Compost Amendment Research Articles

Evaluation of Cynara cardunculus L. and municipal solid waste compost for aided phytoremediation of multi potentially toxic element\u2013contaminated soils

The suitability for aided phytoremediation of Cynara cardunculus L. var. altilis and municipal solid waste compost (MSWC) applied at 2% and 4 % rates was evaluated in a multi potentially toxic element (PTE)-contaminated mining soil (Pb ~ 15,383 mg kg−1, Zn ~ 4076 mg kg−1, As ~ 49 mg kg−1, Cd ~ 67 mg kg−1, Cu ~ 181 mg kg−1, and Sb ~ 109 mg kg−1). The growth of C. cardunculus significantly increased with compost amendment and followed the order: MSWC-4% > MSWC-2% > Control. PTE concentrations in the roots of plants grown on amended soils decreased compared with control plants (i.e., less than ~ 82, 94, and 88% for Pb, Zn, and Cd respectively). PTE translocation from roots to shoots depended on both PTE and amendment rate but values were generally low (i.e., < 1). However, PTE mineralomasses were always higher for plants grown on MSWC-amended soils because of their higher biomass production, which favored an overall PTE bioaccumulation in roots and shoots. After plant growth, labile As and Sb increased in amended soils, while labile Pb, Zn, Cu, and Cd significantly decreased. Likewise, dehydrogenase and urease activities increased significantly in planted soils amended with MSWC. Also, the potential metabolic activity and the catabolic versatility of soil microbial communities significantly increased in planted soils amended with MSWC. Overall, our results indicate that C. cardunculus and MSWC can be effective resources for the aided phytoremediation of multi PTE-contaminated soils.

Securing of an Industrial Soil Using Turfgrass Assisted by Biostimulants and Compost Amendment

This work aimed to study the effects of compost (applied at two rates) and two commercial microbial biostimulants on the mobility and bioavailability of potentially toxic elements (PTEs) in an industrial soil phytostabilized by Dactylis glomerata L. or a mixed stand of grasses (Lolium perenne L., Poa pratensis L. and Festuca arundinacea Shreb.). The soil showed very high pseudototal and bioavailable concentrations of cadmium (Cd) and lead (Pb), due to improper lead-acid batteries storage. Compost amendment in combination with the two biostimulants produced the best outcomes in terms of plant growth and nutrient uptake. The same mix of beneficial microbes improved soil biological fertility enhancing soil nitrogen fixing and ammonia oxidizing bacteria, while reduced the pore water and NH4NO3 extractable concentrations of Cd and at lower extent of Pb in soil. Accordingly, the lower mobility and bioavailability of Cd in soil determined a lower uptake and accumulation of Cd in shoots of different grass species. Our results suggest that a green cap with turfgrass assisted by biostimulants and compost amendment in PTE-contaminated industrial sites could be a reliable and effective practice to protect and restore soil biological fertility and to reduce the risk of PTE dispersion in the surrounding environment.

Comparison of the effects of compost and vermicompost soil amendments in organic production of four herb species

ABSTRACT The aim of this study was to compare the effects of using compost and vermicompost as soil amendments in organic herb production, using four herb species (Dracocephalum moldavica L., Melissa officinalis L., Nepeta cataria L. and Thymus vulgaris L.) as model plants. Plants were cultivated in a greenhouse in containers filled with soil from an organically certified field and that had been amended with equal rates of cow manure compost or vermicompost [0%, 10%, 20% and 30% (v/v) for M. officinalis and N. cataria, and 0%, 20%, 30%, and 40% (v/v) for D. moldavica and T. vulgaris]. The four herbs showed different sensitivity to the incorporation of the organic amendments, with the optimum rate differing between the species: 20% was shown to be optimum for both amendments in the case of M. officinalis and N. cataria, and 20% for compost and 30% for vermicompost in the case of D. moldavica and T. vulgaris. However, at identical amendment rates, the vermicompost treatment resulted in higher plant biomass compared with the compost. The organic amendments tended to increase the concentration of K+ in the leaf tissue in all species. The NO3 – concentration in the leaf tissue tended to increase with increased rates of the organic amendments, but both amendment-specific and species-specific effects were evident. It was concluded that the use of vermicompost was superior to that of compost for organic herb production in containers.

