Search

The morphological and chemical properties of homegardens in the beach ridges with interspersed swales (BRIS) soils were evaluated in order to find a clue for developing sustainable agricultural management. Field survey and soil sampling were conducted at the homegardens and secondary forests in Sungai Ular Village and in the experimental farm of Malaysian Agriculture Research Institute (MARDI), Cherating Station. Chemical fertilizers including ash, charcoal waste and plant litter were applied to the homegardens in both the inland-ward area (HG-I) and in the shoreline area (HG-S). Manure was applied in HG-I and seafood waste from fish processing was buried in the soils in HG-S. High correlation was found between total carbon (T-C) and cation exchange capacity (CEC), indicating soil organic matter was the determinant factor for CEC in the very sandy BRIS soils. The levels of T-C, total nitrogen (T-N), and CEC at 0–10 cm in HG-I in parallel with increasing ages of homegardens. The soils in 0–10 cm an...

Little is known about the effect of soil disinfection on bacterial communities. Soils were treated with an effective chemical fumigant chloropicrin and biofumigant mustard greens (Brassica juncea). While mustard greens did not affect the soil bacterial community structures very much, chloropicrin greatly reduced soil biomass and bacterial species richness. Chloropicrin also influenced the bacterial community structure, making the phylum Firmicutes dominant by occupying about 75%. In more than two months, the proportion of Firmicutes was reduced to the basal level, and the phyla Bacteroidetes and Proteobacteria became dominant. Since mustard greens worked as carbon sources for soil reduction, soils were treated with wheat bran and a low concentration of ethanol. Soil reduction with wheat bran and ethanol did not influence the soil bacterial community structures. Beta diversity analyzed by Principal Coordinate Analysis showed that bacterial communities in the soils except chloropicrin-applied soils formed a cluster. All together, biofumigant mustard greens, a probable substitute for chloropicrin, were demonstrated to cause much less damage on soil bacterial community than chemical chloropicrin.

Soil bacterial community structures in terraced rice fields and abandoned lands in a hilly and mountainous area were analyzed using 16S rRNA gene sequences. The DGGE band patterns of each soil were similar. Based on pyrosequencing data, the richness and diversity of bacterial species were slightly higher in paddy fields than in other soils. A beta-diversity analysis clearly indicated that the bacterial community structure in paddy fields differed from those in non-paddy field lands and crop fields that had not been used as a paddy field. These results may reflect the history of land use.

Soil fertility status under various types of upland farming was evaluated in a village in Mae Taeng District of Chiang Mai Province in northern Thailand. The farmlands were on sloping land in a transitional zone of hill evergreen and mixed deciduous forests (800-1000 m a.s.l.). Miang tea (Camellia sinensis var. assamica ), traditionally cultivated as the sole main cash crop, has been replaced by other cash crops. The studied soils originated from granite (n=30), limestone (n =16), and shale (n =6). Clay minerals were composed mainly of kaolin minerals in the granite soils and quartz, chlorite, gibbsite, mica, and kaolin minerals in the limestone and shale soils. Soil texture classes differed among soil types. However, granite and shale soils showed similar chemical properties to each other with an acidic nature and lower levels of exchangeable bases. Irrespective of the parent material, the CEC values were correlated with soil organic matter contents but not with clay contents. The levels of soil organic matter and the resulting CEC as well as ECEC values were higher in the limestone soils than in the granite and shale soils. These results suggest that higher negative charges in the limestone soils were derived from soil organic matter and that these charges developed under higher soil pH conditions. The C/ N ratios of the limestone soils were lower than those in the granite soils and shale soils, reflecting the well-decomposed status of soil organic matter. The granite soils were classified into three groups based on their physicochemical properties: foresttype soils (remnant forest, secondary forest, miang tea garden and lychee orchard), soils of annual crop fields, and soils of the home gardens. The forest-type soils were characterized by their strong acidic nature with lower contents of exchangeable bases and available P. Soils of the annual crop fields and those of home gardens showed a less acidic nature and nutrient accumulation occurring as a result of fertilizer application. However, a dif ference between these soils was that while the annual crop fields possessed preferable soil physical properties for crops caused by tillage management, soils of home gardens were subjected to compaction throughout soil profiles. In contrast to granite soils, the effects of different land uses on soil fertility were not evident in limestone soils. However, the annual crop fields and orange orchards had low total C and total N, engendering lower CEC values. Although the available P of these soils was high because of fertilizer application, fertilizer N in the annual crop fields seemed not to contribute to a buildup of total N and ammonium N. Both in lychee orchards with the granite soils and orange orchards with limestone soils, fertilizer P had accumulated around trees where fertilizer was usually applied. For shale soils, the subsurface soils under the oolong tea gardens (Camellia sinensis var. sinensis) were rich in total C and N and less compacted than soils of other land uses. Results show that dif ferent farming practices affected soil fertility status depending on soil types with different parent materials. 186 Sota TANAKA, Thanakorn LATTIRASUVAN, Kenji NAKAMOTO, Chalathorn SRITULANON and Katsutoshi SAKURAI

