Substrate Amendment Research Articles

Examining N-limited soil microbial activity using community-level physiological profiling based on O2 consumption

Nitrogen-limited soil microbial activity has important implications for soil carbon storage and nutrient availability, but previous methods for assessing resource limitation have been restricted, due to enrichment criteria (i.e., long incubation periods, high substrate amendments) and/or logistical constraints (e.g. use of radioisotopes). A microtiter-based assay of basal and substrate induced soil respiration based on O2 consumption may be a rapid, ecologically relevant means of assessing N limitation. The present study evaluated this approach by examining 1) the extent and duration of N limitation on soil respiratory activity following different levels of N fertilization in the field, and 2) the relationship between N-limited activities and growth under the assay conditions. Fertilization rate and the time since fertilization had significant impacts on the degree of N limitation of soil microbial activity. The highest fertilization rate showed the earliest and most persistent reduction in N limitation, as would be predicted from the higher concentration of extractable inorganic soil N observed with this treatment. Bacterial growth under the assay conditions, as estimated by quantitative-PCR of 16S rRNA genes, was less than twofold in soils demonstrating a rapid respiratory response (i.e. peak within 6–8h of initiating incubation) to up to fourfold in soils demonstrating a slower respiratory response (i.e., peak response after ∼14h of incubation). Increased respiratory response with N amendment was usually associated with increased cell growth, although for rapidly responding soils some C sources showed N-limited use without growth. This was likely due to exhaustion of the relatively low levels of available C amendment before growth was detected. The method appears useful for assessing N-limited microbial growth, and it may be effective as a rapid indicator of bioavailable soil N. It may also be a tool to evaluate the complexity of N limitation among various metabolic pathways found in soil microbial communities, particularly if linked to dynamics in community structure and gene activation.

Impact of substrate amendment on the polyaromatic hydrocarbon contents of a five month old waste engine oil polluted soil

The present study investigated the impact of substrate amendment on the bioremediation of waste engine oil-polluted soil. Top soil was collected randomly from a 50 × 50 m marked plot on a farmland, sun-dried and weighed. Ten kilogram’s of soil each was placed into perforated 25 L buckets. Waste engine oil (WEO) was prepared at 5 different levels of pollution: 0, 1.0, 2.5, 5.0, and 10.0% w/w, and poured into the measured soil, and thoroughly mixed. The entire set up was left under an open shade for 5 months without mechanically disturbing the soil, after which the polluted soil was amended with sawdust and left for a further 9 months. Significant reductions in polyaromatic hydrocarbon (PAH) content of soils over the experimental period were recorded. Total (100%) remediation of some PAH compounds (benzo[a]anthracene, benzo(a)pyrene, benzo[b]fluoranthene, benzo[g,h,i]perylene, benzo[k]fluoranthene, chrysene, dibenzo[a,h]anthracene, fluoranthene, fluorene, and indeno[1,2,3-c,d]pyrene) was recorded. Total PAH ranged from 1.10 to 6.35 mg/L in the substrate-amended treatment compared to a range of 25.45 to 456.99 mg/L in the unamended soil. Toxicity equivalencies (TEQ) in the unamended soils were generally higher than benchmark values, implying that the cleanup levels were not met. In the amended treatments, however, TEQs were presented for only benzo[a]pyrene (0.7284) in the control and indeno[123-c]pyrene (0.0272) in 2.5% w/w oil in soil treatment. TEQ’s of benzo[a]pyrene in the amended 5% w/w oil in soil treatment was 3.1252 mg/L, also higher than the benchmark TEQ of 1.0 mg/L. Key words: biooremediation, substrate amendment, polyaromatic hydrocarbon

Nitrate removal from groundwater in columns packed with reed and rice stalks

Nitrate leaching contaminates groundwater. The objective of this study was to determine if reed and rice stalks could enhance denitrification and reduce nitrate leaching into groundwater. Artificial groundwater spiked with nitrate and field groundwater samples were tested in the columns in sand reactors packed with either reed or rice stalks. The maximum nitrate removal rates were determined to be 1.93 and 1.97 mg nitrate‐N l−1 h−1, respectively, in the reed and rice stalk‐packed columns. The maximum nitrate‐nitrogen removal rate in reactors packed with reed stalk was 1.33 mg nitrate‐N l−1 h−1 when experimented with natural groundwater. Chemical oxygen demand consumption was higher when rice stalk (176.1 mg l−1) was used as the substrate, compared to reed stalk (35.2 mg l−1) at the same substrate dosage. No nitrite accumulation was detected during the test. The results demonstrate that agricultural byproducts, such as reed and rice stalks, may be used as substrate amendments for enhanced denitrification in natural settings, such as lakeside lagoons, ditches or wetlands.

