Farm-regional evaluation of soil organic carbon (SOC) dynamics for the chernozem zone in northern Kazakhstan is now vitally important for making agro-environmental policy. In this study, the author intends to evaluate spatial and temporal variation of the SOC budget and to seek alternative ways of sustainable land use in northern Kazakhstan. To achieve this final goal, this study established the following objectives: to (1) clarify the spatial patterns of soil organic matter content, (2) clarify the influence of land use on the dynamics of soil organic carbon insitu for the three differential soil classes, and (3) clarify spatial and temporal variability of SOC budget in farm-regional scale. The highest SOC content was found in the northern region and the lowest content in the southern region of the study area. Potentially mineralizable carbon (PMC) content, however, was highest in the mid-western region. Furthermore, fluctuations in CO2 emission from the soils showed a similar pattern to temperature fluctuations. Using PMC, soil temperature, precipitation and/or dryness factor, 40-80% of the variation of CO2 emission could be estimated. From farm-regional evaluation, it is concluded that the spatial and temporal variation of the SOC budget was significantly affected by the crop rotation system in the area. In addition, the fallow- and barley-based crop rotation systems accelerate SOC depletion in the study area.
In this paper, we review the soil fertility characteristics and the nature of material in the West African lowlands in comparison with paddy soils in tropical Asia to examine their potential for rice cultivation. Soil samples collected from major lowland ecosystems, i.e., inland valleys (185 locations) and flood plains (62 locations), in 13 countries (Benin, Burkina Faso, Cameroon, Cote d'Ivoire, Ghana, Guinea, Niger, Nigeria, Liberia, Mali, Senegal, Sierra Leone, and Togo) generally show low values of pH, total C and N, available (Bary-2) P, exchangeable Ca and Mg, effective cation exchange capacity (ECEC), and clay content. These properties of the 87 topsoil samples selected from 247 collected samples are well associated with mineralogical composition. The clay and primary minerals predominantly consist of kaolinite and quartz, respectively, which suggests that the lowland soils in the region have low nutrient-holding capacity and a limited potential for inherent nutrient supply. In general, soil pH, available P, exchangeable bases (Ca, Mg, K, and Na), and ECEC decrease while total C, total N and exchange acidity (Al and H) increase with increasing rainfall. This tendency is mostly explained by the enhanced biomass production and soil weathering sequence governed by the climate. In terms of rice production, the lowland soils in West Africa have lower values of general fertility parameters and poorer mineralogical characteristics compared to paddy soils in tropical Asia, which includes Bangladesh, Cambodia, India, Indonesia, Malaysia, Myanmar, Philippines, Sri Lanka, and Thailand. In addition, deficit levels of S and Zn for rice production are widely observed in the lowland soils in West Africa. These findings suggest that soil fertility characteristics show substantially less potential for rice production in West Africa than in tropical Asia.
Schizophyllum commune is a sap-rot basidiomycete and cosmopolitan species. The fungus is also recognized as a plant pathogen that causes wood rot on living trees, and many plant species including fruit and ornamental trees have been recorded as hosts. In this paper, previous studies on the plant parasitism of S. commune and related information to date were reviewed, in addition to the unique characters of the fungus. Though the fungus is only a poor wood decomposer in vitro, it preferably invades living tissues of plants including bark and sapwood, being exceptional as a wood-rot basidiomycete. Basidiospores are abundantly ejected in the air, and pruning wounds, freeze injuries and sunscald lesions are major infection courts for them. Wood-rot disease by the fungus is promoted by drought, freezing temperatures and other weather conditions unfavorable for plants; the fungus is adapted to such adverse environmental conditions. It is expected that, depending on plant species and localities, ongoing global warming enhances plant damage, which may predispose plants to fungal infection. Schizophyllum rot possibly helps other wood-rot pathogens to infect and establish. More attention should be paid to the wood-rot disease complex in which S. commune is involved. In conclusion, various aspects on the biology of S. commune still remain to be studied in relation to the mechanism of its pathogenesis.
