Organic matter composition, microbial biomass and microbial activity in gravel-bed constructed wetlands treating farm dairy wastewaters

2000 ◽  
Vol 16 (2) ◽  
pp. 199-221 ◽  
Author(s):  
Long M. Nguyen
Keyword(s):  
Organic Matter ◽  
Microbial Biomass ◽  
Microbial Activity ◽  
Constructed Wetlands ◽  
Organic Matter Composition ◽  
Gravel Bed

Accumulation of organic solids in gravel-bed constructed wetlands

1995 ◽  
Vol 32 (3) ◽  
pp. 229-239 ◽  
Author(s):  
Chris C. Tanner ◽  
James P. Sukias
Keyword(s):  
Organic Matter ◽  
Constructed Wetlands ◽  
Loading Rate ◽  
Dairy Farm ◽  
Effective Porosity ◽  
Water Losses ◽  
Gravel Bed ◽  
Tracer Dispersion ◽  
Conservative Tracer ◽  
The Impact

The effects of wastewater loading rate and planting with Schoenoplectus validus (soft-stem bulrush) on the accumulation of organic matter were investigated in four pairs of gravel-bed constructed wetlands. The planted and unplanted wetland pairs, each supplied with a different hydraulic loading of dairy farm wastewaters pre-treated in an anaerobic and aerobic lagoon, had received cumulative suspended solids loadings (∼ 82% volatile) of between ∼ 1.6 and 5.4 kg m−2 over a 22 month period. Vertical and horizontal gradients of organic matter accumulation were sampled by stratified coring, and the impact of solids accumulations on wastewater residence times investigated using bromide as a conservative tracer. Mean accumulations of organic matter in the unplanted wetlands ranged between 0.4 and 2.3 kg m−2, while those in the planted wetlands reached mean levels of nearly 4 kg m−2. Highest levels were recorded in influent zones (up to 9.5 kg m−2) and in the upper 100 mm of the substratum. The effective porosity of the highest loaded wetlands was markedly reduced compared to that in the lowest loaded wetlands, with mean retention times decreasing to around half of their theoretical values (corrected for evapotranspirational water losses). The planted wetlands retained higher apparent gravel porosity, despite greater accumulations of organic matter. High evapotranspiration rates during hot summer days, markedly extended retention times and increased tracer dispersion.

Investigating nutrient controls over microbial activity in tropical soils

2021 ◽  
Author(s):  
Lucia Fuchslueger
Keyword(s):  
Organic Matter ◽  
Microbial Biomass ◽  
Microbial Communities ◽  
Microbial Activity ◽  
Microbial Growth ◽  
Tropical Soils ◽  
Phosphorus Availability ◽  
Soil P ◽  
Soil Microbial ◽  
Low Phosphorus

<p>The Amazon rainforest is an important sink for atmospheric CO<sub>2</sub> counteracting increased emissions from anthropogenic fossil fuel combustion and land use change storing large amounts of carbon in plant biomass and soils. However, large parts of the Amazon Basin are characterized by highly weathered soils (ultisols and oxisols) with low availability of rock-derived phosphorus (and cations), which are mostly occluded in soil or bound in organic matter. Such low phosphorus availability is thought to be (co-)limiting plant productivity. However, much less is known whether low phosphorus availability influences the activity of heterotrophic microbial communities controlling litter and soil organic matter decomposition and thereby long-term carbon sequestration in tropical soils.</p><p>In tropical soils high temperature and humid conditions allow overall high microbial activity. Over a larger soil phosphorus fertility gradient across several Amazonian rainforest sites, at low P sites almost 40 % of total P was stored in microbial biomass, highlighting the competitive strength of microorganisms and their importance as P reservoir. Across all sites soil microbial biomass was a significant predictor for soil microbial respiration, but mass-specific respiration rates (normalized by microbial biomass C) rather decreased at higher soil P. Using the incorporation of <sup>18</sup>O from labelled water into DNA (i.e., a substrate-independent method) to determine microbial growth, we found significantly lower microbial growth rates per unit of microbial biomass at higher soil P. This resulted in a lower microbial carbon use efficiency, at a narrower C:P stoichiometry in soils with higher P levels, and pointed towards a microbial co-limitation of phosphorus and carbon at low soil P levels. Furthermore, data from a multi-year nutrient manipulation experiment in French Guiana and from short-term lab incubations suggest that microbial communities thriving at low P levels are highly efficient in taking up and storing added P, but do not necessarily respond with increased growth.</p><p>Soil microbial communities play a crucial role in soil carbon and phosphorus cycling in tropical soils as potent competitors for available P. They also play an important role in storing and buffering P losses from highly weathered tropical soils. The potential non-homoeostatic stoichiometric behavior of microbial communities in P cycling is important to consider in soil and ecosystem models based on stoichiometric relationships.</p>

