scholarly journals Cadmium Speciation Distribution Responses to Soil Properties and Soil Microbes of Plow Layer and Plow Pan Soils in Cadmium-Contaminated Paddy Fields

2021 ◽  
Vol 12 ◽  
Author(s):  
Xiaodong Hao ◽  
Lianyang Bai ◽  
Xueduan Liu ◽  
Ping Zhu ◽  
Hongwei Liu ◽  
...  
Keyword(s):  
Soil Ph ◽  
Soil Microbes ◽  
Arable Land ◽  
Paddy Fields ◽  
Rice Grain ◽  
Cd Uptake ◽  
Driving Mechanisms ◽  
Vertical Scale ◽  
Cadmium Speciation ◽  
Rice Ecosystem

Cadmium (Cd) speciation ratio in arable land determines the Cd exposure risk and Cd uptake in crops. However, the driving mechanisms of Cd speciation change on the vertical scale of paddy fields remain poorly understood. In this study, the effects of plow layer and plow pan on Cd speciation distribution were investigated in a long-term Cd-contaminated rice ecosystem. The Cd accumulative effect within rice grain was enhanced with high levels of activated Cd speciation ratios in soils. Activated Cd speciation ratios were higher in plow layer soils, while stabilized Cd speciation ratios were elevated in plow pan soils. Soil physicochemical properties and soil microbes synergistically affected the Cd speciation changes in different ways between the two soil layers. Soil pH and organic elements in plow layer environment directly hindered the transformation of stabilized Cd speciation, while in plow pan environment, soil pH and organic elements indirectly decreased activated Cd speciation ratios and resulted in the accumulation of stabilized Cd speciation via regulating the predominant bacterial taxa. This study will improve our understanding of how soil environments regulate Cd speciation distributions in rice ecosystems and help to seek effective remediation methods of Cd-contaminated paddy fields to reduce the Cd accumulation in rice.

scholarly journals Organic Amendments Boost Soil Fertility and Rice Productivity and Reduce Methane Emissions from Paddy Fields under Sub-Tropical Conditions

2021 ◽  
Vol 13 (6) ◽  
pp. 3103
Author(s):  
Md Mahamudul Haque ◽  
Juel Datta ◽  
Tareq Ahmed ◽  
Md Ehsanullah ◽  
Md Neaul Karim ◽  
...  
Keyword(s):  
Soil Fertility ◽  
Soil Ph ◽  
Soil Amendment ◽  
Organic Amendments ◽  
Rice Production ◽  
Inorganic Fertilizer ◽  
Paddy Fields ◽  
Rice Grain ◽  
Ch4 Emission ◽  
Rice Productivity

Deteriorating soil fertility and gradually decreasing rice productivity along with higher greenhouse gas emissions from paddy fields have emerged as serious threats to the sustainability of rice production and food security. Rice production in the subtropical environment in Bangladesh is mostly dependent on synthetic inorganic fertilizer to maintain productivity; however, the inorganic fertilizer has negative effects on global warming. Climate-smart and resilient agricultural production systems are major concerns nowadays to meet sustainable development goals. The study was conducted to evaluate the optimum rate and source of organic amendments on rice productivity and soil fertility along with CH4 emission. A total of nine nutrient combinations were used in the study. The CH4 emission, soil redox potential (Eh), soil pH, soil nitrogen and organic carbon, available phosphorus, rice grain and straw were greatly affected by the application of different rates and sources of the nutrient. However, the soil exchangeable K content, plant height, and harvest index were not affected. Among the treatments, the application of 75% recommended fertilizer (RF) + biosolid 2 t ha−1 (T3) was the most effective and showed the superior performance in terms of available P (12.90 ppm), the number of grains panicle−1 (121), and 1000-grain weight (24.6g), rice grain, and straw yield along with the moderate CH4 emission (18.25 mg m−2h−1). On the other hand, the lowest soil Eh (−158 mV) and soil pH (6.65) were measured from the treatment T3. The finding of this study revealed that the application of 75% of RF + biosolid 2 t ha−1 can be recommended as the preferable soil amendment for boosting rice yield, reduce CH4 emissions, and sustainably maintain soil fertility. Furthermore, this finding may help to introduce preferable soil amendment doses, which will contribute to boosting rice productivity and economic turnouts of the farmers.

