The mapping of elements around the penetration sites of Magnaporthe grisea on rice (Oryza sativa L.) leaf blade epidermis was done by cool stage installation variable-pressure scanning electron microscope (VP-SEM) and energy dispersive X-ray microanalysis (EDX) without any pretreatment. In the fifth leaf blade epidermis of a rice plant which was treated with silicon, 64 hours after injury, the silicon was visible in the epidermal cell knobs except for the guard cells and accessory cells. By that same time, inoculated conidia had sprouted and extended germ tubes, and hemispherical appressoria which were the penetration sites to leaf epidermis were formed at the tip of germ tubes and silicon had accumulated near the appressoria in high density. However, elements such as nitrogen, potassium, magnesium, calcium and chlorine were uniformly distributed in spite of the inoculation on epidermal cells. This is the first report which shows the behavior of silicon on rice leaf blade epidermis after Magnaporthe grisea penetration.

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If a crop has the ability to take up potassium (K) from the firmly held K minerals in a soil, silicate (SiO_2) (which is one of the major mineral constituents) is expected to be released from the soil and/or to be absorbed by the crop. To confirm our hypothesis we compared soil K status in a long-term field experiment that has been in operation since 1976 (Brown Andosol, SL) and the cumulative amounts of K uptake by crops during the past 24 years. 1) Potato showed severe K deficiency without K application and yielded poorly, while maize and sugar beet showed superior ability to take up K. These results showed that there were large differences in K uptake among crops (kidney bean, winter wheat, spring wheat, sugar beet, maize, soybean, potato and cabbage). 2) Insoluble forms of K were exploited in 0-plot, no-K plot and NPK plot. This suggested that crops utilized insoluble forms of K from the soil. 3) We observed a slight accumulation of the released SiO_2 only in 0-plot. But cumulative amounts of SiO_2 uptake by crops during the 24 years were much higher than the decrease amounts of the released SiO_2 in no-K plot and NPK plot. These results indicated that SiO_2 was released from the soil and taken up by the crops. 4) In no-K plot the cumulative amount of SiO_2 uptake by crops and the exploitation of insoluble forms of K were the highest, and in 0-plot they were the lowest. The cumulative amount of K uptake by crops in no-K plot was much higher than that in 0-plot. These results suggested that uptake of insoluble forms of K in the soil is related to solubilization of SiO_2. 5) We estimated the efficiency of K fertilizer in NPK plot to be about 80%. This suggested that approximately 500 kg K ha^-1 of K fertilizer may have leached away during 24 years.

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It is well known that some leguminous plants show phototropism resulting in leaf movement. We analyzed phototropism of soybean leaves in response to sulfur deficiency. No apparent sulfur deficiency symptoms were observed in soybean plants cultivated hydroponically under sulfur deficient conditions (S0) for 10 d as compared to the plants under the sulfur sufficient conditions (S1). However, chlorophyll contents, photosynthetic activities and contents of sulfur, nitrogen and calcium in S0 plants had deceased, as determined on the basis of fresh weight. Sulfate and homoglutathione were severely decreased in S0 plants. These results indicate that the 10-d-old S0 soybean plants were at the initial stage of sulfur deficiency. Leaflets of soybean plants moved in response to irradiation. Major types of the movement were elevation with central leaflets and rotation with right and left leaflets. Pulvinus was an acceptor of the light. Magnitudes of the leaflet movements in S0 plants were larger than those in S1 plants. Thus the leaflet movement in S0 plants resulted in paraheliotropism.

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The concentration of nitrogen and phosphorous in field water standing on soil in twenty-four pots was measured 1, 3, 5 and 7 d after the experiment was conducted. The experimental conditions were as follows: 1. Puddling treatment (Unpuddled or puddled), 2. Fertilizer application (No fertilizer, phosphate fertilizer or synthesized chemical fertilizer) and 3. Kinds of soils (Gley, Kuroboku, Yellow or Masa). Twenty cm of each type of air-dried soil was put into a pot (500cm^2). Fertilizer was incorporated to the plow layer. Water was poured gently until the water level reached 10cm above the soil. Water and the upper soil (10cm) were puddled together for 5min by using a mixing machine. Pots were set in a room controlled at 20℃. The experiment was carried out three times. The analysis of variance shows that the effective factor for nitrogen and phosphorous concentration is the interaction of puddling operation with fertilizer application. It seems that for the T-N and D-N concentration, the influence of fertilizer application is more significant than that of puddling operation, while the influence of puddling operation is more significant for the P-N, T-P, D-P and P-P concentration. The mean value of concentration in the puddled and fertilized pots measured after 7 d was 9.5 mg L^-1 for T-N and 0.74 mg L^-1 for T-P. These values were higher than the irrigation water quality standard, so it seems that it is necessary to continue to reduce runoff from paddy field, 7 d after puddling operation may not be enough time for the water to become purified.

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We measured methane emissions from three different types of paddy fields for two years (1997 and 1998) under identical water management, including midseason drainage. Effect of no-tillage rice (Oiyza sativa L.) cultivation on methane emission under rice straw application was investigated by comparison with tilled rice cultivation. The averaged values of cumulative methane emissions from tillage fields over a period of two years were observed to conform the following order: Kawatabi soil-Haplic Andosol (48.5g CH_4 m^-2) ≧ Furukawa sandy soil-Epi-gray Gley Lowland soil (45.7g CH4 m^-2) > Furukawa clayey soil-Mottled Gley Lowland soil (11.0g CH_4 m^-2). These soils correspond to Umbric Andosol, Areni-Gleyic Fluvisol and Humi-Gleyic Fluvisol according to the WRB (1998), respectively. This difference in methane emissions from three soils is thought to be due to differences in contents of electron acceptors dominated by free iron oxide rather than differences in water percolation rates. The averaged values of cumulative methane emissions from no-tillage fields were 15.7, 18.7 and 16.6 g CH_4 m^-2 in Kawatabi soil, Furukawa sandy soil and Furukawa clayey soil, respectively. No-tillage cultivation decreased methane emissions in Kawatabi soil and Furukawa sandy soil, but increased emissions in Furukawa clayey soil. Soil Eh at a depth of 5 cm was higher under no-tilled conditions than under tilled conditions in all three soils. The increase in methane emission rate observed for the Furukawa clayey soil can not be explained by changes in soil redox conditions. Rather it presumably represents the net result of lower methane production in soil and relatively high methane emission from the soil surface. The former is due to the high concentration of electron acceptors in the soil, and the latter is the result of methane production or suppression of methane oxidation on the soil surface where rice straw was applied. In this study, no-tillage rice cultivation suppressed methane emission from paddy soil with a low concentration of electron acceptors and slightly increased methane emission from paddy soil with a high concentration of electron acceptors, as compared to emissions under tilled cultivation, with rice straw application.

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We examined the reduction of vegetable waste (mainly radish and cabbage in the Miura area of Kanagawa Pref.) produced by an electric garbage processor. All radish and cabbage waste could be reduced by an electric garbage processor. The end products, the vegetable waste reduced by the electric garbage processor, can be used as compost. However, these end products have a high potassium concentration; therefore, we suggest that those products should be mixed with other materials with a lower potassium concentration when used as compost.

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