Flooded Soil Research Articles

Roxarsone transformation and its impacts on soil enzyme activity in paddy soils: A new insight into water flooding effects

The aromatic arsenical roxarsone (ROX) has been used as feed additive for decades worldwide. The past or present application of animal manure containing ROX in paddy fields results in arsenic (As) accumulation in rice grain. However, the degradation and transformation mechanisms of ROX in paddy soil which determine As bioavailability and uptake by rice are still unclear. The current study investigated the variation of As speciation and soil enzyme activities in ROX-treated soils under flooded and non-flooded conditions for six months. Our results showed that 70.2% of ROX persisted in non-flooded paddy soils after 180 d while ROX degraded completely within 7 d in flooded soils. The rapid degradation of ROX under flooded conditions owed to the enhanced biotic transformation that was caused by the low Eh and the predominant presence of Clostridium spp. and Bacillus spp. ROX was not only transformed to As(III) and As(V) in non-flooded soils but also to 3-amino-4-hydroxyphenylarsonic acid and methyl arsenicals in flooded soils. The degradation products significantly inhibited soil enzyme activities for 7–30 d, but the inhibition effects disappeared after 90 d due to the sorption of transformed As products to amorphous Fe oxides. This study provides new insights into the flooding effect on ROX fate in paddy fields, which is important for the management of animal waste and risk control on polluted sites.

Antagonistic Activity of Indigenous Rhizobacteria through Biosynthesis of Indole-3-Acetic Acid (IAA), Hydrogen Cyanide (HCN), and Siderophores

This study aimed to isolate indigenous Antagonistic Bacteria (AB) against common soil-borne phytopathogens, including Rhizoctonia solani, Phythium sp., Fusarium oxysporum. Biosynthesis of Indole-3-Acetic Acid (IAA), generation of Hydrogen Cyanide (HCN), and siderophores production were assessed for their involvement in the antagonistic activities. Rhizospheric soil of bean roots, sunflowers, wheat, rice, and humic and semi flooded soils were used to isolate twenty-one bacterial strains for phytopathogenic antagonism. It was found that nine isolates have potential antagonistic activity against three common soilborne pathogens. Antifungal productivity for IAA, HCN, and siderophores was screened on the isolates while nine ABs were identified. To choose statistically significant isolate for the formulation, the principal component analysis was performed with five variables (IAA production, siderophores production index, antagonistic activities against three phytopathogens). Among the nine isolates, the isolate Pseudomonas alicaligenes shew a positive correlation with all variables. In particular, the strain demonstrated to be an antagonistic strain against the fungal pathogens and a strong producer of siderophores, HCN and IAA, We prepared the biocontrol agents with rice flour, glutinous rice flour, Monosodium Glutamate and Chitosan that were found to maintain the up to three months for convenience of field applications.

Geohazard characterization using remote sensing to model flash floods of the southeast Sinai, Egypt

Flash floods have led to disruptions of human activities and the destruction of properties particularly in the Nuweiba region of southeast Sinai. Despite the arid nature of Sinai, flash floods still pose a great hazard to the region. Using remote sensing characterization, geohazard models were developed to identify flash flood areas; delineate and discriminate morphological features, active channels areas, and soil physiography with a view to categorize risk areas exposed to flash floods hazards in a hazard map; and proffer measures for mitigation. The characterization was achieved using a workflow model developed from spatial data sets of the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) and the red-green-blue (RGB) composites from Landsat bands 7 Enhanced Thematic Mapper (ETM+). The data were used to investigate and assess flash flood areas for morphological attributes, watershed basin characterization, and generation of false color composite from the Landsat 7 ETM+ 7, 4, and 2 RGB bands, and the principal component analysis band from a composite of 742 RGB. Multivariate analysis of generated raster layer attributes provided enhancements and attribute discrimination for delineating areas of active flood channels, upslope zones, and soil physiography discrimination from their spectral reflectance. The results are presented in an integrated approach of remote sensing with geographic information systems (GIS) and indicate that the soil types and geologic units contribute greatly toward activation of these flash floods, which is triggered by intense rainstorms. Components of the generated map attributes of SRTM DEM, gradient of DEM, and Landsat 7 ETM+ composite of 742 bands in GIS were used to generate a hazard map using spatial analysis to depict the nature and scale of the issues identified. Due to the flash flood vulnerabilities, the study area was classified into stable/low-, moderate-, and high-risk areas. Mitigation measures to control flash floods were proposed to enable adequate preparations to mitigate impending flash flood disasters.