In order to improve the work rate of puddling, we developed rotary-type high speed puddling harrows. The stubble burying performance and the soil pulverizing performance of the developed puddling harrows were nearly the same as those of conventional puddling harrows working at 20 to 30% slower travel speeds. Power requirement of the developed puddling harrows were similar to those of conventional harrows. When the developed puddling harrows worked at 24 to 30% higher travel speeds than the conventional harrows, work rates of the developed puddling harrows were 21 to 22% larger, and the fuel consumption of the developed puddling harrows was 13 to 15% less than that of the conventional harrows.
We investigated the effect of operating conditions such as travel gears, PTO gears and engine speed of a 24kW agricultural tractor on fuel consumption. In the indoor tests, we found that as the PTO power and the engine speed increased, the fuel consumption increased and the fuel consumption per power hour became minimum when loads corresponding to 70-90% of the maximum power were applied at each engine speed. In the field tests, the fuel consumption was reduced by shifting to a higher travel and PTO gear and by lowering engine speed. The reduction rates of the fuel consumption by gear up and throttle down compared with those at full throttle were about 15 to 30% with PTO power at 55% of maximum engine output, about 30 to 40% with PTO power at 30% of maximum engine output, about 30 to 45% with PTO power at 20% of maximum engine output, and about 40 to 50% with PTO power at 15% of maximum engine output. In the road tests, the reduction rates of the fuel consumption by gear up and throttle down compared with those at full throttle were about 30 to 50% for traveling at 10 km/h, and about 20 to 35% for traveling at 15 km/h.
Studies on the reproduction and early life ecology of an abalone, Haliotis diversicolor, are reviewed, especially focusing on the results of our recent field and laboratory studies in Sagami Bay, Japan. Our four-year monitoring of the occurrence of newly settled post-larvae and changes in adult gonads clearly indicates that the spawning of H. diversicolor in Sagami Bay was triggered by typhoon events with large-scale storms. The abalone could spawn at least twice in a single spawning season, but required an interval of at least 1 month between spawning events. The proportion of adults releasing gametes and the amount of released eggs/sperms from each individual tended to increase on the spawning events occurring later in a spawning season. Higher mortality rates of post-larvae and early juveniles were detected at places which had greater water turbulences and more frequent stone overturning caused by storms. A storm event caused by a typhoon appears to be a necessary cue triggering the synchronous spawning of H. diversicolor, but the violent water turbulence and overturning of stones caused by storms negatively affect the post-settlement survival. Cohorts experiencing lower seawater temperatures due to the later settlement in the spawning season tended to have a slower growth rate than those experiencing higher temperatures, suggesting the temperature-dependent growth of post-larval H. diversicolor. The timing of typhoon-triggered spawning in H. diversicolor was suggested to be an important factor affecting the growth and survival and eventual recruitment of the abalone.
A model was developed to evaluate long-term temporal changes in disease severity (DS) of the clubroot disease of Chinese cabbage in the field with various management strategies. The model consists of a dose-response curve (DRC) of resting spore (RS) density of Plasmodiophora brassicae and DS, and the rate of RS density change due to leafy daikon cropping as a decoy plant, plowing the clubbed roots in the soil after harvest, and natural reduction. The DRC was estimated by greenhouse experiments. Three DRCs were estimated by experiments carried out in 1995-1997. The DRC in 1996 predicted the highest DS at all RS densities and hence was considered to represent a conducive condition, and that in 1997 predicted the lowest DS and was considered to represent a suppressive condition, respectively. Field data for three years (1996-1998) fell into an area surrounded by both DRC. This result confirmed the validity of the DRCs. Also the model was validated by field experiments where leafy daikon was cultivated before planting Chinese cabbage. The usefulness of the model for long-term prediction of temporal changes of DS was discussed.
