Steelmaking slags such as decarburization slag have attracted attention as new materials for construction of tidal flats and seagrass beds; however, the materials may release alkalines, which results in increase of soil hardness. In addition, the materials are lack of fine particles and organic compounds important for development of a benthic community. In this study, we attempted to reduce release of alkalines and elevation of soil hardness by decarburization slag by a combination of slag-carbonation using CO₂ and addition of dredged soil. In addition, an artificial tidal flat was constructed in an intertidal zone simulator using the carbonated decarburization slag to which dredged soil was added for investigation of the developed macrobenthos community. By this combined treatment, the release of alkalines and elevation of soil hardness /was inhibited. The pH value of the interstitial water at 1 cm depth in the artificial tidal flat was maintained at about 9.5, and its soil hardness was in the range from 7 mm to 15 mm. Furthermore, the number of macrobenthos inoculated into the artificial tidal flat was maintained during the experimental period, thereby indicating that the mixture of carbonated decarburization slag and dredged soil may have capability of producing macrobenthos habitat.

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The pesticide list for drinking water in Japan was revised on March 28, 2013, and the amino acid-based herbicide glufosinate was listed as a target pesticide. However, no official analytical method for glufosinate has been given by the Ministry of Health, Labour and Welfare in Japan. We investigated the simultaneous analytical method for glufosinate, glyphosate, and aminomethylphosphoric acid (AMPA) in tap water with liquid chromatography-tandem mass spectrometry (LC/MS/MS) after derivatization by 9-fluorenylmethyl Chloroformate (FMOC) and solid-phase extraction (SPE) with ODS cartridge following the derivatization. The optimum application volume of sample to SPE was 20 mL and the ratio of acetonitrile/5 mM ammonium acetate was 40/60 (v/v). In the case of derivatization-LC/MS/MS, the recovery rate and coefficients of variation of the three pesticides were 92-116% and 1.2-10.9%, respectively, by using the concentration of 1/100 or 1/10 of the desired values of each pesticides. Similarly, in the case of derivatization-SPE-LC/MS/MS, the recovery rate and coefficients of variation of the three pesticides were 99-118% and 0.9-4.0%, respectively. We concluded that these methods were applicable as the simultaneous analysis of glufosinate, glyphosate, and AMPA in tap water.

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For elucidating process and responding to red-soil runoff from sugarcane field, it is required to detect the harvest date precisely at each land parcel. Because satellite remote sensing provides very limited frequency of observation, it is not appropriate for this case. In this study, we observed sugarcane field continuously by using a digital time-lapse camera, and developed a new method to detect the harvest dates automatically. Color information of red, green, and blue (RGB) digital counts were derived from the images that were taken 3 times a day from January to May. By statistical analysis of RGB values, images taken under bad weather were excluded, and a Green Ratio index (GR) was calculated for each pixel. The values of GR reflected the greenness of plant leaves, and changed in relation to the increasing and decreasing of plants. The maximum ratio of decreasing in the temporal variation of GR indicated the date of harvest, and the pixel based analysis enabled to detect spatial distribution of the dates of harvest at each land parcel. Thus image analysis under high temporal and spatial resolution by use of digital camera is cost-effective and applicable to all over the place for monitoring various ecosystems and fields.

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The red clay outflow has damaged the coral reef and reduced biodiversity in Okinawa. The main source of the outflow is farmland and the crop choice of farmers and land use affects the outflow. The main crop in Kume Island is sugar cane which results in more outflow than the other crops. The purpose of this study is to explore the determinants of farmers in Kume Island on the crop choice and adoption of the measures for prevention of red clay outflow, using the data of the survey for farmers in Kume Island implemented in July, 2014. Our main findings are (1)the older aged farmers are less likely to implement the measures for prevention of red clay outflow, (2) cost and labor to implement the measures reduce the incentive of farmers to implement the measures, (3)the older aged farmers are likely to implement summer planting, which encourages red clay outflow more than spring planting, rather than spring planting, (4)the farmers of sugar cane are older than the farmers of flowers and ornamental plants on average.

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To qualitatively evaluate the reduction effect of a planning measure on red soil runoff, a scenario for reduction of red soil was examined based on the results of sequential hydrological observation and the application of spatially distributed sediment runoff model in the small agricultural catchment (0.28km²) mainly cultivating sugarcane.Reflecting the spatial distribution of sugarcane planting type with a model parameter (C factor) improved the modelʼs performance. This simulated that sugarcane fields in the first year of summer planting were the main source of red soil production in the catchment by leaving the soil surface without any covering from early spring after harvesting to planting period. A proposed scenario simulated the application of cover crop (C.juncea) to the first year summer planting fields prior to planting sugarcane was confirmed to be very effective at the reducing red soil runoff volume in the entire catchment. In addition, the estimated cost for cover crop application corresponding to about 13% of the cultivation income from sugarcane. This suggests that policies should be developed to provide incentives to encourage farmers to voluntarily cultivate a cover crop to sustainably work for the reduction of red soil runoff.

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