. Thus, the study confirms the safety of the non-chemical based approach in maintaining significantly higher level of spider population.

The application of rapidly composted manure decreases paddy CH4 emission by adversely influencing methanogenic archaeal community: a greenhouse study

The application of organic manure can alleviate the deterioration of soil quality. However, it inevitably increases paddy CH4 emissions by introducing more CH4-producing precursors, which further restricts the amendment of organic manure in paddy fields. A 17-week greenhouse pot experiment was conducted to compare the effects of noncomposted manure (NCM), commonly composted manure (CCM), and rapidly composted manure (RCM) on rice yield and CH4 emission. To understand CH4 emissions of these three different manures, both the population size and the community structure of the methanogenic archaea in the soils were also investigated. The experiment was carried out in a greenhouse with three treatments: NCM, CCM, and RCM. The CH4 fluxes during rice cultivation were measured using the closed static chamber technique, and the CH4 concentration was determined by FID gas chromatography (Agilent 7890, USA). Soil DNA was extracted from 0.5 g of moist soil using a FastDNA® SPIN Kit for soil (MP Biomedicals, Santa Ana, CA) according to the manufacturer’s instructions. The population size of methanotrophs and methanogenic archaea was determined by real-time quantitative PCR (qPCR), and the community composition was analyzed using pyrosequencing technology. Rice yield and CH4 emission significantly differed between the groups (P < 0.05) as follows: CCM < NCM < RCM and CCM < RCM < NCM, respectively. These results are, in part, due to the adverse effects of RCM on the soil methanogenic archaeal community. RCM is abundant in nitrogen, which can promote crop growth. The number of methanotrophs with the RCM treatment was the lowest, with no significant difference relative to that with the CCM treatment but significantly lower than that with the NCM treatment. RCM amendment decreased the abundance of total soil methanogenic archaea, specifically decreasing the abundances of two acetoclastic methanogenic guilds (Methanosarcina and Methanosaeta), and differentially altered the paddy methanogenic archaeal community structure at the rice tillering stage. These negative responses by methanogens led to the lower CH4 emissions with RCM treatment compared to that with NCM treatment. RCM amendment can guarantee high grain yield and can significantly decrease CH4 emission compared to the effects of fresh manure amendment. This phenomenon could result from the unique characteristics of RCM and its adverse effects on paddy methanogenic archaeal communities. Overall, RCM can be a beneficial alternative organic fertilizer, which can resolve the problem of increased rice production that leads to increased CH4 emission caused by the application of organic manure in the paddy ecosystem.

Wild harvest: distribution and diversity of wild food plants in rice ecosystems of Northeast Thailand

Rice fields provide not only a staple food but are also bio-diverse and multi-functional ecosystems. Wild food plants are important elements of biodiversity in rice fields and are critical components to the subsistence of poor farmers. The spatial and seasonal distribution of wild food plants were analysed across different sub-systems occurring within paddy ecosystems in two adjacent rice farming villages in Kalasin, Northeast Thailand. Data were collected in 102 sampling sites corresponding to seven sub-systems including tree rows, mounds, field margins, shelters, ponds, pond margins and levees. Frequency of occurrence and absolute abundance were quantified for each species in the two seasons of two years, and data on uses of wild food plant species were collected through focus group discussions. A total of 42 species from 28 botanical families were reported, and one third of these have been classified as weeds of rice by other authors. Results show that species abundance, frequency of occurrence and diversity varied seasonally and spatially within paddy rice ecosystems. Higher diversity indexes were observed in the monsoon in most sub-systems. The most diverse sub-systems in the monsoon were shelters, mounds and pond margins, and tree rows and mounds in the dry season. Field margins, ponds and levees presented lower diversity, but are habitat of aquatic species important for the local diet, such as Ipomoea aquatica and Marsilea crenata. The herbs Lobelia sp. and Glinus oppositifolius, classified as rice weeds, were most abundant species in the dry season and frequently consumed. Leucaena leucocephala, of which the roots, leaves and fruits are commonly consumed as vegetable, was the most abundant tree in most sub-systems. More than half of the species were specific to one or two sub-systems due to particular niche requirements. Three quarters of wild food plant species had additional uses besides food; with ten different types of use and multiple use categories occurring in the different sub-systems. This study highlights that the development of more productive lowland rice systems may jeopardize the diversity of wild food plant species in the rice landscape, which is important for the food security of the rural poor.