A pot culture experiment was conducted to investigate the effects of amorphous iron-(hydr)oxide (Am-FeOH) amendments on arsenic (As) availability and its uptake by rice (Oryza sativa L. cv. BR28) irrigated with As-contaminated water. A rhizobag system was established using 3.5 L plastic pots, each containing one central compartment for plant growth, a middle compartment and an outside compartment. Three levels of laboratory-synthesized Am-FeOH (0, 0.1 and 0.5% w/w) were used to amend samples of the As-free sandy loam paddy soil placed into each compartment of the rhizobag system. The soils were submerged with a solution containing 5 mg L−1 As(V). Two-week-old rice seedlings were planted in the central compartments and cultured for 9 weeks under greenhouse conditions. The addition of 0.1% Am-FeOH to the soil irrigated with As-contaminated water improved plant growth, reduced the As concentration in the plants and enhanced Fe-plaque formation on the root surfaces. Analysis of soil solution samples ...

This study was conducted in order to evaluate the vegetation conditions and soil fertility status of fallow lands under intensive shifting cultivation systems in the Engkari river area in Sarawak, Malaysia. The shifting cultivation by the several Iban communities selected at Engkari area for upland rice farming were currently being conducted with 2 to 7 years of continuous cropping followed by 1 to 6 years of fallow with application of chemical fertilizers and agrochemicals. Since agricultural management methods and land productivity under the current shifting cultivation systems conducted by the Iban farmer were our concerns, we carried out vegetation and soil surveys on fallow lands of which suitability for rice cropping using shifting cultivation had been classified by Iban landowners from their knowledge of vegetation conditions; 20 suitable and 20 unsuitable sites were analyzed. The results of our vegetation survey showed no substantial differences between suitable and unsuitable sites in the species composition and the sizes of tree species, as measured by the stem diameter at breast height (DBH). The plant density of grass and fern groups tended to be higher in most of the sites even after extensive fallow duration. As compared to our previous studies, the DBH of the trees in most of the Engkari area study sites was small even after extensive fallow duration. The soil properties in the study sites could be characterized by a strongly acidic nature with low levels of exchangeable bases. No substantial differences were found in the soil properties in terms of site suitability and fallow duration. Our results suggest that the rationality of farmers’ traditional knowledge related to vegetation-based site selection is no longer applicable under intensive shifting cultivation practices in the Engkari area. Considering the high acidity and poor nutrient contents of the soils, as well as poor aboveground biomass added to soil as ash during burning, certain measures will be necessary for the farmers in the Engkari area to continue rice cropping through the intensive shifting cultivation system. These include effective types of fertilizer and appropriate application methods as well as countermeasures to soil erosion in order to prevent the loss of fertilizer nutrients from soil ecosystems.

