Greenhouse experiments and soil incubation studies were conducted to estimate and compare the availability of N, P and S for African millet due to the mineralization of three kinds of organic matter added to granite regosols. Cattle manure compost, sawdust cattle manure compost and root residue of Italian ryegrass (Lolium multiflorum L., cv. Waseyutaka) which showed varied C/N ratio and N, P and S contents were employed as organic matter. 1) Wagner pots (1/5,000 a) were filled with regosols and each organic matter mixture (100 : 1, w/w). The treatments consisted of two levels of pH (4 and 6), three kinds of organic matter and soil-only pots. African millet (Eleusine coracana GAERTN, Snow Brand) was grown on each treated regosol. The availability of N, P and S for African millet was evaluated through the amount of N, P and S uptake by African millet during cropping.The availability of P through the mineralization of added organic matter was larger than those of N and S. The rates of N and S mineralization in added organic matter, especially in root residue which had high C/N ratio, were extremely low, resulting in lower availability of N and S. The availability of P in cattle manure compost and sawdust cattle manure compost were higher than that of root residue. 2) Soil incubation treatments consisted of five levels of soil temperature (13, 18, 23, 28 and 33℃) and soil pH (4, 5, 6, 7 and 8). Available N, P and S contents in soils were determined 0, 25 and 128 days after treatments. Effects of soil temperature and soil pH on the mineralization of added organic matter were observed at cattle manure compost and sawdust cattle manure compost. Available P and S content in soils with added organic matter were little affected by soil temperature, but available N content increased with increasing soil temperature, especially from 25 days after treatments. Available N, P and S content in soils with added organic matter slightly increased wih increasing soil pH in the range of 4-7.

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Chemical characterization of soil humic acids extracted in seven soils was examined by Curie-point pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). 1) Pyrograms of each soil humic acid (except Nose soil humic acid) showed a lot of peaks. 2) In the pyrograms of soil humic acids the number of greater compounds eluted at higher temperature was compared with soil pyrograms. 3) The multivariate statistical programs of cluster analysis correctly classified pyrograms as each group of soil humic acid. 4) In the first three principal components from principal component analysis of the soil humic acids, 71.8% of the total cumulative variance was retained. 5) The major peaks of the pyrolysis compounds from soil humic acids were identified as toluene, pyridine, acetic acid, furfural, 2-methylpyrrole, 5-methyl-2-furfural, 2-methoxyphenol, phenol, o-cresol, 2,3-dimethylphenol, 2-methoxy-6-vinylphenol, 2,6-dimethoxyphenol, 2-methyl-benzaldehyde.

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Chemical characterization of soil organic matter in soils with different fertilizer histories was examined by Curie-point pyrolysis-gas chromatography-mass spectrometry. 1) Pyrograms of each soil showed more than 90 peaks. The heat decomposition of Nose soil which had been applied with organic matter and fertilizer yielded more abundant decomposition products than the other soils. 2) The multivariate statistical programs of cluster analysis correctly classified pyrograms as each group of soils. No nitrogen fertilizer and chemical fertilizer treatments consisted of one cluster in the both soils. A Hoteiaoi treated soil dissimilated with the other soils in cluster analysis. 3) In the first three principal components from principal component analysis of the soil pyrograms, 97.3% of the total cummulative variance was retained. The data to distinguish between Tomikura and the other soils are present in the first principal component, and it exists in the second principal component at Nose soil and it may be present in the third principal component at Shakudo soil. 4) The major peaks of the pyrolysis cmpounds from the soil organic matter were identified as carbon dioxide, methylfuran, acetic acid, acetamide, pyrrole, 1-methylpyrrole, pyridine, 5-methylfurfural, acetone, furfural, benzene, phenol, methylpyridine, xylene, cresol, etc.

