Rice Bays Research Articles

Сегетальная растительность рисовых полей в Чеченской Республике

According to the Braun-Blanquet approach the segetal communities of rice agrocenoses of Eurasia belong to the class Oryzetea sativae Miyawaki 1960, although there is a lot of species that are diagnostic of different classes — Phragmito-Magnocaricetea Klika in Klika et Novák 1941, Lemnetea O. de Bolòs et Masclans 1955, Potamogetonetea Klika in Klika et Novák 1941, Bidentetea Tx. et al. ex von Rochow 1951, etc. The largest number of the described basic syntaxa (associations, subassociations or communities) are allocated in Eastern, South-Eastern and Central Asia. Lots of new syntaxa specific to the rice fields were described in Japan (Miyawaki, 1960), Southern Thailand (Nowak et al., 2015), Central Nepal (Nowak et al., 2016), North Korea (Kolbek et al., 1996; Kolbek, Jarolímek, 2013), Tajikistan (Nowak et al., 2013), Vietnam and the Philippines (Fried et al., 2017, 2018), many of which have been assigned in the alliance Ludwigion hyssopifolio-octovalvis A. Nowak, S. Nowak, Nobis 2015, the order Cypero–Echinochloetalia oryzoidis O. de Bolòs et Masclans 1955, the class Oryzetea sativae. The rice communities described in Western (Spain, Portugal, Andorra, Italy, France, Hungary, Romania, Bulgaria) and Eastern (Ukraine, Russian Federation) Europe which differ in species composition from those in Asian regions are assigned to the alliance Oryzo sativae–Echinochloion oryzoidis O. de Bolòs et Masclans 1955 within the above order and class. The paper represents the first results of the classification based on 20 relevés of rice communities studied in 2018 in the Gudermessky and Shelkovskoy districts of the Chechen Republic, located on the northern slope of the Great Caucasian Ridge, the Chechen Plain and the Terek–Kuma Lowland. The areas under rice crop rotation are kept at an altitude of 20–35 m above sea level both in the north and in the plain part, mainly in the interfluves of the Terek and Sunzha rivers. The climate in the rice-growing areas is continental, insufficiently humid, with the very warm summers and moderately mild winters and the lot of heat and dryness in the summer months. The mean year temperature is 10.8 °C, during the growing season of rice (May–September) — 20.8 °C; the sum of effective temperatures above 15 °C is about 3100–3400 °C (Tulyakova, 1973; Ryzhykov et al., 1991); the annual amount of precipitation is 400—450 mm with less than 270 mm in summers. The largest areas on the Terek and Sunzha river interfluve are occupied by intrazonal meadow and swamp vegetation. There are two associations and one community belonging to the alliannce Oryzo sativae–Echinochloion oryzoidis have been established within study area. The associations Echinochloo–Oryzetum sativae Soó ex Ubrizsy 1948 (Table 2, rel. 1–8) and Oryzo–Cyperetum difformis Koch 1954 (Table 2, exp. 9–14) are widely distributed in rice fields in Western and Eastern Europe, while the community Setaria pumila–Oryza sativa (Table, rel. 15–20) is a new one. On cultivated lands, the composition and structure of segetal communities depends on the intensity of agrotechnical measures, as well as on the depth and duration of flooding. The species diversity of the communities adjacent to the fields, formed in the discharge channels and on the dams between rice bays, have a significant impact. In the rice fields in the presence of chemical and agrotechnical processing, communities of the ass. Echinochloo–Oryzetum sativae prevail, and the communities of the ass. Oryzo–Cyperetum difformis and Setaria pumila–Oryza sativa are formed where this impact is not strong. The significant participation of Cyperus glomeratus is a distinctive feature of the Chechen Republic segetal communities from the analogous ones compare with the other regions of Europe.

Water resources management in rice irrigation systems and improvement of ecological situation in rice growing river basins

Water resources management in the rice irrigation systems in Kazakhstan as well as water conservation and its efficient use are associated with technological processes control factors such as irrigation efficiency, layout of rice bays and their terracing. Managing technological processes in rice systems is complex, since there are significant deviations in the technological parameters of rice systems from the optimal. Therefore, in order to properly manage these processes, it is necessary to know the impact, its direction, assess the results of these impacts and develop an appropriate scientific and information base. The paper considers the impact of rice bays layout quality and terrace on the water-salt regime of soils, rice productivity and irrigation rate. Also, it proposes improvements to parameters of rice systems, water conservation, environmental situation in areas of rice cultivation and water resources management in rice systems.