This study discusses soil fertility under perennial cash crop farming (para rubber, Hevea brasiliensis ; black pepper, Piper nigrum ; oil palm, Elaeis guineensis ) conducted by local farmers and an oil palm estate in an upland area of Sarawak, Malaysia, in comparison with the surrounding secondary forests. In the farmlands of the local farmers, rubber farming was conducted without fertilizer application, while 2–5 t ha −1 of NPK compounds were applied annually on pepper farms. Soils under rubber farming were acidic with poor nutrient contents, resembling soils in secondary forests. In pepper farms, soils were less acidic and showed high nutrient contents, especially with respect to available P and exchangeable Ca. This trend became stronger with increasing farming duration. Fertilizers applied around pepper vines appeared to migrate and spread across the fields. Bulk density and hardness of surface soils were higher in pepper farms than in secondary forests, indicating soil compaction due to field works. In the oil palm estate, annual fertilizer application rates were moderate at 0.4–0.8 t ha −1 of NPK compound fertilizers. However, the soil properties in the oil palm estate were similar to those of the small-scale pepper farms. Close to the bases of the palms where fertilizers usually are applied, the contents of exchangeable Ca and available P were high. Nutrient uptake by the dense root systems of the palms seemed to prevent excessive loss of nutrients through leaching. Loss of soil organic matter and deterioration of soil physical properties were brought about by terrace bench construction, but the soils seemed to recover to some extent over time. In conclusion, technologies such as intercropping and the appropriate allocation of different crops to specific locations as well as the proper selection and dosage of fertilizers should be developed and adopted to improve fertilizer efficiency and prevent water pollution due to fertilizer wash-off from farmlands.

The effects of burning strength in shifting cultivation on the early stage of secondary succession in tropical rain forest was investigated at four sites (Sabal, Balai Ringin, Niah, and Bakam) in Sarawak, Malaysia. The number and growth (diameter, height, and biomass) of germinated seedlings were measured in experimental shifting cultivation plots in which the burning strength varied between 0, 100, 200, and 300 t/ha at Sabal, Balai Ringin, and Niah and 0, 20, and 100 t/ha at Bakam. Species composition of germinated tree and herbaceous seedlings was surveyed, and a germination test of buried seed was conducted at Niah and Bakam. The number of germinated seedlings decreased with increasing burning strength, whereas seedling growth was promoted by burning. During the first year, growth was best in the intermediate burning strength plots, whereas during the second year, growth was best in the most strongly burned plots. Species composition differed between unburned and burned sites. Site-specific factors such as original stand biomass, soil properties, and invasion of exotic species also affected germination and growth. Buried seeds in the Ao layer were killed by burning, and nearly all seeds in the 0-5 cm layer were killed in the plots with the highest burning strength (> 100 t/ha). On the basis of our findings, we conclude that in shifting cultivation systems burning promotes vegetation recovery when the burning strength is properly managed.

In a region of Lower Northern Thailand, the traditional agricultural system has recently been changing toward a more intensive farming system by shortening the fallow cycle and several years of continuous cropping with significant fertilizer application. This study characterized soil fertility levels under the current intensified shifting cultivation systems, by comparison with the fruit tree plantations in the same area and the traditional shifting cultivation systems reported in the previous studies. Soil samples at surface and subsurface layers were collected from thirty study sites. Those study sites were grouped into 4 locations based on topography and parent material. Based on the PCA analysis of soil properties, soil fertility levels were mainly dependent on locations rather than the differences in land use types. However, some of the soils under maize field and fruit tree plantation showed a very low content of organic matter, suggesting occurrence of soil degradation in terms of organic matter. Burning of biomass still played an important role under the current intensified shifting cultivation systems, which brought positive effects to the soil fertility to alleviate soil acidity and supply exchangeable basis and available phosphorus. In contrast, because appreciable amounts of nitrogen seemed to be lost from soil ecosystems during cropping period, appropriate fertilizing methods should be developed to maintain the level of available nitrogen and to prevent environmental pollution.

