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• We examined the diet of two rice field amphibians across two separate rainy seasons. • We identified prey items and tested for differences in diet composition. • The native Luzon wart frog consumed more rice pests (54.1%) than the cane toad. • The invasive cane toad consumed a disproportionate amount (89.4%) of predators. • The Luzon wart frog may provide pest control in rice agro-ecosystems. Lowland irrigated rice fields serve the dual purpose of providing an essential food crop to the world's most populous regions and functioning as man-made wetlands that harbor a diversity of organisms. Amphibians occupy rice fields throughout Asia and South America, but little is known about their functional role in the rice ecosystem. We conducted field surveys in Los Baños, Philippines over two separate rainy seasons (2015 and 2017) to determine whether native Luzon wart frogs and invasive cane toads consume rice pests, and if so, which species was more effective in doing so. We also examined diet composition to test whether the two species compete for food resources in rice fields. We found that despite smaller body sizes, the Luzon wart frog consumed the same total mass of prey as the cane toad (although it consumed fewer total prey items), and that pests made up the largest proportion (54.1%) of its total diet. In contrast, the majority (89.4%) of the cane toad's diet consisted of beneficial arthropod predators. Taxonomic analyses of diet composition and breadth revealed that the diet of Luzon wart frog was distinct from that of the cane toad, although there was overlap, and that both species consumed diverse array of prey. Taken together, these data suggest adult Luzon wart frogs may provide effective pest control services, and that they may not be in direct competition over food resources with adult cane toads in rice fields. We also present the first evidence suggesting that cane toads may indirectly damage rice crops by consuming beneficial predators integral to the function of lowland rice ecosystems. We suggest that rice agro-ecosystems should be managed to promote species such as the native Luzon wart frog, and to reduce populations of the introduced cane toad in order to safeguard native biodiversity while simultaneously improving yields and reducing insecticide input. [ABSTRACT FROM AUTHOR]

Highlights • Rice crops have recently lost their original value as surrogate wetland habitat. • Ditches may be insufficient to improve paddy suitability for breeding Odonata. • Odonata benefit from a well-developed vegetation, especially on paddy banks. • Semi-natural wetlands are essential to achieve Odonata conservation in rice crops. • Low frequency and rotational mowing should be implemented on paddy and canal banks. Abstract Paddy systems have recently lost their original value as surrogate habitat for several wetland species due to rice farming intensification. Changes in water regimes largely compromised the survival of many aquatic organisms formerly abundant in rice fields, such as Odonata, inducing the introduction of new agricultural practices supposed to mitigate the negative impacts of intensive rice cultivation on biodiversity. For instance, the construction of a water retention structure (ditch) within paddies has been incentivized in Italy, in order to reduce the detrimental effects of drying periods on aquatic organisms. In this research, we investigate the effects of ditch occurrence and dimensions on Odonata diversity in rice fields, and furthermore we evaluate the response of these insects to vegetation height on paddy and canal banks, as an approximation of grass management intensity. Field surveys revealed that ditch occurrence may not be sufficient to improve the suitability of rice fields as breeding habitat for Odonata, especially for sensitive species. Paddies with ditches of larger dimensions supported more abundant adult populations than other field types, but no clear differences have been observed concerning larval stages. Conversely, the occurrence of a well-developed bank vegetation produced clear benefits for these insects in rice fields, while a not significant effect have been observed along irrigation canals. In order to achieve Odonata conservation in rice agroecosystems, together with the excavation of large ditches within paddies, the creation of a network of semi-natural wetlands should be encouraged, as well as the implementation of extensive grass management strategies on rice field and canal banks. [ABSTRACT FROM AUTHOR]

Abstract River deltas are ecologically and economically valuable coastal ecosystems but low elevations make them extremely sensitive to relative sea level rise (RSLR), i.e. the combined effects of sea level rise and subsidence. Most deltas are subjected to extensive human exploitation, which has altered the habitat composition, connectivity and geomorphology of deltaic landscapes. In the Ebro Delta, extensive wetland reclamation for rice cultivation over the last 150 years has resulted in the loss of 65% of the natural habitats. Here, we compare the dynamics of habitat shifts under two departure conditions (a simulated pristine delta vs. the human-altered delta) using the Sea Level Affecting Marshes Model (SLAMM) under the 4.5 and 8.5 RCP (Representative Concentration Pathways) scenarios for evaluating their resilience to RSLR (i.e. resistance to inundation). Results showed lower inundation rates in the human delta (~10 to 22% by the end of the century, depending on RCP conditions), mostly due to ~4.5 times lower initial extension of coastal lagoons compared to the pristine delta. Yet, inundation rates from ~15 to 30% of the total surface represent the worst possible human scenario, assuming no flooding protection measures. Besides, accretion rates within rice fields are disregarded since this option is not available in SLAMM for developed dry land. In the human delta, rice fields were largely shifted to other wetland habitats and experienced the highest reductions, mostly because of their larger surface. In contrast, in the pristine delta most of the habitats showed significant decreases by 2100 (~2 to 32% of the surface). Coastal infrastructures (dykes or flood protection dunes) and reintroduction of riverine sediments through irrigation channels are proposed to minimize impacts of RSLR. In the worst RCP scenarios, promoting preservation of natural habitats by transforming unproductive rice fields into wetlands could be the most sustainable option. Graphical abstract Unlabelled Image Highlights • Altered deltaic systems with intensive rice farming (~65% of land surface) show distinctive habitat shifts. • The SLAMM on Ebro Delta predicts between ~10–22% higher inundation in the pristine system • Without adaptation measures 31–63% of agricultural lands would be lost or naturalized to RSLR by 2100 [ABSTRACT FROM AUTHOR]