Substrate Amendment Effects on Potted Plant Production and Dry Weight Partition of Lantana camara

Ten substrates were evaluated for their capacity to promote the growth of potted Lantana camara. The substrates consisted of different volumetric proportions of sandy loam soil (S), peat (P), perlite (Per), and urea formaldehyde resin foam (UFRF referred to as F), the latter in an effort to substitute peat use in horticulture. The substrates studied were: S, S60:P40, S40:P60, S60:F40, S40:F60, P60:F40, P40:F60, S40:P30:Per30, S40:F30:Per30, and P50:Per50. Measurements included: 1) substrate physical and chemical characteristics such as water characteristic curves, bulk density, total porosity, easily available water, and pH; 2) biometric measurements such as shoot length and number and number of flowers; and 3) determination of main and lateral stems, leaf, flower, and root dry weights. Results showed that substrates P60:F40 and P40:F60 retained excessive water in all tensions, whereas substrate P50:Per50 exhibited increased water retention at saturation that was quickly reduced after 10 cm of tension. The non-amended soil (S) had the least water retention capacity and proved to be a slow-draining substrate. Supplementation either with peat or peat and perlite (S60:P40, S40:P60, and S40:P30:Per30) significantly increased water retention in the soil-based substrates. Soil-based substrates supplemented with UFRF retained less water compared with peat-amended soil-based substrates. Concerning plant growth, Lantana plants growing in the UFRF-amended substrates were unable to recover from frost injury and their evaluation was interrupted after winter as a result of total plant loss. The injury was attributed to the reduction of plant growth in UFRF-supplemented substrates before the occurrence of frost stress events. Soil-based substrates (S, S60:P40, S40:P60, and S40:P30:Per30) provided greater shoot growth, which was almost twofold compared with substrate P50:Per50. Substrate S40:P30:Per30 produced the most lateral shoots and flowers over the whole study period, whereas S40:P60 produced the most flowers during the summer. Dry weights of both stem and lateral stems followed a similar pattern with the biometric measurements. However the non-amended soil (S) produced the highest leaf and root dry weights followed by substrates S60:P40 and S40:P60. It was concluded that both substrates S40:P60 and S40:P30:Per30 can successfully be used for Lantana nursery production as a result of their decreased bulk density, increased water retention capacity, adequate porosity, and promotion of shoot growth and flowering. Despite its high bulk density, substrate S could be used in the production of Lantana plants for landscape use as a result of the increased root production.

Pine Bark Substrates Amended with Parboiled Rice Hulls: Physical Properties and Growth of Container-grown Spirea during Long-term Nursery Production

The decline in the availability of pine (Pinus taeda L.) bark (PB) supplies and increasing prices have caused concerns in the nursery industry. Research was conducted to evaluate the effect of parboiled rice (Oryza sativa L.) hulls (PBH) as a substrate amendment to PB-based container substrates on the growth of Spiraea ×bumalda L. ‘Anthony Waterer’ and to examine the changes in physical properties of the substrates during long-term production cycles under outdoor nursery conditions. Six substrates were formulated by blending PB with 0%, 20%, 40%, 60%, 80%, or 100% PBH (by volume). Substrate composition affected plant growth components evaluated, generally decreasing growth as the amount of PBH increased. However, amending PB with up to 40% PBH did not result in a significant decrease in plant growth or increase the volume or frequency of irrigation for container-grown spirea. Physical properties of substrates amended with PBH improved over time. Based on these results, PB-based substrates amended with up to 40% PBH retained physical properties that were generally within current guidelines for nursery container substrates after one (25 weeks) and two (70 weeks) growing seasons.