Salt tolerance of rice hybrids of the fifth generation

Soil and water salinization differently affects the growth and development of rice at all stages, reducing its productivity. The article presents the results of the analysis aimed to determine salt resistance of 186 hybrid samples of rice F 5 developed in the FSBSI “ARC “Donskoy”. There were studied the samples developed from three hybrid combinations “IR 52713-2B-8-2B-1-2 x Novator”; “IR 74099-3R-3-3 x Novator”; “NSIC Rc 106 x Novator”. The studies were carried out in the ABSIE FSBI HE DonSAU. The rice seeds were germinated in rolls of filter paper on 1.5% NaCl solution and in distilled water. Salt tolerance was determined as the ratio of the percentage of germinated seeds in the experiment to the control. The purpose of the research is to analyze rice samples for salinization resistance. The analysis found out that the rice samples differed significantly among themselves in the length of the sprouts and roots on the salted and control variants. The graphic material of the article reliably shows the relative and absolute values of sprouts and roots in a trial and in a control variant. The analysis showed an average correlation between the length of sprouts in the trial and salt tolerance for sprouts (0.62±0.08), as well as a high correlation between the length of the roots in the trial and salt tolerance for the roots (0.74±0.09). PCR analysis with the help of the markers RM493 and RM7075 made possible to identify in 59 forms the presence of the dominant QTL locus Saltol in the homozygous state. According to the set of indicators 14 best samples were identified. Selected on salt solutions, the best samples with long shoots and roots have been planted on the rice bays of the OS “Proletarskaya” in the form of seedlings.

Bitterns boom in rice bays

Bitterns boom in rice bays

Developmental toxicity of two common corn pesticides to the endangered southern bell frog (Litoria raniformis)

To examine the link between corn agriculture and the observed decline of the endangered southern bell frog (SBF), the effects of two corn crop pesticides on larval growth and development were investigated. Tadpoles were exposed to terbufos sulfone (10 μg/L), a major breakdown product of the insecticide terbufos, and the herbicide atrazine (25 μg/L) individually and as a mixture until the completion of metamorphosis. Atrazine did not interact synergistically with terbufos sulfone or result in significant effects on growth and development alone, although there was some indication of accelerated metamorphosis in the pilot study. Terbufos sulfone alone and as a mixture (terbufos/atrazine) significantly slowed larval development and ultimately delayed metamorphosis. The observed developmental effects from an environmentally relevant concentration of terbufos sulfone indicates a risk posed by this persistent degradation product to the endangered SBF, which breeds and develops in the rice bays adjacent to corn fields treated with pesticides.

Introducing irrigation efficiencies: prospects for flood-dependent biodiversity in a rice agro-ecosystem

SUMMARYWorldwide, irrigation development has affected pre-existing natural habitats and created novel aquatic habitats, and future changes in management will continue to influence flood-dependent vegetation and fauna. Irrigated agriculture has had a profound influence on native biodiversity in the Riverina region of temperate Australia. Current irrigation practices provide large amounts of water to the landscape in the form of constructed wetland habitats: irrigation channels, impoundments and flooded crop-growing areas. Flooded rice bays support many species of native wetland plants, and 12 of the 14 species of frog recorded in the region. All constructed habitats provide a food resource for waterbirds, but not breeding habitat. While a species of tortoise benefits from the provision of constructed habitats, terrestrial reptiles and mammals are most abundant in remaining native vegetation. The climate is predicted to become increasingly hot and dry, with a reduced and more variable supply of irrigation water, thus placing increasing stress on farming and on natural ecosystems. The predicted reduction of constructed aquatic habitats may affect the native species using them, but may not have a major adverse impact on biodiversity regionally because the species recorded in constructed habitats tend be abundant and widespread, and such species also occur in natural wetland habitats. Sensitive species that depend on native vegetation persisting in reasonable amounts and in good condition are at greater risk. In the Riverina, the remaining native vegetation should be managed to protect and improve its condition, including appropriate managed inundation events for flood-dependent communities. The landscape should be managed to provide the best context for the function and health of existing vegetation including moderating the effects of soil disturbance, fertilizers and herbicides. The impacts of changed irrigation practices should be mitigated through managed flooding of remnant vegetation. In countries with more evolved, traditional rice-growing systems than the Riverina, there will be greater emphasis on biodiversity coexistence with cultivation. Nonetheless, in all settings there is value in jointly considering the role of both natural and constructed habitats in biodiversity research and conservation.

