Yasuhiro Nakanishi

Livestock wastes as a source of estrogens and their effects on wildlife of Manko tidal flat, Okinawa.

The Manko tidal flat in the southern part of Okinawa Island is an important visiting and wintering area for migratory birds and was added to the Ramsar Convention Register of Wetlands in 1999. This area used to be an inlet extending to the inner part of Naha Port, but recent reclamation projects have restricted its connection to the East China Sea. As is typical in rural regions of subtropical islands, the inhabitants in the Manko basin raise livestock, especially pigs, without employing sufficient waste treatment methods. As sewage treatment works are considered to be one of the main sources of environmental estrogens in urban areas, the significance of livestock farming as a source of estrogens in rural area is examined in this study. In the present study, total estrogenic activities in water and sediment samples from the Manko tidal flat and its basin were measured using a recombinant yeast screen method. Estrogenic activities (equivalent to 17beta-estradiol, E2) were around 10 ng l(-1) in water samples and more than 10 microg kg(-1) in some sediment samples. In addition, the concentrations of estrone (E1) and E2 in water samples measured using LC/MS/MS indicated a high contribution of environmental estrogens from livestock wastes.

δ13C values of organic carbon in cropland and forest soils in Japan

Abstract The carbon content and natural 13C abundance (δ13C) of soil organic carbon were determined for Japanese cropland and nearby forest soils by continuous flow CN analysis with mass spectrometry. The δ13C values of organic carbon from cropland soils in the Hokkaido District ranged between −27 and −24‰, suggesting that soil organic carbon originated mainly from C3 plants, while the δ13C values from those in Main Island, Shikoku, and Kyushu Districts ranged between −25 and −17‰, indicating that up to 70% of soil organic carbon originated from C4 plants (presumably Miscanthus sinensis). The δ13C values of organic carbon from Imaichi and Tanegashima forest soils showed that carbon was largely of C3 plant origin in the surface soils but in deeper horizons the values were strongly affected by the organic carbon of C4 plant origin. Sugarcane cultivation for 36 y in Tanegashima cropland soils had resulted in the increase of the soil δ13C values to around −15‰. In Shizuoka Prefecture, the δ13C values of soil organic carbon of non-volcanic ash Andosols under forests at Iwata and Makinohara were within the ranges of C3 plant origin. The values in volcanic ash Andosols at Fuji indicated that the soil carbon in the surface horizons mainly originated from C3 plants while that in deep soil horizons largely from C4 plants. Tea cultivation for more than 40 y had led to a decrease of the δ13C values at Fuji by 2-4‰. In the Miyako Island sugarcane fields, the δ13C values of the plow layers were apparently affected by sugarcane, a C4 plant species, compared to the subsoils where a large fraction of carbon originated from C3 forest plants. The shift from forest to sugarcane cultivation markedly decreased the carbon content and increased the δ13C values of soil organic carbon from −27-−25‰ to −17-−14‰ within 25 y.

Estimation of the nitrogen fixation by sugarcane cultivar NiF-8 using 15N dilution and natural 15N abundance techniques

Abstract The high population of endophytic diazotrophs in the stalk of the Japanese sugarcane cultivar NiF-8 described in our previous report suggests the possible significant contribution of biological nitrogen fixation (BNF) to the crop nitrogen nutrition. To estimate the amount of BNF in this cultivar, the proportion of biologically fixed nitrogen (%Ndfa) to the plant total nitrogen uptake was determined by 15N dilution and natural 15N abundance (δ15N) techniques. Using the δ15N method, the estimated %Ndfa by the sugarcane cv. NiF-8 under field lysimeter conditions ranged from 32 to 38% at 6 months after planting (MAP) and from 27 to 34% at 7 MAP. With the 15N dilution method, the estimated %Ndfa by the sugarcane plants was 26.0% for the roots, 14.1% for the stem, and 20.5% for the leaves. These results indicate that the sugarcane cv. NiF-8 obtained part of its nitrogen requirements from BNF.

Nitrogen Fixation in Sugarcane

Nitrogen (N) is a major essential element for all organisms, and generally the amount of available N (mainly inorganic nitrogen such as nitrate or ammonia) in soil is limiting factor for natural and agricultural plant production [40]. Biological nitrogen fixation (BNF) is a process by which atmospheric dinitrogen (N2) is reduced into 2 molecules of ammonia (NH3) by the enzyme nitrogenase with 8H+, 8eand 16 Mg ATP. BNF have important role in N cycle in both global ecosystem and agro-ecosystem. Based on the data compiled by Bezdicek and Kennedy in 1988 [11], about 175 million metric tons of nitrogen per year is estimated to be fixed in global ecosystems, in which 90 million metric tones in agricultural land, 50 million metric tones in forest and non-agricultural land, and 35 million metric tones in sea. At that time, nonbiological nitrogen fixation was estimated about 50 million metric tones per year by industrial nitrogen fixation mainly for the synthesis of ammonia fertilizer, and about 20 million metric tones by combustion, and about 10 million metric tones by lightening. In 2009, the production of N fertilizers increased to 106 million metric tones (FAOSTAT), but the amount of BNF still exceeds over non-biological nitrogen fixation.