About 75% of the tea fields in Japan grow cv. ‘Yabukita,’ which is susceptible to many diseases such as anthracnose and gray blight. Therefore, broad range effective and long-lasting disease control methods are required. Plant activators (PAs) are compounds that induce disease resistance in plants. In the present study, we used AGREVO EX (a yeast extract preparation), probenazole, prohydrojasmon, and tiadinil as PAs and estimated their disease resistance-inducing activity on tea plants by wound-inoculation assays and field trials. An aqueous solution of each PA was sprayed on field-grown ‘Yabukita’. PA-treated leaves were harvested and assayed for disease resistance-inducing activity. Lesion development of gray blight and anthracnose in PA-treated leaves was suppressed by each PA, and the induced resistance continued for at least 30 days after PA treatment. All the tested PAs induced disease resistance in tea plants systemically. In field trials, PAs were effective to the diseases of anthracnose and gray blight with control efficacies from 50.1 to 50.8 and 63.7 to 69.8 respectively. The growth and chemical composition of tea shoots were not changed by PA treatment. Based on these experiments, induced resistance by PAs is useful for the development of new disease control methods for tea production.
Resource recovery and wastewater purification of agricultural waste are currently considered important ways to reduce environmental impact. In the present study, hydrogen fermentation of cow manure mixed with various defined substrates or artificial food wastes was examined by lab-scale batch mode experiments at 60°C, using hydrogen-producing bacteria naturally present in the manure. A variety of carbohydrates including cellulose and xylan were used as substrates for hydrogen production, although no hydrogen production was observed with proteinous substrates (casein, gelatin and albumin), an amino-acid mixture (Casamino acids), or lipids (palmitic acid, linoleic acid, soybean oil, and olive oil). In experiments involving artificial food wastes (boiled rice, bread, cabbage, chicken meat, fish meat, egg, mayonnaise, chocolate, and strawberry jam), the amounts of hydrogen production were positively correlated with the carbohydrate content of the foods, while no significant correlation with protein or fat content was observed. To examine the effect of hydrogen fermentation on methane fermentation, a two-step treatment (hydrogen fermentation followed by methane fermentation) was conducted using cow manure mixed with dog food. The hydrogen fermentation increased methane production two-fold as compared with the one-step treatment (methane fermentation only). In addition, the hydrogen fermentation enhanced the removal of volatile solids and biochemical oxygen demand from the mixture, suggesting that hydrogen fermentation has advantages in wastewater purification.
Frogs often drown in agricultural canals with deep concrete walls that are installed commonly in paddy areas after land consolidation projects in Japan because they cannot escape after falling into the canal. We propose a partial concrete canal with gently sloped walls as a countermeasurefor frogs to escape the canal andinvestigated the preferable angle of the sloped walls, water depth and flow velocity for Rana porosa porosa. Our experiments showed that only 13 individuals (2%) escaped by leaping out of the canal, indicating that climbing up is the main escape behavior of R. p. porosa. Walls with slopes of 30-45 degrees allowed 50-60% of frogs to escape from experimental canals, the frogs especially easily climbed up walls with a 30 degree slope. Adjusting water depth to 5 cm or more would assist the frogs in reaching the escape countermeasures because at such depths frogs are not able to stand on the canal bottom and to move freely about. Flow velocity should be slower around the countermeasures because R. p. porosa is not good at long-distance swimming and cannot remain under running water for a long time. The broadened inlets of this new canal design provide water of slower velocity near the shores of the sloped walls, which encourages frogs to escape.
