We investigated the humic substances of earth worm casts in different vegetation areas (Shiia siebaldii Makino, Pleioblastus linearis Nakai, Pinus luchuensis Mayr and Ardisia quinquegona Blume) in the Okinawa Islands. The study site was located at Yona University Forest, University of the Ryukyu Islands (26°49'N, 128°5'E). Quartz, kaolinite and illite were included in earthworm casts ; it was suggested that earthworms eat them with the soil when they eat fallen leaves. Total carbon contents showed a significant difference among the fallen leaves, earthworm casts and soils in four vegetation areas. There was no significant difference between the contents of humic acid and fulvic acid in earthworm casts and fallen leaves. Since the amount of humic substances (humic and fulvic acids) in earthworm casts was higher than that in soils, it was suggested that the earthworm casts had accumulated humic substances. Humic acid in earthworm casts and fallen leaves indicated Rp type in all four vegetation areas. It is possible that the humic acid of earthworm casts and fallen leaves was similar in character. IR spectra indicated that humic acids from earthworm casts contained a lower proportion of aromatic components and a larger proportion of aliphatic and polysaccharide components.

View full abstract

We attempted to clarify existing forms of silicon in cells of rice plant spikelets before heading. Plants were grown with and without silicon addition from the panicle stage, and spikelets were harvested 10 and 5 days before heading and on the day of heading. The spikelets homogenized in cold water were filtered by nylon mesh, and the filtrate was centrifuged first at 600×g for 10min, and then at 10,000×g for 30min. The residue on the nylon mesh was referred to as F1 fraction, the precipitate from centrifugation at 600×g was F2, the precipitate from 10,000×g as F3 and its supernatant as F4. The main organ of F1 was the cell wall, while that of F2 was the nucleus. After freeze drying, the weight of each fraction and its silicon content were determined ; UV and IR spectra of higher molecular nucleic acids (HMNA) from the nucleus, and the IR spectra of residue extracted the HMNA were recorded. Ten days before heading, there was no significant difference in weight of any fraction outside the F2 fraction among the treatments, but it was greater in the higher silicon spikelets at each day than in the lower ones. The level of silicon in the F2 fraction in every treatment was the same as, or more than, that in the cell wall, and was higher than in other fractions. The level of silicon in the HMNA was slightly more in the higher compared with lower silicon level, while that in the extracted residue was lower in low silicon spikelets, indicating that silicon in the nucleus fraction contains more in the HMNA than in the extracted residue. A bathocromic effect in UV spectra, namely the shifting of the absorption maximum to a longer wavelength, and absorbance bands at 1208, 1137 and 810cm^<-1> in the IR spectra, suggesting the existence of Si-OCH_3, were observed in the HMNA from higher silicon spikelets. While absorbance bands at 790 and 470cm^<-1> in the IR spectra were found in the residue extracted from the HMNA from F2 fraction with silicon supply, there was no peak at 1090cm^<-1> indicating silica gel. These findings suggest that silicon may play an important role in the formation of the nucleus through association with nucleic acid, and as a result, a decrease in the number of spikelets occurs through silicon deficiency in rice plants.

View full abstract

We investigated the degrees of inhibition and the mechanisms by which soil ammonia oxidation is inhibited by a fungicide, chlorothalonil (tetrachloroisophthalonitrile). Chlorothalonil, thiram, triflumizole, tolclofos-methyl, iprodione, flutolanil, hexaconazole, isoprothiolane, benomyl, and metalaxyl (50mg kg^<-1>) were applied to the soil (light-colored andosol) in combination with ammonium sulfate (200mg N kg&<-1>). Chlorothalonil and thiram strongly inhibited soil ammonia oxidation among the fungicides tested. The duration of the inhibition induced by chlorothalonil was longer than that by a nitrification inhibitor, dicyandiamide. The activity of the inhibition of soil ammonia oxidation by chlorothalonil depended on its application rate. The inhibitory activity of 4-hydroxy-2, 5, 6-trichloroisophthalonitrile (TPN-OH), a major metabolite of chlorothalonil in upland soils, was lower than that of chlorothalonil and dicyandiamide. The activity of tetrachloroterephthalonitrile (TTPN), an isomer of chlorothalonil, was lower than that of chlorothalonil. Isophthalonitrile (IPN), terephthalonitrile (TePN), phthalonitrile (PN), benzonitrile (BN), and 1, 2, 3, 5-tetrachlorobenzene (TCB) did not inhibit soil ammonia oxidation. Chlorothalonil (100mg kg^<-1>) and chloramphenicol (500mg kg^<-1>) were added to soil in which ammonium-oxidizing bacteria had been accumulated by repeated application of ammonium sulfate. Both chemicals inhibited soil ammonia oxidation. The number of the ammonium-oxidizing bacteria in the chlorothalonil-treated soil decreased from 10^4g^<-1> to 10^2g^<-1> or less for 14 days, while those in the chloramphenicol-treated soil maintained 10^4g^<-1> for 21 days. These results suggest that chlorothalonil inhibits soil ammonia oxidation by acting on ammonium-oxidizing bacteria lethally, and that both nitrile and chlorine in the structure of chlorothalonil are indispensable to its inhibitory action and that their arrangement in the molecules significantly affects chlorothalonil's activity.