Soil properties under secondary forests were studied in relation to vegetation conditions to clarify the site selection method for shifting cultivation of the Iban in Sarawak, Malaysia. Soils and vegetation were surveyed at 25 suitable sites and 17 unsuitable sites for shifting cultivation, classified by the landowners based on their perceptions through knowledge of vegetation condition. Principal component analysis classified soil properties into three principal components. The first was soil texture and organic matter with high factor loadings of clay content, cation exchange capacity, total C, and total N, and, to a lesser extent, exchangeable K. These properties were little affected by the fallow duration and site suitability. Clay content was regarded as one of important factors related to the levels of organic matter and nutrient retention capacity of the soils. The second component reflected soil acidity and exchangeable bases with high factor loadings of pH, exchangeable Ca and Mg, exchangeable Al, and Al saturation. These properties reflected the remnant effects of ash addition and fallow duration. However, no clear differences were apparent in these properties in terms of site suitability. The third component was linked to N availability, including the C/N ratio and exchangeable NH4. The N availability was higher at suitable sites than at unsuitable sites. At suitable sites, N availability tended to be higher with increasing fallow age. The N availability showed a statistically significant correlation with the site score of the first axis obtained from correspondence analysis of plant density, suggesting a strong relationship between N availability and vegetation condition. That relationship was attributable to depletion of the available N of the soils during cropping and at the initial fallow stage, as well as to improvement of N availability of soils with increasing length of the fallow period. This finding related to N availability was consistent with farmers' criteria for fertile land: leaves of trees in fertile land should be dark green. The presence of some specific plant species might be correlated with levels of available P and soil hardness. Results of this study show that the Iban farmers' vegetation-based site-selection method might reflect the ability of secondary forest ecosystems to supply nutrients for rice plants through burning practices.

Effects of arbuscular mycorrhiza (AM) and phosphorus (P) application on arsenic (As) toxicity were studied in a rhizobox system with As-contaminated soil collected from Shimane Prefecture, Japan. The treatments consisted of a combination of two levels of AM (Glomus aggregatum) inoculation (−AM and +AM) and two levels of P application (−P and +P at 30 mg P kg−1). Sunflower (Helianthus annuus L.) seedlings were cultured in rhizoboxes for 6 weeks. Rates of root AM infection in +AM treatments were about 40% regardless of P application. AM inoculation as well as P application reduced As toxicity symptoms, most clearly so in the +AM−P treatment. Plant growth was highest in the +AM + P treatment. Shoot As concentrations were slightly reduced by AM inoculation but enhanced by P application. Shoot P concentration in the +AM−P treatment was similar to that of +P treatments and was higher than in −AM−P. Analyses of rhizosphere soils at the end of the cultivation period indicated that P application increased water-soluble As (WS−As) in all compartments while AM inoculation increased WS−As in the central compartment only. Both the WS−arsenite [WS−As(III)] and the dominant form, arsenate [WS−As(V)], showed gradients toward the root surface. Dimethylarsine (DMAA) was detected in the +AM treatments only. To our knowledge, this is the first report of the occurrence of DMAA in the mycorrhizosphere. AM inoculation increased WS−P similarly as +P treatments did and promoted acid phosphatase activity in the soil. In conclusion, AM inoculation alleviated the effects of As toxicity by improving P nutrition without increasing As concentrations in the shoots. Moreover, AM appeared to be involved in the transformation of soil inorganic As into less toxic organic forms.

Experimental shifting cultivation was carried out at two sites, Niah and Bakam in Sarawak, Malaysia. The plots (10 × 10 m2) were treated with burning of vegetation biomass (fuel), amounting to 100, 200 and 300 Mg ha−1 with an untreated control at the Niah site and 20 and 100 Mg ha−1 with an untreated control at the Bakam site. At the Niah site, the soils were acidic with a light clay texture. The levels of pH, exchangeable bases and available P of the soils at the depth of 0–5 cm increased by burning while those of exchangeable Al and Al saturation decreased. The changes tended to be more appreciable in the plot treated with fuel at the rate of 300 Mg ha−1 than in the other plots. Based on a comparison between ash alkalinity and the difference in the content of exchangeable Al at 100 d after burning and before burning, it was assumed that 60% of the alkalinity contained in ash was consumed for inactivating exchangeable Al at the depth of 0–5 cm, which resulted in minimal changes in the soil properties in ...

