Microbial biomass and organic matter turnover in wetland rice soils (original) (raw)
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Characteristics of microbial biomass and soil organic matter in newly reclaimed wetland rice soils
Biology and Fertility of Soils, 1995
Microbial biomass C, N, total organic C, N and mineralizable N were measured in newly reclaimed wetland sandy loam rice soil with a very low nutrient status. Microbial biomass C increased 5.4-10.4 times due to application of barnyard manure, but decreased drastically to 2 4-2 7 % during rice cultivation. Organic C and N contents also decreased during cultivation, but to a lesser extent to 5 9-7 6 %. At the tillering stage of the rice plant, microbial biomass N was highly correlated with mineralizable N (r = 0.986).
Microbiological Management of Wetland Rice Fields
2001
Roger et al. a water microflora. The first section presents a brief summary of the major environments of the wetland rice field ecosystem and the major microbial activities they host, and a short overview of research on microbiological management of rice fields. The next sections discuss in detail potential and adopted practices, including (1) the utilization of symbiotic and free-living N,-íìxing blue-green algae as biofertilizers, (2) the inoculation of rice with heterotrophic bacteria and the potential for rhizosphere microflora management, and (3) the utilization of bacterial and algal inhibitors to decrease N fertilizer losses. II. A. Diffusion of air into soil is reduced about 10,000 times when a rice field is flooded and O, supply cannot meet the demand of soil aerobic organisms. Facultative and strict anaerobes proliferate , using oxidized soil substrates for respiration, reducing the soil in a sequence predicted by thermodynamics, and creating anaerobic conditions in a reduced layer a few millimeters beneath the soil surface (Yoshida, 1975). Flooding and crop growth lead to the differentiation of macroenvironments differing in physicochemical and trophic properties: floodwater, surface-oxidized soil, reduced soil, rice plants (submerged parts and rhizosphere), plow layer, and subsoil (Fig. 1). Although those environments can be macroscopically differentiated, they are more or less continuous. In particular, continuous exchanges take place between floodwater and oxidized soil (Watanabe and Furasaka, 1980). Macroenvironments might also be heterogeneous in their oxidation-reduction status at the microsite level because the activity of soil fauna creates microaerophilic sites in the reduced layer, while organic matter debris and aggregates might provide anaerobic microsites in the oxidized soil layer and the water.
Journal of Pharmacognosy and Phytochemistry, 2019
A field experiment was conducted at Annamalai University Experimental Farm, Department of Agronomy, Annamalai University, Annamalainagar to study the effect of spatial arrangements and integrated use of green leaf manure with inorganic nutrition on soil fertility and microbial population of post harvest soil of wetland rice. The results revealed that the spatial arrangements and integrated nutrient management were significantly influenced the post harvest soil health and microbial population. Among the treatment combinations, spot seeding of rice at 30 30 cm spacing for Thaladi and 25 25 cm spacing for Navarai season under the integrated application of 50 per cent N via., Albizia lebbeck along with 50 per cent N via., inorganic fertilizer significantly improved the post harvest soil available N (268.51 and 244.56 kg ha-1), P2O5 (23.89 and 24.67 kg ha-1) and K2O (382.92 and 337.04 kg ha-1) during the Thaladi and Navarai seasons, respectively. The same trend was also recorded in the soil microbial population of bacteria (58.78 and 46.33 x 10-6 g-1 of soil), fungi (39.78 and 34.00 x 10-4 g-1 of soil) and actinomycetes (8.00 x 10-6 g-1 of soil), respectively.
Soil Ecology Letters, 2020
It is well documented that rice paddy fields act as agricultural wetlands that remove or retain nutrients; however, their associated effects on soil microbial communities are rarely reported. The present study evaluates the impact of rice variety on nutrient removal via plant uptake, nutrient retention in the soil, and bacterial associations in rice paddy fields, using a network analysis that compares the soil bacterial communities of two rice varieties. We found that the high-straw rice variety (YD-1) allows uptake of a high amount of nitrogen (N) and phosphorus (P) from paddy rice fields via harvesting, but causes less residual total N and P to remain in the soil. However, both rice varieties (YD-1 and XS-134 (Xiushui-134)) had non-significant effects on the dominant bacterial taxa. The short-term response of bacterial community diversity to rice variety is found to be mainly due to less frequently recovered species. A network analysis that incorporates soil nutrients as nodes, along with bacterial taxa, found that only one node representing the total P related to the non-dominant species had an indirect association with the rice straw biomass. The observed short-term impact of the two rice varieties (XS-134 and YD-1) on soil bacterial diversity and nutrient surplus in these agricultural wetlands is limited under a high level of fertilization.
Biogeosciences
While soil organic carbon (SOC) accumulation and stabilization has been increasingly the focus of ecosystem properties, how it could be linked to soil biological activity enhancement has been poorly assessed. In this study, topsoil samples were collected from a series of rice soils shifted from salt marshes for 0, 50, 100, 300 and 700 years from a coastal area of eastern China. Soil aggregates were fractioned into different sizes of coarse sand (200–2000 µm), fine sand (20–200 µm), silt (2–20 µm) and clay (< 2 µm), using separation with a low-energy dispersion protocol. Soil properties were determined to investigate niche specialization of different soil particle fractions in response to long-term rice cultivation, including recalcitrant and labile organic carbon, microbial diversity of bacterial, archaeal and fungal communities, soil respiration and enzyme activity. The results showed that the mass proportion both of coarse-sand (2000–200 µm) and clay (< 2 µm) fractions incre...