Coupling analysis of short-term weather and runoff in an arid lake basin of China

Changes in the weather will cause variations in the hydrological system. Arid areas, with fragile hydrological systems, are very sensitive to changes in the weather, so the coupling analysis of short-term weather and runoff in arid areas is of great significance. The Daihai Lake is a closed inland lake in an arid area of China. In this paper, Weather Research and Forecasting model mode-Hydrological module (WRF-HYDRO) is used to simulate the coupling of weather and hydrology in the Daihai Lake Basin. Regional optimization of WRF-HYDRO is carried out to determine the optimal parameters. The optimal WRF-HYDRO model is applied to couple the short-term weather and runoff in the Daihai Lake Basin to reproduce several rainstorm and flood events. It is found that runoff infiltration parameter (REFKDT) in WRF-HYDRO is the parameter that has the most severe effect on runoff in the Daihai Lake Basin. WRF-HYDRO can capture the rainstorm moment of the rainstorm events in the Daihai Lake Basin, especially the first rainstorm moment, and its simulation accuracy is good. WRF-HYDRO has a strong ability to capture flood peak, but there is a discrepancy between WRF-HYDRO flood peak and Soil Conservation Service Curve Number (SCS–CN) calculation result at the flood peak moment. The northern part of Zuoyun County should guard against the occurrence of flood disaster in wet season. The coupling of weather and hydrology can not only make up for the lack of runoff data in arid basins, but also provide a basis for water resources management and disaster prevention and mitigation in the basins.

Rice Root-Knot Nematode Meloidogyne graminicola (Nematoda: Chromadorea: Tylenchida: Meloidogynidae: Meloidogyne)

The Featured Creatures collection provides in-depth profiles of insects, nematodes, arachnids and other organisms relevant to Florida. These profiles are intended for the use of interested laypersons with some knowledge of biology as well as academic audiences. Rice root-knot disease is caused by different Meloidogyne species (Meloidogyne graminicola, M. hainanensis, M. incognita, M. javanica, M. arenaria, M. oryzae, M. salasi, and M. tryticoryzae). However, Meloidogyne graminicola is considered the most damaging root-knot species to Asian rice cultivation due to its ability to survive under flooded soil conditions. This nematode has been found in rice nurseries, rainfed upland rice and lowland rice but is also widespread in deep-water, irrigated rice production systems. Yield loss due to Meloidogyne graminicola ranges from 28%–87% depending on disease severity and cultivar.

Free Radicals Produced from the Oxidation of Ferrous Sulfides Promote the Remobilization of Cadmium in Paddy Soils During Drainage.

Most of the cadmium (Cd) accumulated in rice grains is derived from its remobilization in soils during the grain filling period when paddy water is drained. The factors affecting Cd remobilization upon drainage remain poorly understood. Here, we show that the free radical effect produced from the oxidation of ferrous sulfides is an important mechanism affecting the oxidative remobilization of Cd during soil drainage. When soils were flooded, microbial sulfate reduction results in the formation of various metal sulfides including CdS and FeS. Upon soil drainage, the oxidation of FeS produced considerable amounts of hydroxyl free radicals (OH•), which could oxidize CdS directly and thereby promote the oxidative dissolution of CdS and increase Cd mobilization in soils. FeS and CdS could also form a within-sulfide voltaic cell, with FeS protecting the oxidative dissolution of CdS due to the lower electrochemical potential of the former. However, this voltaic effect was short-lived and was surpassed by the free radical effect. The amounts and composition of metal sulfides formed during soil flooding vary with soils, and the oxidative dissolution of CdS is affected by both the free radical and voltaic effects offered by different metal sulfides. These effects are also applicable to the biogeochemistry of other chalcophile trace elements coupled with sulfur and iron redox cycles during the anoxic-oxic transition in many environments.

