We studied dissolution of aluminum ion and silicic acid from six volcanic ash soils in dilute HCl solutions. The initial rapid dissolution reaction terminated within 4 h after addition of acid, but slow dissolution continued even after 72 h. After 24 h, reacting solutions were oversaturated with respect to gibbiste, imogolite and halloysite, indicating that unidentified materials having higher solubilities controlled the aluminum and silicic acid concentration. This also suggests that an equilibrium assumption is not always justified for these soils. Both aluminum and silicic acid concentrations were higher in solutions having lower pH values, but the concentration-pH relations were dependent on soil/solution ratio, particularly for silicic acid. Linear regression analysis gave an equation (Al^<3+>)=3.55(H^+)^<1.06 (r^2=0.828). The moles of Al and Si released from unit weight of a soil were, on the other hand, determined uniquely by the moles of acid added to unit weight of the soil. There was no effect of soil/ solution ratio. This observation was interpreted as indicating the importance of measuring the total proton load in assessing the effects of acid rain on soil properties. The amount of Al released at the same acid addition was much higher for soils dominated by Al-humus complexes than for allophanic and halloysitic soils.

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We grew rice plant (Oriza sativa japonica) on a Gray Lowland soil (GL) and an Andosol (AN), which have been reported to produce rice of different quality, and monitored the soil solution composition during the growing period. We also analyzed the harvested rice straw, brown rice and milled rice for N, Ca, Mg and K. The Ca^<2+>, Mg^<2+> and NH_4^+ concentrations in the soil solution were significantly higher in GL than those in AN, whereas the K^+ concentration was higher in AN throughout the growing season. There was no simple correlation between the soil solution cation composition and the exchangeable cation composition, but the former could be predicted from the latter based on the separately-determined cation exchange selectivity of the soils. Reflecting the soil solution composition, the N, Ca and Mg contents of the rice straw from GL were significantly higher than those from AN, whereas the K content was lower. The difference in N and mineral contents of the brown rice and milled rice from GL and AN, on the other hand, could not be explained by the soil solution composition, indicating that they were under larger influence of translocation physiology in the rice plant.

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To establish the manuring practice which is suitable for sugarbeets seedlings grown with rockwool substrate, and to obtain the same growth conditions between rockwool substrate and conventional paperpots, the effect of the ratio of ammonium to nitrate and the concentration of the nutrient medium on growth of sugarbeets seedlings were studied in this report. 1) A sugarbeets seedlings rapid growth phase with the rockwool started about 10 day later than that with paperpot, but its growth rate did not differ. Consequently, the fresh and dry weight of 40-day-old plants grown with the rockwool were smaller than those with the paperpot. Because leaf emergence date of paperpot seedlings was earlier than the rockwool seedlings, and leaf number of rockwool seedlings at the first period was inferior to paper pot seedlings, but leaf number of rockwool seedlings at the first period was inferior to paperpot seedings, but leaf number of rockwool seedlings was the same paperpot seedlings at the latter period. And leaf length and cotyledon length were similar to rockwool seedlings and paperpot seedlings. 2) The NH_4-N:NO_3-N ratio of 1:1 was optimal for the growth of sugarbeets seedlings. Especially, when the NH_4-N ratio was higher, the increase of fresh weight was more suppressed than that of the dry weight, and the percentage of dry matter was increased. 3) The increase of dry matter production was accelerated with increasing nutrient concentration after 10 days after seeding. 4) NaNO_3 was used as a nutrient for seeding, and then the nutrient solution having 1:1:1 of nitrogen: phosphate: potassium, respectively, NH_4-N: NO_3-N ratio of 1:1 was used for seedlings. And 10 days after seeding, plants were grown with 0.8 g L^<-1> of nitrogen, and then 20 and 30 day after seedling, plants were grown with 1.6 g L^<-1> of nitrogen. The growth of seedlings obtained under the above conditions were comparable to that with paperpots.

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Effect of aerobic incubation with rice straw in soil, followed by submerged incubation, on the decomposition of straw carbon to methane (CH_4) and carbon dioxide (CO_2) was investigated in both laboratory incubation and pot experiment with rice plant. Formation of CH_4 in submerged soil with straw was suppressed to 25% by aerobic incubation for 20 d prior to the submergence to compare with no-preincubation treatment. During this aerobic incubation, 28% of organic C in straw was decomposed as CO_2. The total amount of decomposed C as CH_4 and CO_2 during aerobic and submerged incubations did not change by the length of aerobic preincubation. However, in terms of greenhouse gases, total CO_2 equivalent (assumed as CO_2+30×CH_4) was reduced to about one third by the longer aerobic preincubation. In pot experiment, CH_4 emission through rice plant during cultivation was reduced to 50-14% by incorporating straw 1 to 2 months prior to the submergence, and almost equalled to that from unamended pot.

