Saccharides in some Japanese paddy soils

Monosaccharides released by acid hydrolysis from paddy field soil, from the light and the heavy fraction of soil, front some plant fragment were determined using automated anio-exchange chromatography.

Between 5 and 12 per cent of the organic carbon was present as saccharides.

The monosaccharide composition of the different soils was very similar, in spite of differences in the absolute amount of saccharides present. The amount of the various monosaccharide in the whole soil was found to be in the order glucose»xylose galactose, mannose, arabinose rhamnose ribose.

The monoccharide composition of the soils showed a marked contrast to that of the rice ra8ment, and partially decomposed plant remains taken from the soil. Glucose, xylose, arabi-the predominant saccharides in the rice fragments and the plant remains, while the amounts of galactose, mannose, rhamnose were negligibly small.

It was found that the proportion of galactose, mannose, rhamnose and ribose in the heavy fraction Of soil was greater than that of glucose, xylose, and arabinose

The present observation was in agreement with the view that soil sauharides comprised Pentoses originates in plant materials.

The molar ratio of xylose to mannose was calculated to show the characteristics of the mono-saccharide composition of soils and some plant muerials.     

Microbiological Studies on the Humification Process (Part 2) on the Aerobic Decomposition of the Fresh Plant Residue in the Case of Single Inoculation

The humification of several constituents of plant was studied by Trussow¹⁾ and Waksmans²⁾ in the Past, or by Kononova,³⁾ Tepper⁴⁾ and Laatsch⁵⁾ in recent years. In the previous paper, we experimented the microbial action on humus separated from an uncultivated soil, and showed that the inoculation of Trichoderma koningi and soil extract prqmoted the humification of the sample, but such tendency was not revealed in the case of single inocolation of two strains of Actinomyces and four strains of aerobic bacteria, and that when the humification of the soil humus was promoted it occurred, in the first place, as the transformation of the fulvic acid fraction, not as that of the precipitation part (the humic acid fraction). Following the previous report, we studied the humification process of fresh plant residue (upland rice straw) by a similar procedure.     

The reduction mechanism of manganese in paddy soils

Hydroquinone method manganese (soluble in pH 7.0, 1 N-ammonium acetate solution containing 0.2 percent hydroquinone) and microbially active manganese (soluble in pH 7.0, 1 M-magnesium sulfate solution after flooding soils with or without Chinese milk vetch for 12 or 20 days respectively at 30°C) of 22 paddy soils were determined. The amounts of manganese reduced with sodium oxalate under acid conditions (oxalate method manganese (a) and (b), the former was determined under more rigorous conditions than the latter) were also determined and compared with hydroquinone method manganese and microbially active manganese.

Their levels of many soil samples representing soil groups were also determined to examine the dlfferences In amounts of active manganese among soil groups. The results obtained are as follows.

The relationship between microbially and chemically active manganese. 1) The amounts of microbially active manganese in soils were 48 to 68 mg Mn per 100 g oven-dried soil and these were increased by the addition of Chinese milk vetch. 2) The amounts of hydroquinone method manganese were less than microbially active manganese, and the amounts of oxalate method manganese (b) were larger than microbially active manganese. The amounts of oxalate method manganese (a) were the largest of all the types of manganese. 3) There were high correlations between the amounts of various types of active manganese described in 2). The levels of microbially and chemically active manganese. 1) The amounts of microbially active manganese lay between the amounts of chemically active manganese determined by the hydroqulnone method and by the oxalate method (b) In all soil samples representing soil groups. High correlations were found between these types of active manganese. 2) The hydroquinone method was considered to be unsuitable for quantitatively determining the amounts of chemicallY active manganese in soils of high organic matter content. 3) In both cases of microbially active manganese and chemically active manganese, tha widest range and the largest amount determined were both observed in strongly gley soila. The averages of theae types of active manganese were high in strongly gley soils, pea, and muck soils, and black soils. The differences among soil groups were smalle1 than the differences among soil samples, and little tendency was observed in the differences among soil groups.

From these findings described above it is suggested that the oxalate methoo (b) is more appropriate than the hydroqulnone method for determining chemically active manganese as an index of microbially active manganese.     

