Recovery of Tsunami-Affected Paddy Soil Using Calcium Materials for Sustainable Agriculture

Oral Session

Relationship between the content of expansible 2:1 type clay minerals in paddy soils and the amount of ammonium nitrogen in the ponding water by a laboratory experiment

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 Pape

Measurement of Organic Phosphorus Mineralization in Non-Allophanic Andosols Using Anion Exchange Resin

Original Pape

Effects of available nitrogen and ammonium adsorption of plow layer on nitrogen uptake and yield of paddy rice (Oryza sativa L.)

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 Pape

Ammonia Emission and Carbon and Nitrogen Balances during Acidulocomposting of Garbage

Original Pape

Phosphate Bioavailability of Animal Manure Composts is Higher in Paddy Soil than in Upland Soil

Poster Sessio

Effect of Winter-Flooding and Organic Farming on Density of Aquatic Oligochaetes in Ricefields: Case Study in Miyagi Prefecture, Northeastern Japan

Original Pape