Fate of pendimethalin in soil and characterization of non-extractable residues (NER)

One important route of degradation of herbicide pendimethalin in soil leads to formation of non-extractable residues (NER). To investigate NER nature (irreversibly, chemically bound, including possible biogenic NER, or strongly sorbed and entrapped) residues of 14C-labelled pendimethalin in soil were investigated after conventional extraction with organic solvents by silylation. After 400 days of incubation, 32.0% of applied radioactivity (AR) was transformed into NER, 39.9% AR remained extractable. Mineralization reached 26.2% AR. Additionally, 14C-pendimethalin was incubated in soil amended with compost for 217 days to investigate the influence of organic amendments on NER formation. NER amounted to 37.8% AR, with 57.9% AR remaining extractable. Mineralization was negligible (1.4% AR). For all sampling times only low amounts of radioactivity were entrapped (<5% AR) in soil without compost amendment. Pendimethalin was present only in trace amounts (ca. 0.4% AR), other released residues consisted of undefined fractions (sum ≈2% AR). In soil amended with compost, silylation overall resulted in release of higher amounts of radioactivity (19% AR). Addition of compost led to an increase in potential entrapment and sorption sites for pendimethalin, forming higher amounts of strongly sorbed, entrapped residues. Furthermore, potential release of non-extractable pendimethalin residues was investigated by incubation of solvent-extracted soil (without compost amendment) mixed with fresh soil for additional 3 months. NER were partly mineralized (7% AR) and 20% became extractable with organic solvents. However, no pendimethalin or any known metabolites were found.It can be concluded that no parent pendimethalin was found and NER of pendimethalin in soil are mainly formed by covalent binding to organic matrix with only low potential of remobilization under natural conditions.

Phytoremediation of petroleum hydrocarbon-contaminated soils with two plant species: Jatropha curcas and Vetiveria zizanioides at Ghana Manganese Company Ltd

The study investigated the effects of Jatropha curcas (JC) and Vetiveria zizanioides (VZ) on hydrocarbon concentration levels in mine spoils. A 2 × 2 × 3 factorial arrangement of treatments in a completely randomized design with 3 replications was adopted. With compost amendments, JC caused 78.8 and 82.2% and VZ caused 51.1 and 39.7% decline in soil TPH and TOG concentrations, respectively after 16 weeks. Compost amendments significantly reduced TOG and TPH concentrations compared to the other treatments in both JC and VZ (p < 0.0001). However, the effect of species on TOG and TPH concentrations were marginally significant (p = 0.081 and p < 0.006, respectively). Growth in height, collar diameter and number of leaves in JC were significantly higher in the compost amendment compared to the fertilizer and control treatments (p < 0.0001). Number of leaves (p = 0.009) and collar diameter growth (p = 0.010) were significantly lower in contaminated soils compared to non-contaminated soils. Furthermore, only the number of tillers in Vetiver was significantly influenced by the soil amendments (p = 0.003) and the soil hydrocarbon levels (p = 0.048). It is concluded that phytoremediation particularly with JC is an alternate means to reducing soil hydrocarbon concentration levels. However, soils must be amended with compost for effective remediation and rapid, vigorous, early growth of plants.

Effects of compost and biochar amendments on soil fertility and crop growth in a calcareous soil