Habitat characteristics predict occupancy patterns of the endangered amphibian Litoria raniformis in flow‐regulated flood plain wetlands

AbstractIdentification of habitat features that are strongly associated with the occurrence of threatened species is important in terms of predicting impacts of habitat change and identifying key habitats for conservation. In this paper, we apply habitat‐based statistical models to predict occupancy patterns of the endangered southern bell frog (Litoria raniformis) across inland New South Wales (Australia). Litoria raniformis previously occupied a wide range of natural and man‐made waterbodies across a large geographic range, including flood plain wetlands, oxbow lagoons, irrigation canals and rice bays. Alteration of natural flooding regimes has affected a large proportion of habitats within the historical range of Litoria raniformis, but it is not clear how these changes have influenced habitat occupancy patterns. Fifty‐two waterbodies were surveyed for presence/absence of Litoria raniformis in 2001 and 2004. Stepwise logistic regression models were generated to select a subset of variables that best predicted occupancy. Using three predictor variables, vacant and occupied habitats could be predicted with an accuracy of 90% and 70%, respectively. The predictor variables were: the interaction between wetland hydrology and complexity of aquatic vegetation, complexity of fringing vegetation and water temperature. While this study demonstrated that a range of waterbody types were occupied by Litoria raniformis, these habitats shared common hydrological conditions and vegetation characteristics. Altered flooding regimes and reductions in the complexity of aquatic and fringing vegetation are likely to increase the probability of localized extinctions of Litoria raniformis populations.

Morphological abnormalities in frogs from a rice-growing region in NSW, Australia, with investigations into pesticide exposure

Three frog species (Limnodynastes tasmaniensis, Limnodynastes fletcheri and Litoria raniformis) were surveyed in rice bays of the Coleambally Irrigation Area (CIA), NSW, Australia, during the rice-growing seasons of 2005/2006 and 2006/2007. A total external morphological abnormality index of 7.0% was observed in frogs of the CIA (n=1,209). The types and frequencies of abnormalities were typical of reports from agricultural areas with ectrodactyly being the most common aberration. A relatively low abnormality index of 1.2% was observed in L. raniformis (n=87) compared to indices of 7.1% and 8.2% observed in L. fletcheri (n=694) and L. tasmaniensis (n=428), respectively. No conclusive evidence was found of unnaturally high rates of intersex, gonadal maldevelopment or unbalanced sex ratios in any species. Rice bay surface waters differed significantly in mean pesticide concentrations of atrazine and metolachlor on farms growing rice and corn compared to farms with rice as the sole crop. However, the similar abnormality indices observed in recent metamorphs emerging from these two farm types provided no evidence to suggest a link between larval exposure to the measured pesticides and developmental malformations.

Distribution of frogs in rice bays within an irrigated agricultural area: Links to pesticide usage and farm practices

In the Coleambally irrigation area (NSW, Australia), the occurrence of four tadpole and frog species in rice bays on farms growing either rice only or both rice and corn was studied over two seasons. In addition to analysis of species occurrence, both gonadal histology and assessment of Batrachochytrium dendrobatidis infection rates were performed. The rice acreage available as potential tadpole habitat was extensively distributed throughout the irrigation area, but more corn was grown in the northern region compared with the southern region. The mean abundance of Litoria raniformis tadpoles was significantly lower in the northern sites compared with the southern sites. In contrast, tadpoles of Limnodynastes fletcheri, Limnodynastes tasmaniensis, and Crinia parinsignifera had a uniform distribution across all study sites. A principal components analysis showed a relationship between farm type and the rice herbicide applied when the crops were initially sown, with sites occupied by Litoria raniformis in the beginning being predominantly rice-only farms. A discriminant analysis showed that low concentrations of the corn herbicide metolachlor and increased pH were the main variables studied that determined site occupation by L. raniformis. This suggested that farms growing only rice (and not corn) with high algal production were the preferred sites. The rates of chytrid infection and gonadal malformations were low across both regions. Histology of the gonads of metamorphs showed that L. raniformis gonadal differentiation is slow compared to that of the two Limnodynastes species. We concluded that farm practices associated with increased corn cropping in the northern region, rather than any direct effect of corn herbicides, determine the reduced presence of Litoria raniformis in the northern region.

The impact of rice plant roots on the reducing conditions in flooded rice soils

The impact of oxygen diffusion from plant roots on the soil redox in the root zone in flooded rice bays was investigated using two Australian rice growing soils. The rates of production of Fe(II) and Mn(II) in pore water resulting from the reduction of soil minerals was used to gauge the extent of development of anaerobic conditions and the time taken for equilibrium to establish. Soil concentrations of readily reducible Fe were 13–28 times greater than Mn, making Fe a more reliable indicator of redox conditions than Mn. In addition, Mn(II) concentrations reached equilibrium far more rapidly than Fe, which made the identification of any contribution to soil redox by oxygen diffusing from rice plant roots difficult to observe. Dissection of soil cores showed that more than 80% of the rice root mass occurred in the top 4 cm of soil, suggesting that any contribution roots may make to the redox potential of the flooded soils would occur in this region. However, studies conducted indicated that the diffusion of oxygen from the surface floodwater into soil pore water in the 2.5 cm layer of soil was so substantial that it would mask any contribution made by rice plant roots to the overall soil redox in this root zone.

