The accumulation of organic matter was examined in the sand medium under a long-term mulberry cultivation. Sand of very poor organic matter content was placed 60 cm thick in a lysimeter (65×65×80cm) where mulberry (cultivar : Shinichinose) was cultivated. The experiment was made using 3 plots of lysimeter where a mulberry cutting was planted in each plot and cultivated for 11 years, applying chemical fertilizer at the same nutrient levels to all the plots. The experimental design for each plot was as follows. All the harvest was removed from the lysimeter (Plot No.1). All the harvest was placed on the surface of the sand medium (Plot No.2). Mulberry shoots without leaves, and feces and pupa of silkworm raised on the leaves yielded in this plot were added to the medium (No.3). 1) The average of total leaf yield for 11 years was 4,200, 4,500 and 4,800 g per tree No. 1, 2 and 3, respectively. 2) Loss or gain (g/tree) of organic matter in the sand medium after 11 years as as follows : plot No.1 lost 732 g of carbon, 36 g nitrogen ; plot No.2 gained 838 g of carbon, 40 g of nitrogen ; plot No.3 gained 248 g of carbon, lost 2 g of nitrogen. 3) On the other hand, measurement of carbon and nitrogen in the medium after the 11-year experiment showed that 65, 234, 190 mg carbon per 100 g of medium in plots No. 1, 2, 3 had accumulated and 40% of nitrogen added as fertilizer was taken in plot No.2. 4) In every plot, carbon and nitrogen were preferentially accumulated rich in the top and bottom layer of the medium. Especially, the top layer of plot No.2 contained a large amount of carbon. 5) Analysis of humification revealed that the humification degree was the lowest in plot No.2 and the highest in plot No.1, though plot No.1 showed the poorest organic matter content. 6) The culture medium acidified in all plots after 11 years of treatment ; however, the addition of yielded organic material relieved the acidification and enhanced CaO accumulation in the upper layer. 7) It was also made clear that the application of feces and pupa of silkworm as well as shoots without leaves ensured almost the same level of carbon content of the medium as in the yielded leaf application.

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Mulberry field soil was acidified gradually by continuous cultivation for about 10 years on volcanic ash soils underlying Jyoso-clay bed at Tsukuba upland. The methods of soil management, the important analytical data of soils and the process of acidification over the experimental period were as follows : 1) Two fields were used according to the depth from surface of clay bed. Field No. 205 was characterized at the depth of 150cm and field No. 125 at the depth 300cm. The different properties of the two fields seemed due to the clay bed depth. Field No. 205 has larger content of humus, higher soil moisture potential and shallower ground water table than field No. 125. But the major clay mineral of both fields was allophane. 2) After 8 years, the soil in the control plot (non plantation) showed 5.1-5.2 [pH(H_2O)] and 4.4-4.5 [(pH(KCl)], while the depth of 20cm in the inorganic fertilizer plot showed 4.0-4.2 [pH(H_2O)] and 3.9-4.0 [pH(KCl)] at the depth of 20cm. 3) The exchange acidity Y_1 also exceeded 20 in upper layer in inorganic fertilizer plot ; however, the value of acidity was higher in field No. 205 than in field No. 125. 4) To prevent the acidification, application of lime with organic matter was the most effective. 5) The mulberry roots developed into the deeper layer, avoiding acidified layer. The phenomenon would be able to explain why the leaf yield did not become so much lower in the acidified plot.

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In order to discriminate plant competition in mixed culture, we adapted mixed cultivation experiments by substitutive design. The main characteristic of modification was the separation of underground parts. We tried to separate the competition for nutrients or water and the allelopathic interference by the application of these modified substitutive experiments. The results were as follows. 1) In the mixed culture of taro and upland rice, taro and corn, with common substitutive experiment, plant shoot dry weights of both crops were decreased with the combination of taro and upland rice, but those of both plants were not changed with the combination of taro and corn. These data suggest the allelopathic potential of upland rice and taro. 2) The mixed culture of upland rice and peanut reduced the growth of upland rice and increased the growth of peanut when cultured without separation, but the value of RYT showed always 1. In well-shielded conditions of underground parts, growth of upland rice was not inhibited and that of peanut was increased and RYT exceeded 1. This shows no inhibitory allelopathic relation between rice and peanut. 3) In the mixed culture of oat and peanut with modified substitutive experiment in wooden boxes, cultivated in vermiculite with nutrient solution, oat inhibited the growth of peanut by the reason other than competition for nutrients ore water. Color of peanut leaves in mixed culture with oat turned pale compared to monoculture of peanut. These phenomena suggest the allelopathic potential of oat.