Accumulation of organic matter fractions in a gravel-bed constructed wetland

2001 ◽  
Vol 44 (11-12) ◽  
pp. 281-287 ◽  
Author(s):  
L. Nguyen
Keyword(s):  
Organic Matter ◽  
Microbial Biomass ◽  
Respiration Rate ◽  
Microbial Respiration ◽  
Water Soluble ◽  
Dairy Wastewater ◽  
Total Carbon ◽  
Organic Solids ◽  
Gravel Bed ◽  
Schoenoplectus Tabernaemontani

The function of a gravel-bed wetland in treating wastewaters is dependent on the turn-over rate of organic matter (OM) fractions in accumulated solids. Organic deposits from a gravel-bed planted (Schoenoplectus tabernaemontani) wetland, which had experienced pore clogging after 5 years of receiving farm dairy wastewater were therefore collected and determined for labile (water-soluble) and stable (humic acid, fulvic acid and humin) OM fractions, total carbon (C), microbial biomass and microbial respiration rate. Over 90% of the accumulated organic solids was present as stable fractions, with humic compounds at least 2-fold higher in surface deposits and the top 100mm of the gravel bed than the lower gravel substratum. Clogging of the gravel pore spaces over a 5-year wetland operation was probably due to the accumulation of refractory (stable) organic solids, particularly in the top 100 mm of the gravel bed. Microbial respiration rate and microbial biomass were significantly correlated with stable OM fractions, suggesting that these microbial parameters may be used to predict the nature of accumulated OM fractions. Further research is required to evaluate the use of these parameters as indicators of labile and stable fractions in wetlands with a range of OM loadings and accumulation.

Microbial activity and organic matter composition in Mediterranean humus forms

Geoderma ◽  
2013 ◽  
Vol 209-210 ◽  
pp. 198-208 ◽  
Author(s):  
Anna Andreetta ◽  
Cristina Macci ◽  
Virginia Giansoldati ◽  
Grazia Masciandaro ◽  
Stefano Carnicelli
Keyword(s):  
Organic Matter ◽  
Microbial Activity ◽  
Organic Matter Composition ◽  
Humus Forms

scholarly journals Soil Microbial Activity and Biomass in Semiarid Agroforestry Systems Integrating Forage Cactus and Tree Legumes

Agronomy ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1558
Author(s):  
Dayanne Camelo ◽  
José Carlos Batista Dubeux ◽  
Mércia Virginia Ferreira dos Santos ◽  
Mario Andrade Lira ◽  
Giselle Gomes Monteiro Fracetto ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Biomass ◽  
Microbial Activity ◽  
Rainy Season ◽  
Cropping Systems ◽  
Agroforestry Systems ◽  
Tree Legume ◽  
Δ13c And Δ15n ◽  
Soil Microbial ◽  
Tree Legumes

