Methanogenic bacterial populations in some lowland paddy field soils of Burkina Faso (West Africa)

In wetland ecosystems, such as rice fields, methanogenic bacteria (MB) play important roles in global carbon cycling as terminal organic decomposers and in hydrogen cycling as hydrogen consumers, leading to methane production (Jorgensen 1982). In the global atmosphere, concentration of methane has been increasing by about 1% per year (Blake and Rowland 1986; Bouwman 1989; Dlugokensky et al. 1994) and it is considered that 80% is of biological origin (Seiler 1984). The environmental impact of methane on global warming has also been confirmed (Chappellaz et al. 1990). Rice paddy fields contribute to an estimated 10% of the global methane emission (Bouwman 1989; IPCC 1992) and the intensification of paddy cultivation may contribute considerably to the gradual increase of atmospheric methane (Rasmussen and Khalil 1981). From 1970 to 1990, rice production increased by 110% in West Africa (FAO 1970, 1990), as a direct result of encroachment on new lands throughout most of West Africa (Windmeijer and Andriesse 1993; Issaka et al. 1996a, b). In Burkina Faso, about 85% of the rice cultivation areas are lowlands (Sié 1991). In recent years, many studies on methane emission from paddy fields and limited ecological studies on methanogenic populations have been conducted (Schütz et al. 1989; Asakawa and Hayano 1995; Adachi et al. 1996). However, studies on both methane emission and populations of methanogens in African paddy fields are very limited. Garcia et al. (1974) enumerated methanogenic populations in Sénégal rice soils by the most probable number (MPN) method. With the gradual increase in the land area under rice cultivation, more information is needed on methane fluxes, populations, and species of methanogens in paddy fields of West Africa. We reported here the enumeration of methanogenic populations in the soils of lowland paddy fields located in the Sudan and Guinea Savanna zones of Burkina Faso (West Africa) by the MPN method.     

Characterization of Desulfovibrio sp. isolated from some lowland paddy field soils of Burkina Faso

In a wetland ecosystem such as lowland ricefields, the anaerobic mineralization of organic matter is a key mechanism for nutrient recycling (Jørgensen 1982; Freney et al. 1982). In the process which involves several bacterial groups, sulfate reducers (Watanabe and Furusaka 1980; Widdel 1988; Ouattara and Jacq 1992; Nozoe 1997), methanogens (Asakawa and Hayano 1995; Dianou et al. 1997), sulfur and ferric ion reducers (Jacq et al. 1991) become active when the soil becomes anoxic (Amstrong 1969). Sulfate reducers are common in flooded soils (Watanabe and Furusaka 1980; Widdel 1988; Furusaka et al. 1991). Reported densities in rice soils ranged from 10³ to 10⁵ g^-1 dry soils in Asia (Watanabe and Furusaka 1980) and from 10² to 10⁹ g^-1 dry soil in Sénégal (Ouattara and Jacq 1992). Among the sulfate reducers, the “classical” Desulfovibrio species are known to oxidize typical fermentation products such as hydrogen, lactate, pyruvate, and dicarboxylic acids (Widdel 1988). So far, data on the isolation and characterization of sulfate-reducing bacterial (SRB) strains from African rice paddy field soils study have been very limited.     

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.     

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.     

Effects of underdrainage in lowland poorly drained paddy field

The lowland poorly drained paddy field may be handicapped in general, to the better drained paddy field in soil productivity level for rice crops in Japan. This is principally responsible for the prevalence of reducing characteristics in soils because of the high waterlogging condition all the year round. Therefore, the effects of the soil drying treatment on lowland poorly drained paddy field by any drainage are highly significant for the satisfactory production of rice crops. Kobo0 has noted that, among the numerous soil properties changed after drainage of the lowland poorly drained paddy field, the decreases in soil nitrogen level which will be characterized by the stabilization of soil humus are associated most closely with the promotion of the soil productivity. The present study was set up to ascertain the effects of soil drying by underdrainage of the lowland poorly drained paddy field incomparison with the better drained paddy field under cultivation.     