As the primary rice-producing country in the world, China has applied increasing amounts of synthetic fertilizers on rice fields, which has a large impact on environmental pollution and human health. In this study, a comprehensive inventory of fertilizer application to rice fields was compiled for China from 1979–2015. In 2015, fertilizer application was estimated to be 0.96 × 10 9  kg for early rice, 2.67 × 10 9  kg for single rice, and 1.11 × 10 9  kg for late rice. Based on the fertilizer application and region-specific emissions factors, ammonia (NH 3 ) volatilizations from growing-season rice fields were estimated over the same period. We found that the total NH 3 emissions increased during 1979–1998, while decreased during 1998–2015 with fluctuations. The decreasing trend of NH 3 emission was likely attributed to changes of application proportions of ammonium bicarbonate (ABC) and other fertilizers. ABC and urea were the two dominant contributors, and contributed over 90% of the total NH 3 emissions. Spatially, high emissions were identified in the Middle-lower Yangtze River Plain, Huaihe River Basin, Taihu Lake region, Pearl River delta and Sichuan basin. Monthly emissions patterns were estimated according to rice calendars. The damage from NH 3 emissions was estimated as 26.79 billion yuan and accounted for 0.04% of the Gross Domestic Production of China in 2015. Finally, we discussed the NH 3 reduction strategies from the perspective of both the government and farmers and suggested that an incentive scheme should be established to guide farmers to optimize traditional agricultural management. [ABSTRACT FROM AUTHOR]

Pomacea spp. are freshwater gastropods that significantly reduce rice productivity around the world, particularly in Asian countries. Pomacea maculata was first reported in Europe in 2009 in the rice fields of the Ebro Delta, Tarragona (Catalonia), Spain. At present, tea seed ( Camellia oleifera ) saponins are the only authorized treatment by the Spanish agriculture authorities, but due to its comparatively high toxicity to non-target species such as fish, more environmental-friendly products are urgently needed. This study evaluated the performance of a novel molluscicide based on modified saponins derived from quinoa ( Chenopodium quinoa ) husks against Pomacea maculata under laboratory and field conditions in the Ebro Delta. Under laboratory conditions, the molluscicide killed 100% of the P. maculata above 7 ppm of saponins after 72 h. Field trials performed in three rice fields showed that after 96 h the molluscicide killed 88, 89 and 93% of P. maculata at doses of 6.5, 7.2 and 7.7 ppm saponin, respectively. Toxicological assays showed that the product is highly safe for aquatic environments, with an effect concentration of (EC 50 ) >36 mg saponins/L for crustaceans ( Daphnia) and algae ( Selenastrum capricornutum ) and a lethal concentration (LC 50 ) against common carp >36 mg saponins/L. Studies on rats, rabbits and guinea pigs showed that the molluscicide is generally non-hazardous for acute oral toxicity, slightly hazardous for acute dermal toxicity, a moderate irritant for acute eye irritation/corrosion, a non-irritant for acute dermal irritation/corrosion and a non-skin sensitizer. These results suggest that this novel molluscicide may be a viable product to safely control P. maculata in rice fields. [ABSTRACT FROM AUTHOR]

In rice fields, the cultivation area itself can play an essential role as a habitat for wetland organisms. Many previous studies showed negative impact of agricultural intensification and abandonment on biodiversity in wet farmland ecosystems. However, verification of the direct impact of aquatic environmental change by the paddy improvement and abandonment still remains. Here, we investigated the effects of the intensification and abandonment on the area of wet fields remaining in paddies during the fallow season, as well as the factors driving the population decline of the Japanese brown frog ( Rana japonica ), using data of long-term monitoring numbers of egg masses at multiple sites. To quantitatively estimate the spatial and temporal variation in saturated areas with water in the paddies where the frogs spawn in early spring, we used infrared bands of Landsat images. Both paddy improvements and abandonment have affected R. japonica populations through the reduction of wet areas in the fields. Furthermore, the frog's population size was positively associated with the area of surrounding forest. Our findings suggest that conservation in wet farmland requires appropriate water management inside the cultivation area as well as in other landscape elements that serve as secondary habitats. [ABSTRACT FROM AUTHOR]

Mean residence time (MRT) of carbon (C) in soil is the most important parameter of C sequestration and stability and crucial for CO 2 removal from the atmosphere. Climate and soil properties controls of MRT of upland soils are well known, but the drivers of C stability in paddies were never summarized. Here, we estimated MRT of paddies across monsoon Asia using the stock-over-flux method, i.e., soil organic C (SOC) stock over organic matter input considering the net primary production (NPP), and determined the main factors affecting SOC turnover. The average MRT of paddy soils in monsoon Asia ranges between 19 and 50 yr, depending on straw management. These estimates are similar to recent estimates for the global average MRT across all soils, but longer than for upland croplands. Tropical regions have the shortest MRT for rice paddies (16–42 yr), while the MRT of C in soils of temperate and subtropical regions are longer (20–56 yr). Across a wide range of environmental factors, MRT was most strongly affected by temperature. We estimate that 2 °C warming decreases MRT by 7% on average, with the strongest decreases in the western Indonesian islands and north-east China. Because C stocks per area in paddy soils are larger and the MRT is longer than in corresponding upland cropland soils, paddies play a key role in the global C cycle. Our results emphasize the need for management practices that retain stable soil C input rates to reduce possible positive feedbacks for global warming. • Mean residence time (MRT) of C in paddies ranges 19–50 yr. • MRT was shortest in tropics, while similar in temperate and subtropics. • MAT influenced C turnover more than other environmental factors. • MRT of C in paddies is declining at an average rate of 7% to 2 °C warming. [ABSTRACT FROM AUTHOR]