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In order to know the relationship between velvetbean (Mucuna pruriens) and other crops (corn, soybean, and kidney bean), we conducted the modified-substitutive design. The modification was the separation of underground parts. The results were as follows. 1) In the mixed culture of velvetbean and corn, the growth of both crops increased. This effect was prominent when their roots contacted each other. Even though the competition for light might work to some extent, allelopathy or other competition in underground systems could be suggested. This hypothesis was supported by small-scale modified-substitutive experiment by nutrient culture. 2) In the mixed culture of velvetbean and soybean, there was no inhibitory or stimulatory relationship. 3) In the mixed culture of velvetbean and kidney bean, stimulatory effect by velvetbean was observed, as in the case of velvetbean and corn. Especially, the elongation of vine of kidney bean increased to two or three times.

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We have noticed that hydroquinone drastically inhibited not only denitrification but also sol respiration. Accordingly, compounds relating with hydroquinone were examined for their effects on growth and activities of varying organisms. p-Benzoquinone not hydroquinone was found to be effective in suppressing denitrification and soil respiration : hydroquinone was oxidized to p-benzoquinone in the soil. In spite of this, resorcinol and o-benzoquinone were not effective. p-Benzoquinone was confirmed to be toxic to both aerobic and anaerobic bacteria but no toxic to yeast and A. oryzae and not inhibitory to germination and growth of plants. These results suggested that p-benzoquinone was toxic only to prokaryotes. In addition, a dark-colored humus-like water-soluble compound, which was produced by heating p-benzoquinone, was also inhibitory to microbial activities. Several implications of these results were discussed in connection with the role of organic matter in the soil ecosystem.

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The effects of soil type and manuring practice, such as application of organic matter and/or calcium silicate, on characteristics of silica dissolution and adsorption (CSDA) by soils were analyzed by the incubation of soil with several silica solutions. And the possibility of silica dissolution and adsorption parameters (SDAP) as an index of silica supply ability of paddy soils was verified. The following laboratory conditions clarified CSDA sufficiently : Incubation at 30℃ for five days with soil : water ratio of 1 : 10. The difference between initial and final silica concentration in solutions through incubation (y ppm) was linearly proportional to the initial silica concentration in solutions (x ppm) as the following equation : x/a+y/b=1. Constant-a was the silica concentration of solution at which neither dissolution nor adsorption occurred, and constant-b was the silica concentration dissolved from soil into distilled water. This equation was rewritten as the following equations : u/a+v/c=1, c=a・b/(a-b), where u (ppm) is the final silica concentration in solutions, v (mg/100g soil) is the amount of dissolution or adsorption of silica by a unit soil. Constant-c, which was extrapolated, showed the amount of silica dissolved from soil into vast water. The application of calcium silicate did not affect the a of SDAP at all, but affected much the b/a of SDAP. The c of SDAP correlated highly with the silica content of paddy rice, because it explained the silica supply ability under reductive soil condition, such as silica content in the supernatant obtained by the incubation under submerged condition. It also explained the effect of clay mineral and soil texture on silica supply ability.

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This report clarified the effect of application of three kinds of organic matter on silica uptake by rice plants and on available silica in soil compared with calcium silicate applied as a silica fertilizer. Organic matters used were rice straw and compost containing silica and cattle feces manure containing little silica. 1) The application of organic matter increased the silica uptake during the middle growth stage of rice plant, but had little effect during the ripening stage. The application of organic matter containing silica had much effect on the silica uptake by rice plants because organic matter hastened reduction condition under which soil silica became more available and released the silica contained in organic matter. 2) The application of calcium silicate before plowing increased the silica uptake during the early and middle growth stages of rice plant. Its application at the tillering stage increased the silica uptake not only during the middle growth stage but also during the ripening stage. In the paddy field with successive applications of calcium silicate for a long term, breaking off the application caused a decrease in the silica uptake by rice plant. However, the amount of silica uptake was more than in the paddy field where calcium silicate was not applied at all. In other words, successive applications of calcium silicate produced some residual effects on the silica uptake by rice plant. 3) The silica content in soil solution in the unplanted plot where rice straw or compost was applied and where calcium silicate was applied became higher from the middle growth stage and from the early growth stage of rice plant, respectively, than that i on the unplanted plot where they were not applied at all.

