Use of soil nonexchangeable potassium by paddy rice with clay structural changes under long-term fertilizer management

To prove the hypothesis that paddy rice utilizes soil nonexchangeable potassium (neK) and causes associated structural changes in clay minerals, K status and clay mineralogy of 22 surface soils from three paddy fields under long-term fertilizer management for 51–93 years were investigated. Soil neK content was determined as the difference between 1 mol L⁻¹ hot HNO₃ extractable K and 1 mol L⁻¹ ammonium acetate exchangeable K. Clay mineralogy was identified by X-ray diffraction (XRD). The radiocesium interception potential (RIP), an index of frayed edge sites in the interlayer sites of 2:1 type clay minerals, was also determined. The neK contents under the -K and NPK treatments were considerably lower than those under the unfertilized treatment in all the fields, indicating the exploitation of soil neK by rice. XRD analysis of the clay samples revealed 7% shift from the 1.0 peak to 1.4 nm one under the -K treatment compared with the unfertilized one, and the amounts of neK were negatively correlated with those of RIP (p < .01), suggesting the expansion of interlayer spaces of the 2:1 type phyllosilicates such as mica due to the release of neK. In addition, the neK content positively correlated with K balance of the long-term experiments (p < .05). The differences of neK between unfertilized K and -K treatments corresponded to 22–157 kg K ha⁻¹, or 0.42–1.68 kg K ha⁻¹ year⁻¹. In conclusion, utilization of considerable amount of soil neK under K depleted conditions should be considered to establish sustainable K management for paddy rice.     

Dual inoculation of peanut with Glomus sp. and Bradyrhizobium sp. enhanced the symbiotic nitrogen fixation as assessed by 15N-Technique

Abstract

The response of peanut (Arachis hypogaea L.) to inoculation with vesicular-arbuscular mycorrhizal (VAM) fungi (Glomus etunicatum) and Bradyrhizobiurn sp. was studied in pots by the acetylene reduction activity (ARA) and ‘A-value’ methods. The soil used was a Light-coloured Andosol and the treatments consisted of the inoculation of VAM fungi only, inoculation of Bradyrhizobium only, dual inoculation of VAM fungi and Bradyrhizobium and control, under non-sterilized and sterilized soil conditions.

In the non-sterilized soil the ARA and nitrogen fixation determined by the ‘A-value’ method increased significantly only by dual inoculation of VAM fungi and Bradyrhizobium at 100 days after planting (DAP), but no significant difference was observed at 70 DAP. In the case of dual inoculation, 75% of the nitrogen of the plant was derived from fixation whereas the plants inoculated only with Bradyrhizobium derived 68% of their nitrogen from fixation and the control plants, 64%. Amount of P in plant increased significantly only by dual inoculation with VAM fungi and Bradyrhizobium.

In the sterilized soil a highly significant increase in the ARA was observed of the dual inoculation at all the sampling times. Nitrogen fixation determined by the A-value technique and N and P contents in plant also increased significantly by dual inoculation. Results obtained by the A-value method showed that plants with dual inoculation derived 68% of their nitrogen from fixation while the plants inoculated only with Bradyrhizobium, 38%.

From our this study we conclude that nitrogen fixation as well as N and P contents in peanut increased significantly only by dual inoculation with VAM fungi and Bradyrhizobium.     

The hypocholesterolemic activity of transgenic rice seed accumulating lactostatin, a bioactive peptide derived from bovine milk β-lactoglobulin

Lactostatin is a novel pentapeptide (IIAEK) derived from bovine milk β-lactoglobulin with greater hypocholesterolemic activity than β-sitosterol, the drug commonly used to treat hypercholesterolemia. We developed transgenic rice expressing lactostatin as a fusion protein with seed storage protein (SSP) glutelins under the control of three different endosperm-specific promoters. Lactostatin accumulated in transgenic rice seed at approximately 1.6 mg/g seeds (dry seeds) without any apparent influence on seed traits such as endogenous SSP expression levels or alterations in the intracellular structures of endosperm cells. Short-term (three day) oral administration of the glutelin fraction containing lactostatin (namely three times of 300 mg/kg body weight/day) extracted from transgenic rice seeds resulted in hypocholesterolemic activity in rats; namely, the serum low-density-lipoprotein (LDL) cholesterol level was significantly reduced accompanied by a significant increase in beneficial serum high-density-lipoprotein (HDL) cholesterol.     