Trace elements in Bangladesh paddy soils

Abstract

A study was carried out to investigate the status of four micronutrients, iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn), and five other trace elements, cobalt (Co), chromium (Cr), nickel (Ni), lead (Pb), and strontium (Sr), in paddy soils of Bangladesh. Soil samples were digested by hydrofluoric acid (HF)‐nitric acid (HNO₃)‐perchloric acid (HClO₄) for determination of total contents of the nine elements, while DTPA, ASI and 0.1 Mhydrochloric acid (HC1) methods were used for determination of available Fe, Cu, Mn, and Zn. Total trace element contents were found to vary with physiography on which soils are distributed. In general, Ganges Tidal Floodplain soils had the highest content, whereas terrace soils had the lower content. Among the soil properties examined, clay content had a good relation with total trace element contents in the topsoil, except for Sr. Based on the variation with physiography or clay content, the nine trace elements could be grouped into six groups: Cu, Fe and Zn, Pb, Co and Cr and Ni, Mn, Sr. According to the extractable levels of four micronutrients, Bangladesh paddy soils had the medium to optimum amounts of Fe and Cu, but were deficient sporadically in Mn and extensively in Zn. It was indicated that paddy soils of Bangladesh are yet to be polluted with heavy metals.     

Nitrogen-fixing microorganisms in paddy soils XIV

In the preceeding paper (1), it was reported that when R. capsulatus is mixed with B. subtilis, in spite of no nitrogen fixation in separate cultures, by using a glycerol or starch medium, the combination was able to fix molecular nitrogen and it seems that there is a correlation between the production of pyruvic acid and the nitrogen fixation in the mixed culture.     

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.     

Nitrogen-fixing microorganisms in paddy soils IV

In 1949, GEST and KAMEN (1,2) reported that Photosynthetic bacteria can fix molecular nitrogen. LINDSTROM et al. (3,4) tested the nitrogen fixing ability of five species of photosynthetic bacteria under the following four conditions; 1) anaerobic light, 2) aerobic light, 3) aerobic dark, 4) anaerobic dark. As the result of the experiment, they certified that it Was only under the anaerobic light condition that the bacteria can fix molecular nitrogen.     

Nitrogen-fixing microoganisms in paddy soils XVI

1. It was proved that under aerobic shaking conditions of the system of R. capsulatus mixed with Az. agilis or R. capsulatus mixed with B. megaterium, the bacterial growth of both and the nitrogen fixation were promoted markedly, comp:ired with the non-shaking culture. However, in the system of R. capsulatus mixed with B. subtilis under aerobic shaking conditions. such remarkable stimulative effects were not recognized altough some slow effects were recognized in the nonshaking culture.

2. It was also proved that under aerobic shaking conditions of the system of R. capsulatus mixed with Az. agilis or R. capsulatus mixed with B. megaterium the assimilative activity of carbon dioxide increased over 10 times more than in the separate pure culture.

From these results, it is conceivable that a very good environment was created for the internal metabolism of R. capsulatus in such mixing systems (R-Az and R-Bm).     

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.     

Nitrogen-fixing microorganisms in paddy soils (Part 3) distribution of non-sulphur purple bacteria in paddy soils

The possible significance of blue-green algae in the nitrogen economy of paddy soil has been pointed out by many investigators.     

Trace elements in tropical Asian paddy soils

Attempts were made to evaluate correlations of total trace elements with various soil characters in the hope that such correlations would allow prediction of the trace element status of paddy soils in Tropical Asia.

Among the 11 trace elements studied, Ni and Cr showed by far the highest correlation, followed by the pairs of V and Zn, Ni and Zn, and Cr and Zn.

High positive correlations of trace elements with soil characters were found for the following pairs: total Fe₂O³, and V and Zn, total K₂0 and Rb, total CaO and Sr, total TiO₂, and V, total Al₂0³ and Zn, 10 Å clay content and Rb, clay and V, and sand and Zr. Among the negative correlations, the highest was between total SiO₂ and V, followed by those between total SiO₂ and Zn and sand and Zn.

