The humic substances of soils on raised coral reef terraces were compared by the analyses of optical characteristics and humic acid types. The results are as follows : 1) Free carbonate contents of Initial Rendzina-like soil (Rendzic Leptosol in WRB, Lithic Rendoll in Soil Taxonomy) were high, and decreased rapidly to about 10 g kg^<-1> at the soil formation stage of Rendzinalike soil (Rendzic Leptosol, Lithic Rendoll), and it showed fairly low levels during the subsequent soil development. Organic carbon contents showed a similar trend, suggesting that the decomposition of humus proceeds rapidly along with rapid dissolution and leaching of free carbonates from solum. 2) Humic acids extracted with 0.1 mol L^<-1> sodium hydroxide solutions were classified into Rp or P type, no differences among the soils were recognized. However, in the case of 0.1 mol L^<-1> sodium pyrophosphate solution being used as the extraction solvent, the type of humic acids changed from P type through B or A type to Rp or P type in accordance with soil development. 3) Judging from the iron, aluminum, calcium, and carbon content extracted with 0.1 mol L^<-1> sodium pyrophosphate solution from the soil samples, at the initial stage of soil development on raised coral reef terraces, soil humus was mostly combined with abundant calcium. At the middle stage of soil development, calcium-humus complexes gradually changed to "free form" humus or a part of humus combined with iron and aluminum along with leaching of calcium. Finally, most humus mainly consisted of "free form" or loosely combined with sesquioxide. 4) As the decalcification proceeds rapidly at the initial stage of soil development on raised coral reef terraces, its humus decomposition proceeds, but the degree of humification once increased up to the stage of Brown Rendzina-like soil (Mollic Cambisol, Eutropeptic Rendoll) and gradually decreased there after.

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The objective of this study was to investigate the influence of manufacturing conditions on the inorganic phosphate compositions of composts. The content of total components and the fractions of inorganic phosphate were measured. The sum of the water soluble and the NaHCO_3 soluble inorganic phosphate were labeled as easily soluble phosphate. Carbon content in beef cattle manure compost was higher than that in dairy cattle manure compost, while Ca content was 1.5 times lower than that in dairy manure compost. The organic phosphate content was very low, at 12% of total phosphate on the average. The percentage of water soluble and easily soluble inorganic phosphate in beef cattle manure compost was significantly higher than that in dairy cattle manure compost. This might result from the higher amount of Ca to form insoluble phosphate in dairy cattle manure compost. The content of easily soluble phosphate made in fermentation or drying facilities was lower than those of composts made in enclosed and open air compost depots. There was no significant difference in total phosphate and easily soluble phosphate between the composts made in enclosed and open air compost depots. The easily soluble phosphate decreased with longer composting time. This showed the formation of insoluble phosphate was promoted as the composting time increased. The percentage of water soluble and easily soluble inorganic phosphate was the highest in the cattle manure compost with rice hull, and the lowest in that with bark or sawdust. When the cattle manure composts were divided into 4 groups by the combination of kinds of manure and supplementary materials, 52 to 79% of total phosphate were easily available for crops on average in each of the 4 composts, a figure which was estimated by the percentage of easily soluble phosphate to total phosphate in composts.

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ommon bean root nodulation is easily repressed by nitrate application. To clarify the physiochemical backgrounds of the susceptibility, nitrate assimilation and root nodulation were comparatively studied between common bean and soybean seedlings inoculated with rhizobium under different application levels of ^<15>N-nitrate. Common bean assimilated much larger amounts of medium-nitrate derived nitrogen (MDN) than soybean. Furthermore the root-distribution ratio of MDN was larger in common bean than in soybean at 10 d after sowing (DAS), at which time a substantial amount of MDN was detected in both legumes. In addition to these facts, common bean roots were more abundant in free amino acid form MDN (faa-MDN) than soybean roots, revealing higher activity of common bean roots in uptake and assimilation of nitrate. On the whole, the number of primordial and matured root-nodules was much larger in common bean than in soybean. However, at 10 DAS, both formation and development of root nodule primordia were more strongly suppressed in common bean than in soybean by the application of 30 and 60 mg L^<-1> nitrate. The amount of root faa-MDN per unit of root dry weight showed extremely high correlation with an inhibitory index for the rate of primordial and matured root nodule formation in both legumes. This distinctive correlation suggested that so-called nitrate stress on nodulation arose through MDN assimilation in roots in both legumes. Based on these results, it was concluded that higher susceptibility of common bean root nodulation to applied nitrate was due to more active uptake and assimilation of nitrate by its roots.