Plant growth promoting actinobacteria from rhizosphere soils of black pepper in Wayanad

Actinobacteria isolated from the rhizosphere soils of black pepper comprising both flood affected and non-flood affected areas of Wayanad district. Among different soil samples analysed, Puttad (Ptd) recorded significantly superior actinobacterial population on starch casein aga, Kenknight & Munaier’s agar and actinomycetes isolation agar. Actinobacterial colonies could not be detected in any of the flooded soil samples on any medium, even at a dilution of 10-1, except in Meppadi soil, which recorded a low population of 0.3x101cfu g-1 soil. Starch casein agar is best media to isolate actinobacteria from soil samples compared to other two media. The cultural, morphological and biochemical characterization of thirty-five isolates was carried out. Further the isolates were evaluated for their plant growth promoting traits such as IAA production, nitrogen fixation, P, K and Zn solubilization. The isolates Ptd-A and Amb-C were found to be significantly superior to all other isolates, with IAA production of 15.9 g ml-1 and 15.38 g ml-1 respectively. The four isolates viz. Ptd-A, Ptd-E, Ptd-B and Ptr-A recorded significantly superior nitrogen fixation and the phosphate solubilized was significantly higher in Ptd-E, Ptd-D, Ptr-E, Ptd-A and Ptr-A, as compared to other isolates. All isolates were negative to K and Zn solubilization. Based on in vitro evaluations, three isolates were shortlisted (Ptd-A, Ptd-E and Ptr-A) and subjected to in vivo evaluation for growth promotion in black pepper (variety Panniyur 1). Rooted plants of black pepper were raised in sterile potting mixture. Bioinoculants applied at the time of planting and 45 days after planting. The PGPR Mix-1 and Organic Package of Practices Recommendations (2017) were used for comparison with the microbial inoculants along with control. In the in-planta experiment, biometric characters were recorded at monthly intervals, up to five months. The actinobacterial treatment, T1: Ptd-E, T2: Ptd-A and T3: Ptr-A showed significant increase in shoot length, number of leaves and internode length throughout the growth period from planting to five MAP. Significantly higher root growth was observed in treatment T2: Ptd-A, with significantly higher root volume, fresh and root weight. The potential actinobacteria were identified Ptd-A and Ptr-A as Streptomyces sp. and Ptd-A as Actinobacteria bacterium using 16S r RNA gene sequencing.

Environmental risks, demographic dynamic and Life Quality. Argentina at beginning of XXI century

In this work we analyze the relationship among: 1) Certain environmental risks: Flood problems, Earthquakes, Tornadoes and Soil degradation, 2) Demographic dynamics (inter census growth and migratory balances) and 3) Grade of Life Level Quality of Argentinian people. We use a G eographical Information System (GIS ) in which we have done the digitalization of the respective layers of environmental risks. Following, we examine the information on demographic dynamics. At last, we present a synthetic index of the population’s Life Quality, which was elaborated starting from a combination of weighted indicators of environmental and socioeconomic dimensions (education, health and housing). The next step is to study the demographic behaviour and the grade of well-being of Argentina’s people different segments for each one of the environmental risks. We start from an operation of overlapping of different layers (for example: flood risk, growth rate, migration balance, etc). All previous stepladder let us size and compare the obtained Life Quality Index with Demographic Dynamics according to the degree of affectation of each one of the considered physical-environmental events. Finally we can establish the future scenario by projecting these phenomena impacts into the process of global environmental change.