Incorporation of straw together with microbial inoculant (a microorganism agent, accelerating straw decomposition) is being increasingly adopted in rice cultivation, thus its effect on greenhouse gas (GHG) emissions merits serious attention. A 3-year field experiment was conducted from 2010 to 2012 to investigate combined effect of straw and microbial inoculant on methane (CH 4 ) and nitrous oxide (N 2 O) emissions, global warming potential (GWP) and greenhouse gas intensity (GHGI) in a rice field in Jurong, Jiangsu Province, China. The experiment was designed to have treatment NPK (N, P and K fertilizers only), treatment NPKS (NPK plus wheat straw), treatment NPKSR (NPKS plus Ruilaite microbial inoculant) and treatment NPKSJ (NPKS plus Jinkuizi microbial inoculant). Results show that compared to NPK, NPKS increased seasonal CH 4 emission by 280–1370%, while decreasing N 2 O emission by 7–13%. When compared with NPKS, NPKSR and NPKSJ increased seasonal CH 4 emission by 7–13% and 6–12%, respectively, whereas reduced N 2 O emission by 10–27% and 9–24%, respectively. The higher CH 4 emission could be attributed to the higher soil CH 4 production potential triggered by the combined application of straw and microbial inoculant, and the lower N 2 O emission to the decreased inorganic N content. As a whole, the benefit of lower N 2 O emission was completely offset by increased CH 4 emission, resulting in a higher GWP for NPKSR (5–12%) and NPKSJ (5–11%) relative to NPKS. Due to NPKSR and NPKSJ increased rice grain yield by 3–6% and 2–4% compared to NPKS, the GHGI values for NPKS, NPKSR and NPKSJ were comparable. These findings suggest that incorporating straw together with microbial inoculant would not influence the radiative forcing of rice production in the terms of per unit of rice grain yield relative to the incorporation of straw alone. [ABSTRACT FROM AUTHOR]

Eutrophication is now a serious environmental problem worldwide because it disrupts the metabolism of aquatic ecosystems. In the Ebro Delta, intensive rice farming during the 20th century has increased coastal eutrophication and caused ecological and economic impacts. Marsh restoration is as an effective economic and ecological tool to remove nutrients from agricultural runoff, thereby limiting coastal eutrophication impacts and also providing other ecosystem services. The objective of this experimental study was to assess overall N and P concentration reduction, C accumulation and Si buffering in an oligohaline restored marsh receiving nutrient and sediment inputs from river irrigation and rice field drainage waters under different water levels. We established the experimental restored marsh in abandoned deltaic rice fields from August 2009 to June 2012. The study of changes in nutrient concentration was performed in 2010 from June to November. The study of nutrient and carbon accumulation was performed from August 2009 to May 2011. We used two freshwater input type treatments (riverine irrigation and rice field drainage water) and three water level treatments (10, 20 and 30 cm). Our results showed that higher water nutrient concentrations from rice fields caused significantly higher N- N H 4 + and P- P O 4 3 − concentration reduction (80.76 ± 1.8% and 17.99 ± 3.92% respectively). There was also an export in TP and P- P O 4 3 − (−45.08 ± 13.12 and −23.85 ± 8.15%, respectively) in experimental marsh units receiving river irrigation waters. Significantly lower soil redox conditions and higher total maximum aboveground biomass in the IW treatment were associated with lower N- N O 3 − concentration reduction and higher Si-SiO 2 concentration reduction (94.14 ± 0.72% and 58.54 ± 1.08% respectively) than the DW treatment. Higher sediment concentrations from rice fields were associated with higher C accumulation rates (126.10 ± 6.25 g m −2 y −1 ) compared with experimental marsh units receiving river irrigation waters (99.44 ± 8.23 g m −2 y −1 ). Higher water levels also increased significantly P- P O 4 3 − and Si-SiO 2 concentration reduction and C accumulation rates within both water type treatments. Our experimental study showed how multiple mechanisms control N and P concentration reduction, Si buffering and C accumulation. Plant growth may decrease the ability to reduce the input concentration of N- N O 3 − possibly due to denitrification inhibition via plant oxygenation of marsh soils. Plant uptake may favor Si buffering in the restored marsh, although high water levels may also control Si buffering through higher residence time for diatom uptake. This study indicates that Mediterranean oligohaline restored marshes removed N and P using both river irrigation and rice field drainage waters and also provide C accumulation and Si buffering services. The use of agriculture runoff as a primary source of nutrient and sediment is beneficial for marsh restoration projects focused on C accumulation. In general, higher water levels (20–30 cm) were better for nutrient concentration reduction and C accumulation, but higher water levels were also associated with lower plant biomass. [ABSTRACT FROM AUTHOR]

