To investigate the beneficial effects of sodium related to available potassium levels, three kinds of leafy vegetables-Beta vulgaris, Spinacia oleracea, Amaranthus mangostanus-were pot-cultured with Masa soil with low potassium availability. As to the application rates of potassium (KCl) and sodium (NaCl), seven treatments were set up i. e., K (control ; 1.0 g K_20 pot^<-1>=21.2 mmol K pot^<-1>), 1/2K, 1/5K, -K, 1/2K1/2Na (K=Na=10.6 mmol pot^<-1>), 1/5K4/5Na and -K+Na (Na=21.2 mmol pot^<-1>). Experiments were carried out in triplicate in a hot-house. The results obtained were as follows. 1) The effect of sodium was most remarkable on Beta vulgaris. The growth of -K+Na plants was quite normal and better than that of the control (K) plants, while -K plants showed potassium deficiency symptoms and growth was decreased to half that of the control plants. A similar but lesser effect was obtained for Spinacia oleracea. Differently from these two plants, sodium did not have any effect on Amaranthus mangostanus except for -K+Na treatment. All the plants receiving the -K treatment stopped growth soon after germination and then wilted. However, all the plants receiving the -K+Na treatment continued growth without any abnormal symptoms, though the fresh weight at harvest time was about one-fifth of the control plants. 2) The differences in the effect of sodium were mainly attributed to the difference in the rate of sodium uptake by the plants. In Beta vulgaris and Spinacia oleracea, the decrease in potassium content was compensated by an increase in sodium uptake. As the result, the concentrations of univalent alkali cations (K+Na) in the plants did not decrease. The beneficial effect of sodium in this case seemed to be mainly due to the substitutional effect of sodium for potassium in producing osmotic pressure in the apoplast of the plants. This might contribute to keeping water content in the tissue and increasing the fresh weight. The rate of sodium uptake by Amaranthus mangostanus was very low even in the potassium-deficient condition, so the effect of sodium on -K+Na plants is believed to be different from the case of the former two plants. The cause of this effect should be investigated further.

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In the Makinohara area of Shizuoka Prefecture, by measuring the flow rate and nitrate concentration of a stream throughout the year in 1995, we estimated the nitrogen leaching rate from a tea field in its catchment basin. The nitrate concentration of the stream showed little seasonal variation at each branch, with annual averages of 29.6, 19.0 and 32.5 mgN L^<-1>, respectively. The total annual nitrogen outflow from the stream was 3.34x10^4 kgN y^<-1>. Based on the annual flow rate of the stream, the annual rainfall and the evapo-transpiration data reported for the tea field, we estimated the drainage area of the stream as 137 ha, (mainly composed of a tea field and forest area of 19.4 ha) and estimated the leaching rate from the tea field as 284 kgN ha^<-1> y^<-1>. In the paddy field receiving irrigation water from the small stream above, the nitrogen inflow integrated over the irrigation period of 99 d was 314 kgN ha^<-1> and the nitrogen outflow was 80 kgN ha^<-1> The amount of nitrogen removed in the paddy field reached 234 kgN ha^<-1>. The nitrogen budget and stable nitrogen isotope ratios of nitrate in the inflow and outflow indicate that denitrification was the main contribution to nitrogen removal in the paddy field. Using the leaching rate from the tea field and nitrogen removal rate of the paddy field as obtained above, and agricultural statistical data for the tea and paddy fields in the Makinohara area, we estimated the total amount of nitrogen leached out from the tea field as 1.86x10^6 kgN y^<-1>, and that 3.24x10^5 kgN y^<-1> was removed in the paddy field. In the Makinohara area, the reduction of nitrogen load by the tea and paddy field land system was estimated to be 17.4 % under present conditions.

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The relationship between the nitrogen mineralized after the air-drying treatment of paddy soils and microbial biomass nitrogen was investigated. The amount of nitrogen mineralized after air-drying and water-logging treatment increased throughout the air-drying period and reached the maximum level of two weeks of incubation. The amount of microbial biomass decreased during air-drying. The relationship between the nitrogen mineralized after two weeks of incubation following air-drying treatment and the biomass nitrogen in paddy soils was significantly high. The contribution of biomass nitrogen to total mineralized nitrogen was about 20-48% in paddy soils and lower than that in upland soils (45-50%).