Water management of alternate wetting and drying combined with phosphate application reduced lead and arsenic accumulation in rice

Lead (Pb) and arsenic (As) exist in soil with different ionic forms, and it is difficult to immobilize simultaneously Pb and As in soil. The objective of this study is to determine the effects of water management including flooding (FL), alternate wetting and drying (AWD) and dry farming (DF) combined with addition of phosphate (P) on the accumulation of Pb and As in rice. Our results showed that Pb accumulated in root during vegetative stage, and most of As in root was transported to the above ground parts during the reproductive stage. Pb was evenly distributed in grains, and As was mostly accumulated in bran and aleurone layer. Water management had a reverse effect on the accumulation of Pb and As in rice. However, the effects of P on arid soil environment and Pb, As accumulation in rice were stronger than that in flooded soil. Application of P under AWD treatment could maintain a similar quantity of Fe plaque with flooding, decrease the availability of Pb in rhizosphere soil, reduce Pb and As accumulation in root, and result in the reduction of Pb and As accumulation in grains by 86% and 66% respectively. Besides, our study also found that flooding or AWD during vegetative stage facilitated the formation of iron plaque. In conclusion, AWD combined with P application could maintain a relatively lower concentrations of Pb and As in grains.

Radiolytic degradation of BDE-209 in rice-vegetable rotation soils induced by electron beam irradiation

Deca-brominated diphenyl ether (BDE-209) is shown to be persistent in soil and it's urgent to find an effective method to remove BDE-209 from contaminated soil. In this study, the investigation of BDE-209 degradation in three different rice-vegetable rotation soils induced by electron beam (E-beam) irradiation under flooded and non-flooded conditions was conducted. The reductive efficiency of 14C-BDE209 reached the highest level at 50 kGy and the values in flooded soils of rice-eggplant rotation soil (RES), rice-peanut soil (RPS), and rice-chili pepper soil (RCS) were 93.5%, 87.2%, and 73.8%, respectively. The reductive efficiencies in non-flooded soils of RES, RPS, and RCS were 73.4%, 81.0%, and 78%, respectively. The D0.5 values (dose required for reducing 50% BDE-209) of BDE-209 in non-flooded soils were lower than those in flooded soils, suggesting greater degradation efficiency of BDE-209 in non-flooded soils than in flooded soils. The BDE-209 was degraded into higher-brominated PBDEs and lower-brominated PBDEs by E-beam irradiation. The results demonstrate that BDE-209 in the soil can be degraded by E-beam irradiation, non-flooded condition is better than flooded condition for the removal of BDE-209, and the main degradation mechanism of BDE-209 by E-beam irradiation is debromination. This study provides a rapid and effective method for degrading BDE-209 that is persistent in soils, and has important implications for the remediation of soil contaminated by PBDEs in and around E-waste dismantling areas.

Validation of Sentinel-3 SLSTR Land Surface Temperature Retrieved by the Operational Product and Comparison with Explicitly Emissivity-Dependent Algorithms

Land surface temperature (LST) is an essential climate variable (ECV) for monitoring the Earth climate system. To ensure accurate retrieval from satellite data, it is important to validate satellite derived LSTs and ensure that they are within the required accuracy and precision thresholds. An emissivity-dependent split-window algorithm with viewing angle dependence and two dual-angle algorithms are proposed for the Sentinel-3 SLSTR sensor. Furthermore, these algorithms are validated together with the Sentinel-3 SLSTR operational LST product as well as several emissivity-dependent split-window algorithms with in-situ data from a rice paddy site. The LST retrieval algorithms were validated over three different land covers: flooded soil, bare soil, and full vegetation cover. Ground measurements were performed with a wide band thermal infrared radiometer at a permanent station. The coefficients of the proposed split-window algorithm were estimated using the Cloudless Land Atmosphere Radiosounding (CLAR) database: for the three surface types an overall systematic uncertainty (median) of −0.4 K and a precision (robust standard deviation) 1.1 K were obtained. For the Sentinel-3A SLSTR operational LST product, a systematic uncertainty of 1.3 K and a precision of 1.3 K were obtained. A first evaluation of the Sentinel-3B SLSTR operational LST product was also performed: systematic uncertainty was 1.5 K and precision 1.2 K. The results obtained over the three land covers found at the rice paddy site show that the emissivity-dependent split-window algorithms, i.e., the ones proposed here as well as previously proposed algorithms without angular dependence, provide more accurate and precise LSTs than the current version of the operational SLSTR product.