Abstract: Manure is one of the most important N sources in paddy rice systems, while it poses a great challenge in meeting rice N requirement and simultaneously reduces adverse environmental impacts. The main objective of this study was to design a simple model for assessing N fate in swine manure amended paddy rice systems. A field experiment was conducted for three cropping seasons to determine the effectiveness of different swine manure amended levels (15%, 30%, and 45% of total N applied) on N transformations and seasonal N fate. Based on field observation data, simulation results clearly showed peaks of various N transformation rates appeared within 2~3days after each fertilization. There was an apparent contribution of manure N on N uptake and loss when amount of manure applied was at optimum. However, at supra optimal rate, addition of manure N showed no effect on N uptake of crop and the corresponding N transformations. Across three levels, seasonal ammonia volatilization accounted for 35.6%~38.0% of total N applied, N uptake was 36.7%~41.1%, while N losses via vertical leaching, lateral seepage were 3.9%~4.5% and 4.4%~4.8%, respectively. These results were well predicted by our specific designed model, indicating the model performed effectively at assessing individual transformation process and its associated N fate and help develop efficient management strategies for swine manure amended paddy rice systems. [Copyright &y& Elsevier]

Highlights: [•] Both suitable foraging and roosting areas determined rice fields’ quality for godwits. [•] Godwits minimised their daily movements between roosting and feeding areas. [•] Home range core areas were centred on the roosts. [•] Power lines was the most important landscape factor affecting godwits’ roosts’ location. [ABSTRACT FROM AUTHOR]

Highlights: [•] We perform long-term analysis of non-breeding counts of black-tailed godwits in Doñana. [•] Increasing numbers in winter was observed, but not changes in spring migration. [•] Increase in man-made artificial wetlands were associated to increasing godwits numbers. [•] Man-made habitats need to be considered in conservation plans for the species. [ABSTRACT FROM AUTHOR]

Although rice production landscapes are often the scene of homicides, vertebrate decomposition and associated arthropods have never been described from rice paddies. Tropical rice landscapes are typically composed of irrigated/non-irrigated rice fields, fallow land (i.e., uncultivated fields), and low earthen levees (bunds) used as access pathways. The specific microclimatic and environmental conditions associated with each subunit of rice field landscapes are likely to impact carcass decomposition as well as the arthropod species associated with carrion. Here, we tested the hypothesis that the combined effects of constraints on arthropod colonization and survival, scarcity of necromass, limited habitat architecture, and recurrent disturbance limit the ability of carrion-related arthropods to colonize corpses and large carcasses in tropical rice-fields. Our results from monitoring pig carcasses in Philippine rice fields indicated that vertebrate decomposition in irrigated fields was slower and incomplete when compared to non-irrigated fields and bunds. Carcasses were colonized by a small complex of carrion-related arthropods that differed in composition and relative species abundance between dry bunds and relatively humid rice paddies. Fire ants (Solenopsis germinata) were observed frequently on carcasses exposed on bunds, rarely in non-irrigated fields, and almost never in irrigated fields. The presence of fire ants was associated with reduced blow fly (Chrysomya megacephala) abundance. Taken together, this indicates that the arthropod fauna associated with carcasses in tropical rice fields is relatively simple in contrast to the generally high arthropod diversity reported for other ecosystems at tropical latitudes. The limited richness of the community also means that an understanding of the development of one abundant calliphorid blow fly, C. megacephala, may be sufficient to investigate deaths and homicides under conditions similar to the ones described in this study. [ABSTRACT FROM AUTHOR]

