Effect of heavy application of incinerated sewage sludge on the growth of two species of crop plants was studied in a greenhouse. Ashes prepared from two kinds of sewage sludges conditioned with different dewatering methods (chemical precipitation by lime and ferric chloride, and heat precipitation) were used in the experiment. Ashes were prepared from those sludges by 800℃ incineration treatment. Five application rates of ashes containing 0.5, 1.0, 2.0, 4.0, and 8.0 g P_2O_5/1.5 kg dry soil were as follows. 1) The growth of oats was decreased by application of ash that was prepared from chemical precipitation sludge. It was considered that high chloride ion concentration of soil solution caused by lime and feerric chloride treatment induced the inferior growth of oats. 2) The growth and phosphorus content of oats were increased by application of ash that was prepared from heat precipitation sludge. The utilization percentage of phosphorus in the ash was about 50% compared to superphosphate. 3) When incinerated chemical precipitation sludge was supplied, Zn and Cu concentration of oat tops were increased slightly and Zn and Cr concentration of oat roots were increased. When incinerated heat precipitation sludge was supplied, Zn and Cu concentration of oat tops were increased slightly and Zn concentration of oat roots was increased slightly. Application of both ashes did not effect on concentration of Fe, Mn, Pb, and Cd. 4) The growth of rape was improved by application of the two kinds of ashes, and the rate of the improvement was not different between the ashes. Accumulation of heavy metals such as Mn, Zn, Cu, Cr, Pb, and Cd was not increased in edible parts of rape.

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Effect of application of sewage sludges and their ashes on chemical properties and phosphate forms in a soil was studied. Sludge samples consisted of two limed sludge cakes, two no-limed sludge cakes, and four ashes prepared from their sludge cakes by 800℃ incineration treatment. These materials were applied to soil (volcanic ash soil) at a rate of 2.0 g P_2O_5 per 1.5 kg dry soil in pots. These were incubated in the dark at 30℃ for 52 weeks. The following results were obtained. 1) Soil pH increased by application of limed materials, but was not changed by application of no-limed materials. 2) soil EC was rapidly increased due to mineralization of organic nitrogen by application of limed sludge cakes. 3) Organic matter contained in no-limed sludge cakes that were precipitated by heat reatment seemed to be hardly decomposed, because of time-dependent change of soil EC and water-soluble nitrate in soil. 4) When ashes, particularly from no-limed sludge cakes, were applied, soil EC was maintained at very low levels compared with application of sewage sludge cakes, and water-soluble ion composition in soil did not change during the incubation periods. 5) CEC increased slightly by application of limed sludge, but base-saturation percentage exceeded 100% because exchangeable calcium increased in soil, whereas no-limed sludge and ashes did not change base-saturation percentage. 6) Amounts of acetic acid-soluble phosphate and Bray no 2 phosphate in the soil applied with ashes were about two times higher than those by application of sludge cakes, and they were maintained at higher levels during the incubation periods. Therefore, it suggests that most of available phosphate contained in ashes is not transformed into insoluble form in soil and the availability is maintained.

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A soil sample collected from a paddy field was preincubated under submerged conditions to be strongly reduced. It was anaerobically incubated with various additives: sulfate, propionic acid, acetic acid, molybdate ( inhibitor of sulfate reduction), and 2-bromoethanesulfonate (inhibitor of methane formation) alone or in combination. 1) Addition of either acetic acid or propionic acid enhanced sulfate reduction in the soil added with sulfate. And addition of acetic acid enhanced methane formation. 2) When the sulfate reduction was completely inhibited with molybdate, methane formation proceeded and acetic acid decreased rapidly. 3) When methane formation was inhibited with 2-bromoethanesulfonate, sulfate reduction proceeded and both organic acids were consumed. These results confirmed that acetic acid as well as propionic acid was a good organic substrate for sulfate-reducing bacteria and that sulfate-reducing bacteria and methane-forming bacteria competed for acetic acid in the submerged soil. This may be caused by the fact that acetic acid is a main organic acid formed in the submerged soils.