scholarly journals The pH-based ecological coherence of active canonical methanotrophs in paddy soils

2020 ◽  
Vol 17 (6) ◽  
pp. 1451-1462 ◽  
Author(s):  
Jun Zhao ◽  
Yuanfeng Cai ◽  
Zhongjun Jia
Keyword(s):  
Soil Ph ◽  
Rice Paddy ◽  
Low Ph ◽  
Paddy Soils ◽  
Paddy Fields ◽  
Type I ◽  
Type Ii ◽  
High Ph ◽  
Niche Specialization ◽  
Rice Paddy Soils

Abstract. Soil pH is considered one of the main determinants of the assembly of globally distributed microorganisms that catalyze the biogeochemical cycles of carbon (C) and nitrogen (N). However, direct evidence for niche specialization of microorganisms in association with soil pH is still lacking. Using methane-oxidizing bacteria (methanotrophs) as a model system of C cycling, we show that pH is potentially the key driving force selecting for canonical γ (type I) and α (type II) methanotrophs in rice paddy soils. DNA-based stable isotope probing (DNA-SIP) was combined with high-throughput sequencing to reveal the taxonomic identities of active methanotrophs in physiochemically contrasting soils from six different paddy fields across China. Following microcosm incubation amended with 13CH4, methane was primarily consumed by Methylocystis-affiliated type II methanotrophs in soils with a relatively low pH (5.44–6.10), whereas Methylobacter- or Methylosarcina-affiliated type I methanotrophs dominated methane consumption in soils with a high pH (7.02–8.02). Consumption of 13CH4 contributed 0.203 % to 1.25 % of soil organic C, but no significant difference was observed between high-pH and low-pH soils. The fertilization of ammonium nitrate resulted in no significant changes in the compositions of 13C-labeled methanotrophs in the soils, although significant inhibition of methane oxidation activity was consistently observed in low-pH soils. Mantel analysis further validated that soil pH, rather than other parameters tested, had significant correlation to the variation in active methanotrophic compositions across different rice paddy soils. These results suggest that soil pH might have played a pivotal role in mediating the niche differentiation of ecologically important aerobic methanotrophs in terrestrial ecosystems and imply the importance of such niche specialization in regulating methane emissions in paddy fields following increasingly intensified input of anthropogenic N fertilizers.

Impact of cultivation year, nitrogen fertilization rate and irrigation water quality on soil salinity and soil nitrogen in saline-sodic paddy fields in Northeast China

2015 ◽  
Vol 154 (4) ◽  
pp. 632-646 ◽  
Author(s):  
L. H. HUANG ◽  
Z. W. LIANG ◽  
D. L. SUAREZ ◽  
Z.C. WANG ◽  
M. M. WANG ◽  
...  
Keyword(s):  
Soil Ph ◽  
Soil Salinity ◽  
Irrigation Water ◽  
Northeast China ◽  
Paddy Fields ◽  
Inorganic N ◽  
N Application ◽  
Total N ◽  
Application Rates ◽  
Soil Inorganic N

SUMMARYSaline-sodic soils are widely distributed in the western Songnen Plain of Northeast China and planting rice has been found to be an effective and feasible approach for improving saline-sodic soil and increasing food production. Assessment of the effectiveness and sustainability of this method requires monitoring of the changes in soil salinity and nutrient content. The objective of the current study was to investigate the changes of soil salinity and nitrogen (N) contents over 1, 3, 6 and 9 years of cultivation, four application rates of N (N0: no N, N1: 100 kg N/ha, N2: 200 kg N/ha and N3: 300 kg N/ha) and two irrigation water types: ground water irrigation (GWI) and river water irrigation (RWI). Salinity and N contents of soil and water samples were analysed before planting and after harvest throughout the experiments. Soil pH and electrical conductivity (EC), especially in the surface layer of 0–40 cm depth, decreased with years of cultivation with both GWI and RWI, while soil inorganic N and total N contents increased. Moreover, with increasing N application rates, soil inorganic N and total N contents increased significantly in the 0–20 cm soil layer. Increasing N application had little effect on soil pH and EC. Reclaiming and planting rice promoted desalination of the surface and formation of a fertile tillage layer in saline-sodic paddy fields. In terms of irrigation and drainage in saline-sodic paddy fields, both soil salinity and N contents increased. Soil total salinity increased annually by 34 and 12·8 kg/ha, and inorganic N contents increased annually by 9 and 13·5 kg/ha with GWI and RWI, respectively. Therefore, comprehensive agricultural practices should be adopted for improving and cropping rice in saline-sodic paddy fields.

