In order to understand the effects of soil condition on tree growth and nutrient cycling, we monitored the changes in stem diameter and analyzed the nutrient content of current-year needles and leaf litter of Picea glehinii growing in Gray Upland and Peat soils. Stem diameter showed diurnal changes that reflected transpiration and water uptake in both soils. However, the increase in stem diameter was larger in Gray Upland soils than in Peat soils, probably due to the longer growing period of Picea glehinii in the former than in the latter. During a rainy day within the growing period, the average increase in stem diameter was 35 μm d^<-1> in Gray Upland soils and 23 μm d^<-1>in Peat soils. These results suggested that the excessive soil water content in Peat soils weakened the response to rainfall of Picea glehinii. The poor soil water condition in Peat soils was reflected in the minimal growth of Picea glehinii in this soil. Litterfall production in Gray Upland soils was more than twice of that in Peat soils and the C/N ratio of the litterfall in Peat soils was statistically higher than that of Gray Upland soils. The poor soil water condition in Peat soils may have restricted the growth and nutrient uptake of Picea glehinii, which resulted to a low production of litterfall and its high C/N ratio. Results of this study have shown that soil conditions affect tree growth and nutrient cycling.

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The suitable nitrogen levels in substrates for fruit vegetable plug seedlings were examined from their seed nitrogen contents, growth under substrabtes of different nitrogen levels, and growth after planting. 1) In case of the seedling of its own root, the nitrogen levels to substrates which showed the good growth were 100 to 200 mg mL_<-1> for melon (Cucumis melo L.) and cucumber (Cucumis sativus L.), 0 to 100 mg mL_<-1> for pumpkin (Cucurbita maxima×C. moschata), 100 to 400 mg mL_<-1> for tomato (Lycopersicon esculentum Mill.), 200 to 400 mg mL_<-1>for eggplant (Solanum melongena L.) and 400 mg mL_<-1>for sweet pepper (Capsicum annuum L.). The growth at the 0 mg mL_<-1>of tomato, eggplant and sweet pepper decreased remarkably, while that of pumpkin of its own root and cucumber grafting which used pumpkin as the rootstock were equivalent with the case of the nitrogen application. 2) The ratios of nitrogen absorption of the seedlings for the seed nitrogen contents were 0.7 to 1.8 in pumpkin, under 6 in melon and cucumber, under 27 to 33 in the solanaceae, 0.4 to 0.8 in grafted cucumber. The solanaceae was more greatly affected by the nitrogen fertilization to the substrates than the cucurbitaceae. 3) The nitrogen levels in substrates which showed the good growth after planting were 100 to 800 mg mL_<-1>for melon, 200 to 400 mg mL_<-1>for cucumber, 100 to 800 mg mL_<-1> for tomato and eggplant, and 400 to 800 mg mL_<-1> for sweet pepper. Pumpkin and grafted cucumber were sufficient at 0 mg mL_<-1>.4) It was concluded that the suitable nitrogen levels were 0 to 100 mg L_<-1>for pumpkin and grafted cucumber, 100 to 200 mg L_<-1>for melon, 200 mg L_<-1>for cucumber, 100 to 400 mg L_<-1>for tomato, 200 to 400 mg L_<-1> for eggplant and 400 mg L_<-1> for sweet pepper. The effect of the seed nitrogen contents were important for the growth of the plug seedlings.