Abstract: Mosquito-borne arboviruses are a significant health issue in the irrigation areas of south-eastern Australia. Fipronil, a pyrazole insecticide with strong activity against larval Culex species, was tested for its acute effects on Simocephalus elizabethae (Daphniidae) and Polypedilum nubiferum (Chironomidae), two non-target invertebrates associated with Australian rice field mosquito habitats. Technical and formulated fipronil were assessed in the presence or absence of particulate artificial diets in 48h static bioassays. LC50 values for neonate S. elizabethae ranged from 11.13 to 19.12μgl−1 whilst those for final instar P. nubiferum ranged from 0.89 to 2.18μgl−1. Feeding during exposure significantly reduced the susceptibility of P. nubiferum to both technical and formulated fipronil. The effect of feeding was less consistent in Simocephalus bioassays, where much less food was present. We investigated whether adsorption to unconsumed food particles may have limited fipronil bioavailability by using solid-phase microextraction and gas chromatography to measure the available fipronil from fed and unfed systems 24h after establishment. Differences between the systems were not significant (P >0.05). The significantly higher LC50 values in the fed Polypedilum bioassays do not appear to be a consequence of reduced fipronil bioavailability. Observed differences in toxicity probably reflect increased stresses associated with food deprivation in the unfed bioassays. Our results support published data on the toxicity of fipronil to aquatic invertebrates which suggest that the use of this material as a mosquito larvicide may cause disruption to aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Herbicide contamination of aquatic ecosystems is a serious global environmental concern. Several herbicides enhance the intracellular formation of reactive oxygen species, and can lead to the damage of macromolecules and to a decrease of oxidant defenses in a wide range of non-target microorganisms including cyanobacteria. The effects of molinate (a thiocarbamate herbicide used for controlling grassy weeds in rice fields) on the activities of antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and glutathione S-transferase were evaluated in Nostoc muscorum, a freshwater cyanobacterium with a significant spread in Portuguese rice fields. These were determined in N. muscorum cultures acutely (72h) exposed to concentrations ranging from 0.75 to 2mM of molinate. This study also analyzed the effects of molinate on: (1) the nonenzymatic antioxidant contents (reduced and oxidized glutathione, carotenoids, and proline), (2) the oxidative cell damage measured in terms of lipid peroxidation (MDA level) and electrolyte leakage (intactness of plasma membrane), and (3) the total fatty acid profile. The results showed that the activities of all antioxidant enzymes decreased dramatically with the rising concentration of molinate after 72h. Time-dependent and concentration-dependent increase in MDA and enhanced cell membrane leakage were indicative of lipid peroxidation, formation of free radicals and oxidative damage. Compared to control, 72-h herbicide exposure increased lipid peroxidation by 5.4%, 19% and 28% with 0.75, 1.5 and 2mM of molinate, respectively. Similarly, herbicide stress induced an increase in electrolyte leakage (5.8%, 29.5% and 30.2% above control, with 0.75, 1.5 and 2mM of molinate, respectively). The increased production of proline at higher molinate concentrations (the values rose above control by 45%, 95% and 156% with 0.75, 1.5 and 2mM, respectively) indicated the involvement of this osmoprotectant in a free radical scavenging mechanism. Moreover, a radical decline in both glutathione pool, carotenoids and saturated fatty acids were also observed. The results of the present study lead us to conclude that: (1) both enzymatic and nonenzymatic antioxidative defense system of N. muscorum are dramatically affected by molinate, (2) the herbicide induces peroxidation, (3) it contributes to an increase of the unsaturation level of cell membrane fatty acids. These evidences should be taken in account when using N. muscorum as an environmental indicator species in studies of herbicide biotransformation and biomarker response as well as in environmental monitoring programmes. [Copyright &y& Elsevier]

Abstract: A high proportion of threatened and near-threatened species in the world now inhabit farmland. Although much data regarding the impact of agriculture on farmland biodiversity have been accumulated in Western countries, such information, particularly on the impact of rice cultivation, is fragmentary in other parts of the world and has rarely been disseminated internationally. Therefore, this paper aims to clarify what information has become available through earlier studies in Japan, where farmland mainly consists of rice paddy areas, and give directions for future studies about the impact of agriculture on farmland birds in Japan. This study made three notable observations. First, a review of earlier studies of farmland bird species in Japan uncovered some evidence of both increases (e.g., wildfowl and cranes) and declines (e.g., waders) in population size. Second, this paper closely examined case studies of two types of typical farmland birds: (1) geese and cranes foraging on crops and/or harvested remains of crops and (2) waders and egrets foraging on small organisms in farmland, not agricultural crops. This portion of the study identified some potential routes through which human activities in farmland affect bird species in Japan, and offered practical implications for conservation and management of these species supported by scientific data. Finally, based on the results of this review, three key tasks for future conservation studies and practices in Japanese farmland were suggested: (1) establishing quantitative indices based on monitoring surveys in farmland to track the population status, (2) collecting further evidence of the impact of agriculture, particularly on population-level responses by birds, and in a food-web context, and (3) applying evidence-based conservation to practice. [Copyright &y& Elsevier]

In order to assess pollutant transfer in Camargue ponds from bordering agrosystems, a biomonitoring assay was conducted in irrigation and drainage channels of rice fields in the Rhone Delta (France). A filter-feeding bivalve, the Asian clam, Corbicula fluminea, was used as bioindicator and caged in upstream and downstream channels of an area of conventional rice fields. After 6 weeks incubation, many lipophilic biocides were identified in Corbicula tissues, including pesticides used in rice plantations (pretilachlor, oxadiazon), pesticides presumed in use in the Rhone basin [diuron and its metabolite 3,4 dichloroaniline (3,4-DCA)] and organochlorine pesticides (OCPs) banned for several decades. In addition, PCBs were highly bioaccumulated in Corbicula. Downstream bivalves had significantly lower concentrations of OCPs, PCB and 3,4-DCA. However, the exposure biomarkers (glutathione S-transferase, catalase and propionylcholinesterase) were not correlated with the decreased concentrations. The results of this experiment raise several questions concerning the potential role of immersed plants in a retention process. [Copyright &y& Elsevier]

• Soil degradation and shifts in soil C, N and P in rice fields were examined. • 47% of studied Chinese rice fields have problems with soil degradation. • Soil degradation was associated with declining soil C, N and P levels. • Wetter and hotter conditions are linked to low SOM and high soil degradation. • Soil degradation is associated with declining soil pH. Soil degradation is a multi-factorial process that threatens crop production and the environment. According to the classification method of Pieri et al. (1992), soils are classified into different degradation classes by calculating the soil structural stability index (SSI). Soil nitrogen, phosphorus, labile organic carbon, mineral N and available-P concentration and stoichiometry under different degrees of degradation in rice fields in China were determined and analyzed. The results showed that 47% of the soil in China's rice fields had degradation problems. As the soil gradually degraded, soil N, P, AP concentrations were found to significantly decline (p < 0.05). Soils with lower organic matter levels and higher degrees of degradation were typically found in wetter and hotter climates. Furthermore, soil salinity, pH and bulk density in Chinese paddy fields were 65.7%, 12.3%, and 12.0% higher in the soils with low risk of degradation compared to the degraded soils. Nutrient stoichiometric ratios were found to significantly vary between different stages of soil degradation. Moreover, as the soil degraded, the rate of soil carbon loss was found to be greater than for nitrogen, and alluded a decoupling of soil carbon and nitrogen cycles. Soil degradation also effected other physical and chemical properties, including pH, organic matter, porosity and bulk density. Restraining annual cropping frequencies and adopting sustainable rice farming practises should safeguard against further soil degradation in China. [ABSTRACT FROM AUTHOR]

