Conventional Rice Fields Research Articles

N2O emission and grain yield of rice from organic and conventional farming in the paddy field

Rice cultivation is a significant contributor to N2O. Organic agriculture, which is entirely dependent on the source of nitrogen from organic matter can become an alternative to mitigate the high N2O emission. This research aimed to observe the N2O emission from the organic and conventional rice fields. Two sites of rice fields were selected for this study, i.e. Sawangan, Magelang and Godean, Yogyakarta, Indonesia. Three plots of organic rice field and three plots of conventional rice field were selected as study sites. Gas samples were collected four times during the plant growth, i.e before transplanting, 2 weeks after transplanting, maximum vegetative stages and 2 weeks before harvesting. Godean site shows the emission of 138 µg N2O/m2/hour for organic field and 336 µg N2O/m2/hour for the conventional field. Sawangan site shows the emission of 348 µg N2O/m2/hour for organic field and 444 µg N2O/m2/hour for the conventional field. The results showed organic farming able to reduce the emission of N2O up to 20% on average. Rice growth and grain yield proved that organic rice showed a higher result compared to conventional rice. This study implied that organic rice farming might be promising land management to mitigate N2O emission and produce a higher yield.

Effects of Pesticide Use on the Distributions of Grey Herons (Ardea cinerea) and Great Egrets (Ardea alba) in Rice Fields of the Republic of Korea.

Pesticide use is known to have a negative impact on the habitat use of birds. The decomposition of residual pesticides causes a drastic decrease in the biomass of wildlife food sources, indirectly affecting the ecosystem. In this study, we investigated the effects of pesticide use on the distributions of grey herons (Ardea cinerea) and great egrets (Ardea alba) in rice fields in the Republic of Korea. From early May to mid-June in 2015 and 2016, we recorded the abundance of these birds and their prey (loaches, other fish, tadpoles, and benthic invertebrates) and investigated their dependence on rice agricultural practices (eco-friendly vs conventional) and field types (harrowed, plowed, or transplanted). We found that both grey herons and great egrets preferentially used transplanted fields. Grey herons were observed more in conventional rice fields, while great egrets were observed more in eco-friendly rice fields. This may be driven by the distribution of their preferred prey types; we observed a higher density of tadpoles (the prey type favored by grey herons) in conventional fields and a higher density of loaches (the preferred prey of great egrets) in eco-friendly fields. Pesticides drive these patterns both directly and indirectly; pesticide use in conventional rice fields directly suppresses the abundance of loaches, which frees the tadpole population from predation pressures and indirectly boosts their abundance in conventional rice fields. Our findings suggest that the distributions of grey herons and great egrets vary depending on food availability and are directly and indirectly influenced by pesticide use.

The Diversity of Insect in Paddy Field in Karawang, West Java with Different Pest Management Techniques

The practice of rice crop cultivation will affect the trophic structure and the diversity of insects that are formed. One of the common cultivation practices carried out by farmers was the control of pests by using pesticides. This study aimed to find out which pest management strategies that are effective in maintaining environmental health and understanding how natural enemies were affected by the application of synthetic pesticides. The first treatment was paddy field with integrated pest management (IPM), the second treatment was conventional rice field with a technique of chemical pest management (C-T), while the third treatment was mixed pest management (M-T). Insect sampling was conducted using sweep net, pitfall trap, and direct observation for 10 weeks after planting. Overall, it was found 100 morphospecies, 9 Orders, 56 families, with a total abundance of 6242 individuals per planting season. Based on functional roles it was found 39% as herbivores, 30% as predators, and 14% as parasitoids, 1% pollinators, and 13% decomposers. High insect diversity and abundance were found in the plots using low synthetic pesticides. The C-T control plot had a lower relative abundance of herbivorous insects, parasitoid insects, predators, and decomposers than the other control plots. H' and D index in the Integrated Pest Management (IPM) and Mixed Pest Management (M-T) plots did not show significant differences but differed significantly from the Chemical Control plot (C-T). Therefore, controlling the herbivore insects could apply the pest management based on IPM strategies. Keywords: Diversity of insects, integrated pest management (IPM), natural enemies, pesticides, rice pests

