Natural acidification of lakes and rivers in Japan: The ecosystem of Lake Usoriko (ph 3.4–3.8)

Most of the acid lakes and rivers in Japan have been influenced by acid waters of volcanic origin. Acidophilic and acidotolerant organisms are observed in these natural acid lakes and rivers, each of which has its own ecosystem and history. Lake Usoriko (pH 3.4–3.8) is a lake which.has been acidified by strongly acid water containing sulfuric acid and hydrochloric acid. The ecosystem of Lake Usoriko consists of aquatic vascular plants, aquatic bryophytes (Drepanocladus fluitans, etc.), algae, fish (Tribolodon hakonensis), insects, Zooplankton, fungi and bacteria. The paleosediment distributed along Lake Usoriko's northern shore is partly silicified and it contains fossils of a moss (Drepanocladus fluitans) and diatoms such as Pinnularia braunii var. amphicephala which are also distributed in the present lake. ¹⁴C dating of the specimens in the paleosediment, shoots of D. fluitans and the wood and cones of Picea glehnii gave values in the range 11500–34000y B.P. This record shows how long Lake Usoriko has been an acid lake.     

Organic matter production in rice field flood water

To assess the contribution of organic matter produced in the flood water to the fertility of a rice soil, the primary productivity and the algal biomass therein were examined throughout one crop. Primary productivity was estimated from the diurnal curve of dissolved oxygen.

Just after transplanting, an algal bloom developed due to fert,ilizer or ploughing or both. After submerged weeds occupied the whole paddy no distinct algal growth was found. At the ripening stage, the rice plant canopy suppressed the growth of aquatic plants. Benthic algal biomass did not change much throughout the crop period. The standing crop of algae ranged from 2 to 114 kg/ha by fresh weight, while the maximum standing crop of submerged weeds (Najas sp., Chara sp.) was 400 kg/ha by dry weight.

The primary productivity of the flood water community was high (0.6-3.3 g 0 1 m^-2day^-l) and equivalent to productivity values in eutrophic lakes. The total gross primary production of the flood water community during the cropping period corresponded to 10% and 15% of that of rice plant in the fertilized plot and non-fertilized plot, respectively.

Considering the movement of CO₂ in the flood water, it is suggested that the photosynthesis activity in the flood water prevents surplus CO₂ from being lost.     

The growth of Rhizobium in the Rhizosphere of the host plant

Rhizobia pass through the host root surroundings before they infect the root tissue. Therefore, the environmental condition of rhizosphere is one of the greatest factors in the life of Rhizobia in the soil. It was observed that the nodule number produced on the root of the legume is not proportional to the density of Rhizobia inoculated, but nearly constant within some range. The experience presented in the previous paper showed that one or ten cells of Rhizobia inoculated in a test tube were sufficient to produce a number of nodules on the host plants grown in the tube. Such facts strongly suggest the multiplication of Rhizobia in the soil before infection into tissue.     

Further study on iodine toxicity in relation to “Reclamation Akagare” disease of lowland rice

On the basis of the study on iodine behaviour in soil-plant system and other related informations. Tensho and Yeh(1,2,5) have suggested and demonstrated that the iodine toxicity is responsible for the “Reclamation Akagare” disease of lowland rice. Some additional evidences for this view will be presented. which were obtained particularly in connection with field studies on local problem.     

Water dynamics in soil-plant systems under grain farming in Northern Kazakhstan

The water dynamics and budget in soil-plant ecosystems under dry farming in northern Kazakhstan were investigated for two consecutive years from autumn in 1998 to the end of the cropping season in 2000. In total, 12 plots were established at the experimental farm of Barayev Kazakh Research and Production Center of Grain Farming, Shortandy, and the soil moisture content up to the 90 cm depth was measured several times throughout the period. In spite of snow management during the winter time, in which parallel snow rows were developed in order to accumulate additional snowfall between the rows, the increase in the soil moisture content at the time of thawing widely ranged from -40 to 74 mm in 1999 and from -6 to 84 mm in 2000, respectively. Monitoring of the soil temperature revealed that, in the plots after fallow, a higher moisture content in the frozen subsurface soil layer was responsible for the slow thawing there, resulting in slower water percolation from the overlying layers of the profile and 0n water loss through enhanced evaporation and possible surface runoff. After thawing, the soil moisture content decreased throughout the cropping season, except during several rainfall events. The evapotranspiration was estimated to range between 194 and 259 mm during the cropping season. The bNonmass and yield of wheat at harvest time were linearly correlated with the estimated evapotranspiration, indicating that crop production here was mostly determined by the amounts of available water. The initial soil moisture content accounted for 27 to 52% of the total evapotranspiratiou. In the summer fallow plots, 39 to 104 mm more water accumulated in 1999 and 100 to 119 mm in 2000 than in the cropped plots, respectively. Comparison of the water budgets during the pre-cropping and cropping seasons in the plots under fallow and cropping revealed that both summer fallow and snow management could increase the soil moisture content up to approximately 100 mm, but that the benefit of snow management would be occasionally canceled by the effect of the summer fallow. Given the possibly adverse effects of the summer fallow on enhanced decomposition of soil organic matter, we recommend that snow management should be the main approach for capturing water in the studied plots rather than the summer fallow practice. Further studies should be carried out to determine whether soil and /or topographical conditions are more effective for individual water-capturlng management and also are more suitable from economic and environmental viewpoints.     

