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Original Paper

Effects of available nitrogen (N) and ammonium adsorption of plow layer (PL) on N uptake and brown rice yield were investigated for seven soils. The experiment was conducted in a single paddy field under same conditions except for soils. Rice plants were grown in frames, which the seven different soils (four alluvial paddy soils and three andic paddy soils) were repacked. Not only a small percolation condition (i.e. original subsoil (OS) plot) but also an increased percolation condition was treated by the replacement of subsoil with sand (i.e. sandy subsoil (SS) plot). Percolation rate was lower in clayey smectitic (1-2mm day^) than in sandy and andic (5-9mm day^) soils in the SS plots. In the OS plots, percentage of exchangeable ammonium-N in total soil ammonium N was 89-96% in all soils at 11 days after transplanting (DAT), and was higher in soils with the large ammonium adsorption of PL. Soil ammonium-N at 40 DAT (i.e. at active-tillering stage), N uptake at harvest and brown rice yield were explained by the available N of PL in the OS plots. It is considered that the difference of ammonium adsorption of PL did not strongly affect them, because of its small variation and the small percolation. In the SS plots, the soil ammonium-N at 40 DAT was explained by the ammonium adsorption and the available N of PL. It is considered that soil ammonium-N was much protected from leaching and denitrification in soils with the large ammonium adsorption of PL. However, the total N uptake and the brown rice yield were effectively explained by the available N of PL, and the ammonium adsorption of PL was not selected as an important parameter. It is considered that the ammonium adsorption of PL did not strongly affect the N uptake after maximum tillering stage. The ammonium adsorption of PL did not significantly related to recovery rate of fertilizer N both in the OS and SS plots because of the small variation in the ammonium adsorption of PL among soils., Original Paper

From the viewpoint of ammonium-nitrogen (N) transportation from paddy fields to rivers, estimation of ammonium-N in the ponding water is important for soil management to reduce N outflow from paddy fields. The relationship between the content of expansible 2:1 type clay minerals (i.e. smectite and vermiculite) and the amount of ammonium-N in the ponding water was investigated by a laboratory incubation experiment. Eighteen soils including fifteen alluvial soils and three volcanic ash soils from northeastern Japan were used; the clay content in soils was 116-476g kg^; the content of expansible 2:1 type clay minerals in soils was 0-395g kg^. The experimental condition corresponded to the condition of paddy fields just before transplanting, where readily available N fertilizer was incorporated to plow layers (0.15m) at a rate 5g N m^ as basal fertilizer and submerged water depth was 0.06m. The concentration and the amount of ammonium-N in the ponding water was 1.4-7.5mg L^ and 0.08-0.45g m^. The amount of ammonium-N significantly related to the amount of clay in the calculated plow layer with a depth of 0.15m (R^2=0.42). On the other hand, the amount of expansible 2:1 type clay minerals in the calculated plow layer more strongly related to ammonium-N than the amount of clay (R^2=0.55). These results were attributed to the fact that expansible 2:1 type clay minerals have larger amount of negative charge site per clay and higher selectivity in ammonium adsorption than other clay minerals. From these results it was considered that paddy soils rich in clay fraction or expansible 2:1 type clay minerals could adsorb larger ammonium and mitigate ammonium-N runoff through the ponding water., Original Paper

A pot experiment was carried out to evaluate the effectiveness of co-situs application of ferric and ferrous iron in alleviating iron deficiency in paddy rice grown (Oryza sativa L.) on calcareous soil. Various ferric and/or ferrous iron containing materials were co-situs applied together with rice seedlings. Plants treated with no iron and ferric iron containing material died by 30 days after transplanting. Materials containing ferrous iron were more effective in alleviating iron chlorosis of paddy rice than those containing ferric iron. In this study, iron deficiency in rice was partially alleviated by co-situs application of all materials that contained ferrous iron in the composition, and the co-situs application of controlled released fertilizer containing ferrous iron was proved to be the most efficient method for improving rice growth in the calcareous soil used.

