Organic Matter Mineralization Processes Research Articles

Benthic fluxes and mineralization processes at the scale of a coastal lagoon: Permeable versus fine-grained sediment contribution

Benthic fluxes of biogenic compounds play a major role in the biogeochemistry of shallow aquatic environments. Quantifying these fluxes at the scale of a lagoon is a challenge, especially when sediments are heterogeneous and fluxes at the sediment-water interface combine diffusive and advective transport processes. Diagenetic processes and associated benthic fluxes were quantified across different seasons in a lagoon of the French Mediterranean coast (La Palme lagoon) from vertical profiles of pore water and sedimentary solid fraction carried out at many representative stations of the lagoon. The northwestern part of the lagoon is covered with fine-grained sediment with low permeability and the rest of the lagoon contains permeable sandy sediment. We obtained vertical profiles with centimetre-scale resolution of water content, salinity, and major particulate and dissolved biogenic compounds of C, N, P, Si, S, Fe and Mn. This study allowed us to refine the sedimentary mapping of the lagoon, to specify the spatio-temporal evolution of biogeochemical processes, and to determine more precisely the part of the diffusive fluxes of nutrient compared to advective fluxes. Comparison of the vertical profiles with a molecular diffusion transport model shows that molecular diffusion is the dominant process in fine-grained sediments, while sandy sediments are dominated by advection due to circulation of lagoon water in shallow sediments. Benthic respiration renders fine-grained and sandy sediments anoxic from the first few mm below the sediment-water interface, particularly due to the availability of labile organic matter. Benthic dissolved inorganic nitrogen fluxes are of the same order of magnitude in both sediment types, despite the different flux mechanisms. This suggests that the intensity of organic matter mineralization processes is the same in fine and sandy sediments. Benthic phosphate fluxes are greater in sandy than in fine sediments because phosphorus is more efficiently retained in the solid fraction of fine sediments. Thus, sandy sediments play a dominant role in the pelagic-benthic coupling of the lagoon.

Influence of Chemical Meliorants on Microbiological Activity of Chernozem-Meadow Soils

The study was conducted in the Voronezh FASC “Kamennaya Steppe” in 2020–2022. The assessment of the state of the structure of microbial cenosis in meadow soils with the use of various chemical meliorants is given. Options for reclamation included the introduction of gypsum and defecate at a dose of 5 t/ha and a combination of their half doses. The number of ecological and trophic groups of microorganisms was determined by seeding on solid nutrient media. Accounting for organisms assimilating organic forms of nitrogen – by sowing on meat-peptone agar (MPA), accounting for organisms assimilating mineral forms of nitrogen – by sowing on starch-ammonium medium (SAM), accounting for organisms mineralizing humus – by sowing on nitrate agar, accounting for fungi – on Chapek medium, accounting for the amount of nitrogen – on soil plates, accounting for nitrifiers – on hungry agar, accounting for organisms that decompose fiber – on Vinogradsky’s medium. As a result of chemical reclamation of meadow soils with the use of gypsum and defecate as meliorants, patterns of changes in the activity of soil microorganisms were established. It was possible to identify a fairly clear dependence of the increase in the number of microorganisms that utilize organic forms of nitrogen on the use of meliorants in meadow soil of a hollow-shaped depression. Mineralization processes of organic matter were maximally expressed in meadow-chernozem soil on a plain rise when gypsum was used as a meliorant at a dose of 5 t/ha, while the use of gypsum and defecate at a dose of 2.5 + 2.5 t/ha had a greater effect on the content of nitrifiers in this soil. In the chernozem-meadow soil of a hollow-like decrease, the use of defecate at a dose of 5 t/ha led to an increase in the content of actinomycetes. In the chernozem-meadow soil of the plain depression, the use of all meliorants had an impact on the increase in the number of humus mineralizers, fungi, as well as nitrifiers compared with the control. It was not possible to identify any significant pattern associated with the use of meliorants on these soils for the maintenance of azotobacter colonies. In soils with different degrees of soil moisture, the use of meliorants had an ambiguous effect on the number of cellulolytics: an increase in soil hydromorphism in combination with the use of defecate at a dose of 5 t/ha led to a maximum increase in cellular microorganisms in the chernozem-meadow soil of a hollow-like decrease.