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Membrane vesicles were isolated from homogenates of barley roots by a combination of differential and dextran density gradient centrifugation. The vesicles possessed ATP-dependent and PP_i-dependent proton transport activities inhibited by nitrate and fluoride, respectively, suggesting that the vesicles derive from tonoplast membrane. In tonoplast vesicles, PP_i hydrolysis and PP_i-dependent proton transport showed an absolute requirement for K^+. Rb^+ was able to substitute K^+ in both activities, but Na^+ or Li^+ was not. PP_i hydrolysis was unaffected by anions tested, while PP_i-dependent proton transport was significantly affected. Permeant anions, like NO_3^-, Cl^- and Br^-, were necessary to support proton transport. Stimulation of proton transport by NO_3^- and Cl^- showed saturation kinetics. The result indicates the presence of anion transport systems on the tonoplast.

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In order to apply the internal standard method to the correction of signal variation inherent in the simultaneous determination of 13 elements in higher plants by inductively coupled plasma (ICP) atomic emission spectrometry, changes in emission signals of the analytes with time, with the concentration of mineral acids, and with the concentration of easily ionizable elements were correlated to those of some candidates for internal standard elements (Li, Co, Sr, and Yb). The emission of alkaline metals such as Na and K was subject to remarkable ionization interference from easily ionizable elements, as well as physical interference from mineral acids and time-dependent drift. However, the resulting analytical errors were diminished by the use of Li as an internal standard, since the signal of Li was closely related to those of Na and K. Li was also effective for diminishing errors inherent in the analysis of Al and S due to physical interference from mineral acids. Co was available as an internal standard mainly for heavy metals such as Fe, Mn, and Zn. Time-dependent variation in signals of B, Mo, and P was also significantly corrected by the use of Co as an internal standard. Yb and Sr were very effective for the correction of signals of alkaline earth metals such as Mg and Ca. It was concluded that the use of Li, Co, and Yb (or Sr) as internal standards is necessary adequate for the determination of 13 elements in plants. Satisfactory results were obtained for the analysis of the elements, except Al and Cu, in standard plant samples by use of these internal standards.

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A method of direct measurement of root surface area was developed with image processing using a personal computer. 1) Projection charts were made from pictures of root box and samples of spinach, and the image file was made by inputting the image data using an image scanner. 2) In a method to calculate the surface area of the root from the projection chart, the root was assumed to be a column. The projection area of the column was 2rh (r: a half diameter; h: height) and the lateral area became, therefore, 2πrh, which was regarded as the surface area of the root. Standard samples could be measured until 100μm in diameter accurately. 3) Spinach was cultivated using a root box. Subsequently, the surface area of the root box rapidly increased from day 21 after budding. Surface area increased at day 28 in plots amended with organic matter. 4) After harvesting, total root surface area was large in the plot amended with organic matter, but no significant difference was observed in treatment of pH. For phosphate, the root surface area increased in the plot with 200kg per 10a. 5) The total surface area showed correlation with the leaf length, leaf dry weight, root dry weight, or leaf area.

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Five or 10 weight percentages of 10-20 mesh metal iron was mixed with Masa soil materials (soils derived from weathered granite) to strengthen phosphate absorption capacity. The mixture was packed into jute nets (dimensions: 3×5×10cm). Each of the jute units was surrounded by layer of Zeolite particle of 1-3mm diameter to make a brick pattern with 9 layers in acrylic tank (dimensions: 10×45×45cm). A model waste water containing 40 mg/l of nitrate-N and 20 mg/l phosphate-P was treated at the rate of 50-750 l/m^3/day under non-submerged condition. The system showed the rate of nitrate-N removal 21 g N/m^3/day. Since the treatment was done under non-submerged condition, formation of COD component was only 12 mg/l at the mean level. The percentage of phosphate P removal was 99%. The mixture of metal iron and jute without any addition of soil showed efficient removal of nitrate-N and phosphate-P in column experiment under non-submerged condition. The rate of nitrate-N removal was 47 g N/m^3/day and at the same time 97% of the phosphate-P was removed under the rate of treatment at 1,200 l/m^3/day.

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