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The activities of phototrophic N_2-fixing microorganisms are influenced by the organic nutrients dissolved in the flood water, which in turn are supplied from the soil and the nutrients fertilized to soil. In this report, the effects of surface application of rice straw on the release of nutrients to the flood water from soil and rice straw were investigated first, and then their relationships with the N_2-fixing activities were studied. The results obtained were as follows. 1. The surface application of rice straw suppressed the formation of oxidized layer and advanced the reduction condition. It increased the pH of the flood water and maintained the optimal pH for the growth of N_2-fixing microorganisms. 2. It also supplied large amounts of ferrous iron and phosphorus compounds to the flood water. 3. Several kinds of sugar compounds derived from rice straw and its decomposed products were accumulated in the flood water after the surface application of rice straw. 4. It changed the dissolved gas composition in the flood water; the increase of CO_2, the decrease of O_2 and the appreciable production of CH_4. 5. Thus, the surface application of rice straw increased the release of organic and inorganic materials to the flood water, and contributed to the N_2 fixation through the growth of phototrophic bacteria and blue green algae.

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To clarify the ecology of Fusarium oxysporum f. sp. raphani (F. o. r.) in soil, a pathogen causing a wilt-disease in radish which is the main disease brought by monocropping in Japan, the effects of the long-term application of farmyard manure (FYM) on the growth of F. O. r. in soil, especially on the germination of F. o. r. microconidia and the elongation of F. o. r. germ tubes, were investigated in this paper. The results obtained were as follows. 1) The growth of the inoculated microconidia in soil was measured with soil smear method and sol dilution method. In non-sterile soils, their growth was suppressed both in the soils amended with chemical fertilizer for 13 years (CF-soil) and the soil amended with farmyard manure for 13 years (FYM-soil). Their growth was more suppressed in FYM-soil than in CF-soil. This suppressive effect disappeared completely by sterilizing soils, which suggested that it might be mainly due to the biological factors. 2) The microconidia inoculated between two pieces of Nucleopore Filter (pore size, 0.8μm) were embedded into soils, and incubated at 30℃ for 48 hours. The total mycelial length was longer in the following order : FYM-soil (pH=6.9) <FYM-soil (adjusted to pH=4.3) ≪ CF-soil (pH=4.3) < CF-soil (adjusted to pH=6.6). In FYM-soil (pH=6.9), the total mycelial length after 48-hour incubation was similar to that at 0-time. But in CF-soil (pH=6.6), it was 7.9 times as long as that at 0-time and the active mycelial elongation was observed. 3) Nucleopore Filter inoculated with F. o. r. microconidia was placed on the surface of FYM-soil and incubated, considering the effect of CO_2 concentration on the growth of F. o. r. The growth of F. o. r. on the surface of FYM-soil was suppressed to the same degree as that of F. o. r. embedded into FYM-soil. 3) Nucleopore Filter inoculated with F. o. r. microconidia was placed on the surface of FYM-soil and incubated, considering the effect of CO_2 concentration on the growth of F. o. r. The growth of F. o. r. on the surface of FYM-soil was suppressed to the same degree as that of F. o. r. embedded into FYM-soil. 4) The suppression observed in FYM-soil acted neither on the time necessary for the germination nor on the germination rate, but on the death speeds of microconidia and mycelia in soil, and on their elongation speed.

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In the separation process of leaf protein concentrates (LPC) from alfalfa plant, deproteinized juice of alfalfa (A-BJ) is issued as a by-product, and it contains large amounts of sugars, amino acids, and minerals. The purpose of this investigation is to examine the application effect of A-BJ application on the growth and nitrogen nutrition of alfalfa plant. The results were as follows: 1) The growth of alfalfa in vermiculite pot was stimulated by the application of A-BJ and its dilute solutions. Nodulation, nitrogen fixation, and plant total nitrogen were also increased. This stimulation was observed to be higher in under-ground parts than in above-ground parts. 2) Similar phenomena were observed on the alfalfa plant grown in soil pot condition. Moreover, the application of rhizobial suspension cultured in A-BJ medium and its supernatant resulted in the stimulation of plant growth, nodulation, and plant total nitrogen of alfalfa grown in soil culture condition. Such stimulation of plant growth was probably due to the improvement of the plant nitrogen nutrition on the process of nitrogen fixation. 3) It was considered from this investigation that the deproteinized alfalfa juice, a by-poduct of leaf protein concentrates, was a useful material for the cultivation of a nodulating crop such as alfalfa.