The Stratification of Organic Carbon and Nitrogen in Top Soils as Affected by the Management of Organic and Conventional Rice Cultivation

Organic and conventional management in rice cultivation have an impact on the nature of soil and the sustainability of agricultural system. This study aimed to determine the stratification of organic carbon and nitrogen in top soil from organic and conventional rice management. Top soil samples from organic and conventional rice management were taken before planting rice to find out the parameters of several soil characteristics. After rice was planted, top soil samples were taken at the depths of 0-4, 4-8, 8-12, 12-16, 16-20, 20-24 and 24-28 cm from organic and conventional rice fields, to determine the total organic carbon, total nitrogen and nitrate. The results show that organic rice management will provide better soil properties. Stratification of organic carbon and nitrogen was found in top soil from organic and conventional rice fields. Organic rice field appeared to have organic carbon content that was significantly higher than that of conventional rice field, and it is concentrated on top soil surface. The total nitrogen content in layers 0-4 cm and 4-8 cm in organic rice field was considerably higher than in conventional, but the content was different in layers 8-24 cm. Nitrate content was significantly different in top soil 12-16, 16-20 and 20-24 cm, significantly in top soil 8-12 cm, with nitrate in top soil of conventional rice field higher than in organic rice field. However, it was not significant in 0-4 cm and 4-8 cm top soils. This condition was influenced by organic and synthetic chemical fertilization, nitrification, denitrification and leaching.

Soil Fertility Index on Various Rice Field Management Systems in Central Java, Indonesia

The purpose of this research was to assess the condition of soil fertility and compare the soil fertility index in various rice field management systems. This research was conducted from July until December 2018 in the rice fields of Girimarto District, Wonogiri Regency with a survey method and land sampling by purposive sampling (intentionally) at a depth of 0-20 cm rice fields with organic, semi-organic and conventional management systems. Soil samples were taken from 9 main points with 3 replications so that a total of 27 soil samples were obtained. The chemical properties of the soil tested by the laboratory are soil reaction (pH), Total Nitrogen (Total N), Available Phosphorus (Av-P), Available Potassium (Av-K), Cation Exchange Capacity (CEC), Base Saturation (BS), Soil Oganic Carbon (SOC) and Aluminum Saturation (Al saturation). The results showed that three rice field management systems have the same soil fertility index criteria, which are medium. In organic rice fields that have implemented organic farming systems for 6 years, have a soil fertility index value of 0.630, semi-organic rice fields with a SFI value of 0.557 and also organic rice fields with a SFI value of 0.545. Soil fertility index of organic rice fields is significantly higher than that of semi-organic rice fields and conventional rice fields.

Documenting the first records of myxomycetes on rice litter of Cotabato, Southern Mindanao, Philippines

Although studies of myxomycetes in plantations have started to appear in the last few years, some agroecosystems with homogenous vegetation remain unexplored. This holds true for rice agroecosystems. A study comparing the occurrence of myxomycetes in organic and conventional rice fields in the province of Cotabato was carried out in rice farms in the municipalities of Kabacan and Midsayap. Ground and aerial litters were randomly collected from rice fields to set up moist chamber cultures. Three cosmopolitan species of myxomycetes are reported in this study, namely <em>Arcyria cinerea</em>, <em>Diderma hemisphaericum</em>, and <em>Perichaena depressa</em>. Moist chambers set up with rice litter substrates from organic fields showed significantly higher percentage yield than moist chambers with the substrates from conventional rice farms. This study is the first to explore the distribution of myxomycetes in rice agroecosystems of the Philippines and to compare different farming practices.