DYNAMICS OF SOIL ORGANIC CARBON AFTER MORE THAN 25 YEARS OF FARMING IN THE DANUBE DELTA

Soil organic carbon (SOC) is an important parameter in the context of global warming, and a special attention should be given to its dynamics. The purpose of this paper is to test the existence of SOC losses from the soils taken for farming for more than 25 years in some areas of the Danube Delta. Another objective is to quantify such SOC losses if they exist. The studied soils belong to two land reclamation areas, Carasuhat and Dunavat, from the Danube Delta. Data of present-day SOC stocks were compared to the SOC stocks calculated for the period until year 1996 for the same soil units in order to assess the dynamics of SOC losses for more than 25 years. We have found that a specific process was noted for the organic soils, Histosols, which were turned into histic soils after farming, meaning that there was a significant decrease in SOC pool. Thus, SOC losses due to farming were maximum for Histosols, and SOC stocks were highly significantly lower in 2022 versus 1996, due to increasing mineralization processes of organic matter and subsequent greenhouse gas emissions that occurred in cropland areas. Relationships have been found quantifying SOC losses versus the original 1996 stocks, confirming that Histosols, containing the maximum SOC stocks, present the highest risk of degradation. Lowering of the ground water and consequently the intensified oxidation of peat are very important factors in SOC losses beside the agricultural land use works. Policy makers, decision makers and stake holders should promote conservation of the natural landscape of the Danube Delta in order to increase SOC stocks and decrease CO2 and other greenhouse gas emissions into the atmosphere. Maintaining the former SOC stock at the present-day level and enhancing new organic C sequestration in the renatured parts of the less fertile Delta soils could contribute to global warming mitigation in the future and to supply agricultural products in the cropland already in use. Future research in characteristic stationary sites of the Danube Delta, especially in the farmland area, is recommended to improve our knowledge on SOC evolution.

Mineralization of organic matter in microbialites and implications for microbialite reservoirs in Member IV of the Leikoupo Formation, Sichuan Basin, China

Microbialites are important reservoirs for oil and gas. The mineralization of organic matter in microbialites during early diagenesis can produce acidic fluids that dissolve carbonate grains, and can also result in an alkaline pore water that precipitates cement. The mineralization of organic matter in microbialites and its effect on microbialite reservoirs have not yet been studied in detail. In this study, quantitative statistical analysis of the two-dimensional spatial occurrence of pores and microbial fabrics, in situ geochemical analysis of specific components (microbial, transitional zone, and fine spar fabrics), and qualitative evaluation of the implications for microbialite reservoirs were undertaken on microbialites from Member IV of the Leikoupo Formation, Sichuan Basin, China. The quantitative statistical analysis shows that pores are spatially associated with microbial fabrics, but porosity has a poor correlation with microbial fabric content. In situ geochemical data indicate that microbialites with different porosities experienced different processes of organic matter mineralization. The processes of organic matter mineralization such as oxidation and nitrate reduction can provide more dissolution micropores than the process related with sulfate reduction, whereas the process of organic matter mineralization related with Fe–Mn oxide reduction results in cementation. Micropores created by organic matter mineralization can act as fluid channels for later dissolution and are important in the development of microbialite reservoirs.

Mobile sulphur status in soils of organic and conventional vineyards of the Southern coast of Crimea

The data on the content of mobile sulfur in soils of vineyards on the Southern coast of Crimea with organic and conventional land use systems as well as in fallow soils after long-term application of chemical pesticides are presented. As a result of the use of sulphur-containing pesticides allowed in organic farming and the activation of organic matter mineralization processes due to regional soil and climatic conditions, a significantly higher accumulation of mobile sulphur in the upper soil horizons of organic farms was observed. Higher levels of mobile sulphur in organic vineyard soils can adversely affect the organoleptic and physico-

