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Salt-affected reclaimed tidelands (RTLs) in coastal areas of South Korea are commonly used for rice (Oryza sativa L.) cultivation as excessive salts are removed through leaching by irrigation during rice growth. However, changes in soil properties and rice growth in RTLs by continuous rice cultivation are not well understood. In the present study, we investigated soil salinity indices (ECe, electrical conductivity of soil extracts; SAR, sodium adsorption ratio; ESP, exchangeable sodium percentage), fertility (mineral nitrogen (N), and available phosphorus (P) concentrations), and carbon (C) content as well as rice biomass and yield in 72 paddy fields within 10 RTL areas, which have been cultivated for different time periods (13–35 years). Continuous rice cultivation decreased ECe by 0.36 dS m−1 per year, indicating desalinization, but ESP and SAR were not changed. Available P concentration increased but mineral N concentration did not change with rice cultivation years. There was also an indication of increased soil organic C (SOC) concentration with rice cultivation. However, rice biomass and yield were not different among the RTLs. Instead, rice biomass and yield as well as SOC concentration were negatively correlated with ECe when all individual measurements from 72 sampling sites within the 10 RTLs were pooled, suggesting that salinity is a constraint for both rice production and SOC sequestration at field scales. Interestingly, soil mineral N concentration was positively correlated with ECe but negatively with rice biomass and yield. This result implies that heavy application of N fertilizer in highly saline soils may not benefit rice growth due to salinity stress. Our results show that long-term rice cultivation with fertilization and irrigation decreases salinity while increasing P availability. However, SOC content and rice biomass and yield were more responsive to the salinity status of each paddy field than during cultivation years, highlighting the need for field-specific soil management for improved rice production and enhanced SOC sequestration. [ABSTRACT FROM AUTHOR]

Though construction of vegetated ridge (VR) and placement of sandbag (SB) across the slope of upland fields are believed to be effective in reducing soil erosion and nutrient loss, relevant data are lacking to confirm such expectations. In this study, the effects of VR and SB on loss of soils, carbon (C), nitrogen (N), and phosphorus (P) (CNP) were investigated through both artificial (in dry season) and natural (in rainy season) runoff experiments on upland fields cultivated with maize (Zea mays L. var. ceratina). Contrary to expectations, both VR and SB were not effective in reducing the loss of soils and CNP. For VR, accelerated convergent flow caused by ridge failure, which occurred when part of the ridges collapsed because the amount of water collected in the furrows exceeded the water storage capacity of the ridges, led to excessive loss of soils and CNP. For SB, the loss of soils and CNP could be ascribed to the malfunction of SB; i.e., soil and CNP were lost by seepage through the gaps between SBs and between SB and soil surface. Maize growth and yield were not affected by VR and SB, coinciding with the lack of beneficial effects of VR and SB on soil and nutrient loss. As VR and SB are easy to be implemented and cost-effective, however, further study is necessary to correct the flaws of VR and SB found in this study. [ABSTRACT FROM AUTHOR]

The properties of secondary salt-affected soils developed from improper irrigation and drainage management and their effects on rice growth and yield are well documented. However, relevant information on coastal reclaimed tideland (RTL) soils, which are classified as primary salt-affected soils developed through salt-accumulated sediments is lacking. In this paper, we reviewed the physical and chemical properties of RTL soils in comparison with non-RTL soils and analyzed the relationship between rice production and soil salinity in RTL to suggest agricultural management practices for sustainable rice production and soil carbon sequestration in RTL. Similar to the secondary salt-affected soils, RTL soils were characterized by high alkalinity, salinity, and sodicity, and rice yield was negatively correlated with salinity. However, it was also found that lower fertility (e.g., organic matter and phosphorus) of RTL soils than non-RTL soils might also hamper rice growth and thus carbon input via plant residues in RTL soils. Correlation between years after reclamation and soil properties of RTL showed that cultivation of rice with annual fertilization and organic matter inputs increased soil fertility but salinity and sodicity did not show a significant tendency of change, suggesting that natural desalinization in RTL soils is hard to be achieved with conventional rice cultivation. Therefore, it is suggested that fertilization management as well as salinity management via drainage, gypsum application, tillage, and proper irrigation may be necessary to improve rice production and carbon sequestration in RTL soils. [ABSTRACT FROM AUTHOR]