In 2002, we reported that sweetpotato leaves contained six caffeic acid derivatives, namely, caffeic (CA), chlorogenic (5-O-caffeoylquinic acid, ChA), 3,4-di-O-caffeoylquinic (3,4-diCQA), 3,5-di-O-caffeoylquinic (3,5-diCQA), 4,5-di-O-caffeoylquinic (4,5-diCQA), and 3,4,5-tri-O-caffeoylquinic (3,4,5-triCQA) acids, which are known to have many physiological functions. A new sweetpotato cultivar ‘Suioh’ was developed for use of its tops as an edible green by KONARC. It is important to analyze the caffeic acid derivatives efficiently with high-performance liquid chromatography (HPLC) in order to continue developing or selecting new cultivars with higher contents of these compounds in their tops. For this purpose, a short column (4.6 i.d. × 75 mm) packed with small ODS particles (3 μm) was used without replacing the conventional HPLC apparatus and the time for one analysis per sample was decreased to 26 min, from 90 min, which was the analysis time reported in 2002. With the new HPLC conditions, we could quantify the six caffeic acid derivatives in lyophilized leaf samples from 529 sweetpotato cultivars, which compose approximately one-third of the cultivars maintained at KONARC.
To investigate both aflatoxin contamination in feed produced in Japan and the distribution and movement of aflatoxin-producing fungi in the feed, a survey experiment was performed. Aspergillus fungi were isolated from imported Sudan grass hay, a material used to make total mixed ration (TMR) in Japan. HPLC analysis showed that one isolate produced aflatoxins B1 and B2. Isolates were identified as A. flavus and A. terreus from their morphologies, rDNA-ITS sequences and aflatoxin production. No aflatoxins were detected in the Sudan grass hay source of the isolates or the fermented TMR made from the Sudan grass as one of the raw materials. The fermentation quality of the TMR was good after ensilage for over 60 days, as indicated by increased lactic acid and decreased pH. Only lactic acid bacteria and Bacillus survived in the fermented TMR; no fungi or yeasts were detected. Fermentation is important in preventing aflatoxin contamination of silage.
The methane (CH4) produced by lactating and dry crossbred Holstein cows, together with factors affecting CH4 production, were investigated using data obtained from balance trials of cows in Thailand (48 observations). The CH4 production per dry matter intake (DMI) of lactating cows tended to be lower than that for dry cows (25.7 L/kg vs. 28.7 L/kg DMI; P ‹ 0.10), which was due to the higher energy intake of lactating cows. A positive correlation was observed between CH4 production and DMI (r = 0.70; P ‹ 0.001). The CH4 production was also founded to be related to crude fiber (CF) and nitrogen free extract (NFE) intake from a multiple regression equation (r = 0.77, P ‹ 0.001), and the coefficient of CF was higher than that of NFE, indicating higher methanogenesis of CF than of NFE. The decreasing CH4 production per milk production with the increase in milk production (r = -0.62; P = 0.003) shows that improvements in the individual milk yield suppress the CH4 production per milk production. From the findings of the present study and available statistical information in Thailand, it was estimated that CH4 production by cows increased as the cow population increased over a 5-year period from 1999. Because the CH4 production per milk yield showed little change from 1999 to 2004, in terms of milk productivity and suppression of CH4 production, improving individual milk yield will be important in Thailand.
The Reducing Emissions from Deforestation and Forest Degradation in Developing Countries (REDD) initiative requires accurate estimates of carbon stock changes in forested areas. However, estimating carbon emissions from stumps of various heights left by illegal loggers is difficult. To remedy this problem, we examined two methods of estimating diameter at breast height (DBH) from a reference diameter observation measured at any stump height. The one-reference diameter (OD) observation model estimates DBH from a single diameter observation using empirical coefficients derived mainly from emergent dipterocarp trees. The two-reference diameter (TD) observation model estimates DBH from two diameter observations and assumes a logarithmic relationship between diameter and height. Prediction data to establish the models were collected in Cambodian lowland evergreen forests that are undergoing intensive illegal logging of emergent dipterocarp trees for timber. The OD model performed better than the TD model in predicting DBH and is extremely practical, as it requires only a single diameter observation. Validation data previously collected in the Southeast Asian tropical forests established the general validity of the OD model. This study may improve the reliability of the REDD scheme by providing a reliable method to assess carbon emissions from Southeast Asian tropical forests.