The prediction method of soil solution concentration of volcanic ash soil upon repetitive addition of acid solutions that differ in equivalent ratios of nitrate to sulfate was examined in this study. The method for prediction was composed of chemical equilibrium equation, electrical balance and conservation of mass in soil solutions. The results were summarized in the following.
1) There was a tendency of aluminum concentration upon addition of HNO3 solution > upon addition of acid mixed solution including NO3_ and SO42->upon addition of H2SO4 solution with equal soil solution pH.
2) The model adequately described accumulative release of basic cations. This shows it is ability to estimate acid buffering capacity of cation exchange and mineral weathering.
3) Concentration of monovalent anions was much higher than that of SO42- upon addition of acid solutions. It was considered that monovalent anions that remain in soil solution greatly affected decreasing process of pH and concentration change of basic cations. Therefore, it seemed that NO3-, which are difficult to be adsorbed in soil, are affected the release of basic cations and pH decreasing in soil when acid rain including NO3- and SO42- deposited to volcanic ash soil.
4) The simulation results agreed well with the measured values of pH and accumulative release of basic cations. These represent the most serious effects of the acid deposition on the soil. Therefore, parameters used in this simulation model are useful for predicting the main effects of the acid deposition on the Kanto loam subsoil.
At the upland field in Nakasatsunai village, Hokkaido, heat balance components, soil temperature, and soil water suctions were measured during cultivating periods over ten years. The following results were gained :
1) From the results of the monthly average of heat balance components and soil water suctions, soil moisture for the growth of upland crops decreased or became deficient in late May and June, and there was a surplus from August.
2) The amounts of evapo-transpiration of the monthly average were 3.1 in late May, 3.6 in June, 3.0 in July, 2.7 in August,1.9 mmd-1 in September and early October.
3) In early June and early July, the ratio of soil heat flux during the daytime to net radiation with wet soil condition on a sunny day was more than that with dry soil. In early June, the ratio of latent heat flux during the daytime with wet soil on a sunny day was about 50% and somewhat less than that with dry soil. In early July, the ratio with wet soil on a sunny day was about 80% and more than that with dry soil.
4) In early July, though the range of soil temperature at lcm depth with dry soil on a sunny day was more than that with wet soil, the range at 5 cm depth with dry soil was less than that with wet soil.
5) Numerical analysis of the changes of soil temperatures with wet and dry soil conditions should be carried out to clarify which is better for the raising of the plow layer temperature in early cultivating periods.
An evaluation of crop management factor (C) for coffee using USLE method was conducted in hilly humid tropical area of Lampung, Indonesia. The treatments were as follows : coffee without cover crop (clean-weeded plot) ; coffee with Paspalum conjugatum as cover crop (Paspalum plot); and coffee with natural weeds (natural weeds plot). Weed management was done every two weeks by clearing all the weeds in clean-weeded plot, and cutting the weeds around the coffee trees at a diameter of 1 m for the weedy plots (Paspalum and natural weeds plots). Two methods of estimating C-factor for coffee were used :(1)using similar condition with other crops (Ct), and (2) using equivalent method based on the existing value of coffee-C factor (Ce). The results showed that the use of Ct gave soil loss prediction 9-24 times higher than that measured, while the use of Ce gave 10-81 times higher. The predicted values of soil loss using Ct were 7.7 t/ha/year and 14.1 t/ha/year for Paspalum and natural weeds plots respectively. These values were still acceptable and reasonable to the soil loss tolerance, and very low compared to the other Indonesian studies which could be hundreds of ton/ha/y. This experiment showed that the measured coffee C-factor was 0.045 for clean-weeded plot, 0.006 for Paspalum plot and 0.004 for natural weeds plot, which were lower than the common value (0.2) usually used in Indonesia. By introducing the effect of weeds as the weeds C-subfactor (Cs) and coffee C-factor (Cb) obtained from this experiment measurement, the coffee C-factor (Cc) with various weeds coverage could be estimated by the equation Cc=Cb Cs.
The basic mechanism of acidification on acid sulfate soils (ASS) was studied, but the relation between matric potential (soil moisture) and the behaviour of microorganisms in ASS was still unclear. In this paper, the effects of drying on the mechanism of acidification were identified, especially in relation to different microbial populations and soil respiration through soil incubation experiments. Six soil moisture conditions were set by drying in the incubator at 30°C. Soil pH, soil respiration and total bacterial population, Thiobacillus ferrooxidans (T. ferrooxidans) that had a big role as a catalyst on the acidification of ASS and other gram-negative bacteria were analysed. It was determined that within the matric potential range of —35〜220 kPa (pF 2.55〜3.35),soil respiration was active. Specifically at —35 kPa (pF 2.55), the main bacterial population in the soil was T. ferrooxidans, while population of gram-positive bacteria decreased, though, total bacterial population had a significant relation to soil respiration. Soil acidification was effected not because of the population of T. ferrooxidans but mainly due to the speed in their increase. Carbon dioxide fixation by T. ferrooxidans (per cell) and aerobic respiration (per cell) were active in high matric potential range, but the high population of these bacterium were more effective in increasing the amount of carbon dioxide fixed and aerobic respiration.
We measured thermal conductivity of Tottori dune sand and water using four methods, single heat probe (SPM), twin heat probe (TPM), dual heat probe (DPM), and Decagon probe (KDM). The measured values were compared. The thermal conductivity values measured with SPM and DPM are similar, and those with TPM and KDM are also similar. The thermal conductivity of water measured with KDM was as high as the value reported in literature, on the other hand the values obtained using SPM and DPM were higher than the reported data. As a result, KDM and TPM are recommended to measure soil thermal conductivity.