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The suitable phosphate concentration of substrates for vegetable plug seedlings was evaluated from the growth and phosphate content rates of the seedlings, and their seed phosphate contents, while the phosphate absorption coefficient of the raw materials of substrate was measured. 1 ) Sphagnum peat and coconut husk fiber were 0 g kg^<-1>, calcined vermiculites were 0 to 7.5 g kg^<-1>, and zeolites were 5 to 18.3 g kg^<-1> for the phosphate absorption coefficient of the given figure of the substrate raw materials. The phosphate absorption coefficient for the offered substrates, which consisted of sphagnum peat and calcined vermiculite, was 0.4 g L^<-1>. 2 ) The phosphate content rates from which good growth of seedlings was obtained were 12 to 21 g kg^<-1> for lettuce (Lacutuca sativa L.), 8 to 24 g kg^<-1> for Chinese cabbage (Brassica Pekinensis Rupr), 9 to 33 g kg^<-1> for cabbage (Brassica oleracea L.), 9 to 36 g Kg^<-1> for cucumber (Cucumis sativus L.) and 6 to 38 g kg^<-1> for tomato (Lycopersicon esculentum Mill.). 3 ) The water-soluble phosphate of the substrates from which good growth of seedlings was obtained were over 17 mg L^<-1> for lettuce and cabbage, 17 to 296 mg L^<-1> for Chinese cabbage, over 3 mg L^<-1> for cucumber and 29 mg L^<-1> for tomato. Therefore, the water-soluble phosphate which produced normal seedlings was 29 to 296 mg L^<-1> for each crop. There was no growth control even in phosphate non-use for the cucumber. 4 ) In comparison with the cucumber, the crops on the seeds of which the effect of supplied phosphate was big while the effect of used phosphate on the substrates was small were soybean (Glycine max Merr.), kidney bean (Phaseolus vulgaris L.), pumpkin (Cucurbita maxima×C. moschata), melon (Cucumis melo L.) and okra (Abelmoschus esculentus Moench.). On the other hand, the crops for which the effect of supplied phosphate on the seeds was small while the effect of used phosphate on the substrates was big were tomato, red pepper (Capsicum annuum L. 'tokyo sisitoh'), eggplant (Solanum melongena L.), sweet pepper (Capsicum annuum L. 'suigyoku2goh'), oriental melon (Cucumis melo L. var. flava Makino 'ohgon 9 goh'), wax gourd (Benincasa hispida Cogn.), lettuce, Chinese cabbage and cabbage.

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For plants to grow and develop, the growth pressure of plant roots in soil must exceed the counter pressure generated from the soil. This counter pressure is measured not only by soil hardness but is influenced also by pore deformability and by the water content of the soil. In this study, the root growth pressure of soybean (Glycine max Merr.) taproots at the initial growth stage was measured using packed soil cores having different values of dry bulk density, soil water content and hardness in a temperature and light intensity controlled room. The results indicated that the root growing into loose soil with sufficient water showed low growth pressure, whereas the root growing into soil whose physical conditions began to suppress root elongation showed the highest value of growth pressure. Growth pressure decreased when the soil had high hardness with insufficient air porosity ; and more branch roots were observed under such conditions. It was concluded that root growth pressure was not constant but varied by the counter pressure, which was determined by pore deformability, soil water content and soil hardness.

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Suface peat samples were collected from Sarobetsu peatland, Kiritappu peatland, Bekanbeushi peatland and Tokachi coastal peatland in Hokkaido, Japan. Iron forms in peat soils were determined by using a selective dissolution method, and their relation to the several physical and chemical properties, as well as the indices for the decomposition degree of peat were investigated. Total carbon and nitrogen contents had a significant correlation with the decomposition degree of peat, such as fiber content and the degree of humification, In several samples, an incorporation of inorganic materials, such as volcanic ash and alluvial deposit, rather than the decomposition degree of peat affected ash content of peat. The average total iron content (Fe_t) for all samples was 16.4 g kg_<-1>. When the average was calculated with samples which were less affected by the incorporation of mineral materials, they still had a relatively high average of 11.1 g kg_<-1>Fe_t. In these peat samples, more than half of total iron was extracted with 0.1 mol L_<-1>sodium pyrophosphate solution. The sodium pyrophosphate extractable iron content (Fe_p) had little difference from acid oxalate extractable and dithionite-citrate extractable iron contents, which should be higher than Fe_p, since they have strong abilities to dissolve iron from high crystalline amorphous iron oxides and minerals. These results suggested that a considerable part of the iron was in the form of iron-humus complexes and amorphous iron hydroxidws. The positive correlation between Fe_p and the degree of humification of peat at 340 nm also supported these results. Consequently, iron mainly existed in the iron-humus complexes in the peat samples that were less affected by an incorporation of inorganic materials, while highly crystalline iron oxides and primary minerals were the main pools of iron in the samples that were rich in mixed volcanic ash and alluvial deposit.

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Although silicic acid absorption of paddy rice (Oryza sativa L.) is believed to occur mainly in the uncharged and mono-molecu1ar state (Si (OH)_4°), this has not been elucidated theoretically, yet. Better understanding and elucidation of various phenomena related to silicic acid is possible when we think of silicic acid being absorbed in the ionic state ((OH)_3SiO^-). Using this supposition, nourishment composition and cation-anion balance of paddy rice was investigated. As a result, when evaluated by supposing silicic acid as anion, the equivalent ratio of cation and anion was nearly one, and its equivalent relation was found. But when evaluated not supposing silicic acid as anion, the equivalent ratio is four to five, and anion shortages overwhelmingly lose their ionic balance. Also, when considering the chemical state of silicic acid in soil solution by the chemical equilibria theory, silicate ion is calculated to be present at a level of about 10^<-5> to 10^<-7>mol L^<-1>at pH 6 to pH 8. This concentration corresponds to the level of 10^<-6>mol L^<-1>of Km in system 1 of dual mechanism in ionic absorption mechanism in crops, indicating that silicic acid can be sufficiently absorbed in ionic state. As a result, it was strongly suggested that silicic acid absorption of paddy rice is ionic, acting as a counterion of cation.