Alleviation of Both Water and Nutrient Limitations is Necessary to Accelerate Ecological Restoration of Waste Rock Tips

Hard rock quarries are commonly located close to national parks and special areas of conservation and are generally regarded as visually intrusive. Consequently, restoration strategies that effectively accelerate natural plant regeneration processes are required. Slate waste tips present extreme conditions for plant establishment with multiple potential limiting factors (e.g., lack of organic matter, nutrients, and poor water retention). In this study, we investigated ecological strategies to accelerate natural regeneration at the largest slate quarry in Europe. A field experiment was conducted to assess ecosystem restoration using a contrasting set of native woody species. Treatments included amendments of waste tips with: polyacrylamide gel to increase water-holding capacity; mineral fertilizer to increase nutrient supply; and two treatments that increased both (organic waste or boulder clay addition). Ecosystem recovery was evaluated through above- and below-ground productivity (plant and microbial, respectively) and soil analyses. Neither increasing nutrient supply (with mineral fertilizer) nor water-holding capacity (with polyacrylamide gel) was sufficient, alone, to improve plant establishment. However, both boulder clay and organic waste amendment significantly enhanced plant growth. There was a marked positive interaction in the effects on tree growth of the amendment with organic waste and boulder clay. Large interactions occurred between tree species and substrate amendments. The growth of N(2)-fixing species was strongly favored over non-fixers where there was no addition of material increasing soil nitrogen supply, whereas the growth advantage of pioneer species over non-pioneers was greatest with fertilizer, organic waste, or clay additions. Organic waste addition had the greatest positive impact on soil processes.

Microcalorimetric qualitative analysis of biofilm development in porous media used in wastewater treatment by constructed wetland

In wastewater treatment by constructed wetland, the biodegradation capability of the biomass developed in the soil is one of the most important factors. For this kind of treatment unit, soil properties are studied to improve its filtration capacity and hydraulic residence time of the wastewater. The impact of soil properties like porosity and soil components on biomass development and biodegradation capacity seem to be less studied certainly due to the complexity of microbial identification techniques currently used. The study presented here is a preliminary work to validate that calorimetric technique could be a tool in the understanding of biodegradation capacity of wastewater treatment processes. Biofilm is preliminary developed in columns filled with different porous materials of well known porosity and constitutive components. These columns are fed with the same continuous flow of synthetic solution (C, N, and P) as a substrate amending during 3 weeks. Then each week, 2 mL samples of porous media from these columns are analyzed in isothermal calorimeter for 48 h. Net heat flow is recorded before and after substrate injection. This work results in the definition of the procedure for batch experiments in calorimeter for wastewater process efficiency. The results of these experiments show that the microbial reaction due to substrate amendment is highly depending on the porous material used for biofilm growth. Indeed calorimetric signals recorded lead to conclude that biofilm grown on plastic beads has a faster and more intensive reaction to glucose amendment than biofilm grown on glass beads. At least, two glass beads samples analyzed in the calorimeter after the same duration of feeding with synthetic solution have very different response to glucose or synthetic solution.

Remediation of High-Strength Mine Influenced Water with Crab Shell Substrate Mixtures: Laboratory Column and Field Pilot Tests