植稻年限对土壤铁锰氧化物的影响

以浙江不同耕作年限水田和旱地为研究对象,探讨了植稻年限对土壤铁锰氧化物的影响,并揭示了水稻土发育过程中铁锰氧化物的剖面运移规律和诊断意义。结果表明:①土壤剖面中,全Fe、游离Fe及全Mn的变异随着种稻时间的延长而增大。种植达到一定年限时,全Fe、全Mn以及游离Fe在土壤剖面下层出现淀积。在各种铁锰氧化物中,对水稻土最具诊断意义的是游离Fe和全Fe。②无定形Fe以及络合态Fe、Mn与有机质呈显著正相关。植稻年限对它们的影响是通过对有机质的影响达到的。     

中国某些水稻土中硝态氮向铵态氮的还原研究

Three paddy soils were examined for their capacities of dissimilatory reduction of nitrate to ammonium (DRNA). 15N-labelled KNO3 was added at the rate of 100 mg N/kg. Either glucose or rice straw powder was incorporated at the rate of 1.0 or 2.0 mg C/kg respectively. Three treatments were designed to keep the soil saturated with water: (1) a 2-cm water layer on soil surface (with beaker mouth open); (2) a 2-cm water layer and a 1-cm liquid paraffin layer (with beaker mouth open); and (3) water saturated under an O2-free Ar atmosphere. The soils were incubated at 28℃ for 5 days. There was almost no 15N-labelled NH4+-N detected in Treatment 1. However, there was 1.4 to 3.4 mg N/kg 15N-labelled NH4+-N in Treatment 2, and 2.1 to 13.8 mg N/kg in Treatment 3. Glucose was more effective than straw powder in ammonium production. Because there was sufficient amount of non-labelled NH4+-N in the original soils, 15N-labelled NH4+-N produced as such should be the result of dissimilatory reduction. Studies on microbial population showed that there were plenty of bacteria responsible for DRNA process (DRNA bacteria) in the soils examined, indicating that number of DRNA bacteria was not a limiting factor for ammonium production. However, DRNA bacteria were inferior in number to denitrifiers. The DRNA process in soil suspension started after 5 days of incubation. Glycerol and sodium succinate, though both are readily available carbon sources to organisms, did not facilitate DRNA process. DRNA occurred only when glucose was available and at a C:NO3--N ratio >12. Both availability and quality of the carbon sources affected DRNA.     

泰国水稻土Fe还原细菌对盐分和有机物改良的响应

In paddy soils of Thailand,the addition of organic matter (OM) is used to efficiently limit the effect of salinity on rice culture and production.OM used as an amendment and fertilizer promotes the reduced condition and increases iron solubilization without provoking ferrous toxicity.In this study,the intricate biogeochemical role of iron-reducing bacteria (IRB) involved in the quality of water and soil of paddy fields,particularly when the paddy fields were subject to salinity and organic matter addition,were studied in paddy fields of Thailand.The results demonstrated that the addition of OM increased the proliferation of cultivable IRB and their specific activity.Cultivable IRB communities decreased in the presence of salt.The presence of salt modified the structure of the bacterial populations by favoring the development of alkaline and moderately halophilic bacteria (Virgibacillus spp.,Oceanobacillus spp.,and Paenibacillus spp.).The paddy soils studied contained very diversified (halosensitive,halotolerant,and halophilic) IRB populations that could be adapted to a variety of salinity conditions (0-90 g L 1 NaCl) using different organic substrates (glucose,acetate,and soil organic matter) to maintain significant activities under extreme conditions of salinity.The rhizosphere of rice stimulated IRB community growth without organic matter,whereas organic matter addition limited the rhizosphere effect on IRB cultivable number in saline condition.The interactive action of salinity and organic amendment had a negative impact on the rhizosphere effect.The presence of specific iron-reducing populations (fermentative,iron-respiring,anaerobic,and facultative anaerobic),having different behaviors under salt and redox stresses,appeared to be a key factor that contributed to the control or enhancement of the quality of water and soil in paddy fields.     

Changes in proteolytic bacteria in paddy soils in response to organic management

Proteolytic bacterial communities, which mineralize organic nitrogen, play a key role in agricultural systems. In this study, alkaline metalloprotease (apr) gene fragments from proteolytic bacteria were investigated in bulk and rhizosphere paddy soil from four fields under organic management (for 2, 3, 5, and 9 years), and from one field under conventional management (for 2 years). We analyzed the abundance and structure of the proteolytic bacterial communities using real-time quantitative PCR and denaturing gradient gel electrophoresis. Our results showed that the abundance of proteolytic bacteria ranged from 1.57?×?10⁸ to 8.02?×?10⁸?copies/g of soil. In addition, the abundance of the proteolytic bacteria in the paddy soils under organic management was significantly higher than those in the paddy soil under conventional management. Moreover, the gene copy numbers in the rhizosphere soils were significantly higher than those in the bulk soils. The abundance of proteolytic bacteria tended to increase with the duration of organic management, with the highest abundance being found in the soil that had been under organic management for 5 years. However, the proteolytic bacteria communities in the paddy soils were not significantly affected by management practices. Phylogeny analysis showed that all gel bands obtained represented genes from Pseudomonas. Additionally, correlation analysis and canonical correspondence analysis showed that C/N, C, and N were important factors that influenced the abundance and community structure of the proteolytic bacteria. These results suggest that proteolytic bacteria are indicators in organic management systems, depolymerize organic N and hence maintain soil sustainability.