Carbon and nitrogen stocks and their mineralization potentials are higher under organic than conventional farming practices in Japanese Andosols

ABSTRACT This study aimed at understanding whether and how long-term organic rice farming affects soil carbon (C) and nitrogen (N) stocks and their mineralization potentials in submerged rice paddies in Tochigi, Japan. An incubation experiment was carried out to assess the impacts of internal nutrient cycling after organic farming (OF) for 4–5 years (4OF), 8–9 years (8OF), and 12 years (12OF), compared with a conventional rice field (CF). Soil samples were collected at 0–15 cm and 15–20 cm in flooded rice fields after harvest in October 2013. pH and bulk density at 0–15 cm were significantly lower in 12OF fields than in CF fields (by 0.22 unit pH and 17.5%, respectively). Compared with CF, 12OF fields showed significant differences in soil organic carbon (SOC) and total nitrogen (TN), but 4OF and 8OF fields did not. In 8OF fields, the C decomposition (Co) and N mineralization (No) potentials were significantly higher (by 34.0% and 35.6%, respectively, at 0–15 cm, and by 67.1% and 24.5% at 15–20 cm) than in CF fields. Similarly, in 8OF fields at 0–15 cm, the Co:SOC and No:TN ratios were 19.8% and 23.2% higher, respectively, than in CF fields. Co, No, Co:SOC, and No:TN in 12OF fields were higher than those in CF fields, demonstrating the effects of prolonged organic rice farming. Additionally, in 12OF fields, C and N stocks were significantly higher (by 15.5% and 17.2%, respectively, at 0–15 cm, and by 4.8% and 12.1% at 15–20 cm) than in CF fields. Our findings suggest that long-term organic rice farming increases soil C and N stocks as well as C and N mineralization in Japanese Andosols.

Promotion of rice–duck integrated farming in the water source areas of Shanghai: its positive effects on reducing agricultural diffuse pollution

The paper aims to study the effects of replacing the conventional rice farming by the rice–duck integrated organic farming on the reduction of agricultural diffuse pollution around Dianshan Lake in the suburbs of Shanghai, Southeast China. Agricultural activities of 21 rice farms in Jinze Town nearby Dianshan Lake were tracked and investigated for the consecutive 5 years, with the questionnaires on the inputs of agro-chemicals within the rice-growing seasons under the conventional rice farming in detail. The nutrient amounts discharged from the conventional rice fields were calculated and these from the rice–duck integrated organic farming potentially implemented surrounding the lake were also estimated. The quantities of N and P2O5 applied to the conventional paddy fields of the six towns surrounding the lake were 2.01 × 106 kg a− 1 and 4.59 × 105 kg a− 1 on annual average, respectively; these discharged into the environment were estimated to 1.48 × 105 kg a− 1 and 1.34 × 104 kg a− 1 on annual average, respectively. The quantities of herbicides, fungicides, and pesticides discharged from the conventional rice fields of the six towns were 1.67 × 104 kg a− 1 on annual average. The potential replacement of the conventional rice farming by the rice–duck integrated organic farming around the lake will reduce the amounts of N and P2O5 discharges through runoff and leaching by 83.79% and 92.11%, respectively, and completely prevent the diffuse pollution of biocides. The implementation of the rice–duck integrated organic farming around Dianshan Lake will not only be beneficial to lake protection, but also to raising the incomes of local farmers, and, thus, should be highly encouraged.

Populasi Serangga Hama dan Artropoda Predator pada Padi Rawa Lebak Sumatera Selatan yang Diaplikasikan Bioinsektisida dari Beauveria bassiana dan Insektisida Sintetik