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Nutrient uptake, typically in phosphorus, is depressed by grassland acidification which is caused by fertilizer anions. A purpose of this study is to clarify the mechanisms of nutrient-uptake depression in relation to the root weight or root length and aluminum in the soil. The grass species used in the experiment were orchardgrass, timothy, perennial ryegrass, alfalfa, red clover, and ladino clover. 1) By top dressing aluminum sulfate powder in pot experiment, depression in phosphorus uptake and root weight was observed. However, except for two species, the amount of phosphorus uptake per root weight was not affected by the aluminum treatment. This suggests that the depression of phosphorus uptake under aluminum coexistence is derived from the root weight depression caused by aluminum. In the case of perennial ryegrass or ladino clover, the amount of phosphorus uptake per root weight was depressed in the latter half of the aluminum treatment. This suggests that the physiological relations between phosphorus and aluminum in the root cell are affected. 2) In the solution culture experiment, by increasing the concentration of aluminum in the solution, the weight of shoot and root was depressed, and the extent of the depression was more marked in the root length than in the root weight. The phosphorus content of the grasses or the amount of the phosphorus uptake was in proportional relations with the root length. 3) By top dressing calcium carbonate on the well-acidified grassland, the soil pH, the weight of the root, and the nutrient content of the grasses were increased; however, the effect on the yield was not clear. This could be the result of the liming effect on the root elongation in relation to the aluminum concentrations in the soil solution. 4) From these results, it is considered that the depression of nutrient uptake, especially of phosphorus, on the acidified grassland, and the recovery of the depression by use of liming are phenomena which take part in the varying of the root weight or root length of the grasses.

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A super-water-absorbent polymer was mixed with soils and its effects on the evaporation, leaching of salts, and vegetable growth were investigated by pot experiments. The polymer used was a synthetic vinyl alcohol-Na acrylate co-polymer, and the soils were taken from the A horizon of a granitederived sandy soil, a light clay paddy soil, and a volcanic ash soil. Drying of the soils, in terms of overall water loss from the pots, was slower when the polymer was mixed than when unmixed. In the polymer-mixed soils, however, there was a marked difference between the surface layer and the layer beneath: the former was dried almost extremely, while the latter held still a large amount of water. The difference was much smaller in the control (polymer unmixed). Such observation indicates that the movement of water from subsoil to the surface is restrained by the presence of the polymer. The latter restraint was interpreted in terms of hindrance of water movement by pore space formed by partial drying and shrinkage of the polymer. Leaching of NH_4^+, NO_3^-, and K^+ from soils was reduced by mixing of the polymer. This is probably due to mechanical occlusion of the ions in the micelle and cation retention by the negative charge of the polymer, although negative absorption of the anion (NO_3^-) by the polymer should also be taken into account. Leaching of phosphate from the granite-derived sandy soil was apparently accelerated by mixing of the polymer, probably because of negative absorption. No phosphate was extracted from volcanic ash soil irrespective of the presence or absence of the polymer, and this is due, no doubt, to high phosphate retention of the soil. Mixing of the polymer with soils apparently enhanced the vegetative growth of plants as judged from the increase of fresh and dry weight, plant height, etc. There was not much difference, however, in percentage dry matter and ratio of dry matter to plant height between polymer-mixed and -unmixed soils. Also, mixing of the polymer appeared to have advanced the flowering time of tomato plant. Such observed effects may be due to increase of water-holding capacity and increse of gaseous phase of soils by the polymer. Mixing of the polymer apparently enhanced uptake of N, P, and K and increased ratio of P and K to N for tomato and cucumber plants, presumably because of relaxation of the plants from water stress.

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Behavior of micronutrient elements around the wheat roots were investigated using the rhizobox system. The rhizobox was divided into 15 soil compartments of 1 mm thickness. Wheat seedlings grew in the central compartment. After two months of cultivation, all the compartments were separated from the rhizobox and the soil from each compartment was dried and analyzed for the element content. The plants were also harvested and analyzed for the content of the alements. The results obtained were: 1) The pH values across the rhizosphere of wheat roots decreased by about 2.5 units. The significant decrease in pH was observed about 2 mm from the central compartment. 2) Total Cu, Zn, Mn, Fe, Mg, contents in each compartment showed little or no difference, but total Ca content increased slightly in the central compartment. 3) Most of soluble cations (Mn, Fe, Ca, Mg, and Na) increased near the root, while the content of soluble K^+ and NH_4^+ decreased.

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The amount of brackish lake water seeping through underground into the reclaimed land of Nakanoumi, Shimane Prefecture, was estimated by surveying the monthly water balance for 3 years from January, 1985, to December, 1987. The estimated amount of monthly seeping water was, on the average, 0.7 Mm^3 (standard deviation, 0.3 Mn^3), changed periodically in parallel with the water level of the lake, and was significantly large in summer. The seeping lake water has caused an increase in the proportion of the sodium and chloride ions, together with a decrease in the proportion of the calcium and sulfate ions, contained in underground water from the upland field soil. The effect of brackish lake water on the soil was remarkable in the circumferential field of the reclaimed land.

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[in Japanese]

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