ПОПОВНЕННЯ ОРГАНІЧНИМИ РЕЧОВИНАМИ І ГУМУСОВАНІСТЬ ҐРУНТУ В ЯБЛУНЕВИХ САДАХ ЗА РІЗНОГО УДОБРЕННЯ

The balance of humus in a meter layer of dark gray, podzolized soil and podzolized chernozem of the experimental apple orchads and the study of their long-term fertilization was investigated (from the planting to 50-year old trees) with the use of organic (40 t/ha of cattle manure) and mineral fertilizers (N120P120K120), which were applied once in two years in autumn under the plowing in the row spacings at a depth of 18 20 cm. In the 20-year period (from 30- to 50-year-old experimental gardens) in a meter layer of dark gray podzolized soil on the non-fertilized control plots the amount of humus increased by 27 t/ha, and on the plots fertilized with manure – by 7 t/ha more and on the plots with mineral fertilizers – by 6 t/ha less and in podzolized chernozem – 37 t/ha and 3 t/ha more and 10 t/ha less respectively. Such changes in humus storage were caused by different replenishment of organic substances, and, to a greater extent, an increase in the biological activity of the fertilized soil, in particular the intensity of mineralization processes of organic matter, and in particular the humus compounds. Also, the replanishment of such soils in the gardens by the organic mass of fallen leaves and thin (d≤1mm) small roots, which systematically grows and dies, providing root nutrition of fruit plants, was investigated. These sources supplemented with organic substances the layer of soil of 0 20 cm – with all the mass of leaves and 38,5 43,3% of the total roots, and the increase in humus content was in all roots of the layer of 0 60 cm: in non-fertilized areas of 11 t/ha in dark gray soil and 18 tons per hectare in chernozem, under organic fertilizers, by 14 and 19 t/ha, and under mineral fertilizers – by 3 and 9 t/ha respectively. The greatest quantity of humus was added in the layer 60 100 cm: 16 and 19 t/ha, 20 and 21 t/ha and 18 t/ha. Such results were conditioned by the intensification of biological activity, in particular mineralization processes, in the upper layers of fertilized soils at higher humus content, as well as the migration of soluble humus substances deep into the meter profile.

Influence of Mineral Fertilization and Liming on Maize Production on Argic Chernozem in the Burnas Plain

In order to elucidate some aspects regarding the content of nutrients in the soil or humus, the bioaccumulation and mineralization process of organic matter and correction of the soils reaction in the experimental field, within the agricultural holding SC Orhideea SRL Plopsoru, Locality Daia, Giurgiu County, research has been done with chemical fertilizers with NPK and liming - Ca(OH)2 on argic chernozem in maize culture from the Burnas Plain in different doses.Obtaining appropriate agricultural production on argic chernozems is limited by a number of factors such as relief, clay loam, low-medium permeability just below the plowed horizon advanced degree of soil compaction, located between 20-35 cm from the surface (plow sole) and climatic conditions.

Coupling between sediment biogeochemistry and phytoplankton development in a temperate freshwater marsh (Charente-Maritime, France): Evidence of temporal pattern

In freshwater systems, sediment can be an important source for the internal loading of PO4. The limiting character of this element in such system leads to consider this phenomenon in terms of eutrophication risks and water quality stakes. A four-months follow-up (January, March, April and May 2019) was carried out in a strong phosphate (PO4) limited secondary channel from an artificial irrigation system of Charente Maritime (France) to link the mobilization of remineralization products in the upper 6 cm layer of sediment (conventional core slicing/centrifugation and DET probes) and the phytoplankton biomass dynamics in the water column. Results showed congruent patterns between the temporal succession of the organic matter mineralization processes in the sediment and the primary biomass dynamics in the water column. In January and March (considered in winter), PO4 proved to be retained by adsorption onto iron oxides in anoxic sediment since pore water nitrate inhibited for about a month the respiration of metal oxides in the first cm of sediment, thus limiting PO4 availability and the phytoplankton growth. In April and May (early spring), after exhaustion of pore water nitrate, the dissolutive reduction of iron oxides released PO4 into pore water generated a significant diffusive outgoing flux from the sediment to the water column with a maximum in April (-1.10E-04±2.81E-05 nmol cm−2 s−1). This release coincided with the nanophytoplankton bloom (5.50 µg Chla L−1) and a potential increase of PO4 concentration in the water column. This work provides some insight on the importance of benthic-pelagic coupling in anthropogenic systems. This conceptual model has to be deployed on other sites of interest where internal loading of P takes precedence over external inputs and nitrate mitigation drives its benthic recycling and ultimately its bioavailability. This is to be essential to characterize the aquatic environment quality in order to limit eutrophication risks.