Elucidation of Novel cis-Regulatory Elements and Promoter Structures Involved in Iron Excess Response Mechanisms in Rice Using a Bioinformatics Approach

Iron (Fe) excess is a major constraint on crop production in flooded acidic soils, particularly in rice cultivation. Under Fe excess, plants activate a complex mechanism and network regulating Fe exclusion by roots and isolation in various tissues. In rice, the transcription factors and cis-regulatory elements (CREs) that regulate Fe excess response mechanisms remain largely elusive. We previously reported comprehensive microarray analyses of several rice tissues in response to various levels of Fe excess stress. In this study, we further explored novel CREs and promoter structures in rice using bioinformatics approaches with this microarray data. We first performed network analyses to predict Fe excess-related CREs through the categorization of the gene expression patterns of Fe excess-responsive transcriptional regulons, and found four major expression clusters: Fe storage type, Fe chelator type, Fe uptake type, and WRKY and other co-expression type. Next, we explored CREs within these four clusters of gene expression types using a machine-learning method called microarray-associated motif analyzer (MAMA), which we previously established. Through a comprehensive bioinformatics approach, we identified a total of 560 CRE candidates extracted by MAMA analyses and 42 important conserved sequences of CREs directly related to the Fe excess response in various rice tissues. We explored several novel cis-elements as candidate Fe excess CREs including GCWGCWGC, CGACACGC, and Myb binding-like motifs. Based on the presence or absence of candidate CREs using MAMA and known PLACE CREs, we found that the Boruta-XGBoost model explained expression patterns with high accuracy of about 83%. Enriched sequences of both novel MAMA CREs and known PLACE CREs led to high accuracy expression patterns. We also found new roles of known CREs in the Fe excess response, including the DCEp2 motif, IDEF1-, Zinc Finger-, WRKY-, Myb-, AP2/ERF-, MADS- box-, bZIP and bHLH- binding sequence-containing motifs among Fe excess-responsive genes. In addition, we built a molecular model and promoter structures regulating Fe excess-responsive genes based on new finding CREs. Together, our findings about Fe excess-related CREs and conserved sequences will provide a comprehensive resource for discovery of genes and transcription factors involved in Fe excess-responsive pathways, clarification of the Fe excess response mechanism in rice, and future application of the promoter sequences to produce genotypes tolerant of Fe excess.

Changes in Paddy Soil Properties and Rice Yield as Affected by Application Time of Granular Livestock Manure Compost

Pelletized livestock manure compost is easy to handle and thus increasingly used as an orgranic amendment. The effectiveness of granular livestock manure compost (GLMC) was investigated at different times, with 5, 15, 25 and 35 days before transplanting rice plots. After two years of administration of GLMC, pH, available P2O5, exchangeable K, Ca, and Mg decreased and organic matter content increased, compared to the soil before the test. The faster the treatment time of GLMC, the lower the organic matter content. But the T-N was the same in the control, 5 and 15 days before transplanting rice plots. In flooded soil, the N mineralization of GLMC proceeded 2 weeks later than inorganic fertilizers and 1 week later than livestock manure compost. Rice growth and quantity showed similar results in control and 25 days before transplanting rice plot. When GLMC was used, the protein content of white rice was lower than that of control plot, and there was no difference in amylose, whiteness, and palatability. The correlation between the white rice quantity and the treatment time of the GLMC was Y = -0.075X2 + 3.982X + 492.74 (R2 = 0.7722), and the treatment time to obtain the highest quantity of white rice was 26.5 days. Relationship between rice yield and treatment time of granular livestock manure compost.