Anaerobic passive treatment systems remediating high-strength mine influenced water (MIW) have failed to consistently treat sources with high metals loads and flow rates. For example, the high iron (140 mg/L) and acidity (390 mg/L as CaCO3) of the Klondike-1 discharge near Ashville, PA, caused premature clogging of a vertical flow pond which was filled with a limestone buffered organic substrate (90% spent mushroom compost (SMC) and 10% limestone chips). In this study, continuous-flow columns and pilot-scale field reactors were used to evaluate if treatment of high-strength MIW can be improved using crab shell as a substrate amendment. For the lab study, eight columns were wet-packed with substrate mixtures ranging from 0 - 100% crab shell (with the balance SMC), and fed Klondike-1 water to produce a 16 hr hydraulic residence time (HRT). After determining the best performing substrate mixture in the column test, a pilot-scale field study was initiated in August 2010, in which 1,000 gallon (3,785 L) tanks were filled with a limestone underdrain and an upper substrate layer of: 1) 100% crab shell; 2) 70% crab shell + 30% SMC; or 3) 90% SMC + 10% limestone. A fourth tank containing a sandstone underdrain with a 70% crab shell + 30% SMC substrate layer was installed to determine if similar performance could be achieved without the limestone underdrain. All columns and field reactors also contained sand as a proppant to ensure hydraulic conductivity. Aqueous samples were collected from the columns/reactors over time and analyzed for pH, ammonium, acidity, alkalinity, DOC, anions, and metals. In the column study, an optimum ratio of 70% crab shell + 30% SMC sustained complete iron removal, pH above 5.0, and excess alkalinity generation for twice as long as the traditional SMC and limestone substrate. To date, the field study is still achieving complete iron removal, and other results generally mirror the laboratory findings.

Do Compost and Vermicompost Improve Macronutrient Retention and Plant Growth in Degraded Tropical Soils?

Soil degradation and water pollution are widespread land degradation problems in Southeast Asia. Policy makers are currently faced with the challenge of designing and implementing strategies to maintain soil fertility and avoid off-site effects. The aim of this study was to determine the effect of organic substrate amendments on soil properties, nutrient leaching and the growth of Ipomea aquatica in an acidic degraded soil from northern Vietnam. Plants were grown in an Acrisol in buckets under natural weather conditions for two months. The same amount of nutrients was applied either in a purely synthetic form (mineral fertilizers) or as two alternative organic substrates (three month old compost or vermicompost from buffalo dung) plus additional amounts of synthetic mineral nutrients to ensure the same quantity of NPK. The influence of these respective substrates on the soil's physical and chemical properties as well as plant growth was examined. Both compost and vermicompost led to an improvement in soil properties with an increase in the pH, soil organic matter and nutrient content, compared to soil fertilized with synthetic mineral products. The highest plant productivity was obtained with vermicompost and synthetic fertilizers, with no significant difference between these two treatments. Chemical fertilization, however, is the least effective practice based on the amount of nutrients leached from the soil (about 38% of N and 22% of K, compared to less than 10 and 5% of N and K with organic amendments). P leaching was not influenced by the fertilizer treatments. In conclusion, vermicompost does appear to be a relevant alternative to chemical fertilizers because it leads to similar enhancements in plant growth, at the same time as increasing soil quality and decreasing nutrient leaching.

Modification of Switchgrass Substrate pH Using Compost, Peatmoss, and Elemental Sulfur

Switchgrass (Panicum virgatum) biomass is being evaluated as a potential alternative to pine bark as the primary potting component in containerized nursery crops. Substrates composed entirely of switchgrass have higher pH than what is considered desirable in container substrates. The objective of this research was to evaluate the influence of elemental S, sphagnum moss, and municipal solid waste compost (MSC) as amendments for reducing substrate pH and buffering it against large changes over time. Three experiments were conducted; the first two experiments were conducted using annual vinca (Catharanthus roseus ‘Pacifica Blush’) to quickly assess how pH was affected by the three amendments, and the final experiment was conducted with blueberry (Vaccinium corymbosum ‘Duke’) to assess the long-term effects of substrate amendments. Summarizing across the three experiments, elemental S was effective in reducing substrate pH; however, rates 1 lb/yard3 or greater reduced pH below the recommended level of 5.5 and lower S rates did not maintain lowered pH over time. Sphagnum moss and MSC together at 20% and 10% (v/v), respectively, were effective at reducing substrate pH and buffering against change. Sphagnum moss and MSC provided the additional benefit of improving physical properties of the switchgrass substrates.