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The purpose of this study was to estimate the crop residues (rice straw, wheat straw, corn shoot and chaff, beet leaves, soilage oats and rice husk) and organic materials (farmyard manure, chicken manure, bark compost and sewage sludge compost) as phosphorus materials, and to analyze the dynamics of organic, inorganic and available form phosphorus in soils with crop residues and organic materials applied to them successively for 17 y. Phosphorus contents in organic materials were higher than those in crop residues. Especially abundant were the inorganic phosphorus contents in chicken manure and sewage sludge compost. Among crop residues, the total and inorganic phosphorus contents in soilage oats were abundant. Soil organic phosphorus contents increased with successive application of wheat straw, corn shoot and chaff, beet leaves, rice husk and chicken manure. Soil organic and inorganic phosphorus contents increased with successive application of wheat straw+soilage oats or rice straw. Farmyard manure application increased inorganic phosphorus in soil. And successive application of sewage sludge compost, or bark compost increased organic and available phosphorus in soils. In particular, sewage sludge compost application brought a greater increase of available phosphorus. This probably suggests that sewage sludge compost is a better phosphorus material. It was surmised that the C/N ratio, N/P ratio and ratio of inorganic phosphorus to total phosphorus in crop residues were the main factors for phosphorus addition in soils.

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In order to reduce environmental burdens from grassland, nitrification inhibitors were added to cow's urine before application onto grassland. Levels of nitrous oxide generation, yields of pasture grass, levels of nitrogen absorption, levels of nitrogen in soil solution and levels of inorganic nitrogen in soil were determined A highly humic thick-layer andosol field was sowed with a mixture of Italian ryegrass, orchard grass, tall fescue and red clover, and divided into the following zones : chemical fertilizer, nitrogenfree, cow's urine and cow's urine+Dicyandiamide (Dd). 1. Among three nitrification inhibitors added to solutions of ammonium sulfate to investigate their effects on nitrification inhibition, Dd exhibited the greatest effect. 2. Nitrous oxide generation, nitrogen absorption by pasture grass, yield of pasture grass and levels of nitrogen as NO_3 in underground water and soil were determined. The nitrogen application level was 50 kg ha^<-1> at one time, except for the cow's urine+Dd Zone, which had a nitrogen application level of 55 kg ha^<-1>because of the replacement by Dd for 10% of nitrogen in cow's urine. 3. Nitrous oxide generation was inhibited by 66% and 40%, respectively, in 1998 and 1999 in the cow's urine+Dd zone, compared to that in the cow's urine Zone. Ratios of nitrous oxide generation to nitrogen application were O.22% in the cow's urine+Dd zone and O.36% in the cow's urine zone in 1998 ; and O.23% in the former and 0.08% in the latter in 1999. 4. The nitrogen absorption level and dry matter yield in the cow's urine+Dd zone were higher than those in the cow's urine zone. The increments were 24% for both, which were even greater than those of nitrogen supply through Dd. 5. The determination of nitrogen levels in underground water and soil revealed no downward transfer of nitrogen.

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Tomato plants were grown in a closed hydroponic system using coir or rockwool as substrate (coir-and rockwool-systems) for about 5 months to study the effects of NO_3-N/NH_4-N ratios of nutrient solution on the fluctuation of ion concentration in a recirculating nutrient solution and the growth and yield of tomato. Three nutrient solutions varied in NO_3-N/NH_4-N ratios (14.8 mM/ 1.2 mM=standard solution, 16/0=solution I, 12/4=solution II) were designed to produce neutral, basic and acidic condition in the medium. The results obtained were as follows : 1 . In solution I and standard solution plots, the pH of the recirculating solution was more stable in coir-system than in rockwool-system, whereas in the solution II plot, the pH was drastically decreased. 2 . In coir-system, ion conceuatrations in the recirculating solution were much more stable than those in rockwool-system, especially in solution I. 3 . Plant vigour was the strongest in the standard solution plot in both systems, and in the coir-system, total yields were the highest in the standard solution plot, but marketable fruits yields were the highest in solution I plot. In rockwool-systems, total yields were highest in the solution I plot, and there were little difference between solution I and standard solution in marketable fruit yields. Of all the plots, the marketable fruit yields were the highest in the solution I plot in the coir-system. 4 . In the coir-system, the higher pH of the recirculating solution made the CEC of substrate increase in solution I, which contained NO_3-N alone as its nitrogen source, and reduce the fluctuation of ion concentration. Consequently both marketable fruit ratios and yields became the highest among the treatments.