Effect of watershed environments on river water quality and the subsequent influence of water quality on the growth of diatoms in coastal seawater were studied. Land use in the upper and lower site of the Ohkawa River (O-up and O-low) and the upper site of the Nanakita River (N-up) were dominated by forestry, whereas the lower site of the Nanakita River (N-low) was characterized by urbanization. Seasonal changes in nutrients in the Ohkawa and Nanakita Rivers suggested that the concentrations of NH_4-N, NO_3-N, PO_4-P and acid extractable-Fe were influenced by human activities, while Si concentration reflected geological conditions. The average concentrations of fulvic acid-like Fe (FA-Fe), closely associated with the growth of coastal diatoms, were 1 and 16μgL^ at the O-up and O-low sites, respectively, while those of the Nanakita River were 5μgL^ (N-up) and 53μgL^ (N-low). For each river, FA-Fe concentrations of the lower sites were much higher than the upper sites. Moreover, the concentration of FA-Fe at N-low was much higher than at O-low. Therefore, it was concluded that FA-Fe originates not only from forest vegetation but also from urban activity. The growth of the Skeletonema, a typical diatom of coastal waters, was stimulated by the addition of O-low river water compared to addition of O-up, reflecting the FA-Fe content. Diatom growth stimulation with the addition of lower river water was much more prominent in the Nanakita River, whose watershed is characterized by runoff from Sendai city., Original Paper

The effects of "FeAgri", a novel iron-containing material, on the growth of lettuce (Lactuca sativa), crown daisy (Chrysanthenum coronarium), cabbage (Brassica oleracea) and Chinese cabbage (Brassica campestris) were studied in the greenhouse using Wagner pots with river sand. Cabbage showed the most significant responses in terms of leaf color and fresh weight to different levels of the Fe-containing material. There were also some differences in plant length, leaf width, shoot and root dry weight, but they were not statistically significant. Lettuce showed a significant difference in leaf color and also showed some differences in other growth factors and iron concentration of leaf. Chinese cabbage showed a significant difference in fresh weight and some differences in other growth factor. However, in the case of crown daisy, there were differences in plant length, leaf color, fresh weight, and root and shoot dry weights, but no statistically significant differences in all growth factors examined., Original Paper

Despite of its abundance in soil, iron (Fe) is still one of the most common nutrients limiting plant growth and development because it exists mostly in low-soluble form that is hardly available for plants. Therefore, plants have evolved two distinct uptake strategies, the reduction (Strategy I) mechanism and the chelation (Strategy II) mechanism. This paper reviews some recent studies in regard to both strategies that are important for iron acquisition, mobilization and uptake in plant roots. These key processes are believed to be relevant for the supply of Fe to plants as well as for supplying human nutritional needs., Alkaline soil, Iron nutrition, Mugineic acid, Strategy I, Strategy II

The effects of simulated acid rain and the heavy application of fertilizers on acidification of allophanic Zao Andisol and non-allophanic Kawatabi Andisol were investigated in two studies. One was carried out using a 21cm height and 16.5cm diameter column, and a rain simulator machine. The other, was done using a stirred-flow reaction system to determine the SO_4^ adsorption capacities of Andisols. For both allophanic and non-allophanic Andisols, the amount of soil extractable SO_4^ increased with depth, but the amount of SO_4^ extracted in Zao soil was much higher than that in Kawatabi soil. The rate of acidification of Kawatabi soil due to acid input was higher than that for Zao soil. The amount of M KC1 extractable aluminium was higher than that of water extractable Al, and increased when soil pH decreased. With fertilizer treatments of Kawatabi soil, we found a significant (P adsorbed in Zao soil were much higher than those in Kawatabi soil, which was more sensitive to acid inputs. The amount of M KC1 extractable Al in Zao soil was lower than that in Kawatabi soil; however, in both soils it increased with a decrease of soil pH. It was suggested that if soil pH of Zao soil decreased to low values, the amount of M KC1 extractable aluminium could be reached to toxic levels for crop growth., Andisol, crop growth, heavy fertilization, simulated acid rain