Hanif et al, 2019. Population of Pest Insects and Predatory Arthropods Inhabiting Freshwater Swamp Rice of South Sumatra Treated with Bioinsectide of Beauveria bassiana and a Synthetic Insecticide. JLSO (8)1:31-38.Entomopathogenic fungi, Beauveria bassiana, could kill various species of insect pests, but their impact on predatory arthropods needs to be studied. The aim of this study was to compare population of pest insects and predatory arthropods inhabiting rice sprayed with bioinsecticide of B. bassiana and conventional rice field using a synthetic insecticides. Bioinsecticide was made from conidia of B. bassiana and sprayed on rice canopy. The plot of conventional farmers was sprayed with synthetic insecticides made from Abamektrin. The results showed that the application of bioinsecticide of B. bassiana was not proven to reduce the pest insect population. The abundance of natural enemies of pest insects, such as spiders and predatory insects was also more abundant in plots sprayed with bioinsecticide than conventional plots that used synthetic insecticide. The synthetic insecticides have been shown to reduce the abundance of predatory insects and spiders. Bioinsecticides containing carrier of liquid compost were proven to increase the growth and development of rice, which was an increase in the number of rice tillers per clump in plots applied by bioinsecticide. Thus, B. bassiana of bioinsecticide with liquid compost carrier material was safer and could maintain the abundance of predatory arthropods and increased rice growth.

Soil physical properties and abundance of soil fauna in conventional and organic rice field

Land management affected the physical, chemical and abundance of soil fauna. The aim of the study was to know differences of soil physical properties and abundance of soil fauna in conventional and organic rice field. Another aimed to know long term effect of organic farming to soil physical properties and abundance of soil fauna inrice field. This experiment used nested design which 3 location of sampling. The first location was in Imogiri Subdistrict with conventional rice field and 6 years of organic rice field applied. The second location was in Mojogedang Subdistrict with conventional rice field and 4 years of organic rice field applied. The third location was in Sawangan Subdisctrict with conventional rice field, 4 years and 10 years of organic rice field applied. Soil sample was taken in condition of after plough before planting, maximum plant vegetative phase and after harvesting. Organic rice field gave trend increased percentage of silt fraction and reduced percentage of sand fraction, increased aggregate stability of soil, increased abundance of earthworm, reduced abundance of plant parasitic nematode and increased non-parasitic nematode and increased soil respiration. Organic farming gave trend improving soil physical, chemical and biological parameters.

Effect of flooding duration on nitrous oxide emission from organic and conventional rice cultivation system in Central Java, Indonesia

Majority paddy fields in Indonesia are cultivated under conventional management practices. Recently, organic farming has been developed due to a high demand of more healthy food and soil fertility improvement of farmer field. A greenhouse experiment was conducted to investigate N2O emission from organic (O) and conventional rice field (K) collected from Sragen (S, soils with clay texture) and Magelang (M, soils with coarse texture) region. The soils were treated with different duration of flooding, i.e., no flooding (P0), flooding 2 weeks (P2), and flooding 4 weeks (P4). The result showed that there were no significant differences on N2O emission among the treatments in this study. However, N2O emission (kg N ha−1) was emitted more significant in organic than in conventional management practice in both regions. N2O emission (kg N ha−1) showed the highest value (0.39 – 1.21) when soil was flooded during 2 weeks. Interestingly, N2O emissions from both regions showed the same trend, neglected their different soil texture.

Potential Production of CH4 And N2O in Soil Profiles from Organic and Conventional Rice Fields

The horizons in soil profile will determine the magnitude of greenhouse gas production due to the difference of total organic carbon and other chemical properties. This study aimed to determine the potential production of methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) in each horizon of soil profile from organic and conventional rice fields. Soil samples which were taken from Imogiri Bantul D.I. Yogyakarta were used to determine soil properties, the potential of CH<sub>4</sub>, and N<sub>2</sub>O productions. The correlation analysis was used to determine the relationship between the production of CH<sub>4</sub> and N<sub>2</sub>O with soil properties. The results showed that production of CH<sub>4</sub> and N<sub>2</sub>O will be decreased with the increase of soil depth. Production of CH<sub>4</sub> and N<sub>2</sub>O was higher in organic rice field than in conventional rice field. The total organic carbon (TOC) correlated positively with CH<sub>4</sub>-production (<em>r=0</em><em>.89, P<0.001, n=8</em>) and N<sub>2</sub>O-production (<em>r=0</em><em>.87, P<0.001, n=8</em>). The nitrogen content also correlated positively with CH<sub>4</sub>-production (<em>r=0</em><em>.87, P<0.001, n=8</em>) and N<sub>2</sub>O-production (r=0.94, P<0.001, n=8). Mitigation of CH<sub>4</sub> and N<sub>2</sub>O emissions should consider of C and N in the soil.