Abbreviations: CM: conventional management; OM: organic management; DGGE: denaturing gradient gel electrophoresis; qPCR: real-time quantitative PCR detecting system; COFCC: China organic food certification center; CCA: canonical correspondence analysis     

挪威北部土壤微生物活性的季节变化

Seasonal development of soil microbial activity and bacterial biomass in sub-polar regions was investigated to determine the impacts of biotic and abiotic factors, such as organic matter content, temperature and moisture. The study was performed during spring thaw from three cultivated meadows and two non-cultivated forest sites near Alta, in northern Norway. Samples from all five sites showed increasing respiration rates directly after the spring thaw with soil respiration activity best related to soil organic matter content. However, distributions of bacteria] biomass showed fewer similarities to these two parameters. This could be explained by variations of litter exploitation through the biomass. Microbial activity started immediately after the thaw while root growth had a longer time lag. An influence of root development on soil microbes was proposed for sites where microorganisms and roots had a tight relationship caused by a more intensive root structure. Also a reduction of microbial activity due to soil compaction in the samples from a wheel track could not be observed under laboratory conditions. New methodological approaches of differential staining for live and dead organisms were applied in order to follow changes within the microbial community. Under laboratory conditions freeze and thaw cycles showed a damaging influence on parts of the soil bacteria. Additionally, different patterns for active vs. non-active bacteria were noticeable after freeze-thaw cycles.     

Microbial metabolism in reduction process of paddy soils (Part 2)

The previous experiences^1-3) with incubation experiments of the soils under submargd condition indicated that the disappearance of molecular oxygen and nitrates occurred shortly after sub-emerging, and then the reduction of ferric iron proceeded, being followed by the reduction of sulfates and the formation of methane which nre caused by the activities of strict anaerobes. It was suggested from the above fact that the reduction process in the submarged soils was affected mainly by two factors: namely, the amount of reducible ferric iron and the soil organic matters which are avaiable as substrate for microbial metabolism.     

Changes in soil microbial community composition in response to fertilization of paddy soils in subtropical China

Repeated fertilizer applications to cultivated soils may alter the composition and activities of microbial communities in terrestrial agro-ecosystems. In this study, we investigated the effects of different long term fertilization practices (control (CK), three levels of mineral fertilizer (N₁P₁K₁, N₂P₂K₂, and N₃P₃K₃), and organic manure (OM)) on soil environmental variables and microbial communities by using phospholipid fatty acid (PLFA) biomarkers analysis in subtropical China. Study showed that OM treatment led to increases in soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) contents, while the mineral fertilizer treatment led to increases in dissolved organic carbon (DOC) content. Changes in soil microbial communities (eg. bacteria, actinomycetes) were more noticeable in soils subjected to organic manure applications than in the control soils or those treated with mineral fertilizer applications. Fungal PLFA biomarkers responded differently from the other PLFA groups, the numerical values of fungal PLFA biomarkers were similar for all the OM and mineral fertilizer treatments. PCA analysis showed that the relative abundance of most PLFA biomarkers increased in response to OM treatment, and that increased application rates of the mineral fertilizer changed the composition of one small fungal PLFA biomarker group (namely 18:3ω6c and 16:1ω5c). Further, from the range of soil environmental factors that we examined, SOC, TN and TP were the key determinants affecting soil microbial community. Our results suggest that organic manure should be recommended to improve soil microbial activity in subtropical agricultural ecosystems, while increasing mineral fertilizer applications alone will not increase microbial growth in paddy soils.     

