Search

Biochar (BC), charcoal produced through the pyrolysis of biomass, is reported to adsorb dissolved nitrate-nitrogen (NO3-N). The NO3-N adsorption properties of BC differ depending on the feedstock and the pyrolysis conditions, and the influences have not been systematically clarified. Therefore, we evaluated the dependence of feedstock and pyrolysis temperature on the NO3-N adsorption properties of BC. Wood chips [Japanese cedar [Cryptomeria japonica] (CE) and Japanese cypress [Chamaecyparis obtusa] (CY)], moso bamboo [Phyllostachys edulis] chips (MB), rice [Oryza sativa] husks (RH), sugarcane [Saccharum officinarum] bagasse (SB), poultry manure (PM) and domestic wastewater sludge (WS) were air-dried and heated in a batch-type carbonization furnace at pyrolysis temperatures of 400, 600 and 800°C, with a hold time of 2 h. Among the BC produced from each feedstock, the one produced at 800°C had the greatest NO3-N adsorption. The NO3-N adsorption by BC produced from wood-based biomass at 800°C was sig...

Biochar (BC) is a promising soil amendment that can enhance water retention and plant-available water capacity while mitigating CO2 emissions. We investigated the effect of sugarcane bagasse–derived BC on the water retention properties of a calcaric clay soil amended with 3% (wt/wt) BC produced at three pyrolysis temperatures (400°C, 600°C, and 800°C). For BC pyrolyzed at 800°C (BC800), water retention curves of soil amended at 1%, 5%, and 10% (wt/wt) were also measured. Water retention curves were measured immediately after amending soil with BC (all types and rates) and after a 180-day incubation period for soils amended with 3% BC. The hydrophobicity of BC pyrolyzed at 400°C (B400) was the highest of the three temperatures tested, resulting in the lowest water retained in soil amended with BC400, but only for measurements done before incubation. During incubation, the hydrophobicity of B400 decreased as the aliphatic compounds became exhausted by oxidation of the BC surfaces. The available water capacity of the clay soil increased significantly by more than 60% when amended with BC at rates greater than of 3% wt/wt (P < 0.05).

In this article we have assessed the expected impacts of future climate changes on rainfall erosivity, a rainfall factor associated with soil erosion, of farmlands in Japan. The assessment compared values of R -factors for two future periods with values for a near past period. The R -factor is defined as the mean annual sum of individual storm erosion index values EI 30 , where E is the total energy for a storm and I 30 is the maximum 30-min intensity. The R -values at 1036 meteorological stations for three periods (1981–2000, 2031–2050 and 2081–2100) were calculated with a model that estimates monthly EI 30 values based on daily precipitation data. Subsequently, R -values for farmland areas were obtained. The daily precipitation data were provided from the regional climate model RCM20, which simulates climate change based on the SRES A2 scenario. The model to estimate monthly EI 30 values performed well with a coefficient of determination in excess of 0.5 for 97% of the 1036 stations when parameters of the model were optimized. Therefore, the rainfall erosivity model can be used to accurately estimate the R -factors. Calculations of relative changes in R -values for the two future periods compared to the near past period indicated that rainfall erosivity will increase in most farmland areas due to climate change. The R -values of farmland areas for the two future periods are expected to increase an average of more than 20% when compared to the near past. Additionally, changes in rainfall erosivity during each of the future periods are expected to vary with different seasonal and spatial patterns. The changes in erosivity appear to be attributed mainly to changes in precipitation intensity as well as amount of precipitation. Therefore, these results suggest the scenario of climate changes occurring in the future up to 2100 will increase soil erosion of farmlands in Japan at an average rate of increase greater than 20% based on just the effects of the rainfall erosivity factor.

Summary The incorporation of biochar (BC) into agricultural soil changes the soil's physical properties, which leads to changes in the soil's hydraulic properties, such as water retention and permeability, and alters the soil moisture environment in agricultural fields. To elucidate the effects of the incorporation of BC on the soil moisture environment, measurements of the soil water in biochar-amended agricultural fields are needed. Time domain reflectometry (TDR) is a widely used and established technique for the continuous measurement of the soil water content (SWC) in agricultural fields. However, TDR measurements are affected by the conductivity of soils. Biochar formed at higher pyrolysis temperatures is known to be very conductive. Therefore, we investigated the influence of the incorporation of BC on TDR-based SWC measurements. We examined calcaric dark red soil and the BC produced by pyrolysis of sugarcane bagasse at 400, 600 and 800°C. The apparent relative permittivity (ea) of the BC (800°C)-amended soil was greater than that of the non-amended soil at a given water content, whereas the ea values of the soils amended with the BC (400°C) and BC (600°C) were the same as that of the non-amended soil at a given water content. We concluded that when a calibration curve obtained from a non-amended soil is used, TDR-based measurements tend to over-estimate the SWC containing the BC formed at higher pyrolysis temperatures because of conductive and dielectric losses. Therefore, the use of the real component () of the soil's complex relative permittivity instead of ea is effective when making TDR-based water content measurements of soils that contain BC formed at higher pyrolysis temperatures.