An Assessment of the Vertical Movement of Water in a Flooded Paddy Rice Field Experiment Using Hydrus-1D

A quantitative estimation of the major components of the field water balance provides management decisions on how the scheme ought to be operated to ensure better distribution of irrigation water and increased delivery performance. Therefore, in this study, the water balance component in transplanted and broadcasted rice fields with conventional irrigation (flooding irrigation) in the Tanjung Karang Rice Irrigation Scheme (TAKRIS), Sawah Sempadan were observed and then modeled using Hydrus-1D numerical model during two consecutive rice growing seasons. During the off-season, irrigation water accounted for 59.6% of the total water input (irrigation + rainfall), but about 76.2% of total water input during the main season. During the main season, rainfall water only contributed to 23.8% of total water input and 40.4% during the off-season. Drainage water accounted for 37.3% of the total water input during the off-season and 43.7% during the main season, respectively, which was the main path of water losses from conventional rice fields, which indicates that maintaining a high water level and huge rainfall events during both seasons increased drainage water. Simulated ET during the off-season and the main season accounted for 38.1% and 49.5% of the total water input, respectively. Observed and simulated water percolation revealed about 17.1% to 19.2% of total water input during both seasons, respectively. Additionally, the water productivities analyzed from total water input and irrigation water were 0.43 and 0.72 kg m−3 during the off-season and 0.60 and 0.78 kg m−3 during the main season, respectively. The water productivity index evaluated from observed and modeled evapotranspiration was 1.03 and 1.13 kg m−3 during the off-season and 0.98 and 0.94 kg m−3 during the main season, respectively. The overall results revealed that Hydrus-1D simulations were a reasonable and effective tool for simulating vertical water flow in both broadcasted and transplanted rice experimental fields.

Enhancing the parasitism of insect herbivores through diversification of habitat in Philippine rice fields

The diversification of farming landscapes is proposed as a method to increase farm productivity while at the same time enhancing pest regulation services provided by the natural enemies of insect herbivores. In this study, areas of diversified and conventional rice fields (with 2–14 fields per area = 0.42–1.31 ha) were established at three sites in the Philippines. The diversified areas had a series (> 40 per hectare) of small (< 2 m2) vegetable patches interspersed along rice bunds (levees). The abundance of planthopper and lepidopteran pests in these areas was monitored during two consecutive cropping seasons using sweep nets with rice yield and damage recorded at the end of each season. Mortality of brown planthopper (Nilaparvata lugens) and yellow stemborer (Scirpophaga incertulas) eggs was monitored through field exposures of infested rice plants. There were no differences in rice yields between the conventional and diversified areas; however, a range of vegetables were produced as a supplementary product from the diversified rice areas. Diversification had no effect on planthopper or leaffolder (Cnaphalocrocis medinalis) abundance at the sites. Adult stemborers (Scirpophaga incertulas) were more abundant in the diversified areas; however, stemborer damage was similar between area treatments in both years. Vegetable patches did not increase parasitism of planthopper eggs; however, egg parasitism was highest close to the vegetable patches, suggesting that egg parasitoids interacted with the patches. Mortality of stemborer eggs was higher in the diversified areas than in the conventional areas. Parasitism due to Trichogramma japonicum and other egg parasitoids was also higher in the diversified areas. These results indicate the potential for vegetable patches to enhance the biological control services provided by egg parasitoids in rice fields; however, the study also indicates a need to carefully select vegetable crops that avoid any potential benefits for rice pests. We discuss the need for further research into diversified farms as a means of achieving sustainable rice production in Asia.