We studied the winter foraging activity of the endangered Red-crowned crane (Grus japonensis) and the vulnerable White-naped crane (Grus vipio) in the Cheolwon area of the Civilian Control Zone (CCZ) area of South Korea, adjacent to the Demilitarized Zone with North Korea. Due to its limited development, the CCZ is one of the most critical migratory habitats for these endangered cranes. Farmers in the CCZ now plow most of their fields after the fall harvest rather than in the spring as they did previously. Cranes observed on the few remaining unplowed fields in the CCZ spent more time foraging than cranes on adjacent plowed fields. This behavior is a clear indication that the unplowed fields contain more food resources for the cranes than do the plowed fields. This is the first behavioral demonstration of differences in foraging between plowed and unplowed rice paddies for cranes in one of the cranes’ most important refuges. We believe that the changes associated with plowing rice paddies may be detrimental to these threatened cranes, and efforts to promote unplowed fields in the CCZ should be encouraged. [Copyright &y& Elsevier]

Abstract: We studied the consequences of rice cultivation and its subsequent abandonment for soil organic matter (SOM) dynamics in north-eastern Argentina. Two chronosequences, which included a pristine grassland with C4 vegetation as a control, and several stages of rice (C3) fields abandoned for 1, 2, 4, 6 and 15 years were selected, and soil samples from the first 10cm were gathered from each plot. Natural 13C abundance coupled with particle-size fractionation were employed to characterize SOM changes through time discriminated by SOM origin. Soil samples up to 50cm were also collected throughout one chronosequence. Most changes in SOM occurred on the first 20cm layer and, bulk density, carbon and nitrogen content, as well as δ 13C remained similar at greater depths. After the rice cropping, the bulk density was slightly greater than in the natural grassland, and remained stable after the abandonment. Carbon and nitrogen contents remained almost stable in the surface layer during the cultivation. δ 13C varied accordingly with the changes in vegetation cover with a C4 signature in the natural grassland and mainly a C3 signature in the rice fields. The abandonment of the rice cropping induced a decrease of the soil organic matter content, mainly of natural grassland origin, during the first 4 years. When the abandonment extended, the SOM content (from C4 origin) increased slowly and after 15 years, was almost the same as that of the natural grassland. The carbon turnover was greater in the coarser fractions than in the finer ones, confirming that soil organic carbon in the sand fraction was relatively labile. However, all the fractions were affected by inputs and outputs of C derived from rice and natural grassland. This fact could indicate that the former protected carbon could become less stable due to cultivation. [Copyright &y& Elsevier]

Abstract: The increasing demand of the growing population requires enhancement in the production of rice. This has a direct bearing on the global environment since the rice cultivation is one of the major contributors to the methane emissions. As the rice cultivation is intensified with the current practices and technologies, the methane fluxes from paddy fields will substantially rise. Improved high yielding rice varieties together with efficient cultivation techniques will certainly contribute to the curtailment of the methane emission fluxes. In this paper, the system dynamic approach is used for estimating the methane emissions from rice fields in India till the year 2020. Mitigation options studied for curtailing the methane emissions include rice production management, use of low methane emitting varieties of rice, water management and fertilizer amendment. The model is validated quantitatively and sensitivity tests are carried out to examine the robustness of the model. [Copyright &y& Elsevier]

A 4-year entomological study was carried out in Southern Madagascar to identify malaria vectors, evaluate the transmission and compare the influence of irrigation in the sub-arid and adjacent humid regions. Three villages were involved in this entomological survey: Androvasoa (located in the natural sub-arid ecosystem), Pe´pinie´re (sited at the centre of an irrigated rice scheme in the sub-arid region) and Esana (bordered with rice fields in the humid region). Mosquitoes were collected inside and outside dwellings when landing on human beings, with light traps and with knockdown indoor sprays. Anopheles arabiensis, Anopheles merus and Anopheles funestus were found in every village while Anopheles gambiae s.s. was only found in the village bordering the rice-fields (Pe´pinie´re) and Anopheles mascarensis, a mosquito native to Madagascar, was only found in the humid region (Esana). In Pe´pinie´re, the annual entomological inoculation rate (EIR) was low (EIR=0.4 infective bites/man/year (IBM)). In the irrigated scheme of the sub-arid region, malaria transmission was 150 times higher (mean EIR=63 IBM) than in the natural ecosystem and A. funestus was the main vector, responsible for 90% of infective bites. In Esana, the level of malaria transmission was high (EIR=41 IBM) and 2/3 of the infective bites were due to A. mascarensis, despite the presence of A. gambiae s.s. and A. funestus. These results are discussed with reference to the impact of irrigation on malaria in Africa (“the paddies paradox”). [Copyright &y& Elsevier]