Organic matter mineralization of larch bark and compositions based on it

The process of organic matter mineralization in fertilizer mixtures consisting of larch bark and mineral additives was studied in order to optimize the timing of composting and preparation of high-quality fertilizers. The main factors affecting the process of bark mineralization are the reaction of the medium (pH), the ratio of C:N, mineral additives. The process of larch bark mineralization and compositions based on it is described by the equation of the first order. The calculated decomposition constants of fertilizer compositions exceeded the control by 2-3, 2 times depending on the variant of the experiment.

Effect of Long-Term Application of Organic and Mineral Fertilizers on the Organic Carbon Content and Nitrogen Regime of Soddy-Podzolic Soil

The effect of long-term application of organic and mineral fertilizers on the organic carbon content and nitrogen regime of soddy-podzolic heavy loamy soils (Umbric Albeluvisols Abruptic) was studied in a long-term stationary experiment established in Perm region in 1976. Long-term crop growing (for about 40 years) resulted in the decrease of organic carbon content from 1.28 to 1.13%. The application of cattle manure at the rate of 40 t/ha and mineral fertilizers NRK (I rotation—N120P120K120, II rotation—N90P90K90, III–V rotations—N60P60K60) slowed down the process of organic matter mineralization but did not completely compensate for the organic carbon loss. The application of sewage sludge at the rate of 40 t/ha once in the seven-field crop rotation allowed maintaining the organic carbon content in the soil at the initial level. To assess the composition of soil nitrogen, acid hydrolysis was used. The application of manure reliably increased the contents of difficultly hydrolyzable, hydrolyzable, and mineral fractions of nitrogen in the soil by 1.1–1.4 times Prolonged use of sewage sludge significantly increased (by 1.1–1.6 times) the content of total nitrogen and all its fractions in the soil. The application of mineral fertilizers contributed to an increase in the contents of total, easily hydrolyzable, and mineral nitrogen by 1.1–1.4 times. The maximum positive effect on the organic carbon content and the nitrogen regime was observed in the case of prolonged use of organic fertilizers against the background application of mineral fertilizers. The relative content of nitrogen fractions in the soil remained fairly stable and indicated the stability of nitrogen pool in the soil over time.

Spatial variability of biogeochemistry in shallow coastal benthic communities of Potter Cove (Antarctica) and the impact of a melting glacier.

Measurements of biogeochemical fluxes at the sediment–water interface are essential to investigate organic matter mineralization processes but are rarely performed in shallow coastal areas of the Antarctic. We investigated biogeochemical fluxes across the sediment–water interface in Potter Cove (King George Island/Isla 25 de Mayo) at water depths between 6–9 m. Total fluxes of oxygen and inorganic nutrients were quantified in situ. Diffusive oxygen fluxes were also quantified in situ, while diffusive inorganic nutrient fluxes were calculated from pore water profiles. Biogenic sediment compounds (concentration of pigments, total organic and inorganic carbon and total nitrogen), and benthic prokaryotic, meio-, and macrofauna density and biomass were determined along with abiotic parameters (sediment granulometry and porosity). The measurements were performed at three locations in Potter Cove, which differ in terms of sedimentary influence due to glacial melt. In this study, we aim to assess secondary effects of glacial melting such as ice scouring and particle release on the benthic community and the biogeochemical cycles they mediate. Furthermore, we discuss small-scale spatial variability of biogeochemical fluxes in shallow water depth and the required food supply to cover the carbon demand of Potter Cove’s shallow benthic communities. We found enhanced mineralization in soft sediments at one location intermediately affected by glacial melt-related effects, while a reduced mineralization was observed at a location influenced by glacial melting. The benthic macrofauna assemblage constituted the major benthic carbon stock (>87% of total benthic biomass) and was responsible for most benthic organic matter mineralization. However, biomass of the dominant Antarctic bivalve Laternula elliptica, which contributed 39–69% to the total macrofauna biomass, increased with enhanced glacial melt-related influence. This is contrary to the pattern observed for the remaining macrofauna. Our results further indicated that pelagic primary production is able to fully supply Potter Cove’s benthic carbon demand. Therefore, Potter Cove seems to be an autotrophic ecosystem in the summer season.