Fine Particle Dry Deposition onto a Cropland — a Trial to Estimate Deposition Velocity

The dry deposition velocity of fine particles is usually on the order of several tenths of cm s^?1, and accordingly, the concentration gradient of particles above the surface is very small. This makes the application of the gradient method to the determination of the particle deposition velocity very difficult. This study is a trial to find a way around this difficulty. The idea is to evaluate the thickness of the molecular diffusion layer, zb by simultaneously measuring the concentration gradient of gaseous species such as SO₂ ; zb is obtained by combining the turbulent and molecular transport equations for the gas. Then the particle deposition velocity is estimated on the basis of zb and the Brownian diffusion coefficient with an assumption that zb is equal to the thickness of the Brownian diffusion layer. By applying this method to the data collected in a field observation, the velocity of deposition onto a cropland was estimated for submicron particles.     

Measurement of Indoor Sulfur Dioxide Emission from Coal–Biomass Briquettes

The coal–biomass briquette is an alternative fuel that replaces low-grade coal. It is expected that the use of coal–biomass briquettes will effectively reduce the indoor concentration of sulfur dioxide (SO₂) emitted during raw coal combustion. In this study, indoor concentrations of SO₂ emitted from combustion of either coal–biomass briquettes or low-grade coal in households in Nanchuan, which is in the rural area of Chongqing City, China, were measured. The acidic gases were collected using passive samplers, and the samplers were taken to the laboratory for extraction and measurement. The SO₂ concentrations resulting from the use of coal–biomass briquettes were clearly reduced compared with those resulting from the use of low-grade coal. The concentrations of SO₂ to which the inhabitants (housewives) of the houses were exposed were also measured, and were found to be less with coal–biomass briquettes. Although with coal–biomass briquettes exposure concentrations still exceeded the World Health Organization guideline for SO₂ (125 μ g m^?3), indoor air pollution and adverse effects on human health caused by SO₂ could be decreased by substituting coal–biomass briquettes for low-grade coal as a domestic fuel.     

Bioremoval of Surfactant from Laundry Wastewater in Optimized Condition by Anoxic Reactors

Effects of ethanol and nitrate on linear alkyl benzene sulfonate (LAS) degradation were investigated using central composite design. At experimental design, removal of 99.9% was observed in batch reactors (1 L) with 9.8 to 41.2 mg L^?1 of LAS. The batch reactors were kept under agitation at 120 rpm and 30 °C. Ethanol (co-substrate) and nitrate (electron acceptor) were statistically significant factors (p?<?0.05) in surfactant removal. Optimal values were 97.5 and 88 mg L^?1 for ethanol and nitrate, respectively. LAS removal was kinetically investigated by varying surfactant concentration while using optimal values. Batch I (27 mg L^?1 LAS) exhibited greater degradation rate (K^LAS) (0.054 h^?1) in the presence of ethanol and nitrate. Nonetheless, in Batch II (60 mg L^?1 LAS), the K^LAS values decreased in those reactors probably due to inhibition by excess substrate for same concentrations of nitrate and ethanol added in reactors. As LAS concentration increased, the dominance of bacterial populations also increased, whereas diversity index decreased from 2.8 (inoculum) to 2.4 and 2.5 for reactors with both added nitrate and ethanol and those with only added ethanol, respectively. Probably, a selection of microbial populations occurred in relation to LAS concentration. The nitrate and ethanol, at able concentration, made it possible the induction of denitrifying microrganisms foward to LAS removal.     