The effects of climate change including warming on nitrogen (N) availability and growth ofPinus merkusiiin central Vietnam were investigated using the relationship between climate variables (rainfall and temperature) and tree-ring parameters (ring width, density, basal area increment, and N concentration) for the last five decades. Rainfall was not correlated with any tree-ring parameters, indicating that water availability did not limit tree growth in the study site probably due to sufficient rainfall. Temperature was positively correlated with ring N concentration, basal area increment, and ring density, probably reflecting the positive effects of warming on soil N mineralization, net photosynthesis, and cell wall thickness, respectively. Therefore, this study suggested that global warming during the last five decades increased N availability and the increased N further helped warming-induced increases in the growth ofP. merkusiiin central Vietnam. [ABSTRACT FROM PUBLISHER]

Purpose: The purpose of this study is to evaluate the efficacy of simple aspiration of cystic thyroid nodules by comparing with control groups to exclude the occurrence of spontaneous regression by the definition of current guidelines of American Thyroid Association.Materials and methods: 217 nodules from 210 patients with cystic thyroid nodules (cystic portion >50%) were included. Nodules were classified into three groups as follows: Group 1, observation only; Group 2, fine needle aspiration (FNA) without aspiration of internal fluid; and Group 3, FNA after aspiration of internal fluid. Significant nodule size change was defined as a difference in the largest diameter of 20%, as seen on the last follow-up ultrasound (US) compared to the initial US.Results: Demographic characteristics did not show significant differences among the three groups except for the patient age (p = 0.039). Mean nodule size significantly decreased only in group 3 (p = 0.005). Significant nodule size reductions were observed in 22.0% (13/59) in group 1, 25.7% (28/109) in group 2, and 40.8% (20/49) in group 3, respectively.Conclusions: Aspiration of internal fluid should be considered as the first-line procedure for both the diagnosis and treatment of cystic or predominantly cystic thyroid nodules. [ABSTRACT FROM AUTHOR]

Synthetic fertilizer, livestock manure, and green manure are the typical nitrogen (N) sources in agriculture. This study was conducted to investigate the effects of different N sources on soil chemical environment and N dynamics. Changes in pH, redox potential (Eh), and concentration and δ15N of dissolved N [ammonium (NH4+), nitrate (NO3−), organic N, and total N] of soils treated with urea (U), pig manure compost (PMC), and hairy vetch (HV) were investigated in an incubation experiment under waterlogged conditions. The patterns of pH, Eh, and N concentration reflected both a greater mineralization potential of N derived from U than that from HV and PMC and easier decomposability of HV than PMC. The δ15N further suggested that nitrification was more active for U than for HV- and PMC-treated soils and that N loss via NH3volatilization and denitrification would be greater for HV than U and PMC treatments. [ABSTRACT FROM PUBLISHER]

Sand mixing effects on chloroform fumigation–extraction (CFE) efficiency in the determination of soil microbial biomass carbon (MBC) of water-saturated soils were investigated in two soils with different soil organic C (SOC) contents. Sand mixing increased (P< 0.001) MBC by up to 20% and 107% for the soil with low and high SOC values, respectively, suggesting that the creation of water-empty macropores by sand mixing improved chloroform fumigation efficiency. This study demonstrates that sand mixing is a feasible measure to improve CFE efficiency for the determination of the MBC of water-saturated soils, particularly for soils with a high SOC. [ABSTRACT FROM AUTHOR]