A practical formula for quantifying the thermal conductivity of Tottori dune sand

Abstract

Sustainable agriculture needs appropriate management of water, chemicals and heat in soil. In this study, we focused on thermal conductivity, which is among the various soil physical properties that are crucial for the sustainable management of agricultural fields. To expand the Mochizuki model, which describes thermal conductivity as a function of water content and solution concentration, we considered the water content, solution concentration and temperature as independent variables. The thermal conductivity of Tottori dune sand was measured under conditions of various combinations of these three independent variables. We observed that the thermal conductivity increased linearly with increasing water content, 0.054–0.276 m³ m^?3, for fixed temperature and solution concentration, and varied linearly with solution concentration for fixed temperature and water content. These results are consistent with the Mochizuki model. Using the Mochizuki model, the experimental parameters, which are dependent variables of water content and solution concentration, are shown as functions of water content. From regression analyses of the relationships between the experimental parameters and temperature, we expanded the Mochizuki model into a new practical formula that quantifies the soil thermal conductivity as a function of water content, solution concentration and temperature.     

Metabolism of N-[(R)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (Delaus, S-2900) and its isomer, N-[(S)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (S-2900S), in rats. 1. Identification of metabolites in feces and urine

Rats were orally dosed with a 1:1 diastereomixture of N-[(R)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (Delaus, S-2900) and N-[(S)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (S-2900S), both labeled with 14C, at 200 mg/kg/day for 5 consecutive days, and 16 metabolites in urine and feces were purified by a combination of several chromatographic techniques. The chemical structures of all isolated metabolites were identified by spectroanalyses (NMR and MS). Several of them were unique decyanated and/or cyclic compounds (lactone, imide, cyclic amide, cyclic imino ether forms). Major biotransformation reactions of the mixture of S-2900 and S-2900S in rats are proposed on the basis of the metabolites identified in this study.     

Irrigation practice and water usage characteristics in sand dune upland fields in the Hokuriku Region, with much rainfall in Japan: case studies on watermelon and Japanese radish

We investigated the use of irrigation water for a successive planting of watermelon followed by Japanese radish in a sand dune area in the Hokuriku Region. The main results were as follows: (1) Upland field tested in the study used a large volume of irrigation water in spite of its location in the Hokuriku Region where rainfall was plentiful. Notwithstanding this, frequent irrigation was considered necessary. (2) Watermelon was cultivated as a Spring–Summer crop with a mean cultivation period of 102 days, during which it was irrigated for 59 days at 1.7-day average intervals with an irrigation volume of 7.1 mm/watering and a total irrigation volume of 428 mm over its entire growing season. The amount of rainfall during the period was 604 mm during 42 days of rainfall. Soil moisture levels in the upland field were kept at relatively high values ranging between pF1.3 and pF1.5 at 15-cm depth with frequent irrigation during no-rainfall period. (3) Japanese radish was cultivated as a Summer–Autumn crop with a mean cultivation period of 71 days during which it was irrigated for 39 days at 1.9-day average intervals with an irrigation volume of 9.4 mm/watering and a total irrigation volume of 358 mm over its entire growing season. The amount of rainfall during the period was 376 mm during 29 days of rainfall. Frequent irrigations were used to maintain the soil moisture levels in the upland field within the range of pF1.4–pF1.6 at 15 cm depth. (4) During the irrigation period, the amount of water used for irrigation was 5.9 mm/day in watermelon and 6.1 mm/day in Japanese radish which are greater than evapotranspiration (ET). In addition, during pre-irrigation, the preparation of the seeding bed can be carried out at the right time which contributes to producing high-quality Japanese radish in adequate quantity. In addition, pre-irrigation for preparation of bed for watermelon transplanting is very important for better time management and high-quality production. For this purpose, the irrigation facilities need to be functioning very well.     

Measurement of Indoor Sulfur Dioxide Emission from Coal–Biomass Briquettes

The coal–biomass briquette is an alternative fuel that replaces low-grade coal. It is expected that the use of coal–biomass briquettes will effectively reduce the indoor concentration of sulfur dioxide (SO₂) emitted during raw coal combustion. In this study, indoor concentrations of SO₂ emitted from combustion of either coal–biomass briquettes or low-grade coal in households in Nanchuan, which is in the rural area of Chongqing City, China, were measured. The acidic gases were collected using passive samplers, and the samplers were taken to the laboratory for extraction and measurement. The SO₂ concentrations resulting from the use of coal–biomass briquettes were clearly reduced compared with those resulting from the use of low-grade coal. The concentrations of SO₂ to which the inhabitants (housewives) of the houses were exposed were also measured, and were found to be less with coal–biomass briquettes. Although with coal–biomass briquettes exposure concentrations still exceeded the World Health Organization guideline for SO₂ (125 μ g m^?3), indoor air pollution and adverse effects on human health caused by SO₂ could be decreased by substituting coal–biomass briquettes for low-grade coal as a domestic fuel.     

Isozyme differentiation of Azolla Lam

Summary Enzyme electrophoresis was used to differentiate sections within the genus Azolla Lam. and demonstrate the value of this method in fingerprinting taxa. Polyacrylamide gel methodology has been developed to identify suspected species of this genus. Preliminary examination of selected isolates indicated that allozyme diversity was particularly evident in section Azolla, where specific classification by morphological means is difficult. Leaf tissue was preferable to root tissue for this purpose because of the ease of tissue preparation and the superior resolution and staining intensity of enzymes. Contribution of enzyme bands by the cyanobiont to zymograms was not significant.Scientific paper no. 7962. College of Agriculture and Home Economics Research Center, Washington State University, Pullman WA, Project Number 0708.