This study evaluates a centipede grass field for reduction of reddish fine sediment runoff from agricultural areas in Okinawa, Japan. Grass fields are expected to provide an additional countermeasure for the reduction of sediment runoff. However, the practical effectiveness of grass fields has not been examined under sediment runoff conditions in Okinawa. A numerical model simulating sediment transport in grass was used to analyze the effect of a centipede grass field on sediment runoff. The model was verified using data obtained from flume experiments. The analysis showed that the efficiency of sediment removal decreased with an increase in the inflow rate into the field. However, a grass field with a higher inflow rate removed more sediment and had a greater water treatment capacity under unsubmerged flow conditions. Therefore, the analysis showed that centipede grass fields with inflow control at a higher inflow rate under unsubmerged flow conditions are more effective as an additional countermeasure against reddish fine sediment runoff from agricultural areas.

Reddish sediment runoff from agricultural fields results in coastal environmental problems in Okinawa, Japan. Recent studies have demonstrated the effectiveness of strips of centipede grass (Eremochloa ophiuroides (Munro) Hack.), a perennial turf grass, in reducing the sediment loads from farmlands. However, sufficient information has not been provided to determine the appropriate strip specifications in the grass strip design. This study evaluated centipede grass strips for reduction of reddish sediment runoff from farmlands in Okinawa, Japan. A numerical model simulating the reddish sediment transport in the grass strip was constructed to determine the sediment removal efficiency of the strip. The model was verified using data obtained from field plot experiments with the grass strips under natural conditions. The sensitivity analysis of the model showed that the length of the grass strip (i.e. the dimension of the strip in the direction of flow) and unit inflow discharge have a great effect on sediment removal efficiency. The sediment removal efficiency obtained from the model simulation increased with the length of the strip and the increment of the efficiency decreased with the length of the strip. Therefore, these results indicate that the effective and efficient length of a centipede grass strip is 3 m for the reduction of reddish sediment loads under typical farmland conditions in Okinawa.

TDR (Time-domain reflectometry) is an advanced method for monitoring the water content in fields. TDR measurements can provide accurate information about vegetation effects on both spatial and temporal soil water distribution. The objective of this study was to examine the effects of vegetation conditions on the distribution of the soil water content. Soil water content was measured to express the spatial distribution in the surface layer (0-0.2 m) in grass, corn, and non-planted fields. Additionally, using the TDR method with multiple probes with different lengths, the measurements were conducted on a temporal basis at 4 depths (0--0.1, 0.1-0.2, 0.2-0.3 and 0.3-0.5 m) to determine the soil-water content profiles in the 3 fields. A significantly higher water content in both the grass and cornfields was found, compared to the non-planted field. Moreover, in the cornfield, we observed that microtopographic features significantly affected the spatial water distribution. The lower the soil water content, the higher the coefficient of variation of the soil moisture content. These results indicated that the effects of the vegetation conditions on the soil water distribution in the fields were significant. From the observation of the temporal soil water profiles in the 3 fields, it was found that soil management, i.e. tillage or no-tillage, was a major factor affecting the profiles.

A soil loss estimation of crop fields on a local scale was carried out using the Universal Soil Loss Equation (USLE) and Geographic Information System (GIS) tools. The study site covering 3,009 ha in Kanto, Japan, comprised 11,544 crop fields. The USLE provided an estimate of average annual soil loss based on the following factors: rainfall and runoff (R); soil erodibility (K); topography (LS); crop and management (C); and support practice (P). The dataset of the factors for each field was derived from available land information and field surveys. The K factor was estimated from the sediment yield in the small catchment area. The slope length and steepness of each field, required to compute the LS factor, were derived from field boundary information and a digital elevation model (DEM) constructed using GIS tools. The estimated soil loss rate under the current cropping conditions was found to range from 0.2 to 70.6 t ha - 1 y - 1 , averaging 10.5 t ha - 1 y - 1 . A distribution map of the rate indicated the fields where conservation measures should be taken. The study suggested that combining the USLE with GIS tools was likely to be useful for estimating soil loss on a local scale for soil conservation planning.

Application of biochar has been suggested to improve water- and fertilizer-retaining capacity of agricultural soil. The objective of this study was to evaluate the effects of bagasse charcoal (sugarcane [ L.] bagasse-derived biochar) on nitrate (NO) leaching from Shimajiri Maji soil, which has low water- and fertilizer-retaining capacity. The nitrate adsorption properties of bagasse charcoal formed at five pyrolysis temperatures (400-800° C) were investigated to select the most suitable bagasse charcoal for NO adsorption. Nitrate was able to adsorb onto the bagasse charcoal formed at pyrolysis temperatures of 700 to 800° C. Nitrate adsorption by bagasse charcoal (formed at 800° C) that passed through a 2-mm sieve was in a state of nonequilibrium even at 20 h after the addition of 20 mg N L KNO solution. Measurements suggested that the saturated and unsaturated hydraulic conductivity of bagasse charcoal (800° C)-amended soils are affected by changes in soil tortuosity and porosity and the presence of meso- and micropores in the bagasse charcoal, which did not contribute to soil water transfer. In NO leaching studies using bagasse charcoal (800° C)-amended soils with different charcoal contents (0-10% [w/w]), the maximum concentration of NO in effluents from bagasse charcoal-amended soil columns was approximately 5% less than that from a nonamended soil column because of NO adsorption by bagasse charcoal (800° C). We conclude that application of bagasse charcoal (800°C) to the soil will increase the residence time of NO in the root zone of crops and provide greater opportunity for crops to absorb NO.