Field experiments were conducted in central Kenya, to study the effect of ammonium sulphate fertiliser ((NH4)2SO4) on mosquito larval populations in rice fields. The experiments used a complete randomised block design having four blocks with two experimental ponds per block, and the fertiliser and control treatments allocated randomly among the ponds. Student’s two-sample unpaired t-test was used to test for the significance of differences between the relative counts of larvae in fertiliser and control treatments. The results showed a significant overall increase in the larval populations of An. arabiensis (P<0.01) and culicine mosquitoes (P<0.05), after ponds were treated with the fertiliser. Significantly more fourth instar larvae of An. arabiensis were collected in fertiliser than control plots (P<0.001). An. arabiensis data indicated that the first fertiliser application had the most impact, compared to the second and third applications. This was evident in a significant peak of combined first and second instar An. arabiensis larvae observed 5 days after the first fertiliser application (P<0.05). The studies suggest that ammonium sulphate fertiliser reduces turbidity of water in rice fields, thereby making them visually more attractive for egg-laying by An. arabiensis and culicine mosquitoes. [Copyright &y& Elsevier]

The development of methods and strategies to reduce the emission of methane from paddy fields is a central component of ongoing efforts to protect the Earth''s atmosphere and to avert a possible climate change. It appears from this investigation that there can be more than one strategy to contain methane emission from paddy fields, which are thought to be a major source of methane emission in tropical Asia. Promising among the mitigating options may be water management, organic amendments, fertilizer application and selection of rice cultivars. It is always better to adopt multi-pronged strategies to contain CH4 efflux from rice wetlands. Use of fermented manures with low C/N ratio, application of sulfate-containing chemical fertilizers, selection of low CH4 emitting rice cultivars, and implementation of one or two short aeration periods before the heading stage can be effective options to minimize CH4 emission from paddy fields. Among these strategies, water management, which appears to be the best cost-effective and eco-friendly way for methane mitigation, is only possible when excess water is available for reflooding after short soil drying at the right timing and stage. However, in tropical Asia, rice fields are naturally flooded during the monsoonal rainy season and fully controlled drainage is often impossible. In such situation, water deficits during the vegetative and reproductive stage may drastically affect the rice yields. Thus, care must be taken to mitigate methane emission without affecting rice yields. [Copyright &y& Elsevier]

The abundance of waterbirds was compared in 46 rice fields in relation with the age of the field and the planting practices in spring. Of the 29 species censused, Charadriiformes represented some 73%, Ciconiiformes 6%, and Anseriformes less than 15.5% of the total number of individuals, flamingos and moorhens being also observed. Insectivorous species were the main component of the waterbird community. Bird numbers decreased with increasing field age and were lower in dry-sown than in wet-sown fields. The present results suggest that intensive and/or repetitive soil management and pesticide use may decrease the food resources available to waterbirds. [Copyright &y& Elsevier]

• Diazinon detection in underground drinking water resources by GC - Mass Spectrometry. • diazinon was observed in water resources, up to one month after the last spraying. • There was a direct correlation between diazinon concentration and water turbidity. Widespread and unsupervised use of pesticides in the rice fields of northern Iran has greatly increased the concern about their presence in drinking water resources. This study aimed to determine the effect of spraying of rice fields on the concentration of diazinon in rural underground drinking water resources with depth and water table of about 120 and 30 m respectively. Sampling was performed at regular intervals, before the first and after the last spraying. Diazinon extraction was carried out by USEPA liquid–liquid extraction method and the concentration of diazinon was measured by GC / Mass Spectrometry. No diazinon was observed in any of water resources before spraying, while the average concentration of diazinon after spraying was 0.005 ± 0.007 µg/l. Also there was a significant difference in diazinon concentration between water resources after spraying rice fields. There was a reverse significant correlation between the diazinon concentration and longitudinal distance from water resources to rice farms. Moreover, there was a significant direct correlation between the diazinon concentration in post-spraying samples and water turbidity. In general, spraying rice fields can cause diazinon to enter underground water resources near farms and it can be present in water resources for at least one month after the last spraying. [ABSTRACT FROM AUTHOR]

Farmland abandonment can be a significant driver of biodiversity change in many parts of the world. Knowledge of the ecological impact of farmland abandonment at the landscape scale is particularly limited in Asia. We investigated how rice-field abandonment impacts bird diversity (i.e., species richness and composition) during the breeding and wintering seasons. Birds were surveyed in 31 grids (1 × 1 km) in rice ecosystems in central Japan, 16 of which were dominated by farmland while the others were surrounded by woodland. In each landscape type, survey grids were selected to ensure a broad range of abandonment rates, from fully cultivated to largely abandoned sites. Multi-species occupancy models showed that occupancy probabilities were associated with linear and quadratic terms of the abandonment rate, resulting in the highest predicted community-level occupancies and species richness at moderate abandonment rates (51.5–71%, depending on the season and surrounding landscapes, with the highest percentage in woodland landscapes in winter). Community composition was most associated with surrounding landscapes (i.e., woodland or farmland), followed by the abandonment rate. These results indicate the importance of habitat heterogeneity, related to moderate levels of farmland abandonment, in enhancing bird diversity in both farmland and woodland landscapes. Our findings illustrate the necessity for quantitative measures of farmland abandonment at landscape scales for understanding their nonlinear effects on farmland biodiversity. We suggest that agri-environmental schemes should consider the benefits of enhancing farmland mosaics at landscape scales, especially for small-scale farming in areas where farmland abandonment is increasing. • Bird occupancy and richness were highest at moderate abandonment rates. • Community compositions also changed with the abandonment rate. • Surrounding landscape and season affected the responses of birds. • Mosaics of managed and abandoned rice fields can benefit bird richness. [ABSTRACT FROM AUTHOR]