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Distributions and accumulations of sulfate in soil profiles of Japanese Andisols and Inceptisols under forest vegetation were investigated. The concentration of phosphate-extractable sulfate increased with depth, reaching its maximum at around 50-100 cm in depth. Andisols contained a significantly larger amount of phosphate-extractable sulfate (16-880 mg S kg^<-1>) than Inceptisols (10-296 mg S kg^<-1>). This high concentration of phosphate-extractable S in Andisols was larger than those in other soils reported in North America and Europe. The concentrations of chloride-extractable and water-soluble sulfate were significantly lower than those of phosphate-extractable sulfate in both soils. Thus, adsorbed sulfate was the predominant form of sulfate in the soils, accounting for about 30% of total sulfur in Andisols and Inceptisols. The strong correlations between phosphate-extractable sulfate and inorganic amorphous aluminum and iron oxides, crystalline iron oxide and allophane indicated that these oxides and clay minerals contribute to sulfate adsorption. The relationships between chloride-extractable sulfate and the minerals show that the minerals also affect the exchangeable sulfate concentration. In addition, the large amount of minerals apparently results in a high sulfate adsorption capacity that keeps the concentration of water-soluble sulfate low in subsoils of Melanudands. The accumulation of phosphate-extractable sulfate down to a I m depth ranged from 870 to 2670 kg S ha^<-1> in Andisols, and from 91 to 1440 kg S ha^<-1> in Inceptisols. These high accumulations of sulfate mean that the sulfate adsorption mechanism is important in retaining sulfur compounds in Japanese forest soils.

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Recently, soil sickness due to continuous mono-cropping has become a serious problem in greenhouse culture. In the case of leaf vegetables produced in the greenhouse, problem is compounded by intensive cropping. For such a problem, the establishment of a rotational cropping system is a fundamental solution method. But it is important to develop specialized technology which extends the possible period for continuous cropping. Rhizobacteria have the potential to be useful in agriculture for plant disease control and plant growth promotion. Plant growth-promoting rhizobacteria (PGPR) are soil bacteria that, when applied to seeds or roots, are able to colonize plant roots and stimulate plant growth. Strains of fluorescent pseudomonads, particularly Pseudomonas putida and Pseudomonas fluorescens, belong to a major group of PGPR. In this study, we selected PGPR which promoted the growth of the spinach. 1) We selected PGPR with the function of promoting the elongation of spinach root using the smallscale sterilized hydroponic culture bioassay system. 2) Several fluorescent pseudomonad strains which promoted around 50% increase in growth (aboveground and at the root) of the spinach were obtained. 3) Strains selected as PGPR were separated into 2 types. Type A accelerates the growth of the spinach root from the initial growth stage. Type B suppresses the growth of initial infant spinach root growth. 4) In the hydroponic culture, inoculated Pseudomonas spp. colonized satisfactorily on the spinach root. In the case of PGPR having sufficiently colonized on the root, the growth-promoting effect of PGPR on the spinach could be demonstrated. 5) In the case of diluted liquid of the type B culture being applied to the bioassay, growth suppression at the early stage disappeared. Therefore, the growth-promoting mechanism of type B was thought to be related to bacteria] secretion or microorganism metabolite.