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The gangrene of potato (Solanum tuberosum L.) caused by Phoma exigua developed on the stored seed tubers (cv. Sakurafubuki) harvested from a field with sandy soil (Volcanogenous Regosols) in Hayakita-cho, Hokkaido, Japan in the autumn of 1996 and placed in a storehouse until the next spring. On the other hand, potato gangrene did not occur on the tubers harvested from another field in the same area with sandy soil. In this field, spent flue gas desulfurization absorbent residue (SGDAR) and high analysis mixed fertilizer (HAMF : N-P_2O_5-K_2O-MgO-MnO-B_2O_3 10-20-14-5-0.3-0.15) were applied as soil amendment and supplement fertilizer, respectively. SGDAR is a by-product from the flue gas desulfurization system in thermoelectric power stations, which consists of gypsum (CaSO_4) and coal ash. A field experiment conducted in the above-mentioned area in 1997 showed that the application of SGDAR (10 Mg ha^<-1>) suppressed the development of gangrene on the stored tubers and increased the marketable tuber yield by 30%. However, application of HAMF (200 kg ha^<-1>) as supplement fertilizer did not affect either development of gangrene or tuber yield. By the application of SGDAR the concentration of exchangeable Ca and available B in the soil became twice as high as that of the control and the concentration of Ca and B in tuber and shoot of potato also increased. These results suggest that Ca and B eluted from gypsum and coal ash contained in SGDAR, respectively, increased the resistance of the tubers to the infection with the pathogen, P. exigua, or weaken the pathogenicity of the pathogen in the sandy soil which contains little these nutrients. These nutrients would also increase the tuber yield of potato in the soil.

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The development of gangrene of potato (Solanum tuberosum L., cv. Sakurafubuki) caused by Phoma exigua was suppressed with spent flue gas desulfurization absorbent residue (SGDAR) applied to sandy soil (Volcanogenous Regosols) in Hayakita-cho, Hokkaido, Japan. SGDAR consists of gypsum (CaSO_4) and coal ash which contain a large amount of Ca and B, respectively. A field experiment in the above-mentioned area in 1998 showed that application of Ca with gypsum (1.6 Mg Ca ha^<-1>) suppressed the development of gangrene. However, application of B (1.6 kg B ha^<-1>) with both coal ash and fritted trace element fertilizer (FTE) suppress it. Application of SGDAR and gypsum increased the concentration of exchangeable Ca did not in the soil and the concentration of Ca in tuber of potato. These results suggest that Ca eluted from gypsum in SGDAR increased the resistance of the tuber to the infection with the pathogen, P. exigua, in the sandy soil which contains little Ca nutrients. SGDAR and gypsum promoted the growth of the tuber and increased the tuber yield, and coal ash and FTE increased the number of tubers.

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We analyzed the chemical characteristics of soils under protected cultivation. We applied a fertilizer which was modified with reduction of chemical stress, and showed the effect of the fertilizer on yield and fruit quality of tomato. 1 ) We collected 89 soils under protected cultivation from 7 prefectures (Saga, Yamaguchi, Kagawa, Aichi, Gifu, Shizuoka and Gunma) to estimate current soil chemical property in Japan. We determined the accumulated nutrients from residual fertilizer in soils in protected cultivation to be almost 6 times higher than those in open field cultivation. Although it has been said nitrate was most important residual anion, we showed that excess sulfate was also highly accumulated in the soil of protected cultivation. 2 ) We tried to use low-sulfate slow-release fertilizer (LSR) to control excessive nitrate and sulfate accumu1ation. LSR application made soil condition more correct. That is, LSR made soil pH more neutral and made soil EC low, mainly because residual sulfate was reduced. 3 ) These difference affected the fruit yield and fruit quality of tomato. During the three years' continuous cropping, the rate of blossom end rot (BER) was constantly suppressed using LSR (average BER rate : control 33%, LSR 23%). As far as yield is concerned, the third year yield for LSR application was 1.2 times superior to that for ordinal fertilizer application. 4 ) These differences were caused by chemical or water stress in rhizosphere. Bleeding rate of LSR application was faster than ordinal fertilizer application. this result suggests residual fertilizer reduced the transport of water and nutrient and affected yield and fruit quality of tomato.