Responses of macroinvertebrate communities to pesticide application in irrigated rice fields.

The ability to recover to original states after disturbances makes macroinvertebrates useful tools for assessing the impacts of pesticides. Many studies showed that direct exposure to pesticides decreases macroinvertebrate richness and alters their composition. The main objective of this study was to assess recovery patterns in macroinvertebrate communities after pesticide application in irrigated rice fields. We analyzed short-term temporal dynamics of macroinvertebrate communities after application of the herbicides bispyribac-sodium and clomazone and the insecticide chlorantraniliprole, over the rice-growing season in southern Brazil. We selected three conventional rice fields and the recovery of macroinvertebrate communities was also compared with three adjacent natural ponds. The study was developed from November 2011 to February 2012 (rice-growing season). Five macroinvertebrate collections were carried out 3, 7, 14, 38, and 60days after pesticide application (November 25). Rice fields showed lower richness and abundance than ponds in the period immediately after pesticide application, and recovery rates in the richness of macroinvertebrate communities were more conspicuous as pesticide residuals dissipated from the fields. Macroinvertebrate community structure in rice fields also became more similar to natural ponds as pesticide traces were scarcer. However, macroinvertebrate abundance patterns were not related to pesticide concentrations in the fields. Our results supported the general hypothesis on the negative effects of pesticide application on macroinvertebrate community in irrigated rice fields, although other environmental features (e.g., length of the flooded period) also contributed to explain temporal dynamics in the macroinvertebrate communities from irrigated rice fields.

Kajian Kebutuhan Air dan Produktivitas Air Padi Sawah dengan Sistem Pemberian Air Secara SRI dan Konvensional Menggunakan Irigasi Pipa

Kondisi air yang semakin terbatas untuk lahan pertanian dapat menyebabkan penurunan produksi padi. Peningkatan produksi tanaman saat ini menempati prioritas utama dalam pembangunan pertanian. Produktivitas dapat dikaji melalui subsistem tanah, air dan pola lahan untuk penggunaan pada periode tertentu. Aplikasi irigasi pipa dengan kombinasi sistem pemberian air secara SRI mampu memanfaatkan air dengan efisien. Oleh karena itu penelitian mengenai perhitungan produktivitas air padi sawah yang menggunakan input irigasi pipa dengan sistem pemberian air secara konvensional dan SRI penting untuk dilakukan. Tahapan penelitian yang dilakukan yaitu pengamatan langsung dilapangan, pengukuran terhadap evapotranspirasi, perkolasi, kebutuhan air netto di sawah dan perhitungan produktivitas air. Hasil penelitian menunjukkan bahwa produksi padi lebih tinggi dengan sistem pemberian air System of Rice Intensification (SRI). Produktivitas air padi dengan sistem pemberian air secara SRI juga lebih tinggi di mana kebutuhan air dengan kombinasi irigasi pipa dan sistem pemberian air secara SRI menjadi perlakuan terbaik. Produktivitas air pada sawah konvensional yaitu 0,82 kg/m3 dan sawah SRI yaitu 1,12 kg/m3. Kombinasi penggunaan irigasi pipa dengan sistem pemberian air secara SRI menunjukkan produktivitas air yang tinggi dan efisien dalam pemakaian air.