Estimation and temporal-spatial variation analysis of non-point source pollution in China's planting industry

2020 ◽  
Author(s):  
Wang Yafei ◽  
Zuo Lijun ◽  
Zhao Xiaoli ◽  
Zhang Zengxiang
Keyword(s):  
Point Source ◽  
Arable Land ◽  
Fertilizer Application ◽  
Paddy Fields ◽  
Land Resource ◽  
Point Source Pollution ◽  
Plain Area ◽  
P Loss ◽  
Wide Range ◽  
Non Point Source Pollution

<p>Nitrogen (N) and phosphorus (P) are important elements of the life system. China is the most populous country and the population continues to grow, causing an increasing demand for food. But China's arable land resource is limited, and as is the effective means to improve crop yields, fertilization also has resulted in the excessive use of nitrogen and phosphorus in crop planting systems at the same time. Non-point source pollution of planting industry is becoming more and more serious, which poses a great threat to water quality.</p><p>In this study, 14 kinds of major crops accounting for 76% of the sown area and 87% of the yield in China were selected. Based on land use/cover data, crop spatial distribution data and agricultural economic statistical survey data (from the 2010 China Statistical Yearbook), the data were distributed by spatial allocation model according to the county code, and the results of different crop fertilizer application rates were obtained. Then, the results were summed up to get the overall fertilizer application status of N and P in China.</p><p>Under this premise, combined with terrain data (DEM), arable land information (distribution of paddy fields and upland), planting patterns of 14 kinds of crops and non-point source pollution control division classified by climate types, the cropland is divided into 56 different N and P loss modes. In the first national agricultural non-point source pollution census, N and P loss coefficients under different modes were obtained through field monitoring and local investigation. On the basis of the coefficient table and fertilizer application rate, the N and P loss of planting industry in 2010 was calculated, and the results were analyzed to reach the following conclusions:</p><p>1.Fertilization of cultivated land in China covers a wide range, and the amount of fertilization varies greatly between different regions. The basic distribution law of N and P fertilizer application is relatively consistent across the country, and both more in the north than in the south, more in the east than in the west, more in the plain than in the mountain and plateau, and more in the dry land than in the paddy fields. The areas with high fertilization account for about 1/4 of the total fertilizing area in China, presenting a state of spatial aggregation.</p><p>2.Fertilizer loss amount of each kind of crops are not identical. Taking winter wheat, one of the most important major food crops in China, as an example, its P loss mainly concentrated in the semi-humid plains of the Huang-Huai-Hai Sea, the Chengdu Plains in the southern wet plain area and parts of Jiangsu Province and Anhui Province, while the central and southern are of Henan and Hebei provinces and Hanzhong plain area suffered the most severe loss.</p><p>The above research can provide scientific theoretical basis and decision-making support for the formulation of sustainable agricultural development strategy in China, and it can also be for the reduction of N and P loss and the control of water eutrophication worldwide.</p>

Effects of Soil Microbes on Methane Emissions from Paddy Fields under Varying Soil Oxygen Conditions

2018 ◽  
Vol 110 (5) ◽  
pp. 1738-1747
Author(s):  
Xu Chunmei ◽  
Chen Liping ◽  
Chen Song ◽  
Chu Guang ◽  
Zhang Xiufu ◽  
...  
Keyword(s):  
Soil Microbes ◽  
Methane Emissions ◽  
Paddy Fields ◽  
Soil Oxygen ◽  
Oxygen Conditions

scholarly journals Derivation of ecological standards for risk assessment of molybdate in soil