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The palatability of rice produced on Andosol has been reported to be inferior to that of rice produced on the other soil types, such as Brown Lowland soil. The effects of zeolite application on the nitrogen and mineral contents and palatability of rice were studied in order to improve the eating-quality of rice grown on Andosol. The content of silicic acid in rice straw produced on Andosol was slightly increased with zeolite application. On the other hand, the contents of Ca, Mg, K and N in the rice straw were constant. With zeolite application to Andosol, the N content of milled rice was decreased and the palatability of milled rice had no clear difference as compared to that grown in Brown Lowland soil. The percentage of ripened grains was increased in spite of an increase in the number of unhulled rice per square meter. These results lead to the conclusion that the improvement of palatability of rice produced on Andosol with zeolite application could be attributed to the decrease in N content of milled rice due to the increase of the percentage of ripened grains.

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The saccharide compositions of peat and peatland plants were compared using 42 peat samples and 25 plant samples from Hokkaido, Japan. The amounts of hemicellulosic and cellulosic saccharides changed according to the type of peat and the depth in the profile. In general, the proportion of hemicellulosic glucose decreased while that of xylose increased with the increasing depth of peat layers. The proportion of galactose and mannose, which are dominant saccharides in Sphagnum, were higher in the upper layers than in the lower layers. Rhamnose, fucose and ribose, which are indicators for microbial saccharides, were contained in large amounts in the highly decomposed peat samples. While glucose was the dominant component in the cellulosic saccharides, the proportions of mannose (ca.20%) and xylose (10-30%) were also high in the fraction. A cluster analysis of peat and peatland plants was carried out using the composition of hemicellulosic saccharides as statistical data. Peat samples were grouped very well according to the type of peat. The clusters of most peats were separated from peatland plants, but some peat samples showed a very high similarity to Sphagnum, Eriophorum vaginatum and Myrica gale. The saccharide compositions of most of the other peats were more similar to that of Sphagnum than those of grasses and woods.

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Much waste ash has been released due to the incineration of massive refuse from daily life. The waste ash causes enormous problems from the viewpoint of environmental protection. The amountof ash is expected to increase based on a serious increase in rubbish disposal, not only in Japan but also throughout the world. So far, little is known of a suitable treatment for waste ash. The development of a new technical method has been required for the treatment and/or recycling of waste ash. The ash is composed mainly of amorphous silica and alumina with some alkaline and alkaline earth-metal ions. We tried to treat the ash with an alkali solution in order to crystallize it. Namely, the waste ash was heated with a sodium hydroxide solution at about 90℃ for up to 90 h. The products of the heating reaction were analyzed by means of a X-ray diffraction method, infrared spectroscopy, thermal analysis and scanning electron microscopy. These instrumental analyses showed that the reaction could transform the ash into hydroxy sodalite, one of the zeolites, crystalline aluminosilicates. The amount of zeolite increased with prolongation of the reaction time, reaching a maximum at about 60 h. Zeolite has some useful properties and functions, such as adsorption, cation exchange and catalytic activities, and is utilized as a material in many fields of industry. For example, the material is used for soil amendment, removal of heavy metals from wastewater, deodorization and moisture desorption. Thus, the present result is promising in opening the way for the disposal of waste incineration ash through application as a recycling resource and to control pollution for environmental preservation.

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We investigated the contribution of N through microbial biomass (biomass N and its debris N) to plant N uptake in upland soils with different physicochemical properties. Our experiment was carried out in concrete plots using different 5 types of upland soils (Light-colored Andosol, Humic Andosol, Brown Lowland soil, Dark Red soil and Sand-dune Regosol). Nitrogen fifteen-enriched ammonium sulfate was amended to the field soil in order to label microbial biomass N with ^<15>N. At 3 weeks after amendment, upland rice was sowed and cultivated in 15 weeks. Soil and plant samples were taken at every 3 weeks after sowing (WAS), and the ^<15>N abundance of soil microbial biomass N, soil total N and plant N were analyzed. The results we obtained are summarized as follows. 1) The amount of microbial biomass N in the soils was higher in the following order : Dark Red soil>Humic Andosol≒Brown Lowland soil≒Light-colored Andosol>Sand-dune Regosol. The amount of microbial biomass N in all of the soils was almost constant during the cropping period. 2) The amount of plant N uptake was higher in the following order : Brown Lowland soil>Humic Andosol>Dark Red soil>Light-colored Andosol>Sand-dune Regosol. The amount of plant N uptake in all of the soils was highest in the heading stage, suggesting that the amount of plant N uptake is high in the reproductive stage. 3) At 0-3 WAS, the ^<15>N abundance of plant N uptake in all of the soils was close to that of the microbial biomass N. At 6-15 WAS, however, it was close to that of soil total N. Based on this result, we assume that the N taken up by the plant is mainly derived from the N produced through the microbial biomass in the vegetative growth stage (0-6 WAS), and mainly organic N except for the microbial biomass N in the reproductive stage (6-15 WAS). 4) In all the soils except Dark Red soil, the amount of plant N uptake was closely correlated with the amount of microbial biomass N at the vegetative growth stage (R : 0.995^<**>, n= 4), supporting our hypothesis that the N through the micobial biomass is a major source of N for plants at this stage.