Diversity of Blue Green Algae from Paddy Fields

Blue green algae are found in all types of aquatic bodies. Paddy fields represent one such habitat. An attempt has been made to isolate cyanobacteria from paddy fields of Siddipet region in Telangana State. Blue Green Algae are the most important nitrogen fixing organisms because of their autotrophic nutrition and flourish in paddy fields and known to sustain the fertility of this ecosystem. This paddy ecosystem allows BGA to function properly, selectively and effectively.To initiate the study, soil samples were collected in clean polythene bags. At the time of collection, the surface of the sampling station was cleaned by removing small stones, pebbles and grasses. The collected samples were brought to the laboratory, cultures were maintained and periodical observations were made on alga appearing in the cultures. As many as 34 species of cyanobacteria were identified.Both heterocystous and non- heterocystous forms were observed. The Nostocaceae has been reported by maximum number of genera and species. The genera Scytonema, Oscillatoria, Nostoc and Lyngbya were represented by maximum number of species.

Resource conservation technology in different paddy ecosystems

Different paddy cultivation methods were introduced to offset the heavy cost of traditional paddy cultivation by minimizing the use of fertilizers, pesticides and water utility by scientific management practices thereby increasing the profits of the farmers. As the agricultural land is shrinking and water availability for irrigation is declining with time. Rice consumes 3000–5000 litres of water for producing one kg of rice depending on different methods of cultivation. To find out efficient resource utilization methods, a long term investigation was carried out on conservation agriculture in paddy eco-systems at Agricultural and Horticultural Research Station, Kathalagere, Tq. Channagiri, Davanagere District, Karnataka, India from 2009 to 2013. Among different methods of rice cultivation, system of rice intensification (SRI) paddy cultivation has recorded highest grain yield of (5471 kg/ha), water use efficiency (101.8 kg/ha-cm) and 40.15% water saving over normal/traditional method of rice cultivation. Similarly, it was recorded 14.29% higher grain yield and additional returns of Rs. 23431 over normal/traditional rice cultivation. Adoption of drum seeder has given 6.6% higher grain yield with an additional return of Rs. 20168 and 2.70% water saving over normal planting. Among different rice cultivation methods, highest water saving was recorded in Aerobic method of paddy cultivation (50.05%). Based on the above results, we conclude that adoption of system of rice intensification (SRI) showed higher water use efficiency, productivity and profitability and it was found to be the best method of effective utilization of available natural resource (water) in paddy cultivation.

Sulfur Fertilization Changes the Community Structure of Rice Root-, and Soil- Associated Bacteria.

Under paddy field conditions, biological sulfur oxidation occurs in the oxidized surface soil layer and rhizosphere, in which oxygen leaks from the aerenchyma system of rice plants. In the present study, we examined community shifts in sulfur-oxidizing bacteria associated with the oxidized surface soil layer and rice roots under different sulfur fertilization conditions based on the 16S ribosomal RNA (rRNA) gene in order to explore the existence of oligotrophic sulfur-oxidizing bacteria in the paddy rice ecosystem. Rice plants were grown in pots with no fertilization (control) or CaCO3 or CaSO4 fertilization. A principal-coordinates analysis (PCoA) showed that CaSO4 fertilization markedly affected bacterial communities associated with rice roots and soil, whereas no significant differences were observed in plant growth among the fertilizer treatments examined. In rice roots, the relative abundance of Acidobacteria, Alphaproteobacteria, Gammaproteobacteria, and TM7 was significantly higher in CaSO4-fertilized pots than in control pots. Alphaproteobacteria, Bradyrhizobiaceae, and Methylocystaceae members were significantly more abundant in CaSO4-fertilized roots than in control roots. On the other hand, the abundance of Actinobacteria and Proteobacteria was lower in CaSO4-fertilized soil than in control soil. These results indicate that the bacteria associated with rice roots and soil responded to the sulfur amendment, suggesting that more diverse bacteria are involved in sulfur oxidation in the rice paddy ecosystem than previously considered.