As a case study, the seasonal changes of diatom community in flooded water of paddy fields were discussed. The investigations were conducted on Andosols (Field 1) at Field Science Center, Tohoku University, and on Fluvisols (Field 2) at Furukawa Agricultural Experimental Station, located at Miyagi Prefecture, Japan, during the rice-growing season of 2004. The results obtained are as follows: 1) Diatom cell density at Field 1 ranged between 2.1x10^5 and 1.1x10^6 cells L^. There was no large difference during the experimental period in Field 1. Diatom cell density in Field 2 ranged between 4.3x10^5 and 5.3x10^6 cells L^. Diatoms in Field 2 were low in the end of May, and increased gradually thereafter. 2) Nineteen genera were observed in Field 1 and twenty-four genera in Field 2. In general, Nitzschia was predominated genus in the both fields. In Field 1, Melosira became predominated from June to August. In Field 2, Navicula was also predominated in July.

Using a single basal application of controlled-release fertilizers for bell peppers is a perspective method, because by the elimination of top-dressings, labour and energy costs can be reduced. In this study, effects of band and nursery pot applications of polyolefin-coated fertilizers (POCF) on bell peppers grown in the field were compared at two different application rates, in 1997 and 1998. As a consequence of continuous nutrient supply, a good yield could be achieved in case of both application methods. Application methods significantly affected the generative/vegetative balance of the bell pepper plants, and thus the yield. Both years, early plant development and early yield were much better for the nursery pot application treatments than for the band application treatments, due to the better seedlings and to the quicker seedling establishment. Results of total yield were unambiguous for the two years. It was concluded that the nursery pot application method can be a very effective fertilization method for reducing labour and energy costs, but seedlings must be transplanted before the lag time of the sigmoid-type POCF ends. Using POCFs, 25% decrease in the amount of fertilizer applied did not decrease the yield of bell peppers.

Softwood cuttings of 'Earlyblue', 'Spartan', 'Blueray', and 'Bluecrop' cultivars of highbush blueberry (Vaccinium corymbosum L.) and those of the wild species Oobasunoki (Vaccinium smallii) were planted in a moisture peat moss medium and were grown in growth chambers at ambient (current atmospheric concentration) or elevated (1, 000 mg l ^1) levels of carbon dioxide from the July 16 to November 14, 2002. The experiment was finished on April 8, 2003. The carbon dioxide enrichment had a definite positive effect on the growth of blueberry softwood cuttings. The effect was manifested in improved rooting and surviving ratios, earlier root induction, longer roots, and increased branch growth. It was concluded that carbon dioxide application is a feasible means for achieving faster and efficient propagation of highbush blueberry softwood cuttings., CO_2 enrichment, highbush blueberry, propagation, softwood cuttings

The fate of polyolefin ^N coated urea (POCU S-100) in a nursery box for the no-tillage transplanting system as compared with ^N ammonium sulfate (AS) in the conventional tillage system had been investigated in light clay alluvial soil, sandy loam alluvial soil, and clay loam soil (Andisol) in 1994 and 1995. Rice (Oryza sativa L. cv. Hitomebore) was used as the test plant. The nitrogen concentration of the leaf blade of the rice plant in the no-tillage without rice straw (NT) and no-tillage with rice straw (NTS) treatments tended to be greater than those of the conventional tillage with rice straw (CTS) treatments in all types of soil at all growth stages, and there was no definite increasing or decreasing tendency in the N concentration of the leaf sheath and stem, and panicles of the rice plant among the treatments in all types of soil. Nitrogen recoveries from POCU S100 in the NT and the NTS systems were 77-79% and 78-83%, 61-73% and 66-78%, and 74-76% and 80-81% for light clay soil, sandy loam soil and clay loam soil, respectively, which is around 65.5-96% of the nitrogen released from POCU S100. Thus, this could reduce the environmental pollution. The straw application in the NT system increased the N recovery of POCU S-100 by 1-5%. On the other hand, nitrogen recoveries from ammonium sulfate applied as basal fertilizer in the CTS system were 35-43%, 20-29% and 23-32% for light clay soil, sandy loam soil and clay loam soil, respectively. Whereas those applied as a top dressing were 50-83%, 49-73% and 40-65%. Nitrogen uptake by the rice plant in the NT system was relatively higher than that in the CT system. The uptake of soil nitrogen by the rice plant in the NT system was lower than that in the CT system.