Crop performance in calcareous and alkaline soils is often limited by low nutrient availability and uptake following poor soil fertility. The positive agronomic effects of compost and biochar originated from a distinct biomass on soil fertility, nutrients uptake and crop growth were previously reported in a wide range of different soil types. However, a little is surfaced about the contrasting effects of compost and biochar produced from the same biomass on soil fertility, nutrients uptake and crop growth in the calcareous and alkaline soils. A greenhouse experiment was carried out with an eye of contrasting the effects of compost and biochar made from the same pioneering Oleaster (Oleaster angustifolia L.) tree on improving these limiting factors for crop performance found in the calcareous and alkaline soils. The calcareous and alkaline soil used was either untreated (control) or treated with compost and biochar at a rate of 1, 2 and 4% w/w. The experimental layout was laid in line with completely randomized plot design in quadruplicate. Across the experiment, compost significantly (p < 0.05) exhibited the striking impacts on soil fertility, nutrients uptake and maize growth than biochar treatments. To put the effects of compost and biochar into perspectives, compost exhibited the highest rally in soil fertility through enriching pH, electrical conductivity (EC), extractable cations (Ca, Mg, K and Na), available micronutrients (Fe, Mn, Cu and Zn), available phosphorous (P), NO3-N, NH4-N, total nitrogen (TN) and organic matter (OM), nutrients uptake via enhancing the uptake of total nitrogen, P, K, Ca, Mg, Fe, Zn, Mn and Cu, as well as maize growth via improving leaf chlorophyll content (LCC), plant height (PH), stem girth (SG), aboveground fresh biomass (APFB), aboveground plant dry biomass (APDB), fresh root biomass (FRB) and dry root biomass (DRB) than biochar amendments due to most likely sorption effects of biochar and its recalcitrance to microbial activities. Overall, soil fertility and crop performance increased in the order control < biochar < compost. Based on the findings of this study, it is concluded that compost can be suggested under such type of soils for improving soil fertility and crop performance at the expenses of biochar applications, nonetheless, field demonstration is highly essential for more conclusive results prior to recommending either compost or biochar in soil management practices.

Leaching behaviour appraisal of eight persistent herbicides on a loam soil amended with different composted organic wastes using screening indices

The addition of organic wastes is a common agronomic practice in some Mediterranean regions to increase soil organic matter. In addition, they consume high amounts of agrochemicals. Hand-packed soil columns were used to evaluate the effect of three different composted organic soil amendments (agro-forestry, agro-industrial and animal manure) on the leachability of eight persistent herbicides. A new leaching index based on the amounts recovered from leachates and referred as Experimental Leaching Index (ELI) is proposed according to the mean annual precipitation in a specific place. This index is compared with others such as Groundwater Ubiquity Score (GUS), Relative Leaching Potential Index (RLPI) and Leachability Index (LIX), which only include degradation (DT50) and sorption (KOC) parameters. According to ELI, metribuzin is very mobile in all cases, while terbuthylazine, chlorotoluron and isoproturon present high leachability only in unamended soil reducing their leaching potential in amended soils. Aclonifen, oxyfluorfen, trifluralin and pendimethalin behave in all cases as immobile (non-leacher) compounds.

Short-Term Effects of Sewage Sludge Compost Amendment on Semiarid Soil

The adoption of sewage sludge as an agricultural management strategy to improve soil properties and crop production is attracting great interest. Despite many positive effects on soil inorganic and organic components reported for different soil types, little information is available on sewage sludge application on Mediterranean soils, as well as on its use at different dose rates. The objectives of the present research was to evaluate, through an integrated approach, the effects of sewage sludge compost from urban wastewater on physicochemical, hydrological, biochemical parameters, and microbiota composition in soil pots under a three-year crop rotation system. Four different doses of sewage sludge compost (C3, C6, C9, C12) from municipal wastewater and a dose of them in combination with mineral fertilizer (C6N) were used. We have used 3-6-9-12 Mg/ha of sewage sludge compost for the treatments C3, C6, C9 and C12, respectively, and 6 Mg/ha of sewage sludge compost in combination with 60 kg/ha of ammonium nitrate for the treatment C6N.The effects were compared to non-fertilized (C0) and mineral fertilized (Min) sets of controls. The electrical conductivity, soil pH, stability of soil aggregates, percent of moisture of the dry soil both at the field capacity and at the wilting point, available P, and exchangeable K were all positively affected by increasing the amounts of composted sludge. The organic carbon and total N increased up to 66% and 39%, respectively. Increased enzymatic activities and microbial biomass were also observed in soil after the application of sewage sludge compost when compared to un-amended control. A higher richness and evenness among the soil plots amended with sewage sludge compost was observed, with no significant differences among the application dose rates, when compared to the un-amended soil control and soil treated with a mineral fertilizer. A three-year amendment was able to separate soil plots amended with high doses of sewage sludge compost from the low dose amended and control samples. Among the microbial groups responsible for such marked separation, bacteria belonging to Actinobacteria, Acidobacteria, Cyanobacteria and Bacteroidetes contribute the most, with a shift from oligotrophic to copiotrophic taxa. Significant changes in bacterial composition and taxonomic structure should be considered in order to properly balance agronomic and economic advantages with environmental concerns. After all, our results have evidenced the effects of sewage sludge amendment on different soil properties, microbial activity, and composition already after a short period of application. The findings are particularly relevant in semiarid soils, where an immediate restoration of soil fertility by short-term compost application is needed.