Life History and Morphological Responses of Daphnia similis against Chemical Compounds Exuded by Various Cohabiting Animals and Triops longicaudatus in the Rice Paddy Ecosystem

Life History and Morphological Responses of Daphnia similis against Chemical Compounds Exuded by Various Cohabiting Animals and Triops longicaudatus in the Rice Paddy Ecosystem

Occurrence and bioaccumulation of polybrominated diphenyl ethers in sediments and paddy ecosystems of Liaohe River Basin, northeast China

Concentrations of 16 polybrominated diphenyl ether (PBDE) congeners were measured in river sediments, paddy soils and three species of paddy-field organisms (crab, loach and carp) collected from the Liaohe River Basin, northeastern China. The total contents of PBDEs (∑16PBDEs) in sediments and paddy soils were in the ranges of 273.4–3246.3pg/g dry weight (dw), and 192.1–1783.8pg/gdw, respectively. BDE 209 was the dominant congener both in sediments and paddy soils. The concentrations of ∑16PBDEs in sediments were significantly higher than those in the adjacent paddy soils, indicating a potential transport of PBDEs from river to paddy ecosystems via river water irrigation. The biota–soil accumulation factor (BSAF) was calculated as the ratio between the lipid-normalized concentration in paddy-field organisms and the total organic carbon-normalized concentration in paddy soil. The average BSAF values of ∑15PBDEs followed the sequence of crab (3.6)>loach (3.3)>carp (2.1). BDE 154 had the highest BSAF value, and a parabolic trend between BSAF values of individual PBDE congeners and their logKOW values was observed. In view of the fact that crab had the larger BSAF value and higher lipid content, the ecological risk and health risk for crab cultivation in paddy fields should be of particular concern.

Populasi Penggerek Batang Padi pada Ekosistem Sawah Organik dan Sawah Anorganik

Rice stem borer (RSB ) is a major pest for rice in Central Java in the past ten years as well as previous years . The presence of RSB occurs during the rice growing season with a high intensity , especially in the rainy season . RSB which is the main type, yellow RSB Scirpophaga incertulas Walker and white S. innonata. Walker . Other types are pink Sesamia inferens Walker , striped Chilo suppressalis Walker, headed black C. polychrysus Meyrick , and shiny C. auricilius Dudgeon. Organic farming in Central Java is still not widely applied so it is still very less information available, including information on the fluctuations in species diversity and population abundance of RSB. In this study examined the types and abundance fluctuations keenekaragaman RSB populations in rice field ecosystem organic and inorganic. Research will be conducted for one year (3 times transplanting rice) paddy ecosystems in organic and inorganic Bakalrejo Village, District Susukan, Semarang regency. The results showed that the dominant RSB is yellow S. incertulas. Yellow RSB found in every season paddy rice planting in both organic and inorganic rice. While the pink, shiny and white RSB, occasionally encountered. The RSB encountered seem to prefer the ecosystem tend rice paddy organic than inorganic . Keywords : rice stem borer ( RSB ) , organic rice ecosystem, inorganic rice ecosystem.

Controlling light quality and intensity can reduce N2O and CO2 emissions of mature aging rice

AbstractN2O, CO2, and CH4 are important greenhouse gases (GHGs) in paddy fields, and rice plants play an important role in GHG emissions in paddy fields. However, the relationship between light and rice plant GHG emissions is unclear. In this study, we monitored N2O, CO2, and CH4 emissions of mature aging rice under different light qualities and intensities. The results showed that (i) under natural sunlight, the rice phyllosphere N2O emission rate was 22.94 μg pot–1 h–1, accounting for 60% of the whole rice plant total N2O‐N evaporation loss. The CO2 emission rates from the phyllosphere and the root system were 27.82 mg pot–1 h–1 and 8.02 mg pot–1 h–1, respectively. However, no CH4 net emission effects were observed. (ii) Under a constant LED monocolor light intensity (1600 Lux), red, blue, and white light can inhibit N2O and CO2 emissions from the rice phyllosphere, resulting in lower emissions than yellow light. White light can also inhibit N2O and CO2 emissions from rice roots. (iii) Within the range of 0‒6000 Lux, increases in light intensity can reduce rice phyllosphere CO2 emissions, but such increases also promote N2O emissions from the rice phyllosphere and the roots. In contrast, natural sunlight can promote rice phyllosphere N2O and CO2 emissions and can inhibit root N2O emissions. The measure of light control may be the key to low‐carbon technology for GHG emission reductions in mature paddy ecosystems. © 2015 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Agronomic and environmental aspects of diazotrophic bacteria in rice fields

This article provides an overview of the free-living and plant-associated nitrogen (N)-fixing bacterial communities in wet rice fields, with a focus on describing the elements affecting community assemblages in this waterlogged soil–plant system. Nitrogen is a crucial nutrient for rice yield and growth. Characteristics of the rice paddy ecosystem promote N-fertilizer losses, resulting in negative impacts on the environment. Public concerns on sustainable rice crop production and food security have accentuated interest in exploring biological supplementary nitrogen sources. Biological N-fixation is a significant source of the nitrogen in agroecosystems. The nitrogen requirement of rice crops can be partly remedied by managing and promoting the activities of N-fixing microorganisms. These changes are leading towards a cleaner approach that maintains sustainability while simultaneously improving crop production targets. The use of N-fixing microorganisms as biofertilizers and the factors driving the success of this technology in wet rice paddies are also discussed.