Microbial Sulfate Reduction Potential in Coal-Bearing Sediments Down to ~2.5 km below the Seafloor off Shimokita Peninsula, Japan.

Sulfate reduction is the predominant anaerobic microbial process of organic matter mineralization in marine sediments, with recent studies revealing that sulfate reduction not only occurs in sulfate-rich sediments, but even extends to deeper, methanogenic sediments at very low background concentrations of sulfate. Using samples retrieved off the Shimokita Peninsula, Japan, during the Integrated Ocean Drilling Program (IODP) Expedition 337, we measured potential sulfate reduction rates by slurry incubations with 35S-labeled sulfate in deep methanogenic sediments between 1276.75 and 2456.75 meters below the seafloor. Potential sulfate reduction rates were generally extremely low (mostly below 0.1 pmol cm−3 d−1) but showed elevated values (up to 1.8 pmol cm−3 d−1) in a coal-bearing interval (Unit III). A measured increase in hydrogenase activity in the coal-bearing horizons coincided with this local increase in potential sulfate reduction rates. This paired enzymatic response suggests that hydrogen is a potentially important electron donor for sulfate reduction in the deep coalbed biosphere. By contrast, no stimulation of sulfate reduction rates was observed in treatments where methane was added as an electron donor. In the deep coalbeds, small amounts of sulfate might be provided by a cryptic sulfur cycle. The isotopically very heavy pyrites (δ34S = +43‰) found in this horizon is consistent with its formation via microbial sulfate reduction that has been continuously utilizing a small, increasingly 34S-enriched sulfate reservoir over geologic time scales. Although our results do not represent in-situ activity, and the sulfate reducers might only have persisted in a dormant, spore-like state, our findings show that organisms capable of sulfate reduction have survived in deep methanogenic sediments over more than 20 Ma. This highlights the ability of sulfate-reducers to persist over geological timespans even in sulfate-depleted environments. Our study moreover represents the deepest evidence of a potential for sulfate reduction in marine sediments to date.

Patterns of nutrients distribution along salinity gradient in the estuaries of the rivers Sukhodol and Razdolnaya/Suifen (Peter the Great Bay, Japan Sea)

Sign of production-destruction balance is determined for different parts of two rivers estuaries in Peter the Great Bay (Razdolnaya/Suifen and Sukhodol) on the data of chemical samplings in different seasons of 2010-2013. For this purpose, the nutrients concentration dependence on ratio of river and sea waters mixing is determined. In the case of conservative behavior of nutrients, their concentration should have negative linear dependence on increasing salinity, but its non-linearity shows removal or addition of the nutrients by processes of biological production or destruction: negative deviations indicate production and positive deviations indicate destruction. The concentration of mineral nitrogen is close to zero everywhere in the estuaries in spring, so below the line of conservative behavior that is the evidence of active nitrogen consumption. Patterns of silicon and phosphorus distribution are similar to the distribution of nitrogen. Summer nutrients concentrations are mainly below the conservative values, as well, with exception of the areas at the river bar, so production prevails in the external estuaries of both rivers, but remineralization prevails in the lower parts of the internal estuaries in this season. In autumn, destruction of organic matter becomes more important in both estuaries, so heightened values of nutrients are observed in all their parts, in particular in the «silicon belt» of brackish water (≈ 13-17 eps). The silicon concentration increasing at the river bar (above the concentration in the river water) is the most significant in the Razdolnaya estuary which is generally poor by this nutrient. There is concluded that terrigenous nutrients of the river water are utilized for new production mostly in the external estuaries, whereas the process of organic matter mineralization dominates in the internal estuaries. Besides of the production-destruction processes, changes of the mineral silicon concentration are determined by transformation of its inorganic forms, as dissociation of low-soluble silicates to silicon acid under heightened pH. Principal difference of the production-destruction balance between the internal and external parts of estuary could be an ecological basis for formation of different ecosystems in these zones, with principally different structure and functioning patterns.