Influence of Rice Husk Biochar and Compost Amendments on Salt Contents and Hydraulic Properties of Soil and Rice Yield in Salt-Affected Fields

Soil salinity may damage crop production. Besides proper management of irrigation water, salinity reduction can be achieved through soil amendment. The objectives of this study were to evaluate the effects of rice husk biochar and compost amendments on alleviation of salinity and rice growth. Field experiments were conducted at two salt-affected paddy rice fields located in distinct sites for five continuous crops. Treatments, with four replicates, consisted of continuous three rice crops per year (RRR), two rice crops rotated with fallow in spring–summer crop (FRR), FRR plus compost at 3 Mg ha−1 crop−1 (FRR + Comp), and biochar at 10 Mg ha−1 crop−1 (FRR + BC). Salt contents and hydraulic properties of soils, plant biomass, and plant uptake of cations were investigated. Soil bulk density (BD), exchangeable sodium (Na+), and exchangeable sodium percentage (ESP) were reduced remarkably by biochar application. Biochar application significantly increased other soil properties including total porosity, saturated hydraulic conductivity (Ksat), soluble and exchangeable potassium (K+), K+/Na+ ratio, available P, and total C. Compost application also improved BD, total porosity, and available P, but not exchangeable Na+ and ESP. Total aboveground biomass of rice showed a trend of FRR + BC &gt; FRR + Comp &gt; FRR &gt; RRR. Relatively higher K+ uptake and lower Na+ uptake in rice straw in FRR + BC resulted in a significant two times higher K+/Na+ ratio over other treatments. Our results highlight that biochar amendment is a beneficial option for reducing ESP and providing available K+ and P under salinity-affected P-deficient conditions, hence improving straw biomass.

Harnessing the Microbiomes of Suppressive Composts for Plant Protection: From Metagenomes to Beneficial Microorganisms and Reliable Diagnostics.

Soil-borne diseases cause significant yield losses worldwide, are difficult to treat and often only limited options for disease management are available. It has long been known that compost amendments, which are routinely applied in organic and integrated farming as a part of good agricultural practice to close nutrient cycles, can convey a protective effect. Yet, the targeted use of composts against soil-borne diseases is hampered by the unpredictability of the efficacy. Several studies have identified and/or isolated beneficial microorganisms (i.e., bacteria, oomycetes, and fungi) from disease suppressive composts capable of suppressing pathogens (e.g., Pythium and Fusarium) in various crops (e.g., tomato, lettuce, and cucumber), and some of them have been developed into commercial products. Yet, there is growing evidence that synthetic or complex microbial consortia can be more effective in controlling diseases than single strains, but the underlying molecular mechanisms are poorly understood. Currently, a major bottleneck concerns the lack of functional assays to identify the most potent beneficial microorganisms and/or key microbial consortia from complex soil and compost microbiomes, which can harbor tens of thousands of species. This focused review describes microorganisms, which have been isolated from, amended to or found to be abundant in disease-suppressive composts and for which a beneficial effect has been documented. We point out opportunities to increasingly harness compost microbiomes for plant protection through an integrated systems approach that combines the power of functional assays to isolate biocontrol and plant growth promoting strains and further prioritize them, with functional genomics approaches that have been successfully applied in other fields of microbiome research. These include detailed metagenomics studies (i.e., amplicon and shotgun sequencing) to achieve a better understanding of the complex system compost and to identify members of taxa enriched in suppressive composts. Whole-genome sequencing and complete assembly of key isolates and their subsequent functional profiling can elucidate the mechanisms of action of biocontrol strains. Integrating the benefits of these approaches will bring the long-term goals of employing microorganisms for a sustainable control of plant pathogens and developing reliable diagnostic assays to assess the suppressiveness of composts within reach.

Effects of Zinc Pollution and Compost Amendment on the Root Microbiome of a Metal Tolerant Poplar Clone.