View full abstract

1) The loads of copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb) from farmyard manure (FYM) in grasslands and forage cropping areas in each region were estimated to be in the range of 38-980, 330-4400, 0.51-9.4, and 5.6-61g ha^<-1> yr^<-1>, respectively. There were 11- to 26-fold differences among regions. 2) The loads of Cu, Zn, Cd and Pb from fresh feces and slurry in grasslands and forage cropping areas in each region were estimated to be in the range of 95-630, 380-2900, 1.0-6.4, and 5.7-38g ha^<-1> yr^<-1>, respectively. There were 6- to 8-fold differences among regions. 3) The uptake of Cu, Zn, Cd and Pb by grass and forage crops in each region were estimated to be in the range of 26-81, 150-320, 0.26-2.2, and 1.7-6.2g ha^<-1> yr^<-1>, respectively. There were 2- to 9-fold differences among regions. 4) In Japan's agricultural lands, the total amounts of Cu, Zn, Cd and Pb derived from FYM, fresh feces and slurry exceeded their uptake by crops. These elements were densely loaded in grasslands and forage cropping areas that received excessive amounts of FYM, fresh feces and slurry. 5) The loads of Cu, Zn, Cd and Pb from FYM, fresh feces and slurry in grasslands and forage cropping areas were found to be greater in regions outside of Hokkaido due to the difference in stocking rates.

View full abstract

Among the investigated soybean cultivars, Japanese cultivars that have possibility for the highest productivity of isoflavone were Hougyoku and Wasegurodaizu, followed by Akisirome and Fukuyutaka. Because the isoflavone content of soybean seeds harvested in summer was lower than of those harvested in autumn, it was decided that the autumn cropping was superior to the summer cropping for the period of cultivation. From the above, the cultivation form constructed from a late sowing after mid-July and a harvesting after mid-November was understood to be most suitable for the cultivation of soybeans with high isoflavone content in the seeds.

View full abstract

The temperature of the filling of soybean seeds had a drastic influence on the isoflavone content in the seeds. The content of isoflavone was the highest at 20℃, followed by 25℃, and the lowest at 30℃. Moreover, the 100 grains weight of soybeans grown at 20℃ and 25℃ was large in comparison with that of the soybeans grown at 30℃. From the above, a temperature of 20℃ was concluded to be the environment to increase most greatly the isoflavone content in soybean seeds among these conditions. In all the soybean cultivars used in this experiment, the main isoflavones accumulated in soybean seeds were malonyldaidzin and malonylgenistin, and the content of glucosides and malonylglucosides increased with the filling of the seeds. Therefore, it became clear that the main storage form of isoflavone in the soybean seeds was malonylglucosides. In the soybean cultivation of Fukuoka Prefecture, the present seeding period is mid-to late-July, and the maturity period is early-to mid-November. To increase the content of isoflavone in seeds, the seeding period must be reexamined to keep the temperature of the maturity period at less than 20℃. For that achievement, it is necessary to delay the seeding period from early-to mid-August so that the maturity period may be late-November. As a result of that, it is estimated that the isoflavone synthesis ability of soybean seed will be brought out to the full and that the soybean seeds with a high content of isoflavone can be produced.