Canada bluejoint grass [Calamagrostis canadensis(Michx.) P. Beauv., hereafter referred to as bluejoint] outcompetes overstory tree species such as white spruce [Picea glauca(Moench) Voss] by creating a thick litter layer and competing for the available nitrogen (N). This study was conducted to investigate the effects of bluejoint litter layer (with or without litter removal) and N fertilization on soil water and N availabilities using principal component analysis (PCA) and foliar δ15N and δ13C of bluejoint in a plantation in north-central Alberta, Canada. PCA using soil properties and understory growth data demonstrated that N fertilization was more effective in changing the soil environment and resource availabilities for bluejoint growth than litter layer removal. The increase in soil N availability by N fertilization was linked with increased bluejoint foliar δ15N (by around 3‰) in fertilized plots, as a result of greater N isotopic fractionation in the fertilized plots. The more negative δ13C (by around 1‰) of bluejoint in litter layer-removed plots suggested that litter layer removal increased soil water availability, indicating that the litter layer reduced soil water availability on the site. Therefore, results from this and previous studies showed that the litter layer decreased both soil water and N availabilities. Although the exact mechanisms of the benefit of the litter layer for bluejoint remains unknown, bluejoint likely adversely impacted tree growth by competing for N due to its strong N acquisition ability under soil resource-limiting conditions. [ABSTRACT FROM PUBLISHER]

Methane (CH4) emission from flooded rice fields was measured hourly over 24 h for rice (Oryza sativaL.) seasons in 2008 and 2009. The objectives of this study were to identify typical diel variation in CH4emission and to estimate the best time of day for optimum extrapolation of daily CH4emission. Our results showed distinct diel variation in CH4emission, which exhibited a maximum at 14:00–15:00 and a minimum at midnight. About 5.2–5.6% of total CH4emitted per day (110–160 mg CH4m−2d−1) was released at 14:00–15:00. The diel pattern of CH4emission resembled that of air temperature (Ta). The Tacoupled with solar radiation could cause a difference in partial pressure of CH4(DPPC) through the gas conduit of the plant. The best extrapolation of daily CH4emission was achieved with data observed at 10:00–11:00. We concluded that DPPC-induced CH4emission is an important mechanism causing diel variation.Present address of Seok-In Yun, Department of Bio-Environmental Chemistry, Wonkwang University, 460 Iksandae-ro, Iksan, Jeonbuk 570-749, Korea. [ABSTRACT FROM AUTHOR]

A column leaching experiment using three soils (Inceptisol, Ultisol, and Andisol) and seven livestock manure composts that had different characteristics was conducted for 19 weeks to investigate the interactive effects of composts and soils on the phosphorus (P) leaching potential of compost-amended soils and to identify the principal variables that affect P leaching. Cumulative total P leaching (TPcum) tended to increase with increasing total and available P concentration in the soils. Among various compost properties, total P concentration was positively correlated with TPcum from the compost-amended soils, except for the Andisol, which has a high P-sorption capacity. There was no significant relationship between TPcum and water-extractable P concentration of the composts, suggesting that total P rather than inorganic P concentration of composts may be successfully used in predicting P leaching potential from compost-amended soils except for soils that have a high P-sorption capacity, as in Andisol. [ABSTRACT FROM AUTHOR]

Hydrocarbon-contaminated wastes generated from oil and gas drilling activities may be used as a soil amendment once composted and further decomposition of residual hydrocarbons can be accomplished after the composts are applied to soils. To test if N fertilization may enhance hydrocarbon decomposition, we investigated the effects of N application on hydrocarbon degradation in different-aged composts (1-, 2-, 3-, and 4-year-old composts, coded as 1Y, 2Y, 3Y, and 4Y composts, respectively) through a pot experiment planted with white spruce (Picea glauca [Moench] Voss) seedlings. The percentage degradation of total petroleum hydrocarbon (TPH, C11 to C40) in the composts without N fertilization was correlated to initial NH4+ concentrations (R = 0.99, P<0.001). The percentage degradation of TPH was highest in the 3Y compost (41.1%) that had an initial level of 325.3 mg NH4+-N kg-1 and the lowest in the 1Y compost (9.3%) that had an initial level of 8.3 mg NH4+-N kg-1. The degradation of TPH was enhanced by N fertilization in the 1Y (from 9.3 to 15.3%) and 4Y composts (from 14.3 to 22.6%) that had low initial NH4+ concentrations. Our results show that application of NH4+-based fertilizers may enhance the degradation of TPH when initial NH4+ concentrations in the compost are low. [ABSTRACT FROM AUTHOR]