Soil Biology and Biochemistry, 2011
Two adjacent paddies of an experimental rice field, subjected to organic and conventional farming, were characterized aiming the comparative assessment of microbiological variations occurring in the bulk paddy soil over the rice cycle. This study comprehended the simultaneous characterization of general physicochemical soil properties [total carbon and nitrogen, pH (H 2 O and KCl), C:N ratio and water content], biochemical properties [enzymatic activities and Community Level Physiological Profiles (CLPP)], the estimation of cultivable organisms (enumeration of fast growing heterotrophic bacteria, actinomycetes and fungi) and the assessment of bacterial diversity using a culture-independent method (PCR-DGGE fingerprinting). The linkage of the parameters measured was analysed by canonical correspondence analysis (CCA). CCA ordination plots of the CLPP showed a similar pattern of microbial functional activity in both agronomic management systems, except in June. Enzymatic activity, water content and fungi counts were the main factors affecting the observed CLPP time variation. Such a variation was not expressed by the Shannon and evenness indices, which did not evidence significant differences in the bacterial and functional diversity between or within farming type over the analysed period. The cluster and CCA analyses of the DGGE profiles allowed the distinction of the bacterial communities of both paddies, with temporal variations being observed in the organically managed field but not in the conventional paddy. Enzymatic activity, pH and molinate content were the factors which most contributed to the observed variations. Altogether these results underline the functional redundancy of the rice paddy soil and evidence the temporal variations on the metabolic activity of soil, irrespective of farming type.
Nutrient cycling through microbial biomass under rice-pasture rotations replacing native savanna
Soil Biology and Biochemistry, 1997
area of native savanna on an acid, strongly P-sorbing Oxisol in the Eastern Plains of Colombia was opened and sown to various rotations of grass pasture with rice, grass-legume pasture with rice or rice monocrop. After 4.5 y, the soil under each cropping system was sampled and analysed for total organic matter, microbial C, N and P content, and mineralization rate of C and N. Microbial biomass C did not vary much among treatments, whereas the N and P contents of the biomass were considerably lower in rice monocrop than in any crop-pasture treatment. Biomass P was also low under native savanna. The contribution of microbial N or P to soil-organic-matter N or P was lowest under the rice monocrop and highest under the grass-legume pasture. Microbial C-to-N ratios fell in ranges commonly reported, but C-to-P ratios were rather wide (34-50), indicating that the microbes may have adapted themselves to the low-P conditions of these soils. The contribution of microbial P to soil-organic-matter P, however, was about the same as usually found in soils of much higher P fertility. As microbial biomass nutrients cycle relatively rapidly and P availability in these strongly P-sorbing soils is low, the microbial biomass may play an important role in supplying P to plants growing in these soils. A similar conclusion was reached for N. The microbial respiration rate per unit of microbial biomass C (qCO& as determined during an ll-day incubation, was higher under rice-pasture rotations-particularly in the presence of a legume-than under rice monocropping. This suggests that a greater fraction of microbes was active under rice-pasture rotations, probably because of a more continuous and higher input of fresh organic matter. The fraction of organic matter mineralized during the incubation was also highest for the rice-pasture treatments. 0 1997 Published by Elsevier Science Ltd Biology and Biochemistry 22, 251-255. Zeitschriff fur Pflanzenerniihrung und Bodenkunde 157, 359-367.
Ecological Indicators, 2017
Soil microbial communities play an essential role in maintaining soil fertility and considered as ecological indicators to evaluate soil health. In the present study, long-term effects of organic and inorganic fertilizers on functional diversity of soil microbial communities, and their correlation with soil organic carbon, microbial biomass and activities, were observed under sub-humid tropical rice-rice cropping system. This experiment comprises six treatments viz. control (plots without application of chemical fertilizers and farm yard manure), nitrogen (N at the rate of 60 & 80 kg ha −1 in wet and dry seasons, respectively), nitrogen + phosphorus + potassium (NPK), farm yard manure (FYM), FYM + N and FYM + NPK. The results indicated that pH of the soil under the treatments decreased from its initial value, whereas total organic carbon increased in FYM-treated plots. Microbial biomass carbon and nitrogen in FYM + NPK were increased by 50.0 and 46.4%, respectively as compared to control treatment. Carbon and nitrogen mineralization; and soil enzyme activities were significantly (p ≤ 0.05) higher in FYM + NPK over control. The average well color development (AWCD) values derived from Biolog ® eco-plates followed the order of FYM + N > FYM > FYM + NPK > NPK > N > Control. Shannon index was greater (p ≤ 0.05) in FYM-treated soil as compared to control and chemical treated soil. Principal component analysis (PCA) indicates a clear separation of the cluster of treatments with FYM application (FYM and FYM + NPK) and treatments without FYM (N and NPK). Shannon index was significantly correlated with available phosphorus (p ≤ 0.002) and carbon mineralization (p ≤ 0.015). Biplot analysis suggested that polymer and amino acid utilizing microbes were dominant, irrespective of all treatments. These results revealed that continuous application of nitrogen fertilizer alone has responded a shift in soil microbial community in the long run and decreased the functional diversity of microbes. However, application of FYM either alone, or in combination with chemical fertilizers, could restore soil fertility. Moreover, the information generated from this experiment though Biolog ® may be the first particularly with reference to the dominance of polymer and amino acid utilizing microbes, irrespective of treatments under long-term fertilized paddy soil.