The effects of burning on the levels of soil organic matter, soil nitrogen, and soil microbial biomass were studied by carrying out experimental shifting cultivation at two sites, Niah and Bakam in Sarawak, Malaysia. Vegetation biomass was burned in plots (10 × 10 m2) at the rates of 0 (control), 100, 200, and 300 Mg ha−1 at the Niah site and 0, 20, and 100 Mg ha−1 at the Bakam site. At the Niah site, the levels of total C and N of the soils did not change throughout the experiment in spite of enhanced soil respiration until 2 months after burning. Although burning induced an increase in the amount of NH4-N of the soils, the readily available pool of N (the sum of the NH4-N, NO3-N, microbial biomass N, and extractable organic N pools) in the burned plots was depleted appreciably at the end of rice cultivation. The effects of burning on these properties tended to be substantial with increasing amounts of the vegetation biomass burned. On the other hand, the levels of total C and N and the readily available...

Experimental shifting cultivation was conducted at the Balai Ringin (B. Ringin) and Sabal sites in Sarawak, Malaysia. At the sites, plots (10 x 10 m2) were burned with the fuel of aboveground biomass amounting to 0 (control), 100, 200, and 300 Mg ha-1. At the B. Ringin site, the soils were clayey and strongly weathered with a strongly acidic characteristic. Ash addition enabled to alleviate the soil acidity and to increase the amounts of nutrients of the soils, especially the surface soils. It was indicated that 1) N addition from ash to the soils was negligible, 2) the losses of nutrients by runoff water were not substantial compared with the amounts of nutrients contained in ash, 3) ash alkalinity seemed to be consumed for inactivating exchangeable AI mainly in the surface soils, and 4) development of variable negative charges could contribute to the retention of inorganic bases derived from ash. After harvest of upland rice, the soil chemical properties in the plots treated with 100 and 200 Mg...

Experimental shifting cultivation was conducted at two sites, Balai Ringin (B. Ringin) and Sabal in Sarawak, Malaysia. The soils at the B. Ringin site were clayey with strongly acidic nature while those at the Sabal site were sandy with a very low nutrient status. The plots (10 x 10 m2) were burned with vegetation biomass (fuel) amounting to 0 (control), 100,200, and 300 Mg ha-1 for the cultivation of upland rice. At both sites, the fire severity was found to range from moderate to high for the treatments with 200 and 300 Mg ha-1 fuel, and from low to moderate for the treatment with 100 Mg ha-1 fuel. At the B. Ringin site, the content of total C (T-C) of the soils decreased during rice cultivation which could be ascribed to the rapid decomposition of soil organic matter (SOM) and the loss of SOM due to soil erosion. One year after burning, the T-C content returned to the initial level before burning, suggesting that SOM was replenished by the addition of fresh organic matter derived from rice str...

In spite of the significant increase in the frequency and extent of fire occurrence in Indonesia recently, little information is available about the immediate, short-term, and long-term effects of fire on soils. To investigate the effects of wildfires on the dynamics of T-C, T-N, available P, pH, exchangeable bases, and cation exchange capacity (CEC) of Ultisols from South Sumatra Indonesia, surface soils of an unburnt 9-year old Acacia mangium plantation and of A. mangium plantations burnt in 1995, 1997, 1998, and 2000 were sampled in triplicate consecutively from December 1998 until December 2000. The values of T-C, T-N, available P, pH, and exchangeable bases significantly increased immediately after the fire while the levels of Al saturation and CEC significantly decreased. Soil nutrients were still accumulated 1 year after the fire but by the end of the second year, they were depleted and returned to the pre-fire levels. Although fallowing aggraded the burnt sites, the nutrient levels in the...

In the traditional shifting cultivation system practiced by the Karen people in northern Thailand, the effects of burning on the content of extractable organic matter, microbial biomass, and N mineralization process of the soils were studied. Five plots (5×5 m2 quadrat) with 0, 10, 20, 50, and 100 Mg ha-1 of slashed materials were arranged and burned. Ten to 20 Mg ha-1 of slashed biomass corresponded to the amount commonly burned by the Karen people. During the burning process, the soil temperature at the depth of 2.5 cm in the 100 Mg ha-1 plot almost evenly increased to 300°C while the temperature in the 10 to 50 Mg ha-1 plots increased with large variations from 50 to 300°C. Burning caused a conspicuous increase in the contents of organic C and (organic + mineral)-N extracted at room temperature and a simultaneous decrease in the contents of microbial biomass C and N, especially in the soil of the 100 Mg ha-1 plot. In the rainy season, the values of the changes induced by burning reverted to th...