水稻土中外源铅和苄嘧磺隆交互作用对碳源矿化的影响

Little information is available on the interactive effects of inorganic and organic pollutants on carbon utilization by soil microorganisms.This study examined the effects of two common soil pollutants,lead (Pb) and bensulfuron-methyl herbicide (BSM),on decomposition of an adscititious carbon source (¹⁴C-glucose).Two contrasting paddy soils,a silty clay soil and a clay loam soil,were incubated with different concentrations and combinations of pollutants for 60 days.Orthogonal rotatable central composite design was adopted to design the combinations of the pollutant concentrations so that rate response curves could be derived.Rapid decomposition of ¹⁴C-glucose occurred in the first three days for both soils where no Pb or BSM was added (control).Overall,63%-64% of the added ¹⁴C-glucose was decomposed in the control over the 60-day incubation.The addition of Pb or BSM significantly decreased the decomposition of ¹⁴C-glucose during the first week but increased the decomposition thereafter;as a result,the percentages of ¹⁴C-glucose decomposed (57%-77%) over the 60-day period were similar to or higher than those of the control.Application of the pollutants in combination did not further inhibit decomposition compared with the control.Overall,decomposition rates were lower in the silty clay soil than in the clay loam soil,which was related to the soil texture,cation exchange capacity,and pH.The relationship between the decomposition rates and the pollutants could be well characterized by the quadratic regression orthogonal rotation model.The initial antagonistic effects of the pollutants followed by the synergistic effects on microbial activity might result from changes of the concentrations of the pollutants.     

Effects of organic matter application on microbial biomass and available nutrients in various types of paddy soils

Abstract

The effect of the addition of bromacil (pesticide) or/and a sewage sludge on the urease, phosphatase and dehydrogenase activities of soil was studied. Urease and phosphatase activities increased initially with the addition of bromacil. This effect disappeared after 28 d of soil incubation. The increase in the urease and phosphatase activities caused by the addition of sewage sludge was more pronounced than that of bromacil. The combined addition of sewage sludge and bromacil also led to an increase in the activity of both hydrolases. Dehydrogenase activity was affected negatively by the addition of bromacil and positively by the sewage sludge addition. When sewage sludge and bromacil were added simultaneously, dehydrogenase activity was higher than when sewage sludge alone was added.     

Nitrogen fixation in paddy soils

Several important features of the N. fixation in paddy fields which were reported previously were confirmed and some new additional results regarding the evaluation of the N₂ fixation in the rhizosphere were obtained by reinvestigation in the fields. In addition, rice plants were cultivated in the submerged soil in pots and various parts of the soil were analyzed for the N₂-fixing activity as well as several other properties. The results of the pot experiments were found to be fairly similar to those observed in the field investigations, indicating the validity of the submerged soil in a pot as a rather simulated model for the actual paddy field. By using this model system, the following facts were ascertained: (1) Water-percolation had almost no effect on the N₂-fixing activities of both the rhizosphere and the non-rhizosphere soils. (2) Suppressing effect of washing the root of rice plant on the N₂-fixing activity was slight in the seedling stage and marked in the tillering and flowering stages. (3) The N₂-fixing activity of a single rice root varied from tip to base.     

Nitrogen fixation in paddy soils

The 4 long-term experimental plots (Umbric haplaquept) with different fertilizer treatment at Cent. Agric. Exp. Sta. in Konosu City, Saitama Prefecture, were used for the sites of investigation. The 4 plots were NF (applied with no fertilizer), IF (applied with inorganic fertilizers), GM (applied with green manure and CaCO₂), and OM (applied with manure and inorganic fertilizers). Flooded water, floating weed, upper (0-2cm) and lower (2-10cm) parts of Apg horizon and rhizosphere were collected from each plot before flooding, during flooding, and after drainage. These samples were analyzed for N₂-fixing activity by acetylene reduction method, pH, Eh, and contents of Fe²⁺, NH₄ ⁺, chlorophyll-type compounds, and water-soluble carbohydrates.

The N₂-fixing activity of all samples showed almost the same pattern of change with time: very low before flooding, rapidly increased after flooding, the maximum value at the maximum tillering stage of rice plant, declined afterwards and reached a very low value after drainage.

Rough estimation of the “N₂-fixing capacity” of each part of the paddy field revealed that the most important site of the N₂ fixation was the reduced Apg horizon, that the importance of flooded water and/or the oxidized layer in the N₂ fixation was rather low except in infertile soil, and that the role of rhizosphere in the N₂ fixation could not be neglected also in Japan.

Reduced condition and content of easily decomposable organic substances were judged to be main factors which control the N₂-fixing activity in the flooded soil on the basis of correlations between the Nt-fixing activity and several analytical data of the paddy soils.     