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From a result of soil analytical data, it was ascertained that no suppression soil of potato scab occurrence had had a condition of low exchange acidity y_1. And potato scab was suppressed with a high level of exchange acidity y_1 by decreasing soil pH at an open-air field experiment on no suppressible potato scab soil. The results were as follows: 1) The severity of potato scab occurrence varies with different soil groups at the same soil pH. Soil groups can be separated to easily controllable areas and incontrollable areas of potato scab by exchange acidity y_1. The exchange acidity y_1 reaches 7-8 at soil pH 5.3 in the high level soil groups of Yotei and Kuriyama areas in which potato scab is easily controlled by simply decreasing soil pH. Few to no cases of potato scab are observed below soil pH 5.3 in the soil groups. 2) On the other hand, exchange acidity y_1 in the low level soil group is only 3.8 soil pH 5.3; here, potato scab is incontrollable. The soil pH of about 4.5 is needed for exchange acidity y_1 7-8 in the low level soil group of Abashiri-Shari area. 3) The exchange acidity y_1 is a practical measure of exchangeable aluminum (ex. Al) which is analyzed from same 1N KCl extractions with exchange acidity y_1 in soil samples. The correlation coefficient was found high level value of 0.99 between exchange acidity y_1 and ex. Al. Exchange acidity y_1 0.6 is almost 0 mg kg^<-1> of ex. Al, and exchange acidity y_1 7=ex. Al 44 mg kg^<-1>, exchange acidity y_1 10=ex. Al 65 mg kg^<-1>. The equation is ex. Al=-4.31+6.9 exchange acidity y_1. 4) The averages of Si/Al mol. ratio are 0.23 in all soil types in Niseko, Kuriyama areas, and 0.48 in ordinary Andosols, 0.54 in Acid Brown Forest soils, 0.67 in Brown Andosols of Abashiri area where there is the worst area for potato scab suppression. 5) At the open-air field in Brown Andosols, the y_1 reaches 7-3 at soil pH4.5~4.6 during potato tubering with aluminum sulfate and ferrous sulfate of 4g kg^<-1> added to the soil, and potato scab could be suppressed in Abashiri-Shari area. an exchange acidity y_1 that is too high hinders the growth of potato plants.

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Changes in dry weigh to top and root, inorganic nutrient content and storage carbohydrate content in root were investigated for 2 years. The following results were obtained: 1) The dry weight of leaves and stems was greatest in summer and gradually decreased in late autumn and early spring. The root dry weight, which showed a remarkable seasonal change, decreased sharply on harvest and thereafter just before over wintering increased about 2 times as much as that just after harvest. 2) Terrestrial nutrient uptake was taking place concentrically from just harvest finishing to foliage luxuriant stage, and just before over wintering; terrestrial nutrient was transiting to the root region. Inorganic nutrient in root, which was represented most by nitrogen and potassium, repeated such a pattern as decreases just after harvest finishing and increase before over wintering. 3) The rate of nitrogen, phosphate and potassium requirement of asparagus in a year were 200, 60 and 120 kg ha^<-1>, respectively. 4) Carbohydrate content in the root, which was richest in non-reducing sugar, remarkably was exhausted sharply on spears harvest, but increased about 3 times from harvest finishing to over wintering. 5) The above results suggested that early completion and proper maintenance of leaves and stems as well as substantiality of root to increase storage carbohydrate quantity in root were necessary for improving and maintaining the production of asparagus.

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A new fertilization technique for soybean, a deep placement of coated urea, promotes seed yield by supplementing N without depressing N_2 fixation activity. The seed quality related to chemical composition of soybean cultivated with deep placement was compared with those with a conventional basal dressing of small amount of ammonium sulfate or top dressing of coated urea. The N in seed was mostly distributed in 80% ethanol insoluble fraction, and only a small fraction (2%) was soluble form. The concentration of soluble N, primarily in the form of free amino acids, was almost the same among treatments. The insoluble N concentration was almost the same between control and deep placement. Also the concentration of starch and oil was similar among treatments or years. The soluble carbohydrate, especially sucrose, was significantly abundant in seed with deep placement of coated urea. The level of oligosaccharides, galactinol, raffinose, stachyose, was not consistently affected by fertilizer treatments. The concentration of P, K, Ca, Mg, Na, and Fe in the seed was almost the same among treatments. Concerning the storage protein, the relative abundance of glycinin and β-conglycinin was not affected by fertilizations, but the β-subunit of β-conglycinin increased a little by top dressing and deep placement treatments compared with control. Based on the analysis of chemical composition, it was concluded that the seed quality of soybean was not deteriorated dy deep placement of coated urea and was essentially the same as conventional fertilization treatment.

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