Oxygen demand for the stabilization of the organic fraction of municipal solid waste in passively aerated bioreactors

Conventional aerobic waste treatment technologies require the use of aeration devices that actively transport air through the stabilized waste mass, which greatly increases operating costs. In addition, improperly operated active aeration systems, may have the adverse effect of cooling the stabilized biomass. Because active aeration can be a limiting factor for the stabilization process, passive aeration can be equally effective and less expensive. Unfortunately, there are few reports documenting the use of passive aeration systems in municipal waste stabilization. There have been doubts raised as to whether a passive aeration system provides enough oxygen to the organic matter mineralization processes. In this paper, the effectiveness of aeration during aerobic stabilization of four different organic fractions of municipal waste in a reactor with an integrated passive ventilation system and leachate recirculation was analyzed. For the study, four fractions separated by a rotary screen were chosen. Despite the high temperatures in the reactor, the air flow rate was below 0.016m3/h. Using Darcy’s equation, theoretical values of the air flow rate were estimated, depending on the intensity of microbial metabolism and the amount of oxygen required for the oxidation of organic compounds. Calculations showed that the volume of supplied air exceeded the microorganisms demand for oxidation and endogenous activity by 1.7–2.88-fold.

The pH and pCO2 dependence of sulfate reduction in shallow-sea hydrothermal CO2 – venting sediments (Milos Island, Greece)

Microbial sulfate reduction (SR) is a dominant process of organic matter mineralization in sulfate-rich anoxic environments at neutral pH. Recent studies have demonstrated SR in low pH environments, but investigations on the microbial activity at variable pH and CO2 partial pressure are still lacking. In this study, the effect of pH and pCO2 on microbial activity was investigated by incubation experiments with radioactive 35S targeting SR in sediments from the shallow-sea hydrothermal vent system of Milos, Greece, where pH is naturally decreased by CO2 release. Sediments differed in their physicochemical characteristics with distance from the main site of fluid discharge. Adjacent to the vent site (T ~40–75°C, pH ~5), maximal sulfate reduction rates (SRR) were observed between pH 5 and 6. SR in hydrothermally influenced sediments decreased at neutral pH. Sediments unaffected by hydrothermal venting (T ~26°C, pH ~8) expressed the highest SRR between pH 6 and 7. Further experiments investigating the effect of pCO2 on SR revealed a steep decrease in activity when the partial pressure increased from 2 to 3 bar. Findings suggest that sulfate reducing microbial communities associated with hydrothermal vent system are adapted to low pH and high CO2, while communities at control sites required a higher pH for optimal activity.

Microbial mineralization of organic matter in sinking particles, bottom sediments and seawater in a coastal fish culturing area

Microbial mineralization rates in sinking particles, bottom sediments and seawater were determined in a coastal fish (red sea bream Pagrus major) culturing area to clarify the mineralization process of organic matter (OM) in the entire water column. The mineralization rates of 14C-labelled glutamate and glucose per unit volume were highest in the sinking particles and were 131–572 and 7–49 times higher than those of the seawater and bottom sediments respectively. The turnover time of glutamate tended to be shorter than that of glucose at all three sites of the water column. Bacteria appeared to prefer amino acids to monosaccharides because amino acids could be utilized as both energy and nitrogen sources. The sedimentation rate of particulate organic carbon (POC) derived from phytoplankton accounted for 9–61% of the total POC, and it was particularly high in early summer (61% and 50% at fish cage and non-cage stations respectively). The present study clearly shows that sinking particles serve as an important site of microbial mineralization process of OM within the water column, and that phytoplankton production was another serious cause of organic pollution of the seafloor in addition to the organic wastes directly discharged from fish farms.