Autecology of Bradyrhizobium japonicum in soybean-rice rotations

The effect of rice culture on changes in the number of a strain of soybean root-nodule bacteria, (Bradyrhizobium japonicum CB1809), already established in the soil by growing inoculated soybean crops, was investigated in transitional red-brown earth soils at two sites in south-western New South Wales. At the first site, 5.5 years elapsed between the harvest of the last of four successive crops of soybean and the sowing of the next. In this period three crops of rice and one crop of triticale were sown and in the intervals between these crops, and after the crop of triticale, the land was fallowed. Before sowing the first rice crop, the number of Bradyrhizobium japonicum was 1.32×105 g−1 soil. The respective numbers of bradyrhizobia after the first, second and third rice crops were 4.52 ×104, 1.26×104 and 6.40×102 g−1 soil. In the following two years the population remained constant. Thus sufficient bradyrhizobia survived in soil to nodulate and allow N2-fixation by the succeeding soybean crop. At the second site, numbers of bradyrhizobia declined during a rice crop, but the decline was less than when the soil was fallowed (400-fold cf. 2200-fold). Multiplication of bradyrhizobia was rapid in the rhizosphere of soybean seedlings sown without inoculation in the rice bays. At 16 days after sowing, their numbers were not significantly different (p<0.05) from those in plots where rice had not been sown. Nodulation of soybeans was greatest in plots where rice had not been grown, but yield and grain nitrogen were not significantly different (p<0.05). Our results indicate that flooding soil has a deleterious effect on the survival of bradyrhizobia but, under the conditions of the experiments, sufficient B. japonicum strain CB 1809 survived to provide good nodulation after three crops of rice covering a total period of 5.5 years between crops of soybean.

Emergence phenology of Chironomus tepperi Skuse and Procladius paludicola Skuse (Diptera: Chironomidae) during rice crop establishment in southern New South Wales

Midge emergence from untreated rice bays was monitored with conical traps during crop establishment. Chironomus tepperi Skuse was the numerically dominant species in all 3 seasons of the study, and generally had only 1 generation, although there was some evidence of a minor, non-overlapping second generation in the 1992 season. Emergence of first generation C. tepperi was highly synchronised, with peaks occurring 16-17 days after flooding. Procladius paludicola Skuse became the dominant species in trap collections after C. tepperi emergence declined, and had multiple overlapping generations. Members of the genus Procladius are predacious rather than phytophagous. Chironomus tepperi and P. paludicola together comprised 45.6-80.4% (mean 68.1%) of midges emerging during the first 48 days after flooding. More than 30 midge species were recorded from the trial site, but C. tepperi was the only phytophagous species recorded in sufficient numbers to warrant individually targeted control. Although C. tepperi has, in a practical sense, only 1 generation in establishing rice bays, growers have consistently reported that multiple chemical treatments are necessary to prevent crop damage. There are several possible explanations for this apparent anomaly. Chemical seed treatments may be failing to disperse sufficiently to control the first C. tepperi generation. Also, the elimination of chironomid larvae through the use of seed treatments may be making fields receptive to reinfestation by C. tepperi if oviposition is being regulated by the presence of larval populations. A third possibility is that phytophagous species other than C. tepperi, although poorly represented individually, may sometimes be abundant enough collectively to cause significant crop damage.

Field evaluation of plaster-based temephos pellets for residual control of midge larvae (Diptera: Chironomidae) in establishing rice crops

A pelletised formulation of temephos (5% a.i.) was evaluated as a potential control agent for chironomid midge larvae in establishing rice crops. Four application rates between 0.03 and 0.53 mg a.i./L (42-732 g a.i./ha) were applied to 80 m2 experimental rice bays immediately after flooding. Water samples and soil core samples were taken at regular intervals until 29 days post-treatment. Larvae were extracted from core samples using magnesium sulfate (MgSO4) flotation, whilst laboratory-reared fourth instar Chironomus tepperi Skuse larvae were used in bioassays with field-collected water samples to determine pesticide activity in the water column. All treatments significantly suppressed C. tepperi-type larvae in the field for at least 13 days. Some suppression of non-C. tepperi-type larvae was obtained at 0.27 mg a.i./L, whilst at 0.53 mg a.i./L all chironomids were reduced to negligible levels for the full period of the trial. In bioassays, significant levels of water column toxicity to fourth instar C. tepperi larvae were only recorded for 2 days after treatment at the highest application rate. Our results indicate that plaster-based temephos pellets have the potential to provide effective, single application control of chironomid larvae in establishing rice crops without the risk of spray drift inherent in the aerial application of liquid insecticides.