Until recently, many phytoremediation studies were focused solely on a plants ability to reclaim heavy metal (HM) polluted soil through a range of different processes, such as phytoextraction and phytostabilization. However, the interaction between plants and their own rhizosphere microbiome represents a new research frontier for phytoremediation. Our hypothesis is that rhizomicrobiome might play a key role in plant wellness and in the response to external stimuli; therefore, this study aimed to shed light the rhizomicrobiome dynamics after an organic amendment (e.g., compost) and/or HM pollution (e.g., Zn), and its relation with plant reclamation ability. To reach this goal we set up a greenhouse experiment cultivating in pot an elite black poplar clone (N12) selected in the past for its excellent ability to reclaim heavy metals. N12 saplings were grown on a soil amended with compost and/or spiked with high Zn doses. At the end of the experiment, we observed that the compost amendment strongly increased the foliar size but did not affect significantly the Zn accumulation in plant. Furthermore, the rhizomicrobiome communities (bacteria and fungi), investigated through NGS, highlighted how α diversity increased in all treatments compared to the untreated N12 saplings. Soil compost amendment, as well as Zn pollution, strongly modified the bacterial rhizomicrobiome structure. Conversely, the variation of the fungal rhizomicrobiome was only marginally affected by soil Zn addition, and only partially impaired by compost. Nevertheless, substantial alterations of the fungal community were due to both compost and Zn. Together, our experimental results revealed that organic amendment increased the bacterial resistance to external stimuli whilst, in the case of fungi, the amendment made the fungi microbiome more susceptible. Finally, the greater microbiome biodiversity does not imply, in this case, a better plant wellness or phytoremediation ability, although the microbiome plays a role in the external stimuli response supporting plant life.

Effect of Biochar and Compost Amendments on Soil Biochemical Properties and Dry Weight of Canola Plant Grown in Soil Contaminated with Heavy Metals

ABSTRACT Soil contamination with heavy metals has resulted in a reduction of crop productivity and soil quality. We studied the effects of rice straw biochar (RB), rice straw compost (RC), and their mixtures at rates 0.5% and 1.0% on soil biochemistry and dry weight of the canola plant (Brassica napus) grown in contaminated soil with heavy metals. The results showed that the addition of the RB or RC alone or their mixtures together significantly increased contents of soil exchangeable cations, microbial biomass carbon (MBC), organic matter (OM), cations exchange capacity (CEC), availability of nutrients, NPK uptake, and dry weight of the canola plant. Soil microbial biomass carbon increased by 20.2% and 59.3% for RB, while it increased by 69.5% and 79.8% for RC with the addition of 0.5% and 1.0%, respectively, compared to the control. The results of this study reveal that the co-application of biochar with compost can be a promising strategy for improving soil productivity and soil quality in soil contaminated with heavy metals.

A new in-field indicator to assess the impact of land management on soil carbon dynamics

The assessment of the impacts of land-use and management on soil organic carbon (SOC) dynamics is a major environmental concern, as the soil carbon cycle underpins key ecosystem services. However, assessments based on short-term SOC dynamics face methodological and experimental difficulties. Hurisso et al. (2016) proposed a method to assess SOC dynamics by coupling two methods: Permanganate Oxidizable Carbon (POXC) and Basal Soil Respiration (BSR). This method has been used in laboratory on dried and re-wetted soil samples from temperate regions mainly. In our study, we adapted this method to the field and proposed a cost-effective in-field indicator combining the POXC and in situ Basal Soil Respiration (SituResp® method).We tested the indicator at four study sites (n = 169 points) within various tropical land-use and management contexts based on rubber, soybean and oil palm cropping systems respectively in Thailand, Cambodia and Indonesia. The results demonstrated the relevance, sensitivity and robustness of the POXC-SituResp® indicator to characterize the impact of a gradient of disturbance on SOC dynamics. The results also highlighted the potential of conservation agriculture (no-tillage and crops residues) and compost amendments to accumulate SOC. Rock-Eval® analysis showed that POXC-SituResp® indicator is negatively linked to excess of potentially mineralizable labile carbon. Carbon pools targeted by the POXC were specified by Rock-Eval® pyrolysis measurements to be a rather thermal resistant pool of SOC.Our study confirms that the integrated indicator based on POXC and BSR assess a relative carbon stabilization of SOC pools. This indicator can be measured in the field by a rapid and cost-effective method.