Total extractable phosphorus in flooded soil as affected by struvite and other fertilizer‐phosphorus sources

AbstractA sustainable P source is imperative to ensure that food production can supply a growing global population. Wastewater‐recovered struvite (MgNH4PO4 · 6H2O) has emerged as an attractive option because of the ability to recover P from waste streams. This study aimed to evaluate total extractable soil P from electrochemically precipitated struvite (ECST) compared with other fertilizer‐P sources [chemically precipitated struvite (CPST), diammonium phosphate (DAP), and rock phosphate] in two soil textures (two different silt loams and a silty clay loam) over time in a flooded soil environment. An equivalent fertilizer rate of 24.5 kg P ha–1 was used. The change in water‐soluble (WS) and Mehlich‐3 (M3)‐extractable nutrient concentrations (P, K, Ca, Mg, and Fe) from their initial concentrations was determined five times over a 4‐mo period. After 0.5 mo, WS‐P increased the most from the initial value with DAP (27.6 mg kg–1), which did not differ from CPST or ECST. After 0.5 mo, M3‐P increased the most in ECST (82 mg kg–1), which did not differ from DAP. After 1 mo and thereafter under flooded conditions, M3‐P increased the most from the initial value and was similar among ECST, CPST, and DAP. After 3 and 4 mo, WS‐P was greater than the initial value in DAP only, but remained similar to CPST, ECST, and rock phosphate, which did not differ from the initial value. Comparable WS‐ and M3‐P concentrations among ECST, CPST, and DAP under flooded conditions support struvite's agronomic potential as a prospective sustainable fertilizer‐P source.

Biodiversity of the Regional Landscape Park Samara Plavni within the first large reservoir in Europe Biodiversity of the Regional Landscape Park Samara Plavni within the first large reservoir in Europe

The creation of reservoirs in river valleys for the accumulation of fresh water has been and remains an important issue around the world. This process has both positive and negative consequences for people and nature. Significant changes in the regime of rivers and their valleys, flooding of meadows and forests, flooding of soils and changes in the composition of flora and fauna of adjacent territories are taking place. In this article, we consider the restoration of the biodiversity of a site of disturbed lands after the creation of one of the first large reservoirs in Europe – the Dnieper (Zaporozhe) on the River Dnieper, which has existed since 1933. The territory of the Samara floodplains was formed on the floodplain of the mouth of the Samara River, as a result of which the territories of various forest, meadow and bog biotopes were flooded. For almost 90 years, new biotopes have been developing, and populations of plant and animal species, especially waterfowl, have been renewed and enriched. In the conditions of climate change and anthropogenic pressure, the existence of this territory has fallen into question. To control the conservation of biodiversity, it is necessary to apply various management methods, one of which is creation of nature reserves. The article presents the results of a complex of scientific studies that were carried out during the zoning of the regional park Samara Plavni to improve the management of the protection of water areas and river banks. We have investigated: hydrological features, species diversity of the flora and coenotic diversity of the vegetation, fauna of aquatic invertebrates, and terrestrial vertebrates. Zoning of the Regional Landscape Park was based on the composition of stable components of ecosystems. When applying the protected regime in different zones, conditions will be created for the preservation of habitats of species, including those protected in Europe: higher plants (Senecio borysthenicus (DC.) Andrz. ex Czern., Tragopogon borystenicus Artemcz.), reptiles (Emys orbicularis (Linnaeus, 1758), Vipera renardi (Christoph, 1861)), birds (Aythya ferina (Linnaeus, 1758), Vanellus vanellus (Linnaeus, 1758), Haematopus ostralegus Linnaeus, 1758, Numenius arquata (Linnaeus, 1758), Alcedo atthis (Linnaeus, 1758), Lanius excubitor (Linnaeus, 1758)), mammals (Lutra lutra (Linnaeus, 1758)). Such changes would increase the implementation of the reproductive potential of all species without exception in the studied ecosystems.