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The influence of air-drying treatment on changes in the form of Mn, Co, Zn and Cu was investigated using air-dried and field moisture soils which included Fluvaquent (paddy), Dystrochrept (paddy) and Melanudand (upland). The sequential extraction method was used to evaluate the different chemical forms of the elements in the soils. 1) Compared with the field moisture. soils, the exchangeable forms of Mn, Co and Zn in the air-dried soils increased 9-25 times, 6 times and 1.4-1.7 times, respectively. Acid soluble forms of Mn and Co increased approximately 2 times, but that of Cu decreased. The Mn oxide occluded forms of Mn and Co decreased approximately 10% and 9%, respectively. The elements in organically bound, Fe oxide-occluded and residual forms were unchanged. 2) Changes in the chemical forms subjected to the air-drying treatment differed according to soil and element. The effects of drying were more strongly exhibited in the paddy soils than in the upland soil, and more noticeably in regards to Mn and Co as compared to Zn and Cu. 3) These results indicate that the increase in certain heavy metals with the air-drying treatment was caused by the dissolution of Mn oxides, which occluded those heavy metals. From a comparison between the redox potential of soils and MnO_2 calculated from the standard free energies of formation, it can be seen that MnO_2 in air-dried soil could be dissolved below pH2-3. Though surface or organic acidity may have occurred, it is believed that soil pH could not drop to 2-3 due to the buffering action of the soils. It is believed that organic matter derived from humus or microorganisms could dissolve Mn oxides.

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Field studies were carried out throughout the rice cultivation period at three different paddy fields (poorly drained paddy field, medium-drained paddy field and well-drained paddy field) located in Okayama Prefecture in 1992 and 1993. 1) The amount of methane emission greatly varied between the two years, and a stable tendency in the pattern of methane emission was not observed. 2) The amount of methane emission from the poorly drained paddy field was largest among the fields, and methane emission from the medium-drained paddy field and well-drained paddy field greatly varied as the years passed. 3) The oxidation reduction potential was influenced both by the period of surface drainage, such as mid-summer drainage, and the weather conditions during surface drainage. 4) One problem in surface drainage is that the soil is hard to oxidize during rainfall or in poorly drained paddy fields. Thus, effective drainage, such as prolonging the drainage period during rainfall, is necessary in order to suppress methane emission by water management.

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Nitrogen balance was measured in lysimeter experiments to clarify nitrate leaching in Ando and sandy soils. The amount of leaching water was increased in proportion to precipitation. The percentages of leaching water to precipitation was 39 in the Ando soil and 59 in the sandy soil. Crop uptake of the fertilizer nitrogen in the sandy soil was smaller than that in the Ando soil in all of the crops investigated. The percentage of leached fertilizer nitrogen was 25-32 in the Ando soil and 58-66 in the sandy soil. In the Ando soil, the leaching of fertilizer nitrogen under winter cropping was more than that under summer cropping. It was suggested from the hydrograph of upland rice cultivation that fertilizer nitrogen started to leach in the small-pore volume (amount of leaching water/whole pore space) in both the Ando and sandy soils.

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Nitrogen balance was measured in a lysimeter experiment to clarify the effect of using coated fertilizer on nitrate leaching. The amount of leaching water was increased in proportion to precipitation, and the ratio of leaching water to precipitation decreased during the active growth stage. The tuber yields of taro plants in the sandy soil increased by the use of coated fertilizer, but no remarkable effect of the coated fertilizer was observed in the Ando soil. The yields of unhulled rice were smaller and the straw weights were larger in the fields using the coated fertilizer for both sandy and Ando soils. Nitrogen uptake by taro and upland rice was increased by use of the coated fertilizer in the sandy soil, but no difference was found between the fields with conventional and coated fertilizer applications in the Ando soil. Nitrate leaching was suppressed by the use of coated fertilizer in both Ando and sandy soils.

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