• Optimisation of benthic invertebrate surveys from a Spanish rice field was studied. • Faunistic diversity studies require high sampling efforts of minimum 20 samples. • Three samples provide acceptable benchmarks for environmental quality assessment. • Our guidelines for cost-effective monitoring will help refine sampling efforts. The analysis of macroinvertebrate communities is essential in aquatic ecology studies. Nonetheless, sample collection, processing and species determination of macroinvertebrates are extremely time-consuming and require huge efforts. Moreover, despite the crucial need for refined sampling protocols, investigations on viable benchmark sampling efforts are still scarce. This study provides a preliminary analysis on the optimisation of the sampling effort required to study macroinvertebrate communities from rice fields. Twenty core sediment samples were collected from a non-vegetated Mediterranean lagoon (rice field) in Valencia (Spain), and their macroinvertebrate community assemblages were obtained. Characterisations of the minimum number of samples needed for both faunistic inventories and environmental quality assessments were carried out using diversity indexes (number of taxa, Shannon, Simpson, and Margalef indexes), ecological indicators (Nutritional Mode Index, IMN) and several species richness estimators (Chao 1, Chao 2, Jacknife 1, Jacknife 2, ACE, ICE, Bootstrap and EstimateS 9.1.0). Our results indicate that in surveys in which the taxa richness of the communities is the objective, 20 samples or even more could be needed. However, when the objective of the study is to assess the environmental quality by means of ecological indexes such as the IMN, three samples could be an acceptable benchmark. Our findings, despite being limited by our experiment conditions, can provide methodological guidelines for ecological assessments in Mediterranean rice fields and shallow non-vegetated lagoons. Further research involving multiple study areas and seasonal patterns will help meliorate the accuracy of this protocol and refine sampling efforts in wetlands. [ABSTRACT FROM AUTHOR]

• More bird activity was observed on flooded rice fields than non-flooded rice fields. • Fecal matter input from birds correlated to enhanced soil fertility. • Bird fecal matter can potentially replace ≥13 % of nitrogen fertilizer application. This study investigated a low-external-input sustainable-agriculture (LEISA) rice production system in the Mississippi Alluvial Valley (MAV) that applied ecological principles to create waterbird habitat and enhance soil fertility. Two production sites were selected for this study (LEISA and conventional). Each production site applied a flooded treatment and a fallow treatment to select fields during the non-growing season (November 2017- March 2018). Bird fecal matter inputs and soil microbial bacteria/activity and nutrient content were quantified and compared between fields. Significantly more % total nitrogen, % total carbon, microbial richness and activity (P < 0.05) were found in flooded LEISA than other study fields. Bird fecal matter inputs on LEISA flooded fields contributed an estimated 6.1–48.9 kg N/ha/season, whereas 1.9–14.8 kg N/ha/season were added to conventionally flooded fields. Long-term application of the unique LEISA rice farming system can reduce the need for synthetic fertilizer application by > 13 %, while increasing soil organic carbon. This case study provides a foundation for future research into the agronomic benefits of creating bird habitat in rice fields, while documenting how conservation strategies support agronomic production and sustainability to foster conservation adoption. [ABSTRACT FROM AUTHOR]

• 8890 sites were sampled to identify spatial variability of eight soil properties. • High levels of SOC, TN, and AN were found in paddy fields at a large scale. • Distribution maps of eight soil chemical properties were produced. • Ordinary kriging method performed better than the inverse distance weighting method. Rice is one of the most important crops in the world. It provides food for 40% of the world's population and 60% of China's population. Soil nutrients have a significant impact on both agriculture and the environment, particularly with regards to soil fertility, soil quality, and rice production. However, minimal research has been conducted to address spatial patterns of soil nutrients at a large scale within paddy fields. This information is crucial for improving not only soil nutrient management, but also rice yields. Soil surface samples (0–20 cm of plough depth, totalling 8890) were collected from paddy fields to determine the spatial variability of eight soil chemical properties (soil organic carbon (SOC), total nitrogen (TN), available N (AN), total phosphorus (TP), available P (AP), total potassium (TK), rapidly available K (RAK), and slowly available K (SAK)). Inverse distance weighting (IDW) and ordinary kriging methods were applied to produce a continuous soil nutrient surface. Results indicated that soil chemical properties vary substantially. Paddy fields were characterized by high mean concentrations of SOC (19.7 g kg−1), TN (1.91 g kg−1), and AN (164.7 mg kg−1), implying that no additional C and N fertilizer was needed in regions with high SOC and N. SAK and AP demonstrated moderate (36.9%) and weak (96.2%) spatial dependence, respectively, while strong spatial dependence (10.1–13.5%) was observed across the remaining six soil chemical properties. Regional distribution maps of soil chemical properties were produced and ordinary kriging methods interpolated more accurately than the IDW method. [ABSTRACT FROM AUTHOR]