View full abstract

It was shown in the watercourse that running water is stagnant for 4 to 5h in each stage of the flood and ebb tides in a mangrove forest. The water samples were collected at the points of 0, 45, 105, 175, 245, 300m from the lower watercourse during the each stagnant stage. The highest value for the water corresponded to 0.25 molarity of NaCl at 45m, the stage of flood tide. The other points were about 0.1M NaCl. Six surface sediments were collected along the watercourse in the mangrove forest. The sediment samples were prepared to leave untreated or treat decomposing organic matter with 6% H_2O_2. The fine particles were collected by repletion of desalting treatment from each of the sediments without and with organic matter. Organic carbon contents and CEC values of the sediments without organic matter registered 4.4-7.3g kg^<-1> and 3.5-5.0cmol_c kg^<-1>, respectively. Both were lower than those with organic matter, which were 42.9-70.9g kg^<-1> and 46.2-58.1cmol_c kg^<-1>, respectively. The fine particles without organic matter were finer and more numerous than those with it. The particle size was less than 60μm in both cases. The relationship between the movement of fine particles and the saline concentration indicated a tendency for the effect of 0.25M NaCl solution to be lower than 0.1M NaCl in the ratio of dispersion of fine particles, and the former sedimented more easily than the latter. In addition, the ratio of dispersion of fine particles without organic matter was less than 10% and that with was about 80% in 0.1M NaCl solution. Hence it was suggested that the fine particles with organic matter did not sediment easily in the low concentration of sea-water. Moreover, there was shown a tendency for higher content of particles in suspension to sediment more easily. Therefore, it was suggested that in mangrove forests the fine particles, including organic matter, floated and sedimented in the lower level of the watercourse, depending on the tidal current at each stage of the flood and ebb tides. They were then diffused and sedimented on the surface sediments in mangrove forests by the repletion of the turbulent waves.

View full abstract

We studied the effect of hairy vetch planting on changes in soil physical properties and soybean early growth in a heavy clayey soil field. Hairy vetch (Vicia villosa Roth) was planted in an upland field converted from a paddy field from October, 2004 to June, 2005. Then soybean (Glycine max [L.] Merr.) seeds were sown in the field after cutting and incorporating of the hairy vetch plant. Hairy vetch grew vigorously and its roots elongated into the subsoil (about 40cm in depth). In the surface layer, the soil aggregate structure was developed by hairy vetch root growth compared with the control. There were large soil cracks from the surface to deep layer (until 50cm in depth) where the hairy vetch root elongated along with the soil cracks. In hairy vetch treatment, the water retention capacity of the soil was increased especially at surface layer by forming micro-pores or interaggregate pores. The rate of the soil drying after precipitation was faster than that in the control caused by the high water permeability of the soil with large soil cracks and transpiration of the hairy vetch plant. At 30d after soybean seed sowing, the dry weight of each part of soybean in hairy vetch treatment was higher than that in the control. The root activity of N absorption and N_2 fixation activity of the nodules in hairy vetch treatment were higher than those in the control. Therefore, it is concluded that soybean early growth is promoted in hairy vetch treatment where the physical properties of the heavy clayey soil are improved by planting hairy vetch.

View full abstract

To elucidate the effect of the soil dioxin concentration on the dioxin concentration of wheat foliage (Triticum aestivum L.), we measured the dioxins and the titanium concentrations of wheat foliage grown in two soils with different dioxin concentrations (PCDDs+PCDFs+Co-PCBs concentration is 150000 (H plot) and 2700 (L plot) pg g^<-1>) and estimated the contribution ratio of the dioxins derived from the soils attached to the wheat foliage to the dioxin concentration of the wheat foliage. There were difference in the PCDDs (especially, 1, 3, 6, 8-TeCDD, 1, 3, 7, 9-TeCDD and OCDD) concentrations of the wheat foliage and the exposed part (leaf blade, leaf sheath and exposed stem) among two soils, and these PCDDs concentrations in the soil of H plot were much higher than that of L plot. However, those concentrations in the unexposed part (unexposed stem) of the two soils were comparable. The concentration ratios of wheat foliage to soil show the concentrations of congeners which existed in large amounts in the soil and had a relatively high volatility were high in the wheat foliage. It was estimated that almost all OCDD and OCDF in the wheat foliage grown in the H plot were derived from the soil attached to the wheat foliage. In contrast, the contribution ratios of the attached soil to the wheat foliage of TeCDDs were very low, in spite of high TeCDDs concentration in soils and wheat foliage. This suggested that the TeCDDs concentrations of wheat foliage were influenced by the slightly vaporized TeCDDs from the soil because the low chlorinated congeners have relatively high vapor pressures compared to high chlorinated congeners. These results show that the dioxin concentrations of soils had an influence on the concentrations of wheat foliage when soil dioxin concentrations were very high.

View full abstract

[in Japanese]

View full abstract