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The objective of this study was to investigate the current soil properties in lowland paddy fields in Peninsular Malaysia and to assess the long-term changes in the soil fertility status during 50 ...

Understanding of the long-term soil fertility trends is the basis for rational and sustainable management of the soil resources in agricultural fields. In tropical Asia, the Green Revolution initia...

This study investigated general physicochemical properties of tea garden soils at the alluvial plain of Cong River in Tan Cuong commune, Vietnam. Four gardens were selected as study sites on three ...

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...

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.

In Vietnam, the Co Dinh mine is the largest chromite mine in the country. Mining, ore dressing and disposal of the tailings provide obvious sources of heavy metal contamination in the mine area. The present study examined the influence of chromite mining activities on the adjacent lowland paddy field by investigating heavy metal and As levels in the mine tailings, sediments, paddy soils and water. At paddy fields located near the mine tailings, the total contents of Cr, Co and Ni were 5,750, 375 and 5,590 mg kg−1, and the contents of their water-extractable form were 12.7, 1.16 and 32.3 mg kg−1, respectively. These results revealed severe contamination of lowland paddy soils with Cr, Co and Ni as a result of mining activity, suggesting serious health hazards through agricultural products, including livestock in this area. The principal source of the pollution was sediment inflow owing to the collapse of the dike, which was poorly constructed by heaping up soil. Moreover, water flowing out from th...

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 ...

The effects of steam sterilization (SS), methyl bromide (MeBr) fumigation and chloropicrin (CP) fumigation on soil N dynamics and microbial properties were evaluated in a pot experiment. All disinfection treatments increased the NH+ 4-N level and inhibited nitrification. The additional NH+ 4-N in the CP treatment probably originated from the decomposition of microbial debris by surviving microbes, while that in the SS treatment was attributable to deamination processes of soil organic N occurring in a less labile fraction in addition to the decomposition of microbial debris. The MeBr fumigation increased the level of NH+ 4-N without changing the soil microbial biomass. Based on the determinations of soil microbial biomass, substrate utilization activity (Biolog method) and microbial community structure (phospholipid fatty acid method), the effects of the MeBr, CP and SS treatments on the microbial community were compared. The MeBr fumigation had relatively mild and short-term effects on microbial...

The role of arbuscular mycorrhizal fungus (AMF) on biotransformation of arsenic (As) in the rhizosphere of sunflower (Helianthus annuus L.) was studied in a rhizobag system with As-contaminated soil. The treatments consisted of a combination of two levels of AMF (Glomus aggregatum) inoculation (–AM and +AM) under sterile and non-sterile soil conditions (S and NS). Each treatment was designated as –AM/S, –AM/NS, +AM/S and +AM/NS. Sunflower seedlings were cultured in the rhizobag for 6 weeks. Rates of root AMF colonization in +AM treatments were approximately 40% and 0% in –AM/S treatment. The AMF inoculation reduced As toxicity symptoms and improved plant growth. Shoot As, but not the root As, concentrations were reduced by AMF inoculation. Shoot and root P concentrations increased in +AM treatments regardless of soil sterilization. Analyses of water soluble (WS) As in the soils at the end of the cultivation indicated that the amount of WS-arsenite (AsIII) was higher in the central compartment com...

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.

Sustainability of the local shifting cultivation practice in the mountainous region of Northern Laos was investigated. Due to low fertility of the soils derived from shale and its strongly weathered and acidic nature in the eastern side of the Nam Khan River watershed, shortening of the fallow period to produce enough amount of upland rice for the local population would not be sustainable any more. On the other hand, the eroded materials from limestone range were added to the soils in the western side of watershed which made the soil more fertile. Based on the calculated population capacity by Carneiro's equation, a system with 2- or 3-year fallow for 1-year cultivation can be the maximum to afford the current population. To make the shifting cultivation system more sustainable, introduction of fallow system with a tree species, paper mulberry (Broussonetia papyrifera) could be a good option to be proposed.

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...

The effects of steam sterilization (SS) on soil microbial properties including metabolic diversity of the microbial communities were examined in a greenhouse compared with those of two fumigants, methyl bromide (MB) and chloropicrin (CP). The numbers of fungi decreased in all the treatments. Nitrifiers, both ammonium-oxidizing bacteria and nitrite-oxidizing bacteria, were severely affected by the SS and CP treatments, resulting in their virtual disappearance. The decrease in the levels of microbial biomass C and N after the treatments suggested that the SS and CP treatments eradicated the microorganisms more effectively than the MB treatment and that the influence of the former persisted until the end of the experiment, 4 months after the treatments. Accumulation of NH4-N was observed after the SS and CP treatments mainly due to the partial decomposition of the dead microorganisms and the marked decrease in the number of ammonium-oxidizing bacteria. The richness and average well color development...

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...

In order to analyze the N mineralization process under shifting cultivation in northern Thailand, labile pools of soil organic matter were studied, which were considered to be the factors contributing to the N mineralization process. Organic C, (organic + NH4 +)-N, and hexose-C were extracted from fresh soils in the surface 0–5 cm layers with a 0.5 M K2S0. solution at 110°C in an autoclave (fraction A) or at room temperature with a reciprocal shaker (fraction B), and analyzed as labile pools of organic matter. In the traditional shifting cultivation system, the content of organic C in fraction A in the fallow fields for 8 to 15 y was 3,710 mg kg-1 while that in the fallow fields for 1 y and 3 to 5 y was 2,640 and 2,600 mg kg-1, respectively. A high correlation was observed between the contents of the labile pool in fraction A and total soil organic matter. The ratio of the pool in fraction A to total soil organic matter apparently remained constant through the input-output balance in the pool. Th...