The large-scale distribution of ammonia oxidizers in paddy soils is driven by soil pH, geographic distance, and climatic factors.

Paddy soils distribute widely from temperate to tropical regions, and are characterized by intensive nitrogen fertilization practices in China. Mounting evidence has confirmed the functional importance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in soil nitrification, but little is known about their biogeographic distribution patterns in paddy ecosystems. Here, we used barcoded pyrosequencing to characterize the effects of climatic, geochemical and spatial factors on the distribution of ammonia oxidizers from 11 representative rice-growing regions (75–1945 km apart) of China. Potential nitrification rates varied greatly by more than three orders of magnitude, and were significantly correlated with the abundances of AOA and AOB. The community composition of ammonia oxidizer was affected by multiple factors, but changes in relative abundances of the major lineages could be best predicted by soil pH. The alpha diversity of AOA and AOB displayed contrasting trends over the gradients of latitude and atmospheric temperature, indicating a possible niche separation between AOA and AOB along the latitude. The Bray–Curtis dissimilarities in ammonia-oxidizing community structure significantly increased with increasing geographical distance, indicating that more geographically distant paddy fields tend to harbor more dissimilar ammonia oxidizers. Variation partitioning analysis revealed that spatial, geochemical and climatic factors could jointly explain majority of the data variation, and were important drivers defining the ecological niches of AOA and AOB. Our findings suggest that both AOA and AOB are of functional importance in paddy soil nitrification, and ammonia oxidizers in paddy ecosystems exhibit large-scale biogeographic patterns shaped by soil pH, geographic distance, and climatic factors.

Nitrogen fixing Cyanobacterial flora of Nadia District in West Bengal, India

Cyanobacteria play an important role in maintenance and build-up of soil fertility, consequently increase rice growth and yield as a natural bio fertilizer. The paddy field ecosystem provides a favourable environment for the growth of Cyanobacteria with respect to their requirement for light, water, temperature and nutrient availability. Continued three successive years (2011 -2014) studied the Occurrence of Cyanobacteria in rice growing fields of Nadia district in West Bengal, India. We survey and studied 3 different rice growing fields of Nadia district namely Haringhata, Kalayani and Jaguliya for studying the cyanobacterial diversity. These rice growing fields mainly comprises unicellular, non-heterocystous and heterocystous cyanobacteria. Total 37 species of Nitrogen fixing Cyanobacteria samples belonging to 21 genera and four orders i.e., Chroococcales, Oscillatoriales, Nostocales, and Stigonematales were isolated from various rice growing localities. Present investigations revealed that the pH range of soil was mostly acidic in Rabi season and it was more than Kharif crop season. Three major Cyanobacterial groups; Unicellular and colonial were slight more than Non-heterocystous i.e., 6 genera and 8 species. Non-heterocystous filamentous cyanobacteria were minimum and its 5 genera and 8 species and heterocystous filamentous cyanobacteria were maximum, its 10 genera and 19 species were occurrence in most of all low and upland rice growing areas.

Bahasa Indonesia

Spiders are the main predators in paddy ecosystem. Application of entomopathogenic fungus, such as Beauveria bassiana (Balsamo) is not expected to have any negative effect on spiders in the paddy field. This research was aimed to compare species composition, abundance, and species richness of spiders in ratoon paddy. The research was done on three hectares of rice fields that were treated with the following treatment, (i) 2 L/ha/application of liquid B. bassiana, (ii) 2 L/ha/application compost extract (without liquid B. bassiana), and (iii) a combination of liquid B. bassiana and compost extract with each using the same 2L/ha/application dose. The result of this research showed that B. bassiana bioinsecticide application did not affect the abundance and species richness of spiders in ratoon paddy. The treatments did not significantly affect species richness and abundance of the canopy-inhabiting spiders. The species richness and abundance of the soil-dwelling spiders on the paddy field applied by the bioinsecticide was not different from those without the bioinsecticide. The treatments did not effect species composition of the canopy-inhabiting and the soil-dwelling spiders. Application of B. bassiana bioinsecticide was not harmful for the spiders in the rice field.