Phenology Effects on Physically Based Estimation of Paddy Rice Canopy Traits from UAV Hyperspectral Imagery

Radiation transform models such as PROSAIL are widely used for crop canopy reflectance simulation and biophysical parameter inversion. The PROSAIL model basically assumes that the canopy is turbid homogenous media with a bare soil background. However, the canopy structure changes when crop growth stages develop, which is more or less a departure from this assumption. In addition, a paddy rice field is inundated most of the time with flooded soil background. In this study, field-scale paddy rice leaf area index (LAI), leaf cholorphyll content (LCC), and canopy chlorophyll content (CCC) were retrieved from unmanned-aerial-vehicle-based hyperspectral images by the PROSAIL radiation transform model using a lookup table (LUT) strategy, with a special focus on the effects of growth-stage development and soil-background signature selection. Results show that involving flooded soil reflectance as background reflectance for PROSAIL could improve estimation accuracy. When using a LUT with the flooded soil reflectance signature (LUTflooded) the coefficients of determination (R2) between observed and estimation variables are 0.70, 0.11, and 0.79 for LAI, LCC, and CCC, respectively, for the entire growing season (from tillering to heading growth stages), and the corresponding mean absolute errors (MAEs) are 21.87%, 16.27%, and 12.52%. For LAI and LCC, high model bias mainly occurred in tillering growth stages. There is an obvious overestimation of LAI and underestimation of LCC for in the tillering growth stage. The estimation accuracy of CCC is relatively consistent from tillering to heading growth stages.

Aging and phytoavailability of newly introduced and legacy cadmium in paddy soil and their bioaccessibility in rice grain distinguished by enriched isotope tracing

Phytoavailability of Cadmium (Cd) plays a critical role in its accumulation in soil-rice systems. However, differential aging and phytoavailability of newly introduced Cd (CdN) and legacy Cd (CdL) in the soil-rice system remains unknown. Moreover, distinguishing their aging and phytoavailability is challenging. Enriched 112Cd isotope was introduced into a series of pot experiments, combined with sequential extraction and isotope dilution (110Cd isotopic spike), to investigate the aging and distribution of CdN and CdL under different treatments. The treatments included simulated acid rain, slaked lime, and biochar. CdN aged quickly than CdL in flooded soil and its availability was similar to that of CdL after tillering stage. The grain Cd contents were positively correlated to Cd concentrations in the overlying water. Acid rain reduced the soil pH, increasing the grain Cd, while slaked lime reduced grain Cd content. The acidic biochar used in this study increased grain Cd, possibly through soil acidification-induced Cd release. The differences in bioaccumulation and translocation factors between CdN and CdL in rice plants under slaked lime and biochar treatments suggested their different in vivo complexations and translocations. Analysis of bioaccessibility of CdN and CdL in rice grains provided valuable insights regarding human Cd exposure.