Modification of Switchgrass Substrate pH Using Compost, Peatmoss, and Elemental Sulfur

Switchgrass (Panicum virgatum) biomass is being evaluated as a potential alternative to pine bark as the primary potting component in containerized nursery crops. Substrates composed entirely of switchgrass have higher pH than what is considered desirable in container substrates. The objective of this research was to evaluate the influence of elemental S, sphagnum moss, and municipal solid waste compost (MSC) as amendments for reducing substrate pH and buffering it against large changes over time. Three experiments were conducted; the first two experiments were conducted using annual vinca (Catharanthus roseus ‘Pacifica Blush’) to quickly assess how pH was affected by the three amendments, and the final experiment was conducted with blueberry (Vaccinium corymbosum ‘Duke’) to assess the long-term effects of substrate amendments. Summarizing across the three experiments, elemental S was effective in reducing substrate pH; however, rates 1 lb/yard3 or greater reduced pH below the recommended level of 5.5 and lower S rates did not maintain lowered pH over time. Sphagnum moss and MSC together at 20% and 10% (v/v), respectively, were effective at reducing substrate pH and buffering against change. Sphagnum moss and MSC provided the additional benefit of improving physical properties of the switchgrass substrates.

Evidence for syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis in the high‐temperature petroleum reservoir of Yabase oil field (Japan)

The methanogenic communities and pathways in a high-temperature petroleum reservoir were investigated through incubations of the production water and crude oil, combined with radiotracer experiments and molecular biological analyses. The incubations were conducted without any substrate amendment and under high-temperature and pressurized conditions that mimicked the in situ environment (55°C, 5 MPa). Changes in methane and acetate concentrations during the incubations indicated stoichiometric production of methane from acetate. Rates of hydrogenotrophic methanogenesis measured using [(14)C]-bicarbonate were 42-68 times those of acetoclastic methanogenesis measured using [2-(14) C]-acetate, implying the dominance of methane production by syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis in the environment. 16S rRNA gene sequence analyses of the incubated production water showed bacterial communities dominated by the genus Thermacetogenium, known as a thermophilic syntrophic acetate-oxidizing bacterium, and archaeal communities dominated by thermophilic hydrogenotrophic methanogens belonging to the genus Methanothermobacter. Furthermore, group-specific real-time PCR assays revealed that 16S rRNA gene copy numbers of the hydrogenotrophic methanogens affiliated with the order Methanobacteriales were almost identical to those of archaeal 16S rRNA genes. This study demonstrates that syntrophic acetate oxidation is the main methanogenic pathway in a high-temperature petroleum reservoir.

Suppression of other soil microorganisms by mycelium of arbuscular mycorrhizal fungi in root-free soil

The influence of mycelium of two arbuscular mycorrhizal (AM) fungi, Glomus intraradices and Glomus mosseae, on other soil microorganisms, was examined in root-free soil with and without organic substrate amendment in terms of cellulose. The AM fungi were grown in symbiosis with cucumber in a compartmented growth system, which allowed AM fungal external mycelium to grow into root-free compartments. The fungicide Benomyl was applied to the root-free compartments to create an alternative non-mycorrhizal control treatment. Whole cell biomarker fatty acids were employed to quantify different groups of soil microorganisms including the two AM fungi. Abundance of most microbial groups were reduced by external mycelium of both AM fungi, though differential effects on the microbial community composition were observed between the two AM fungi as revealed from principal component analysis. Inhibition of other soil microorganisms was more pronounced in root-free soil with mycelium of G. mosseae than with mycelium of G. intraradices. In general, cellulose increased the amount of biomarker fatty acids of most groups of soil microorganisms, but cellulose did not affect the influence of AM fungi on other soil microorganisms. Benomyl suppressed growth of the external mycelium of the two AM fungi and had limited non-target effects on other microbial groups. In conclusion, our results show differential effects of external mycelium of AM fungi on other soil microbial communities, though both AM fungi included in the study overall inhibited most microbial groups as examined using whole cell biomarker fatty acids.

Evaluation of Composted Poultry Litter as a Substrate Amendment for WholeTree, Clean Chip Residual, and Pinebark for Container Grown Woody Nursery Crops

Abstract WholeTree (WT) and clean chip residual (CCR) are potential new nursery substrates that are by-products of the forestry industry containing high wood content. Initial immobilization of nitrogen is one concern when using these new substrates; however the addition of composted poultry litter (CPL) to substrates containing high wood content could balance initial nitrogen immobilization and provide an inexpensive fertilizer source for growers. This study evaluated five woody nursery species being grown in WT, CCR, and pinebark (PB) with the addition of CPL or peat as a substrate amendment. Results indicate that these species can be grown successfully in WT and CCR substrates 6: 1 (by vol) with CPL. Use of CPL in WT and CCR substrates may provide an alternative to traditional PB plus peat based combinations in container plant production while providing poultry producers an environmentally sound means of waste disposal.