Management implications inferred from the multivariate analysis of vadose zone chemical variables in Las Tablas de Daimiel National Park (Spain)

A multivariate analysis approach has been developed in order to explain the observed variability in soil chemistry at Las Tablas de Daimiel National Park (TDNP). Either natural or anthropogenic alterations of the amount or distribution of these chemicals may have severe consequences not only on the Tablas ecosystem itself, but also downstream the watershed (i.e. eutrophication), given the actual system functioning as recharge area for the Western La Mancha aquifer. The analysis has been carried out over 20 chemical variables measured at different depths in 22 sites along TDNP (n = 111), considering their interaction with 3 environmental factors: soil type, microtopographic variation and position upstream or downstream the central dam. Statistical analysis consisted on bivariate correlation, trend surface analysis, analysis of variance, principal component analysis and redundancy analysis. The results allow defining the vadose zone in TDNP as a highly saline carbonated media, with a large accumulation of solutes in the topsoil (0–20 cm). Recent drainage conditions favor the process of organic matter mineralization and subsequent nutrient release, thus increasing the risk of groundwater pollution. The multivariate model approximately explains 60% of the observed variability, 40% in terms of the environmental factors, and allows distinguishing three main domains: saline, organic and carbonated. This paper discusses the management implications derived from this analysis taking into account that the environmental factors considered are susceptible from being modified by certain managing activities such as reed reaping, construction of ditches and artificial ponding with brackish groundwater.

Evolution of Humic Fractions in Calcimagnesic Soils And Brown Isohumic Soils Amended With Compost and Manure

The composting process of organic wastes consists of the bioconversion of biologically unstable wastes to stabilized products for application to soils. This study was carried out on different soils (brown isohumic soils in Sfax region in southern Tunisia and calcimagnesic soils in Korba region in northern Tunisia). The mineralization process of organic matter is more important in isohumic soils, showing less tenors of fine fractions than in calcimagnesic soils. The study of different humic fractions in amended soils shows that humic acid tenors and the polymerization rates are linked to soil nature. Calcimagnesic soils ensure a more important humification than isohumic soils.

Chemical and Microbiological in situ Characterization of Benthic Communities in Sediments with Different Contamination Levels

Background River sediments are natural habitats of complex bacterial and fungal communities and therefore play a decisive role in the mineralization process of organic matter in freshwater systems. By means of comparative temporal and spatial analyses of microbial communities, the in situ impact of anthropogenically generated pollutants on these biofilm associations can be assessed and discriminated from seasonal variations.

Efficient use of animal manure on cropland – economic analysis

Manure contains all the macro- and microelements needed for plant growth; however, it represents one of the most underutilized resources in the US. The major problem with the use of manure on cropland is the direct effect of its composition on application cost. This cost is a function of the mineralization process of organic matter. The mineralization process is influenced by the properties of the manure, properties of the soil, moisture, and temperature. This study evaluates the simultaneous effect of these variables on the optimal use of manure on cropland. The results show that the properties of manure and soil significantly affect the mineralization of organic nitrogen and thus the optimal quantity of manure required to satisfy the nutrient requirement of crops in a given rotation system. Manure application costs range from a low of 18% of the cost of commercial fertilizer for chicken manure applied to one type of soil, to a high of 125% of the cost of commercial fertilizer for cow manure applied to another type of soil. The maximum distance to transfer manure to the field, that will equate its application cost to the cost of commercial fertilizer, ranges from a high of 35 km (22 miles) for chicken manure applied to one type of soil, to a low of 1 km (0.62 miles) for cow manure applied to another type of soil. For rotation system 2, manure application costs range from a low of 37% of the cost of commercial fertilizer for chicken manure applied to one type of soil, to a high of 136% of the cost of commercial fertilizer for cow manure applied to another type of soil. The maximum distance to transfer manure to the field, that will equate its cost to the cost of commercial fertilizer, ranges from a high of 20 km (12.5 miles) for chicken manure applied to one type of soil, to a low of 0 km (0 miles) for cow manure applied to another type of soil.