Polyolefin coated fertilizer as a new type of controlled release fertilizer (CRF) has began to be used in upland crops in Japan due to its high N recovery rate and environmental friendly characteristics under humid climate. The objective of this paper lies in investigating the response and adaptability of dent corn (Zea mays L. var. indentata Sturt.) and sweet corn (Zea mays L. var. saccharata Sturt.) to two forms of co-situs application methods (co-situs band application and co-situs spot application) of CRF in upland field of a volcanic ash soil (Alic Pachi Mellanudand) under humid climate conditions. The results obtained showed that, compared to the conventional side-band application of urea, for sweet corn and dent corn, in co-situs spot application of LP70 (polyolefin coated urea, 70 day type), the mean germination percentage at each sowing point greatly decreased by 66.7% and 50%, respectively ; In co-situs band application of LP70, the germination percentage decreased by 26.7% and 10.0%, respectively ; under the condition of co-situs band application of urea, nearly all the seeds of two corns did not germinate and the germinating power was inhibited completely ; The weather conditions with less rainfall and higher temperatures at the germination stage probably increased tendency of poor germination under the co-situs application conditions ; Co-situs spot application of LP70 further retarded seedling development, but such retardation was not obvious at the late growing period because of good water conditions, and in this treatment, the grain yield of both corns as well as the uptake amount of N, P, K decreased significantly, too, but there were no significant difference for harvest index and nitrogen harvest index as compared with control, suggesting that poor germination and less plant number is the main reason for significant decrease of yield and nutrients uptake. Based on the above results, it is therefore recommended that the co-situs application of CRF especially the co-situs spot application would not be applied in sweet corn production, and the co-situs band application of CRF is ideal fertilization method for dent corn production under upland conditions without irrigation in humid area., Controlled release fertilizer, Co-Situs application, Dent Corn, Germination, Sweet Corn

The effect of linear type of polyolefin coated urea (POCU) 10 or 30 in combination with sigmoid type of POCU S100 in the nursery box on the improvement of the initial growth of rice in no-tillage transplanting system was studied in light clay soil (alluvial soil) and clay loam soil (Andisol) in Miyagi prefecture, Japan. POCU-10 or POCU-30 (short release type of POCU) in combination with POCU S100 was remarkably more effective in increasing the leaf color value and the number of tillers than those in the POCU s100 treatments, reflecting the rapid release of N from POCU-10 or -30 at the initial growth stage. POCU-10 or POCU-30 in combination with POCU s100 increase the dry matter yield at young panicle initiation stage. The N recoveries from the linear type of POCU-10 and POCU-30 at the young panicle initiation stage were 41 and 30% and 33 and 34% in light clay soil and clay loam soil, respectively. At the harvest time, they were 53 and 53%, and 51 and 68% in light clay soil and in clay loam soil, respectively. The yields of brown rice of NTS 30 were almost the same or higher than those of NTS, whereas those of NTS 10 tended to be lower because of a fewer number of spikelets per m^2.

Food production systems have been studied in order to improve production capacity and quality in individual bio-production fields, and these advances have contributed to establishing a sufficient food supply to meet the needs of the increasing world population since the industrial revolution. However, it has also been clarified in the last two decades that agricultural activity has also contributed to increases in environmental loading such as global warming gas increase, stream and subterranean water pollution, soil degradation, etc. The development of environmentally friendly bio-production systems that integrate high production efficiency with the ecosystems, including human society, is expected to be of great interest. To facilitate the development of environmentally friendly bio-production systems that consider the ecosystem, the new Field Science Center was established in 2003 through the merger and reorganization of two former educational and research facilities for field science : the University Farm, and the Education and Research Center of Marine Bio-resources. The new center has three educational and research stations : the Field Control Station (Sendai), the Terrestrial Field Station (Naruko), and the Marine Field Station (Onagawa). It also has five following research cores : the Forest-Andisols Research Core, the Ruminant Production Research Core, the Rice Production Research Core, the Marine Bio-production Research Core, and the Integrated Field Control Research Core. The Integrated Field Control Core was formed to promote an environmentally, friendly, high quality and high yielding bio- production and to hasten the integrated field science in terrestrial-marine ecosystems.

Poster Session