2016 ◽  
Vol 13 (1) ◽  
pp. 168 ◽  
Author(s):  
Koen Oorts ◽  
Erik Smolders ◽  
Steve P. McGrath ◽  
Cornelis A.M. van Gestel ◽  
Michael J. McLaughlin ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Soil Quality ◽  
Soil Ph ◽  
Anthropogenic Activities ◽  
Arable Land ◽  
Sodium Molybdate ◽  
Quality Criteria ◽  
Clay Content ◽  
Field Conditions ◽  
Toxicity Tests

Environmental context In order to assess the potential risks of elevated molybdenum concentrations in soil due to anthropogenic activities, toxicity thresholds must be known and environmental criteria defined. Setting such criteria for metals is not straightforward because of varying natural background concentrations and differences in toxicity between typical laboratory and field conditions and across soil types. Toxicity data and models were derived that account for these parameters so that soil quality criteria can be derived based on total molybdenum concentrations in soil. Abstract An extensive testing programme on the toxicity of sodium molybdate dihydrate in soil was initiated to comply with the European REACH Regulation. The molybdate toxicity was assayed with 11 different bioassays, 10 different soils, soil chemical studies on aging reactions, and toxicity tests before and after 1-year equilibration in field conditions. Differences in molybdate toxicity among soils were best explained by soil pH and clay content. A correction factor of 2.0 was selected to account for the difference in molybdate toxicity between laboratory and field conditions due to leaching and aging processes. Toxicity thresholds were determined as the HC5–50 (median hazardous concentration for 5% of the species, i.e. median 95% protection level) derived from the species sensitivity distribution of ecotoxicity data after bioavailability corrections. Uncertainty analysis illustrated that the HC5–50 provides a robust and ecologically relevant predicted no-effect concentration (PNEC) for risk characterisation. The 10th and 90th percentiles for site-specific PNEC values in European agricultural soil are 10.7 and 168mgMokg–1 dry weight respectively based on a large survey of metal concentrations and soil properties in arable land soils. Total soil Mo concentrations in these soils are below corresponding PNEC values at most locations, suggesting no regional risks of molybdate to soil organisms at this scale. The information presented can be used in the EU risk-assessment framework as well as for national and international regulatory purposes for the setting of soil quality criteria based on total molybdenum concentrations, soil pH and clay content.

scholarly journals Effect of introducing frogs and fish on soil phosphorus availability dynamics and their relationship with rice yield in paddy fields

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Kaimiao Lin ◽  
Jianping Wu
Keyword(s):  
Best Practice ◽  
Rice Yield ◽  
Soil Phosphorus ◽  
Farming Systems ◽  
Paddy Fields ◽  
Rice Grain ◽  
P Availability ◽  
Soil P ◽  
Labile P ◽  
Rice Fish

AbstractThe long-term impacts of introducing frogs and fish on rice yield and soil P availability are largely underestimated and undervalued. A 9-year field experiment compared the soil phosphorus fraction dynamics and their relationship with rice yield in rice-frog-fish (RFF) cultures, rice-fish (RF) cultures and rice-only (RO) cultures in southeastern China paddy fields. The yields in the RFF and RF cultures were notably higher than those in the RO culture, by 22.1% and 6.8%, respectively. Soil total P ranged from 345.5 to 385.6 mg kg−1 among all the farming systems, with the smallest amount found in the RO culture. There were only slight changes in the distribution of soil phosphorus fractions with time. The concentrations of NaHCO3-Pi and NaHCO3-Po were significantly higher in the RFF and RF cultures compared with those in the RO culture, and most of the NaOH-Pi and NaOH-Po fractions were greater in the RFF and RF cultures compared with those in the RO culture. The rice grain yield was significantly correlated with labile P and slowly cycling P. Introducing frogs and fish might be useful for increasing soil active P supplies and meeting rice nutrient requirements. This study concluded that RFF is the best practice for improving rice grain yields and soil fertility in paddy fields.

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