Rice (Oryza sativa L.) cultivar ‘Leaf Star’ produces high foliage yield and is commonly used for whole-crop silage (WCS). Nitrate concentrations in aboveground biomass of ‘Leaf Star’ plants did not differ among growth stages, but increased when additional nitrogen fertilizer was applied. However, they remained safe for ruminant consumption, even at the highest amount of nitrogen fertilizer applied, 24 g N m^-2 (24 N plot) and 6 kg m^-2 of composted cattle manure. At the yellow ripening stage, the nitrogen content in the foliage increased with the application of a large amount of nitrogen fertilizer. That in the panicles increased by a smaller amount. The rate of nitrogen translocation from the foliage to panicles was lower in ‘Leaf Star’ than in common rice cultivars that do not produce high foliage yield. In ‘Leaf Star’ plants, nitrogen uptake but not dry weight was higher in the 24 N plot than in plots treated with lower concentrations of nitrogen fertilizer. The quality of WCS was lower in the 24 N plot than in other plots because of a higher volatile basic nitrogen content. Therefore, the production of volatile basic nitrogen in WCS was promoted by a decrease in the ratio of total nitrogen to nitrogen in the cell wall–free extract of aerial tissues at high rates of nitrogen application. Thus, the application of appropriate concentrations of nitrogen fertilizer is vital for the maintenance of both dry matter production and feed quality.

We expected that hydroxyapatite prepared from cattle bones (cattle-derived HAp) would immobilize soil cadmium and reduce its long-term availability to crops, because insoluble cadmium is stable in weakly acidic regions. To evaluate this expectation, we added cattle-derived HAp to soil and performed x-ray absorption fine structure analyses. We found that insoluble cadmium differed from plant-available cadmium: cadmium was fixed at calcium sites of cattle-derived HAp.

We investigated the effects of salt removal by soil puddling on the concentrations of Cl^-, Na⁺, and soil nutrients in three sandy paddy fields (A, B, and C) on the Kujukuri coast of Chiba prefecture, Japan, which was flooded by the tsunami caused by the Great East Japan earthquake on 11 March 2011. All three fields had high concentrations of Cl^- (108.5–240.1 mmol kg^-1), soluble Na⁺ (64.7–137.0 mmol kg^-1), and exchangeable Na⁺ (15.2–48.8 mmol kg^-1), particularly in the plow layer. Salt removal decreased ion concentrations by 49%–99% (to 1.3–16.7 mmol kg^-1) for Cl^-), 2.2–23.1 mmol kg^-1 for soluble Na⁺, and 1.8–12.0 mmol kg^-1 for exchangeable Na⁺). It also decreased the percentage of exchangeable sodium from 17%–67% to 2%–18%. In field A, the concentrations of both Cl^- and total Na⁺ (soluble + exchangeable) were <4.4 mmol kg^-1 at a depth of 0–75 cm. In fields B and C, they were 1.0–23.6 mmol kg^-1 (both Cl^- and Na⁺) at a depth of 0–30 cm, and 2.4–29.6 mmol kg^-1 (Cl^-) and 6.1–31.4 mmol kg^-1 (Na⁺) at 30–90 cm. The concentrations of exchangeable Ca²⁺, Mg²⁺, and K⁺ increased after the tsunami by 1%–52% and decreased after salt removal by 3%–37%. Paddy rice was transplanted after salt removal without midsummer drainage. The yield of brown rice per unit area was lower by 19% in field A and by 28% in field B than the average annual yield.

Agriculture, including livestock husbandry, is a major source of nitrogen (N) in surface waters. The difficulty of detecting source areas of N on a catchment scale makes it a challenge to prioritize sites with N pollution of surface waters that require urgent management. This study aimed at delineating N-vulnerable zones within a catchment on the basis of pathways of N transport from each site to the river. Topographic data (differences in elevation between adjacent cells with a threshold value of 3 m) were used in a GIS model to create a spatial distribution of gaps in shallow groundwater in a catchment. Areas between the river and the first gap were considered as less vulnerable zones (LVZs), where loss of N originating in LVZs by denitrification in riparian subsoil was expected. The other areas were considered as more vulnerable zones (MVZs). The area ratio of MVZ (R_MVZ) varied between 6.8% and 52.4% among catchments. In both zones there was a linear relationship between potential N loads and N concentrations in effluents among catchments. The MVZ/ LVZ ratio of both slopes was 6.25. The N concentration in river water was calculated from concentrations in effluents from both zones and R_MVZ. These results indicate that in catchments with R_MVZ>13.4%, N load reduction in MVZs would be most efficient at lowering N concentrations in river water, and in catchments with limited MVZs, reduction in LVZs would be also helpful.