We investigated the effects of applying methane-fermentation-digested slurry, derived mostly from dairy cattle waste, on the formation of soil aggregates in grassland. The carbon content of the surface soil (0–5 cm) increased more in the NPK₊ digested slurry plot than in the NPK-only plot, indicating the contribution of digested slurry to the storage of carbon in the soil. This greater increase was seen only in the surface soil, and took at least 5 years of application to become significant. In the 7th year of application, the increase in the formation of macro-aggregates (>1000 µm) and grass root weight in the surface soil was greater in the NPK₊ digested slurry plot than in the NPK plot. We assume that the grass roots bind micro-aggregates (<250 µm) in the soil. The macro-aggregates of the NPK₊ digested slurry plot showed a particularly high accumulation of carbon in particulate organic matter (>53 µm). Both easily decomposable organic matter and recalcitrant organic matter accumulated in macro-aggregates in the NPK₊ digested slurry plot. We assume that dead grass roots contributed to the retention of macro-aggregates. The formation of macro-aggregates had no significant effect on the physical properties of the surface soil.

Clayey paddy soils drain poorly because of their low unsaturated hydraulic conductivity, and they can hold limited plant–available water. The Farm–Oriented Enhanced Aquatic System (FOEAS) water table management system was developed to overcome both problems. We investigated the effect of subirrigation on barley yield in clayey fields with the FOEAS system in a region with heavy snowfall in two cycles of a 2-year rice–barley–soybean crop rotation. Discharge of water via subsurface drains was less in the subirrigation (SI) plot than in the free drainage (FD) plot because of insufficient development of shrinkage cracks upon drying in the subsoil, which act as pathways for the water. The barley yields were 568 g m^-2 in 2012 and 482 g m^-2 in 2014 in FD, and 374 and 239 g m^-2 respectively in SI. In SI, the distance from the top of the plow sole to the surface at the outside rows of each ridge was 11–12 cm, and the perched water depth on the plow sole during the snowfall periods was 12–14 cm, thus submerging the outside rows. This caused poor growth of barley in the outside rows of ridges and low yields in SI. The lower yield in FD in 2014 than in 2012 was due to a decline in the thousand-kernel weight. Because the readily available water in the topsoil disappeared during the hot and dry conditions in the late spring, crop ripening was poor. From these results, we recommend that in clayey soils with the FOEAS system, no irrigation be applied so as to allow subsurface cracks to develop and thus maintain subsurface drainage, except in extremely dry conditions.

We determined the deposition of fluorine, bromine, and iodine in atmospheric deposits collected in Kagoshima city, Japan, from August 2012 through July 2013. The depositions were 6.39–266 mg F m^-2 month^-1 (323 mg m^-2 year^-1), 0.314–2.51 mg Br m^-2 month^-1 (18.3 mg m^-2 year^-1), and 0.0487–0.351 mg I m^-2 month^-1 (2.32 mg m^-2 year^-1). The annual deposition of fluorine was eight times that previously recorded in Tokyo and Niigata. To evaluate the contribution of volcanic ash from Sakurajima and sea salt, we estimated the deposition of each from reported depositions of falling volcanic dust and sodium. We estimated that 7 to 57% of the F was derived from Sakurajima, but little from sea salt. In contrast, 56 to 138% of the Br and 29 to 92% of the I was derived from sea salt.

We examined the contents of organotoxic materials in a calcium phosphate product made by alkaline extraction of sewage sludge ash with alkaline wastewater (0.5 mol NaOH L^-1) from electronicfactories in Japan. Generally, raw materials from industrial wastes contain heavy metals and organotoxic materials. However, this method can produce calcium phosphate at high purity, excluding organotoxic substances to below Japanese legislated criteria. Many large industrial corporations in Japan are required to follow the European RoHS Directive and minimize the contents of heavy metals and organotoxic materials in their wastes. Our calcium phosphate product met the criteria for alkyl mercury compounds, cyanide compounds, PCBs, fluorine and its compounds, trichloroethylene, tetrachloroethylene, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloropropene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,3-dichloropropene, benzene, thiram, simazine, thiobencarb, phenols, and 1,4-dioxane. These results show that it is possible to support a sustainable society through agriculture.