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The behavior of PGPR (plant growth-promoting rhizobacteria), which promotes the growth of spinach was examined. 1) In the case of the bacterial density of the suspension which soaks the seed being over 10^5 cfu m L^<-1> there was no difference in the bacterial population which adhered to the seed. In addition, there was no remarkable difference within the bacterial density which colonized on the spinach root, though the bacterial density per seed differed. 2) In the case in which the bacterized seeds were preserved at 4℃, the decrease in the bacterial population on the seeds was considerably gentle. The lowering of the bacterial population on the seeds was maintained by soaking the seeds in 10 g L^<-1> methyl cellulose (100 degrees of polymerization). The bacterial population on the seeds was maintained at a high level for a long time (6 months), in the case of methyl cellulose being used. 3) There was no remarkable growth-promoting effect, in the case of the fluorescent pseudomonad being inoculatecl to the spinach in soil culture, while growth-promoting effects of the spinach were observed in hydroponic culture. 4) The lowering of the bacterial population of inoculum was gentle, when rice straw cattle feces compost, sawdust horse feces compost or rice straw horse feces compost were added with the PGPR. The high PGPR population was maintained in the soil with use of these organic materials.

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The efficiency of additive agents to remove copper from Cu-mixed soils by Brassica juncea and Zea mays L. was studied. The plants were grown in decomposed granite soil (Regosol) and volcanic ash soil (Andosol) for 3 weeks. To simulate actually contaminated soil, copper contents of 25 and 250 μg Cu g^<-1> were prepared for Regosol and Andosol, respectively. EDTA was found to be an excellent additive agent to raise the availability of Cu in soils. The effect of EDTA on Cu absorption by plants was limited in Regosol. On the other hand, in Andosol the Cu accumulation in shoot in Z. mays for the 100 mM EDTA treatment was 3.7 times larger than that for the 0 mM EDTA treatment. The Cu absorption by B. juncea was not affected by the EDTA addition to Andosol. It was observed that the effect of EDTA on Cu absorption into the vegetable parts fluctuated not only with EDTA concentration, but also with plant species.

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Tomatoes were planted in containers to which liquid mixed fertilizer was drip-applied during the cultivation at different rates. In the control plot, straight N, P, K fertilizers were applied before planting. Uptake of plant nutrients was determined and the nitrogen recovery was calculated. Growth of tomatoes depended upon the rates of nitrogen. At 5 g N plant^<-1>, the level usually recommended for the tomato culture, the nitrogen recovery by drip application was 62%, whereas it was 44% in the control plot. The nitrogen recovery with the preplant application was lower at 5 g N plant^<-1> (44%) than at 2.5 g (70%), whereas it did not decrease with the drip-application (from 64 to 62%). This strongly indicated the latter application was more efficient in supplying nitrogen to a crop which has comparatively small root zones. The nitrate concentrations in petiole sap and bleeding sap were higher, when compared at the same rates, for drip application than for the preplant application. In the drip-applied plot, the nitrate concentrations in petiole sap increased with the increasing rate of fertilization. On the other hand, the anion concentrations other than nitrate in petiole sap decreased with an increase in the rate of fertilization.

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Population of GUS marked bradyrhizobia inoculated in five different soils including calcined vermiculite increased over 10 times in a week. Each soybean seed was planted in a paper pot filled with vermiculite inoculated with or without bradyrhizobia, and the 10-d-old seedlings were transplanted with a paper pot to the first cropping reclaimed field in Niigata. In addition to the conventional fertilization (1.6 g N m^<-2>), deep placement of urea, 100 d type coated urea, or calcium cyanamide (10 g N m^<-2>) was applied. In conventional fertilization the soybean plants transplanted with non-inoculated paper pot did not nodulate due to the absence of indigenous bradyrhizobia, and the seed dry weight was lowest, about 9 g plant^<-1>. Seed dry weight of the plants either with paper pot inoculation or seed inoculation was higher, about 22 g plant^<-1>. Soybean plants with deep placement of calcium cyanamide exhibited prolonged leaf activity. With deep placement of urea, coated urea and calcium cyanamide, seed dry weight increased to 32-37, 40-44 and 38-47g plant^<-1> respectively. The highest average seed yield was obtained in the inoculated paper pot transplantation with calcium cyanamide.

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