N mineralization process (ammonification plus nitrification) in the surface 0-5 cm soil layers under shifting cultivation in northern Thailand was studied. Labile pool of organic matter extracted with a K2S04 solution at 1l0°C in an autoclave (fraction A) or by shaking at room temperature (fraction B) was used as factor to evaluate the N mineralization process which was examined in an incubation experiment. In the soils, in which the N mineralization pattern was fitted to a first order kinetics model, the content of (organic + NH4 +)-N in fraction B determined the initial rate of N mineralization. The soils, which showed a short lag time of less than 7 d both in the N mineralization and nitrification processes, had a high ratio of organic C to (organic + NH4 +)-N in fraction B, exceeding the value of 7. The soils, which showed a long lag time of more than 7 d only in the nitrification process, had a low pH(KCI) (less than 4.2). Thus, the rate of N mineralization was affected by the labile pool in...

There is a large number of hill people in northern Thailand, who practices shifting cultivation. In order to analyze the soil ecological problems involved in the transition from traditional shifting cultivation to more intensive upland farming, the authors carried out comparative studies on the dynamics of organic matter and its related properties in soils both in the traditional shifting cultivation systems adopted by Karen people and more intensive upland farming practiced by Thai and Hmong people in the area. The contents of organic matter and available N in the surface 10 cm layers of soil from the fields continuously cultivated were lower than those in soils under prolonged fallow (more than 10 y) or natural forest. Based on the rate of soil respiration, the amount of organic matter decomposed within 1 y was estimated to reach nearly 10% of that stored in the upper 50 cm layers of the soil profile in the upland crop fields. These results indicate that the organic matter-related resources mar...

Recently agricultural activity in the mountainous area of northern Thailand has increased and problems relating to soil fertility have arisen. In order to gain basic information about the soil properties associated with shifting cultivation, physicochemical properties of the surface soils (0–10 cm) and subsoils (30–40 cm) were investigated in selected villages in the area. The physicochemical properties of the soils studied are summarized as follows: 1) The soils were rich in organic matter, content of which ranged from 11.4 to 63.3 g C kg−1 in the surface soil. 2) The pH(H2O) of the soils mostly ranged from 5 to 7 and soil acidity was more pronounced in the deeper horizons. In the surface soils, exchangeable Ca and Mg were generally dominant, whereas exchangeable Al was often predominant in the subsoils. 3) Most of the soils showed a medium to fine texture with more than 30% clay. The clay mineral composition was characterized by various degrees of mixture of kaolin minerals and clay mica with, ...

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...

(Jpn. J. Soil Sci.Plant Nutr., 77, 257–263, 2006) The symptom of blighted leaves was observed for the melon plants grown on an isolated soil bed after steam sterilization (SS) in a greenhouse in Kochi Prefecture, Japan. To clarify the causes of this symptom, soil and plant analyses were conducted in the first experiment. Manganese concentrations in the leaves with the symptom were higher than 1,000 mg kg−1and exchangeable Mn in the soil was higher than 30 mg kg−1, which indicated the observed symptom was due to Mn excess. In the second experiment, formation of Mn oxide-dissolving substances after SS was examined for several organic amendments, because large amounts of palm chips had been supplied to the soil before SS in the first experiment. As a treatment similar to SS, palm chips, bark compost, and cattle feces manure were autoclaved. The water extracts were collected before and after the autoclave treatment and the Mn oxide-dissolving capacities of the extracts were evaluated. The Mn oxide-dissolving capacity of the water extracts after SS was remarkably higher than before SS, and the value was highest in palm chips, and followed by bark compost, and cattle feces manure. Fractionation and HPLC analysis of the water extracts after SS revealed that the main substance behind Mn oxide reduction in palm tips was arabinose and that in bark manure was malic acid. Further, Mn oxide-dissolving capacities of the water extracts were almost completely explained by the amounts of arabinose or malic acid found in these materials. From these results, it was considered that reducing substances such as arabinose were released by SS from the palm chips which had been applied in large quantity before SS and these reducing substances dissolved the soil Mn oxides and increased the amounts of available Mn, which led to the occurrence of Mn toxicity to the plants.

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...

In order to provide appropriate soil information for the rehabilitation of tropical rainforest ecosystems, we examined the soil morphological, physico-chemical, mineralogical properties and charge characteristics in a degraded mixed dipterocarp forest with three type of vegetation, namely grassland, secondary forest, and remnant forest in Japan Sarawak Friendship Forest, Sarawak, Malaysia. We compared the soil properties at six representative locations differing in topography and vegetation types, with special reference to the effect of anthropogenic activities on the catenary sequence. All the soils were acidic or weakly acidic. Contents of clay, exchangeable Al, Alo, Ald and Fed and the values of the cation exchange capacity and Al saturation increased with depth. The clay mineral composition was dominated by kaolin minerals. The value of point of zero salt effect ranged from 3.0 to 4.0, indicating that the soil was not yet strongly weathered. A catenary sequence of the soils was observed; softer in soi...