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We made successive experiments on sodium uptake by two rice varieties, which were cultured on the different soils (grey lowland soils and wet andosols). 1) The strong negative correlation was observed between the amount of absorbed sodium not only at the final stage but also at the early growing stage of rice plants and the weight of abortive grain yield in spite of he different kinds of soils and rice varieties. 2) We considered that the depression of potassium uptake was caused by the low temperature of the irrigated water, and the nutriophysiological character of rice seedlings brought on the uptake of sodium in the early growing stage. 3) The substitute sodium absorbed during 35-45 days before the heading time for potassium brought about the decrease of abortive grain yield and the increase of percentage of ripened grains. 4) The absorbed sodium had the negative correlation for the weight of abortive grain and rice screenings, but it was positive for the percentage of ripened grains. In contrast to sodium, the absorbed potassium showed the negative correlation for these factors consisting yield. 5) Based on the above results, sodium and potassium are antagonistic to each other when they are absorbed into the rice plants, but we supposed they act independently of each other in the rice plant. 6) The amount of absorbed sodium was closely related to the limiting factor for the increase of brown rice yield.

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The dissolution of silica in soil in rotational paddy fields and the assessment of a new variant of the surface water dissolution (SWD) method were examined. 1) The silica dissolution patterns by the usual method had a lower curve than that by SWD method. It is considered that the dissolution of silica into surface water by SWD method was not inhibited. It is concluded that the silica dissolution patterns can be estimated by using the SWD method. 2) The silica dissolution patterns in rotational paddy fields had a higher curve than that in non-rotational paddy fields. It was found that the silica dissolution patterns can be approximated by an exponential equation model. 3) It was suggested that the amounts of silica dissolution from transplanting to maturing time was little influenced by the fluctuation in temperature in the growing period. It is concluded that the silica dissolution patterns can be estimated by using an exponential equation model at 30℃ irrespective of the soil type. 4) The amount of silica, estimated from the silica dissolution model of soil and the water supply pattern, were close to the amounts of silica uptake by rice plant except in the initial stage. The amounts of silica uptake by rice plant on rotational paddy fields were higher than that on non-rotational paddy fields. It is concluded that the silica dissolution patterns on rotational paddy fields can be estimated by using the SWD method.

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The effects of various ATPase inhibitors and ionophores on both H^+-K^+ exchange by excised rice roots, ATPase activity, and formation of pH gradient in the reconstituted plasma membrane vesicles were investigated. The inhibitors and the ionophores completely inhibited H^+-K^+ exchange, but partially both ATPase activity and formation of pH gradient. In some cases, these reagents resulted in reverse H^+-K^+ exchange that mediated influx of H^+ and efflux of K^+. These results suggest that the electrochemical gradient across the plasma membrane controls the H^+-K^+ exchange in point of the rate and the direction. Rb^+ and NH_4^+ were also effective for the exchange K^+, while Na^+, Li^+ and Cs^+ were ineffective.

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A potato variety, "Danshakuimo" was grown with 0, 150 and 300 kg N/ha (0N, 150N and 300N, respectively) under a condition of one stem per hill supported with sticks. Various observations were made during the growth, and the following results were obtained. 1) The plant growth rate and the tuber growth rate were high at 150N until the mid-tuber swelling stage, and then those became low at 0N and 150N, but they remained high at 300N until harvest. Therefore, the tuber yield and total dry weight were 0N<150N<300N. 2) The amount of nitrogen absorbed by the plants and that accumulated in the tubers increased with an increase of nitrogen application. The higher the nitrogen applied, the higher the nitrogen content of tubers was. The nitrogen content of tubers was stable after tuber started to swell. There was no difference in the nitrogen content at harvest among the tubers at different positions. These indicate that the demand of tubers for nitrogen is increased by nitrogen application. 3) With nitrogen application, the rate of leafing on main stem became high, and leaf number on main stem and total node number of branches increased. 4) With nitrogen application, the growth stage when the number of tubers determined became earlier. The mean dry weight of tubers increased after flowering, and was in the order of 0N<300N<150N. 5) There were seven nodes on the under ground part of stem. The number and the average weight of tubers on each node at harvest was the largest at the 3rd and 4th node from the top, regardless of the nitrogen application. With an increase of the nitrogen application, the average weight per tuber on each node fluctuated, and, both the number of small and large tubers increased.