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This study is a technical cooperation between JICA/Japan and EMBRAPA/Brasil on the project of developing sustainable agriculture of Cerrados for management and conservation of natural resources. One of the soil genetic characteristics of Cerrado Oxisol is that the amorphous-silica content of the soil is very low. Silica is known as an essential element for rice plants and is effective in controlling rice blasts. It has also been expected to function positively for mechanical strength of plant tissues with some plants. However, there hasn't been much data collected on the silicate application to Cerrado Oxisols in relation to crop productivity. In this study, we carried out a survey on the available silica content of main Cerrado soils and an investigation on the effect of silicic materials application to plant growth by pot experiments and field examination. The result has been obtained as follows : 1 ) In the result of the soil survey in Planaltina-DF (CPAC) and Pedro Afonso-TO, the available silica (Si) content of the soil was Latossolo (10-40 mg kg^<-1>)glt;Glei pouco-humico (40-60 mg kg^<-1>)glt;Glei humico (50-120 mg kg^<-1>), and silica content has been increased in the order from low humic soils such as Red-Yellow soils to high humic soils such as black soils. 2 ) In the result of the general pot experiment (using Latossolo) on the effect of silicic materials application by using 2 kinds of silicate calcium (Japan), nickel steel sludge (Brasil) and diatomaceous soil (Brasil) for corn, soybean and rice, roots of plants from each management soil increased in proportion to application quantities of each material. In the result of particular pot experiment with root-split (using Latossolo), roots of plants in each compartment also increased in proportion to application quantities of each material and it was considered that the root property had to expand selectively into the soil with high silica content. Furthermore, the silica (Si) density of the plant had increased in proportion to application quantities of silica materials, and the dry matter of plants also had increased. From these results, it was guessed that the effect of silica application was large on field crops growth. 3 ) In the field examination on Latossolo, we investigated the effect of 3,000 kg ha^<-1> of powdery nickel steel sludge applied at one time primarily for annual crops (corn and millet). The grain yield of corn had been increased by 5% by applying silicic material. This rate of yield increase was not worthwhile as a primary outcome, but it is certain that the quantity of roots had been increased and insect damage had been decreased by a single application. The silica (Si) density of plant (leaf+stalk) after applying silica was kept at a high level until the fruition stage compared to no application, and from this result, it was guessed that this situation was one factor in the decreased insect damage. The yield of millet planted secondary also showed the same tendency. From these results, it can be seen that there were certainly effects from silica application for field crops.

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Revolving furnace slag (RFS), which is and industrial by-product, and spent disposable portable body warmer (PBW) were applied to paddy soil as oxidation materials. Portions of 4 kg of Coarse and Medium Textured Gley soil were placed into plastic pots (1/5,000a). RFS was added to the pots at the rate of 0 (control), 10,20,40,100 ton ha^<-1>, and PBW at 10 ton ha_<-1>only. Methane flux from the potted soil planted with rice was measured by the closed chamber method during the 1999 cropping season. Pots that received RFS showed lower. Eh values compared with the control pot, although the RFS was applied to keep soil oxidative in the early period of cultivation. The strong decrease in Eh under a high rate of RFS application may be due to the high pH of the RFS (pH (H_2O) = 12.2). On the other hand, methane flux was suppressed under a high rate of RFS application, during the early period of cultivation. However, this flux trend was reversed during the midgrowing period. This may be due to disturbances in the soil environment caused by dissolving elements from RFS. Total methane flux during the cultivation period was significantly decreased, about 10%, when 10-40 ton ha^<-1>of RFS and 10 ton ha^<-1> of PBW were applied. Methanogenic activity was not significantly different when 0-40 ton ha^<-1> of RFS were applied, while that of RFS pots at 1OO ton ha^<-1> and of PBW pots at 10 ton ha^<-1> were decreased. However, methane oxidizing activity was increased, max 15%, when 10-40 ton ha^<-1> of RFS were applied, while that of RFS pots at 1OO ton ha^<-1> and of PBW pots at 1O ton ha^<-1> were decreased. The decrease in total methane flux may be attributed to enhanced methane oxidizing activity rather than inhibition of methanogenic activity. The grain yield was significantly increased, about 30%, when 40 or 1OO ton ha^<-1> of RFS was applied. It was also partly due to the dissolving inorganic substances from RFS. From this study it is clear that the use of RFS and PBW in paddy field are desirable because they led to increased grain yield as well as decreased methane emission.

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