Automated analysis of fine‐root dynamics using a series of digital images

Information related to the growth of fine roots is important for understanding C allocation in trees and the mechanisms of C cycling in ecosystems. Observations using a camera or scanner embedded in the soil enabled us to obtain continuous images of fine‐root‐growth dynamics. However, these methods are still labor‐intensive because the image analysis has to be conducted manually. We developed an automated method for tracking movement or elongation of fine roots using a sequence of scanner images. We also show how data obtained with these methods can be used for calculating fine‐root behavior. Two A4‐size scanners were buried in a mixed forest in Japan and images were taken continuously from within the soil. We preprocessed these images by extracting the fine‐root area from the images and developed an automated calculation plug‐in we named A‐root for tracking growth movement of the tips of fine roots. A‐root and manual‐tracking results were compared using the same images. The results show the A‐root and manual‐tracking methods yielded similar levels of accuracy. The average growth rate of 17 fine roots tracked using the program was 0.16 mm h^–1. The observation of the direction of growth in fine roots showed the direction may be influenced by the original root's growth where the fine roots branched, distribution of soil particles, other roots, and the force of gravity. The A‐root analysis also suggested there may be an interaction between speed of growth and changes in direction of growing fine roots.     

Estimation of Changes in Available Soil Phosphate under Submerged Conditions Associated with Temperature during the Tillering Stage of Rice Plant in the Cool Climate Region of Japan

This study was performed to investigate changes in available soil phosphate associated with temperature under submerged conditions and to explore the possibility for estimating those under submerged conditions during the early growth (tillering) stage of rice plants (Oryza sativa L.). An incubation experiment was conducted under submerged conditions at three temperatures (10°C, 17.5°C and 25°C) using paddy soils collected over a widespread area in Japan. In most soils, significant positive correlations were observed between available soil phosphate and cumulative temperature to 650°C, which corresponded to the tillering stage in Japan. Relationships between the regression formulae of the available phosphate against cumulative temperature to 650°C and soil chemical properties measured in air-dried soil were investigated. The results indicate that the available phosphate of paddy soil against cumulative temperature during tillering stage under submerged conditions can be estimated from the results of air-dried soil analyses which can be conducted before a crop season.     

Ferric iron transformation in soils with rotation of irrigated rice-upland crops and effect on soil tillage properties

We examined the relationship between the form of iron and the tillability (defined as the degree of ease of pulverizing a soil into small clods) of soils in upland fields that had been converted from paddy fields. The amount of iron (Fe.e) extractable with acetate buffer (pH 3.0) decreased from 0.959 g kg_-1 in a field that has been continuously used as a paddy field to 0.104 g kg-I in a field that had been converted into an upland field for a period of 5 y. There was no significant change in the free iron oxide content under upland conditions. These results indicate that ferric iron oxides are gradually crystallized to less reactive forms after the conversion of a paddy field into upland conditions. Both soil tillability (represented by the mean clod diameter after tillage) and the stability of the soil microstructure (represented by the sediment volume) also increased during the 3-y period after conversion and then remained constant for the last 2-y period of the study. On the basis of these results, two mechanisms for the improvement of soil tillability can be proposed as follows: crystallization of ferric iron oxides increased their resistance to microbiological reduction and due to this stabilization the iron oxides as a cementing reagent that contributed to the soil microstructure, which in turn affected the soil tillability. During the first year after drainage, however, there was no significant correlation between the soil tillability and amount of Fe_ac, presumably because the soil was not sufficiently dry in the first year after conversion, and the iron oxides did not affect appreciably the soil structure.     

Itokawa dust particles: a direct link between S-type asteroids and ordinary chondrites

The Hayabusa spacecraft successfully recovered dust particles from the surface of near-Earth asteroid 25143 Itokawa. Synchrotron-radiation x-ray diffraction and transmission and scanning electron microscope analyses indicate that the mineralogy and mineral chemistry of the Itokawa dust particles are identical to those of thermally metamorphosed LL chondrites, consistent with spectroscopic observations made from Earth and by the Hayabusa spacecraft. Our results directly demonstrate that ordinary chondrites, the most abundant meteorites found on Earth, come from S-type asteroids. Mineral chemistry indicates that the majority of regolith surface particles suffered long-term thermal annealing and subsequent impact shock, suggesting that Itokawa is an asteroid made of reassembled pieces of the interior portions of a once larger asteroid.