Diversity of Aquatic Insects in the Organic and Conventional Rice Fields in Khon Kaen Thailand

Diversity of Aquatic Insects in the Organic and Conventional Rice Fields in Khon Kaen Thailand

Evaluation of Herbicide Options for Alligatorweed (Alternanthera philoxeroides) Control in Rice

Alligatorweed is a perennial, invasive weed in southern United States rice production, but knowledge on effective management of this weed is limited, especially in conventional (non-imidazolinone-resistant) rice fields. Field studies were conducted in multiple environments in southeastern Texas to evaluate different herbicide options involving penoxsulam, propanil, triclopyr, halosulfuron, bispyribac-sodium, bensulfuron, and quinclorac for alligatorweed control in conventional drill-seeded rice when applied at early POST (EPOST), late POST (LPOST), or both. Among the herbicide options evaluated, penoxsulam alone (up to 83%), penoxsulam plus triclopyr (up to 87%), or bispyribac-sodium plus triclopyr (92%) provided superior alligatorweed control. Plots treated with penoxsulam plus triclopyr EPOST produced the highest yields (9,550 kg ha−1), which were comparable to plots receiving penoxsulam plus triclopyr LPOST (9,320 kg ha−1), penoxsulam alone EPOST (9,280 kg ha−1), and penoxsulam plus halosulfuron LPOST (9,180 kg ha−1). Considering both weed control and rice grain yields, penoxsulam plus triclopyr applied EPOST was found to be the best option among the treatments tested. The treatments bensulfuron alone, bensulfuron plus propanil, penoxsulam plus propanil, triclopyr plus propanil, and bispyribac-sodium plus propanil provided poor (≤ 65%) alligatorweed control. Results also suggest the likelihood for antagonistic interactions when tank-mix combinations tested in this study included propanil.

Can organic and conventional agricultural systems affect wetland macroinvertebrate taxa in rice fields?

The use of agrochemicals, water management and intense mechanization is compromising species diversity in rice fields. Organic agriculture has been proposed as a way to reduce the pressure on biodiversity in agricultural landscapes. Therefore, the following hypotheses were tested: (1) Taxonomic richness and abundance of macroinvertebrates are lower in rice fields than in natural ponds; (2) Conventional rice crops decrease taxonomic richness and abundance of macroinvertebrates compared with organic crops; (3) Taxonomic macroinvertebrate composition in organic rice crops is more similar to the composition in natural ponds than conventional fields; and (4) A reduction of taxonomic richness, abundance as well as a modified composition during soil preparation and the initial growth phases of the rice cultivating cycle were expected. To test these hypotheses, four natural ponds, four organic and four conventional rice fields were selected in southern Brazil. In each area, six collections were carried out over the rice cultivation cycle (August 2010 to August 2011). A total of 25,449 individuals from 73 different taxa were sampled. The richness and abundance were higher in ponds than in rice crops in the anterior and posterior off-season and in the soil preparation periods. However, organic and conventional rice fields showed similar taxonomic richness and abundance. Although the taxonomic composition differed only between rice crops and ponds, the presence of many taxa that only occur in organic crops and ponds indicates that organic management favors the establishment of some pond macroinvertebrate taxa in rice agroecosystems, mainly predators. Our results should be seen as an incentive for more sustainable production with less impact on the environment.

How does the management of rice in natural ponds alter aquatic insect community functional structure?

Changes to biodiversity have mainly been assessed using taxonomic diversity indices. Although these approaches contribute to our scientific understanding of species richness and composition patterns, trait-based metrics may be more useful for detecting responses to land-use change. We compared functional diversity of aquatic insect communities along a gradient of agricultural intensification. Our goal was to compare functional redundancy, functional richness, functional evenness and functional divergence among natural ponds, and organic and conventional rice fields. We recorded 15606 aquatic insects distributed across 61 genera. The highest functional redundancy and richness were observed in the natural ponds, followed by organic rice fields and conventional ones. The functional composition varied among natural ponds and rice fields, and differed between organic and conventional rice fields. Organic management favoured the establishment of some pond insect traits, such as predatory taxa, in rice agroecosystems. Our analysis suggests that the conversion of ponds to rice fields results in a shift to less specialised aquatic insect communities with altered functional composition groups. Nevertheless, this result should not be seen as a negative reflection on organic rice fields, because organic rice production affords a better compromise between agricultural production and ecosystem function than conventional agriculture.