Arbuscular mycorrhiza and Aspergillus terreus inoculation along with compost amendment enhance the phytoremediation of Cr-rich technosol by Solanum lycopersicum under field conditions

Chromium (Cr) contamination is a potential threat to the agricultural soil. Arbuscular mycorrhizal (AM) fungi have potential to remediate the heavy metal polluted soils. It was hypothesized that Cr phytoremediation potentiality of AM fungi could be enhanced in combination with saprophytic filamentous fungi and soil amendment. Tomato plants were raised in Cr polluted technosol amended with compost, inoculated with mixed-culture of AM fungi and Aspergillus terreus. It was found that, triple treatment (soil amendment with compost along with AM fungi and A. terreus inoculation) enhanced biomass production (up to 315%), fruit setting (up to 49%), photosynthetic pigments (up to 214%) and carbohydrate content (up to 400%) whereas reduced the proline (up to 76.5%), catalase (up to 34.2%), peroxidase (up to 58.9%) and root membrane permeability (up to 74.2%). The effect of AM fungi with compost amendment was additive, while it was synergistic with A. terreus. AM fungi enhanced the extraction of Cr from the substrate, but retained in the mycorrhizal root, thereby reduced the translocation into shoot and in fruit, Cr translocation was undetectable. At the end of experiment Cr content in the substrate was significantly decreased (up to 37.9%). Soil amendment with compost along with AM fungi and A. terreus inoculation can be used for reclamation of Cr polluted soils at field scale.

Impact of long-term agricultural management practices on soil organic carbon and soil fertility of paddy fields in Northeastern Thailand

Soil organic carbon (SOC) is an essential indicator of soil quality and soil fertility. Agricultural management practices can influence SOC and soil fertility. The objective of the present study was to evaluate the impact of agricultural management practices on SOC and soil fertility of paddy fields in the northeastern region of Thailand over a 10-year period. Initial data on SOC and soil fertility parameters in the top 20 cm under indigenous management (compost amendment) in Maha Sarakham Province were collected in 2007 by the Khon Kaen Rice Research Center. The data on SOC and soil fertility parameters were collected again in 2016 after 10 years from 130 farmers' fields located in close proximity to the sites from where the initial data were collected in 2007. The impacts of the conversion of indigenous agricultural management practice into government-promoted management practices on SOC and soil fertility were evaluated. The practices were continuous compost amendment (CA) during 10 years as the control, the shift from CA to biofertilizer (BF), to green manuring (GM), and to rice straw (RS) incorporation. Measurements made at the end of the 10-year period showed that the adoption of government-promoted agricultural management practices generally increased SOC and soil fertility. The incorporation of RS resulted in the largest change in total nitrogen (156% increase), SOC concentration (152% increase), and SOC density content (149% increase) over the 10-year period. The same management practice (RS) had the greatest SOC sequestration rate (1.43 Mg ha−1 yr−1). Results demonstrate the value of RS incorporation into agricultural soils over time for improving SOC and soil fertility. Soil incorporation of compost (CA) could be another option for its potential to improve soil fertility.

Fly Ash and Compost Amendments and Mycorrhizal Inoculation Enhanced the Survival and Growth of Delonix regia in Cu-Ni Mine Tailings

Delonix regia, an ornamental tree that can tolerate an elevated level of heavy metals, was evaluated for phytoremediation potential in mine tailings with fly ash, compost, and mycorrhiza. A two-factorial experiment was conducted under screen house conditions using mine tailings from Bamangwato Concessions Limited (BCL) Cu-Ni mine. The treatments are mine tailing (MT) without mycorrhiza (MT – AM), MT with mycorrhiza (MT + AM), MT with 10% fly ash (FA) without mycorrhiza (MT + FA – AM), mine tailings with 10% FA with mycorrhiza (MT + FA + AM), MT with 10% compost (CP) without mycorrhiza (MT + CP – AM), and MT with 10% CP with mycorrhiza (MT + CP + AM). After 40 wk, results showed an interaction effect of amendments and mycorrhiza wherein compost and FA enhanced the survival, AM root colonization, plant height, and dry matter yield of D. regia seedlings. Mycorrhiza further enhanced these growth parameters, especially in pure mine tailings. The As, Cu, Mn, Ni, Pb, and Zn concentration in plant tissues were reduced substantially by FA and compost amendments. Mycorrhiza also reduced the As, Cu, Ni, Pb, and Zn in pure mine tailings but enhanced the concentration of these metals in the presence of FA and compost. These results could be attributed to the decrease of heavy metal availability and increase of nutrients due to FA and compost while mycorrhiza decreased the translocation of heavy metals regardless of the presence of FA and compost. Overall, results indicated that the survival and growth of D. regia in BCL Cu-Ni mine tailings could be enhanced by the combined application of fly ash, compost, and mycorrhiza.