Vegetation cover affects soil organic matter and activity of soil microorganisms. We investigated the intercropping effect of forage cactus with tree legumes on soil microbial biomass and organic matter in the semi-arid tropic, state of Pernambuco, Brazil. We assessed the following cropping systems: (i) Gliricidia sepium intercropped with cactus cv. IPA-Sertânia; (ii) Leucaena leucocephala intercropped with cactus cv. IPA-Sertânia; and (iii) Cactus cv. IPA-Sertânia in monoculture. Samples were collected during the dry and rainy seasons in the 0- to 0.10- and 0.10- to 0.20-m soil layers at 0, 1.5, 3.0, and 4.5 m in a perpendicular gradient from tree legume rows. The following responses were determined: δ13C and δ15N, C and N, microbial activity and biomass, and metabolic, microbial, and mineralization quotient. δ13C and δ15N varied with the distance from the trees. In the dry season and beginning of the rainy season, the cropping systems showed similar values for C, N, microbial activity, carbon, and nitrogen in the microbial biomass. The presence of tree legumes at the end of the rainy season favored soil microbiota, which showed a reduced loss of C-CO2, with no indication of metabolic stress and greater microbial biomass and microbial quotient in relation to forage cactus in monoculture.

Soil organic matter composition and microbial activity in urban soils

1995 ◽  
Vol 168 (3) ◽  
pp. 267-278 ◽  
Author(s):  
Lothar Beyer ◽  
Hans-Peter Blume ◽  
Dirk-Christian Elsner ◽  
Antje Willnow
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Microbial Activity ◽  
Urban Soils ◽  
Organic Matter Composition ◽  
Soil Organic Matter Composition

Changes in microbial biomass and organic matter levels during the first year of modified tillage and stubble management practices on a red earth

Soil Research ◽  
1994 ◽  
Vol 32 (6) ◽  
pp. 1339 ◽  
Author(s):  
V Gupta ◽  
MM Roper ◽  
JA Kirkegaard ◽  
JF Angus
Keyword(s):  
Organic Matter ◽  
Microbial Biomass ◽  
Microbial Activity ◽  
Management Practices ◽  
Microbial Respiration ◽  
Microbial Biomass C ◽  
First Year ◽  
Tillage Practices ◽  
Red Earth

Farming practices involving stubble burning and excessive tillage in Australia have led to losses of organic matter from the soil. Crop residue retention and reduced tillage practices can reverse these trends, but changes in organic matter levels are evident only after a long term. Microbial biomass (MB), the living portion of soil organic matter, responds rapidly to changes in soil and crop management practices. We evaluated changes in microbial biomass and microbial activity in the first year following the modification of stubble management and tillage practices on a red earth near Harden, New South Wales. Following an oat crop harvested late in 1989, seven treatments involving stubble and tillage management were applied in February 1990. Wheat was planted in May 1990. Measurements of total organic carbon (C) and total nitrogen (N) in the top 15 cm of soil indicated no significant changes after 1 year, although there was a significant effect on the distribution of C and N. However, significant changes in MB were observed in the first year. Microbial biomass C in the top 5 cm of the soil ranged from 25 to 52 g C m-2 and these levels dropped by 50% or more with each 5 cm depth. Implementation of treatments altered MB, particularly in the top 5 cm where MB-C and MB-N were significantly greater in stubble-retained than in the top 5 cm where MB-C and MB-N were significantly greater in stubble-retained than in the stubble-burnt treatments, and in the direct drill treatment than in the stubble-incorporated treatment. Microbial biomass in soil increased during the growth of wheat in all treatments, but this was slower in the standing stubble-direct drill treatment, probably due to the delay in the decomposition of stubble. Microbial respiration, which was concentrated in the surface 5 cm of soil in all treatments, was greatest in the direct drill treatments. Microbial activity below 5 cm was higher with stubble incorporation than with direct drill. Specific microbial activity (microbial respiration per unit MB) had the greatest response to tillage at 10-15 cm depth. Microbial quotients (MB as a percentage of C or N) responded to changes in tillage but not significantly to stubble retention. Our studies, during the first year following the modification of stubble management and tillage practices, suggested that changes in MB and microbial activity may be sensitive and reliable indicators of long-term changes in organic matter in soils.

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