Soil material classes and inherent potentiality ratings previously established were found to have some value for the prediction of the status of certain trace elements in soil.     

Nitrogen-Fixing microorganisms in paddy soils VII.

In the previous paper (1) it has been repored that the the amount of nitrogen fixed was very much increased when Rhodopseudomonas capsulatus was cultured with Azotobacter vinelandii probably due to their symbiotic relationship.     

Nitrogen fixing microorganisms in paddy soils XII

Introduction

We have been studying the interrelation between R. capsulatus and other various microorganisms, in which there are symbiotic relationships (I). When R. capsulatlls and Az. vinelandii co-existed, molecular nitrogen was fixed much more than in each pure culture and many slime substances (polysaccharides, muco-polysaccharides etc.) were produced (2). In order to study symbiotic nitrogen fixation between the two microorganisms, first, the nature of the cell wall of both bacteria has to be known.     

Nitrogen-fixing microorganisms in paddy soils: VI

During the experimental study of the role of blue-green algae in the nitrogen economy of paddy fields which were hitherto carried out in our laboratory, it was observed that small animals in paddy fields such as water fleas, mud snails, small freshwater fish, tadopoles or larvae of small insects had a preference for feeding on blue-green algae.     

Inhibitors of methane production in paddy soils

Global warming is now attracting the world attention. Methane is an important greenhouse gas next to CO₂. Prather et al. (1995) estimated that rice paddy fields account for 14% of all biogenic atmospheric methane. It is considered that methane production from rice paddy fields is increasing along with the increase of the population. Therefore, the development of rice cultivation techniques for reducing methane production is essential, in order to preserve the global environment.     

Movement of ammonium in paddy soils in Taiwan

The movement of ammonium due to diffusion in paddy soils in Taiwan was investigated in the laboratory. The movement of ammonium in flooded soils was inversely proportional to the concentration of ammonium in the soil solution, which was a function of the quantity of ammonium present, the content of solid matter in a unit volume of soil (bulk density), and the adsorptive property of soil. Although there was a considerable variation in the value of both the ammonium adsorption and bulk density of soils, the adsorptive property was more variable. Therefore, the adsorptive property seemed to be the most influencial factor on the movement of ammonium in flooded soils, where the property had a close relation to the cationexchange capacity.

The bulk density of flooded soils in the field could be reproduced in glass tubes under percolating condition in the laboratory. The values of bulk density determined on paddy soils after harvesting or on air-dry soils were considerably different from those in the flooded soils in the field. A simple determination method of bulk density was proposed for paddy soils.     

Biomorph silica in meadow soils of the Mid-Amur lowland

On the basis of an analysis of the gross composition and morphology of the particles of soil samples from the Mid-Amur lowlands, it is shown that the biomorph silica of the meadow soils with bleached horizons is represented by meadow forms of phytoliths (mainly true grasses). In the upper profile part of the AUg horizon, frustules of diatom algae are found, while no spicules of sponges are registered. The upper part of the profile is characterized by the highest degree of weathering of the phytolith silica. In the lower part, they are better preserved. In this part of the profile, diatoms are represented by small-celled species around 2 μm in size (supposedly, spores of Cyclotella sp.). The presence of such algae in the water-peptized silt is associated with the process of migration down the profile.     

Methane uptake by unflooded paddy soils

Abstract

Methane (CH₄) is one of the most abundant organic gases in the atmosphere. Recently the importance of CH₄ as a greenhouse gas has been recognized and studies have been carried out to assess its contribution to global warming. Although the rate of increase has slowed down in the last decade (Steel et al. 1992; Rudolph 1994), the results from some of these studies have shown that the atmospheric concentration of CH₄ is increasing at a rate estimated to be approximately 1% per year (Rowland 1991; Blake and Rowland 1988; Bolle et al. 1986; Graedel and McRae 1980). Clearly it is important to identify sources and sinks of CH₄, in both terrestrial and oceanic ecosystems, in order to estimate global methane budgets (Cicerone and Oremland 1988).