Reddish sediment runoff from land areas during rainfall causes environmental problems in coastal areas of the Okinawa region, Japan. Sediment delivered to the coastal areas causes water pollution, sedimentation and degrades the coastal ecosystems and fisheries resources. Agricultural fields are a major source of sediment runoff in the region (Yoshinaga & Onaga, 1993; Minami et al., 2002). Nakasonoe et al. (1998) reported that sediment from agricultural fields accounts for 70% of the total sediment runoff in the region. Countermeasures for runoff in agricultural fields are promoted as an important issue in the Okinawa region. Countermeasures so far proposed include terrace work, drainage canals, sediment ponds, grass strips, cover cropping, mulch farming, contour farming, deep tillage, crop rotation and green manure (Hudson, 1995; Morgan, 1995). The grass strip countermeasure involves installing grass bands at the downstream end of an agricultural field to reduce the amount of non-point source pollutants, such as sediment and nutrients from an agricultural field into the stream (Dillaha et al., 1989). Grass strips are currently installed by prefectural governments assisted by the Ministry of Agriculture, Forestry and Fisheries as public work projects for water conservation, and also as a measure to help conserve agricultural land, water and the environment in rural areas. Grass strips can also be installed by farmers themselves as one of agricultural activities. There are various factors affecting how effectively grass strips reduce sediment runoff, such as flow rate of inflowing water, sediment properties, slope conditions and features of the grass (Haan et al., 1994). When installing grass strips as a countermeasure for sediment runoff, various conditions must be taken into consideration. In designing grass strips, it is necessary to know the quantitative relationships between the various factors influencing grass strips and their effects on reduction of sediment runoff, and to determine appropriate and reasonable parameters for installing grass strips. In previous studies, Sugawara et al. (2001), Osawa et al. (2005) and Shiono et al. (2005) conducted field experiments in Ishigaki Island and the northern part of the Okinawa Main Island, and reported their results on the effects of grass strips for reducing reddish sediment runoff. Shiono et al. (2007) also reported the influence that the length of grass strips in the direction of flow and particle sizes of sediment flowing into grass strips have on the ability of grass strips to reduce reddish sediment runoff. These results were obtained from field

We report a case of intrahepatic splenosis in a 55-year-old man. The lesion in the right lobe of the liver appeared similar to hemangioma on dynamic CT and MRI, but was compatible with normal splenic tissue. On T2WI after the injection of superparamagnetic iron oxide (SPIO), the lesion showed a loss of signal intensity but remained slightly hyperintense relative to the hypointense liver parenchyma. Reports on the radiographic features of intrahepatic splenosis are rare, and a combination of the findings of CT, MRI (including SPIO injection), and angiography might lead to the diagnosis of splenosis.

FUNCTIONAL magnetic resonance imaging (fMRI) at 1.5 T using a gradient echo echo-planar sequence was employed to identify brain regions activated during the performance of a mental writing task using phonograms. Four regions were activated in all six subjects ; the region surrounding the left intraparietal sulcus, the region surrounding the middle part of the left precentral sulcus and the posterior part of the left superior frontal sulcus, the region surrounding the right intraparietal sulcus, and the region surrounding either or both of the left and right cingulate sulci. The left intraparietal region was usually the most extensively activated. The results suggest that these four regions particularly the left intraparietal region, are essential in writing with phonograms. Since the left hemisphere was more extensively activated than the right, fMRI during the mental writing task is a good candidate for determining non-invasively which hemisphere is dominant for language.

Reddish fine sediment runoff from upland fields has been one of the causes of coastal environmental pollution in Okinawa, Japan. Planting grass strips is a well-known measure to reduce runoff of non-point-source pollutants from agricultural fields. In this study, we investigated the performance of a centipede grass (Eremochloa ophiuroides (Munro) Hack.) strip for reducing sediment runoff from an upland field in Okinawa, focusing on strip length and sediment aggregate size as factors affecting performance. Field experiments were conducted in field plots with a 4.0-m by 31.5-m bare source area on a Kunigami-Maji soil using three strip lengths (0.5, 1.5 and 3.0 m) under natural conditions. The sediment removal efficiencies were 24% for the 0.5-m strip, 36 to 54% for the 1.5-m strip and 73% for the 3.0-m strip. The strips trapped well the sediment aggregates larger than 0.02 mm in diameter, regardless of strip length. The longer strip trapped more aggregates of the 0.002-0.02-mm size class, which were dominant in the eroded sediment runoff from the plots. The strips poorly trapped aggregates smaller than 0.002 mm. The sediment trapping resulted primarily from deposition of sediment due to slowdown of surface flow.