Assessment of Physical Properties and Stonecrop Growth in Green Roof Substrates Amended with Compost and Hydrogel

There is a lack of quantifiable data concerning physical analyses specific to shallow-depth green roof substrates and their effects on initial plant growth. Physical properties were determined for green roof substrates containing (by volume) 50%, 60%, or 70% heat-expanded coarse slate and 30% heat-expanded fine slate amended with 20%, 10%, or 0% landscape and greenhouse waste compost. Each substrate also was amended with hydrogel at 0, 0.75, 1.50, or 3.75 lb/yard3. There were no differences in total porosity among substrates containing 0%, 10%, or 20% compost, although total porosity increased for all substrates amended with hydrogel at 3.75 lb/yard3. Container capacity increased in substrates containing 3.75 lb/yard3 hydrogel, except for substrates containing 10% compost where hydrogel had no effect. Aeration porosity decreased when 10% or 20% compost was added to substrates. Determination of aeration porosity at an applied suction pressure of 6.3 kPa (AP-6.3 kPa), indicated that AP-6.3 kPa was higher in substrates containing 0% compost than substrates containing 20% compost. Shoot dry weight and coverage area measurements of ‘Weihenstephaner Gold’ stonecrop (Sedum floriferum) and ‘Summer Glory’ stonecrop (Sedum spurium) were determined 9 weeks after plug transplantation into substrates. Both stonecrop species responded similarly to substrate amendments. Initial plant growth was greater in substrate containing 20% compost and 3.75 lb/yard3 hydrogel than nonamended substrate resulting in 198% and 161% higher shoot dry weight and coverage area, respectively. Alkaline heat-expanded slate and acidic compost components affected initial pH of substrates, but there was less variation among final substrate pH values. We conclude that compost and/or hydrogel amendments affected physiochemical properties following incorporation into slate-based green roof substrates, resulting in greater initial plant growth, and that these amendments may have practical applications for improving growing conditions on green roofs.

Nutrient Contribution and Release Kinetics of Vermicompost Amended Pine Bark

The composting of organic waste materials using earthworms yields the value-added product vermicompost (VC). The use of VC as a growing substrate amendment for containerized horticultural crop production is a sustainable nutrient management approach which can benefit crop production by providing plant nutrients and improving crop growth. In order to provide nutrient management guidelines for users of VC amended container substrates, a study was conducted to quantify nutrients supplied to substrates solution and to develop nutrient release kinetic models to predict plant available nutrient based on total initial loading rates. Experimental treatments and results were expressed on a volume basis (4-L container) for easy interpretation and application by growers of crops in containers.

Impact of simultaneous Cd and Zn substrate amendments on metal accumulation in two Cd/ Zn hyperaccumulating Thlaspi species

The impact of simultaneous Cd and Zn amendments in the substrate on the accumulation of Cd and Zn were studied in a recently discovered Cd/ Zn hyperaccumulating Thlaspi praecox (Brassicaceae) and compared to a model hyperaccumulating plant species T. caerulescens. The plants were grown in pots with added Cd or Zn or both for three months in a greenhouse. The addition of Zn in the substrate increased Cd extractability in the substrate significantly without a significant pH change and this increase resulted in increased concentration and content of Cd in the shoots of both species indicating that species have similar abilities to extract Cd from the substrate. In the combined treatment (Cd and Zn) an increase in shoot biomass accompanied with a decrease in Zn concentration in roots and shoots of both species was observed, while no changes in total accumulated Zn in shoots were seen. These results suggest different uptake and translocation systems for Cd and Zn in T. praecox, positioning this plant species in the superior Cd hyperaccumulating league of T. caerulescens Ganges ecotype.