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Rapid and accurate method for determination of hot water soluble boron in soils by ICP-AES was studied. In order to estimate the interference of concomitant elements, the concentration of major elements (Ca, Mg, K, Na, Fe, Mn, Al, P, S and Si) in hot water extracts of 35 soils were determined by ICP-AES. Calcium and sulfur were dominant concomitant elements especially in cultivated soils, and the ranges of them were Ca 0.22-172 ppm ; S 0.13-96.5 ppm. On the other hand, the concentration of iron and aluminum in the extracts were very low (Fe 0.01-0.77 ppm ; Al 0.02-5.43 ppm). About 5% of positive interferences by 100 ppm of Fe (B 249.77 nm), Al (B 208.96 nm) and S (B 182.64 nm) to 0.5 ppm of B were observed, but there was no interference by 10 ppm of each concomitant element. Boron in the extracts of 35 soils were determined by ICP-AES using three analytical lines (182.64, 208.96 and 249.77 nm), and their values were compared with values determined by curcumin colorimetric method. The best agreeing was obtained when 249.77 nm was used for analytical line of ICP-AES. The coefficients of correlation and regression were 0.9991 and 0.9925 respectively. In the ICP-AES measurement, in order to prevent memory effect of high concentrate boron, it was suitable to use 0 and 2.5 ppm of standard solutions as B, and spray 1% sodium hydroxide solution for 1 min after each sample spraying. The analytical time of ICP-AES measurement was about 2 min per sample, and the determination limit (5 times that of detection limit) was 0.02 ppm in soils. The repeatable accuracy of this analysis included extraction of boron from soils and ICP-AES measurement was about 4% as coefficient of variance.

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Relationship between yield components of rice plant and mineralization potential (N_0) of paddy soil was evaluated. The mineralization potential was obtained using sulfic acid extraction method. Furthermore, map of N_0 was made. The mean value of N_0 of topsoil was 14.4 mg/100g soil, which ranged from 8.7 to 21.6 mg/100g soil. On the other hand, that of subsoil was 5.7 mg/100g soil. and ranged from 2.5 to 14.8 mg/100g soil. It was found that yield of rice plant increased with increase in N_0 of topsoil and subsoil of paddy field. There was correlation (r=0.684***) between N_0 of subsoil of paddy soil and percentage of bearing tillers among the fields which had same number of maximum tillers. The number of grains per panicle was highly correlated with total amount of N_0 from topsoil and subsoil of paddy field in which the panicle number was almost the same. According to difference in N_0 of topsoil and subsoil of paddy fields, map of N_0 was made. The map of N_0 was appropriate in comparison with map of yield of rice plant in Shonai district.

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General conditions under which the activity ratio of potassium ion to those of calcium plus magnesium ions (AR^K) are kept constant during diluting soil solutions without disturbing cation exchange equilibria were derived based on the thermodynamics of ion exchange. They were i) that the selectivity coefficients of K-Ca and K-Mg exchange reactions depend only on the exchangeable cation composition and ii) that Ca and Mg ions behave identically in the cation exchange reactions. Experimental data from the literature showed that neither of these conditions is met strictly in actual soil systems but the deviation is not large. Practically, however, dilution of soil solutions disturbs the cation exchange equilibria. Numerical simulations on the variance of the AR^K during dilution showed that the cation exchange capacity had the largest effect among the factors such as the exchangeable potassium content, selectivity for potassium, and initial ionic concentration in the soil solution. The change in AR^K caused by forty-fold dilution of a soil solution was calculated to be less than 25% for soils having a CEC of 30 meq/100 g while it was more than 150% if the CEC was 1 meq/100 g.

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