Characteristics of the Ugandan rice varieties grown in the Rostov region

Rice is a valuable agricultural crop that is used as food for more than half of the world's population. The development of highly productive varieties and hybrids with high product quality assumes the utilization of new initial material from different countries in the breeding process. The purpose of the current research was to conduct an ecological testing of the rice varieties from Uganda in the Proletarsky district of the Rostov region in Russia and use them in the breeding process. There were studied the Ugandan rice samples ‘Nerica 1’, ‘Nerica 4’, ‘Komboka’, ‘Wita 9’, ‘Namche 1’, ‘Namche 2’, ‘Namche 3’, ‘Namche 4’, ‘Namche 5’, ‘Namche 6’ (NaCRRI) in comparison with the Russian variety ‘Komandor’ (FSBSI “ARC “Donskoy”). The study of the Ugandan rice varieties according to a number of economically valuable traits and biological properties showed that the vegetation period from soil flooding to rice maturing took 100–113 days, the standard variety ‘Komandor’ needed 83 days. The varieties ‘Komboka’ and ‘Wita 9’ did not bear blossom. All samples had a short habit, with 63-95 cm of plant height. The long drooping panicles of 18.5–22.3 cm carried from 122 to 213 seeds. The caryopses were elongated, the length of the caryopses varied from 9.0 to 9.5 mm, and the width ranged from 2.7 to 3.1 mm. 1000 seed weight varied from 26 to 34 g, number of seeds per panicle ranged from 122 to 213 pieces. Genetic analysis of the second generation hybrids ‘Kontakt × Nerica 1’ and ‘Boyarin × Nerica 4’ showed different types of traits’ inheritance, from negative dominance (vegetation period) through the absence of dominance (caryopses size) to overdominance (plant height, seed weight per panicle and number of seeds per panicle).

Water management effect on soil oxidation, greenhouse gas emissions, and nitrogen leaching in drained peat soils

AbstractSoil subsidence of peatlands occurs worldwide due to drainage. The Everglades Agricultural Area (EAA), located in South Florida, has been drained for agriculture since 1914, with subsidence resulting in shallow soils in certain areas. The purpose of this study is to determine the impact of water management strategies on soil oxidation and N release as affected by differences in proximity to the bedrock. Oxidation rates (CO2 efflux), as well as CH4 and N2O emissions, were measured in lysimeters filled with shallow and deep peat subjected to four water treatments. Additionally, NO3–N, NH4–N, soluble organic N, and dissolved organic C were measured in leachate obtained from the collected soils. Average annual emissions from constantly drained soils were 298 g CO2–C m–2 yr–1, with most of the oxidation taking place between June and October. Short flood cycles increased annual oxidation rates compared with constantly drained soils, which had the second highest oxidation rate. Constantly flooded soils had the lowest annual oxidation rates, followed by summer flooded soils. Total N lost in leachate was highest for constantly drained soils, with NO3 being the dominant form. The deep soils had higher losses of soluble N and C, whereas NO3 losses from shallow soils were higher. Soil oxidation rates did not differ depending on proximity to the bedrock. We conclude that strategies that avoid short flooding cycles and include crop rotations that allow flooding during summer can reduce oxidation and N losses in leachate from EAA peats.

Restored river-floodplain connectivity promotes woody plant establishment

Riparian forest ecosystems are declining globally. Many floodplains no longer flood and thus cease to satisfy the hydrologic requirements for riparian tree maintenance and regeneration. To promote woody riparian plant recruitment where flood regimes have been altered by flow regulation, effective approaches to restoration need to be developed. We implemented a landscape-scale experiment in a remnant, temperate floodplain forest. By constructing two weirs within channelized reaches of a stream, we redirected flows into networks of historic distributary channels, which facilitated widespread floodplain inundation. Using a control-reference-impact study design, we assessed the establishment and growth of planted seedlings of three woody species (Eucalyptus camphora, Leptospermum lanigerum and Melaleuca squarrosa) over 13 months in response to flooding achieved by floodplain reconnection. Planted seedlings had higher height and diameter growth rates at both induced (19–29 cm, 1 mm) and naturally flooded (34–44 cm, 3–5 mm) than at non-flooded (4–10 cm, −5 to −3 mm) sites. However, survival rates and temporal growth patterns differed between species according to variation in flood duration and soil moisture, illustrating the different hydrological requirements of the coexisting species. This highlights that variable flooding and drying patterns are essential to create recruitment niches for different riparian plant species and shows the importance of river-floodplain connectivity for providing adequate flooding regimes. Our study demonstrates the suitability of two complementary restoration approaches – restoring hydrology and active revegetation – for promoting the regeneration of riparian forests.