Soil degradation caused by excessive land use is presently one of the major constraints on sustainable agriculture in the mountainous area of northern Thailand. In order to obtain basic information about soil fertility problems involved in the transition from traditional shifting cultivation to more intensive upland farming, the dynamics of K, Mg, and Ca, and soil acidity in the farming systems of both Karen and Hmong/Thai peoples were investigated. In the fields that lay fallow for more than 5 y, the soils were highly acidic and poor in exchangeable bases, mainly due to the fact that the fallow vegetation rapidly absorbed inorganic bases (K, Mg, and Ca) in the soils. In the fields both under fallow and cropping within 3 y after the slash and burn practice, the high acidity observed in the soils at the fallow stage seemed to be alleviated by ash input with high alkalinity. The aboveground biomass ranged from 9 to 10 t ha−1 in the 8 y fallow field and the sum of inorganic bases and alkalinity, whi...

To investigate the dynamics of micronutrients in the rhizosphere under the application of sterile and non-sterile arbuscular mycorrhizal inoculum, sunflower plants were grown in a rhizobox system. When the non-sterile mycorrhizal inoculum was supplied in the central compartment of the rhizobox, concentration of N, P, K, Mg, Fe, and Zn in the shoots increased without reducing the plant growth. Analyses of the rhizosphere soil showed an increase in the amount of water soluble Fe in addition to that of P, and a higher activity of phosphomonoesterase. Fractionation of P in the rhizosphere soil indicated a decrease in the amount of Fe-P. Neither the excretion of low-molecular-weight organic acids specific to the treatment nor the increase in amounts was observed. These results suggested that the enzymes originated from arbuscular mycorrhiza and/or mycorrhizal roots caused the dissolution of Fe-P with a resultant release of both Fe and P.

In order to understand the influence of the Fukushima Daiichi nuclear power plant accident on the ecosystem in hilly and mountainous areas of Fukushima Prefecture, chronological changes in the levels of radiocesium in arthropod species were investigated. From 2012 to 2014, arthropods from different trophic levels were sampled and the air radiation dose rates at the sampling sites were analyzed. The air radiation dose rates showed a significant and constant reduction over the 2 years at the sampling sites in Fukushima. The median radiocesium concentration (134Cs + 137Cs) detected in the rice grasshopper, Oxya yezoensis, and the Emma field cricket, Teleogryllus emma, dropped continuously to 0.080 and 0.078 Bq/g fresh weight, respectively, in 2014. In contrast, no significant reduction in radioactive contamination was observed in the Jorô spider, Nephila clavata, in which the level remained at 0.204 Bq/g in 2014. A significant positive correlation between radiocesium concentration and the air radiation dose rate was observed in the rice grasshopper, the Emma field cricket and the Jorô spider. The highest correlation coefficient (ρ = 0.946) was measured in the grasshopper.

A pot culture experiment was conducted using a Cu-spiked soil to compare the effects of the application of ethylenediamine-N,N′-tetraacetate (EDTA) and [S,S]-ethylenediamine-N,N′-disuccinate (EDDS), a biodegradable chelating agent, on the soil Cu distribution, Cu uptake by brown mustard and on the metabolic activity of the soil microorganisms for substrate utilization. Seedlings of brown mustard were planted in the pots fitted with hollow fibers for soil solution suction, and cultivated for 12 weeks. Solutions of chelating agents with pH 6.0 at a concentration of 1.0 mmol kg−1 soil were supplied on the 35, 43, and 51 d after transplanting (total 3.0 mmol kg−1). The addition of EDTA and EDDS enhanced plant Cu uptake by 2.9 and 1.8 times compared with the uptake of the control plants which were grown without chelating agent supply. However, EDTA addition caused a significant growth reduction compared with the control, while the application of EDDS did not reduce the dry matter yield of the plants. The conce...