Effect of Spent Mushroom Substrate Amendment of Vineyard Soils on the Behavior of Fungicides: 2. Mobility of Penconazole and Metalaxyl in Undisturbed Soil Cores

Mobility of fungicides penconazole and metalaxyl in unamended and amended vineyard soils with fresh and composted spent mushroom substrates (F-SMS and C-SMS) was studied. Experiments were performed in non-incubated and incubated (outdoors for 77 days) undisturbed soil cores under non-saturated flow conditions. Breakthrough curves (BTC) of metalaxyl leaching were delayed with regard to the tracer ion, and they showed an incomplete leaching in all soil cores after the addition of 2.5-4.5 pore volumes. A decrease of the maximum peak concentration in C-SMS soils with regard to unamended soils (up to 24-fold in Viana soil) and an increase in the fungicide retention by soils (up to 8-fold in the first segment of Viana soil core) was observed. However, a decrease (up to 2.6-fold in Sajazarra soil) or an increase (up to 1.4-fold in Aldeanueva soil) of the maximum peak concentration in F-SMS soils was observed. No leaching of penconazole was observed in all cases. After fungicide incubation in soil cores, the amounts of metalaxyl retained and leached decreased significantly by 1.24-37.8-fold and 1.17-302-fold, respectively, whereas no changes were observed for penconazole. Degradation of metalaxyl occurred in non-incubated soil and increased after incubation (two metalaxyl metabolites were detected in the leachates and the soil extracts), but it was not seen for penconazole in any case. In consequence, the addition of SMS as amendment to soil (especially C-SMS) enhanced adsorption of both fungicides, although metalaxyl could be available for degradation. This effect contributes to prevent groundwater contamination by metalaxyl, but it could contribute to increase the surface water contamination by penconazole, because adsorption protects this fungicide from degradation, increasing its persistence in soils.

Effect of Spent Mushroom Substrate Amendment of Vineyard Soils on the Behavior of Fungicides: 1. Adsorption−Desorption of Penconazole and Metalaxyl by Soils and Subsoils

The effect of the addition of fresh and composted spent mushroom substrates (F-SMS and C-SMS) to vineyard soils on the adsorption-desorption of penconazole and metalaxyl was studied under laboratory conditions. SMS is a promising agricultural residue as an amendment to increase the soil organic matter (OM) content. It may also modify the behavior of fungicides applied to vineyards. Freundlich Kf adsorption constants of both fungicides by soils and subsoils from three experimental plots unamended and amended in the field ranged between 2.78 and 13.4 (penconazole) and 0.14 and 0.67 (metalaxyl) with scant differences for unamended soil and subsoil. However, Kf values of amended soils were higher than those corresponding to subsoils and generally higher than those of unamended soils (up to 2.3 times for penconazole and 1.3 times for metalaxyl). The influence of SMS treatment (fresh or composted) was observed in the adsorption of the most hydrophobic fungicide penconazole. Simple and multiple correlations between soil and subsoil properties and adsorption constants indicated the influence of the OM on the adsorption of both fungicides, together with the clay, silt, and CaCO(3) content for metalaxyl and the pH for penconazole. The results revealed changes in the adsorption-desorption processes of these fungicides, which could give rise to a decrease in the mobility of metalaxyl (highly water-soluble) and an increase in the retention of penconazole (more hydrophobic). These effects could have an impact on surface and/or groundwater contamination.

Serpentine Revegetation: A Review

Centuries of mining economically valuable minerals from serpentine have left a legacy of drastically disturbed landscape. Asbestos and nickel-laterite mining from serpentine is estimated to have degraded 11,130 and 19,070 ha, respectively, in 18 countries. Increasing mineral extraction, fueled by increasing global demand for industrial commodities, will continue to have devastating impacts on serpentine landscapes. Simultaneously, increasing environmental awareness is motivating nations to balance economic advancement with environmental protection. Revegetation of landscapes degraded by mining provides a way to address these issues. This review highlights some advances of the past decades in serpentine revegetation and ecology, and provides a framework of concepts, including physical stabilization, substrate amendment, and plant-materials selection, by which drastically disturbed serpentine substrates may be revegetated.