Potential nitrogen immobilization as influenced by available carbon in Japanese arable and forest soils

Abstract

Iron oxide is the most important electron acceptor in paddy fields. We aimed to suppress the methane emission from paddy fields over the long term by single application of iron materials. A revolving furnace slag (RFS; 245 g Fe kg^-1) and a spent disposable portable body warmer (PBW; 550 g Fe kg_-1) were used as iron materials. Samples of a soil with a low iron level (18.5 g Fe kg^-1), hearafter referred to as “a low-iron soil” and of a soil with a high iron level (28.5 g Fe kg^-1), hearafter referred to as “an iron-rich soil,” were put into 3 L pots. At the beginning of the experiment, RFS was applied to the pots at the rate of 20 and 40 t ha^-1, while PBW was applied at the rate of 10 t ha^-1 only, and in the control both were not applied. Methane and nitrous oxide emissions from the potted soils with rice plants were measured by the closed chamber method in 2001 and 2002. When RFS was applied at the rates of 20 and 40 t ha^-1 to the low-iron soil, the total methane emission during the cultivation period significantly decreased by 25–50% without a loss of grain yield. Applied iron materials clearly acted as electron acceptors, based on the increase in the amount of ferrous iron in soil. However, the suppressive effect was not evident in the iron-rich soil treated with RFS or PBW. On the other hand, nitrous oxide emission increased by 30–95%. As a whole, when the total methane and nitrous oxide emissions in the low-iron soil were converted to total greenhouse gas emissions expressed as CO₂- C equivalents in line with the global warming potential, the total greenhouse gas emissions decreased by about 50% due to the application of RFS.     

Chloritization in lowland paddy soils

This paper is concerned with the alteration of clay minerals which takes place when well-aerated lowland soils (Brown lowland soils) are cultivated for growing rice. For this purpose the clay mineral compositions of paddy soils were compared with those of adjacent arable soils at four locations.

In the case of arable soils a larger part of the 14Å spacings collapsed to 10Å on treatment with NH₄NO₃ solution, or on drying at about 100°C, whereas in paddy soils the spacings were more stable to thelie treatments. Cation exchange capacities of clays were always smaller In paddy soils than in arable soils. Alternate treatments of reduction and oxidation somewhat increased the stability of the 14Å spacings to heat treatment.

These results indicate that chloritization is a very common process occurring in lowland paddy sons. Chloritization In paddy soils appears to be closely associated with the seasonal cycle of reduction and oxidation.     

Driving factors of soluble organic nitrogen dynamics in paddy soils: Structure equation modeling analysis

Soil soluble organic nitrogen (SON) is one of the most active components in soil nitrogen pools; however, limited information is available with regard to its driving factors, as well as their pathways and degrees of influence. In this study, structural equation modeling was used to analyze the driving factors, their significance, and pathways that affected SON dynamics in a waterlogged experiment of two typical paddy soils incubated for 80 d after green manure application. Soil pH, Eh, microbial biomass, enzyme activity, and SON dynamics were used to construct the structural equation model. Results showed that soil microbial biomass carbon (MBC), protease, glutamine, and initial organic matter (OM) directly and significantly affected soil SON with path coefficients corresponding to 0.405, 0.547, 0.523, and -0.623 (P < 0.01), respectively. Soil microbial biomass carbon and initial OM affected the SON dynamics indirectly through protease and glutamine activity. In addition, pH indirectly affected SON dynamics by glutamine activity. It is implied that soil MBC, protease, glutamine, and initial OM are the key factors affecting SON dynamics in the waterlogged paddy soils after green manure application. Our research indicated that structural equation modeling could provide an effective method to clearly recognize the impact, significance, and pathways of multiple factors on SON dynamics in paddy soils.     

浙江慈溪不同利用年限水稻土肥力特征的比较

温室盆栽条件下比较了浙江慈溪不同利用年限水稻土（50至2000年）水稻生长与谷物产量的差异,以及无施肥条件下种植水稻对水稻土微生物生物量与转化酶、脲酶活性的影响。结果发现,利用年限较长水稻土上种植的水稻植株相对较高（p 0.10）,水稻秸秆、根系及谷粒的生物量均随水稻土利用年限延长而显著增加（p 0.05）;N、P、K等营养元素在植株不同部位的分异状况不同,其中秸秆的全P和全K含量均随水稻土利用年限延长而显著升高（p 0.05）,而米粒的全N含量也趋于升高（p 0.10）。温室盆栽试验之后,水稻土的微生物生物量及酶活性与利用年限之间的关系规律和种植水稻之前基本一致,且整体上又趋于下降,即无施肥条件下种植水稻转化利用了土壤部分微生物生物量,并减弱了与碳氮转化相关酶的活性,对保持水稻土的营养水平造成不利影响。结果表明,水稻土的肥力质量历经两千年的长期稻作长盛不衰、粮食生产能力不减反增,而且是在作物有效养分可循环利用（如秸秆还田或外施肥料）的前提下实现持续利用的。     

Nitrogen-fixing microorganisms in paddy soils (Part 1) Characteristics of the nitrogen fixation in paddy soils

In most paddy soils, as is already well-known, the crop yield goes on decreasing just for the first few years and then stabilizes at a comparatively high level with no supply of fertilizer or manure.