Insecticide Treatments Used Against a Rice Bloodworm, Chironomus tepperi (Diptera: Chironomidae): Suppression of Larval Populations

We assessed the effect of six organophosphorous insecticide treatments on larval chironomid populations in establishing rice. Treatments were applied to miniature rice bays (20 by 4 m) that contained heavy infestations of Chironomus tepperi Skuse-type larvae. Mud samples were taken immediately before insecticide application and subsequently at 3-d intervals for 15 d. Larvae were extracted by MgS04 flotation. Chlorpyrifos (0.07 ppm), malathion (0.26 ppm), diazinon (0.10 ppm), and temephos (0.05 ppm) provided highly effective control. Trichlorfon (0.38 ppm) and, to a lesser extent, chlorfenvinphos (0.22 ppm) were not as effective, allowing some larval resurgence 6 d after application. We consider trichlorfon at 0.38 ppm to be unsuitable for C. tepperi control.

Insecticide Treatments Used Against a Rice Bloodworm, Chironomus tepperi (Diptera: Chironomidae): Toxicity and Residual Effects in Water

The toxicity and persistence in water of six organophosphate insecticide treatments used for control of Chironomus tepperi Skuse was evaluated. Each insecticide was applied to three rice bays (20 by 4 m) at the maximum recommended field rate. Fourth-instar C. tepperi were tested with water samples taken at various intervals after insecticide application. All treatments caused high (>97%) initial mortality of larvae with the exception of diazinon (0.13 ppm; average initial mortality, 47.3%). Temephos (0.06 ppm) showed the least residual activity, with no mortality occurring 5 d after application. Chlorfenvinphos (0.27 ppm) had the longest residual effect in water, resulting in 61.5% mortality 15 dafter application but only nominal activity at 20 d. The remaining treatments, diazinon, chlorpyrifos (0.08 ppm), trichlorfon (0.47 ppm), and malathion (0.32 ppm), provided <10% mortality after 7 d.

Ammonia volatilization from drill sown rice bays

Ammonia volatilization losses and other N transformations were studied in drill sown rice bays fertilized with urea at various times between permanent flooding (PF) and panicle initiation (PI). Ammonia loss was measured directly with flow chambers and indirectly through application of Freney et al.'s (1985) model. Both techniques indicated that ammonia volatilization was negligible from fields fertilized immediately before PF. Applying 100 kg urea-N ha−1 to floodwater one day after flooding significantly increased floodwater ammoniacal-N and urea-N content, however the concentrations fell rapidly over the following five days. Fertilizer-N dissolved in the floodwater was in the urea rather than the ammoniacal-N form, indicating slow hydrolysis until it moved into the soil. Floodwater on plots receiving urea one day after PF frequently had more than double the NO3-N concentration of plots fertilized before flooding. Applying up to 140 kg urea-N ha−1 at PI increased floodwater ammoniacal-N concentrations from almost zero to over 27 g m−3, but three days after fertilization there was less than 3 g m−3 present. Fertilization also increased NH4-N concentration in the top 40 mm of soil. Higher ammoniacal-N concentration at PI suggests higher urease activity. Floodwater pH at PI was low, with a mean daily maximum of 7.8 and this reduced ammonia loss to less than 1% of the applied N. The results indicate that volatilization from fields fertilized prior to PF is minimal because of the low floodwater pH and ammoniacal-N concentration, while low floodwater pH restricts volatilization from fields topdressed at PI.

The effects of rice growing on soil phosphorus immobilization

Representative rice soils of the Murrumbidgee and Coleambally Irrigation Areas, New South Wales, were analysed for phosphate (P) sorption characteristics and active iron. Samples analysed were taken before and after flooding (in the field and glasshouse) and from rice bays, irrigation control banks and nearby, non-irrigated fencelines. Previously flooded soils showed greater P sorption capacities than their non-flooded soil counterparts. It was indicated that soils that had previously grown rice required more P for upland cropping than non-rice soils. P sorption was significantly positively correlated with active (acid ammonium oxalate extractable) iron. It was proposed that prolonged waterlogging mobilized iron from relatively well ordered iron oxides of low P sorption capacity but on oxidation formed disordered iron oxides with a large capacity to immobilize P.