Characteristics of denitrification genes and relevant enzyme activities in heavy-metal polluted soils remediated by biochar and compost

Denitrification is an important process affecting nitrogen dynamics in soils. In this study, abundances of denitrification genes (narG, nirK, nirS, and nosZ) and activities of nitrite reductase (S-NiR), nitrate reductase (S-NR) were measured in heavy-metal polluted soils with different amendments of biochar and compost. The relationships between physical-chemical parameters, denitrification gene abundance, and enzyme activity were analyzed by Pearson correlation method. Results showed that compost addition significantly increased the abundances of functional genes (nirS, nosZ, narG), and the abundances of nirK and nirS might be sensitive to compost and biochar addition. Compost addition and its combination with biochar significantly decreased the S-NiR enzyme activity and stimulated the S-NR enzyme activity. Negative relationships were obtained between S-NiR activity and electric conductivity (EC), water soluble carbon (WSC), nitrate, ammonium, nirK, narG gene abundances. While S-NR activity significantly positively correlated with soil EC, WSC and nirK gene abundance. Biochar and compost amendments can alter soil nitrogen cycling by changing denitrifying functional gene and relevant enzyme activities in soils polluted by heavy metals.

Salinity derived from sludge compost amendment is a crucial influencing factor of qualitative performance of sports-field turf.

Treated sewage sludge (or biosolid) is a suitable alternative substrate for use in turf production, but the potential of this resource remains to be explored in higher value-added field. In this study, the negative effects of sludge compost and biochar-amended sludge compost amendment on the qualitative performance of sports-field turf, including vegetation stolon index, grade for turf, and sports performance index, were investigated. It was found that sludge compost and biochar-amended sludge compost amendment induced a significant increase in organic matter, total nitrogen, total potassium, and electrical conductivity. In addition, biochar-amended sludge compost also resulted in a significant increase in turf chlorophyll content and the rate of turf weed emergence. Interestingly, electrical conductivity explained 55.4% of the qualitative changes, and electrical conductivity and pH together explained 68% of the qualitative changes. In summary, salinity was the main factor responsible for the negative effect of sludge compost amendment on qualitative performance of sports-field turf.

Effects of Selected Soil Amendments and Mulch Type on Soil Properties and Productivity in Organic Vegetable Production

The potential benefits of different types of soil amendments and mulch ground covers on soil chemical and biological properties, crop development and yield, and disease and pest issues in organic vegetable production, as represented by legume (green snap bean), cucurbit (green zucchini squash), and brassicaceous (turnip) vegetable crops, were evaluated in a two-year field trial in Maine, USA. Soil amendments evaluated (following an initial fertilizer base) included a commercial organic fertilizer alone, composted dairy manure, compost plus fish meal, and compost plus Wollastonite, a natural source of silicon (Si). A paper mulch was also compared with a woven polypropylene fabric mulch for their performance and effects as weed barriers within these systems. Mulch type significantly affected soil properties, with the fabric mulch associated with increases in soil moisture, organic matter, and other soil chemical and biological properties relative to the paper mulch. The fabric mulch also resulted in earlier emergence and earlier harvests for bean and zucchini. Soil amendments affected soil properties and crop growth and yield of bean and zucchini, with compost amendments increasing soil pH, organic matter, and several nutrient concentrations, as well as crop emergence and yield relative to a fertilizer-only treatment. Compost treatment also reduced the infestation and damage caused by mites on beans in 2018. Addition of fish meal increased most nutrient element concentrations and microbial respiration, and Si amendment increased emergence of beans, and reduced powdery mildew on squash and late season browning of beans. These results help define specific management practices to improve organic vegetable production and provide useful information and options for growers.

Modeling Soil Nitrate Accumulation and Leaching in Conventional and Conservation Agriculture Cropping Systems

Nitrate is a major groundwater inorganic contaminant that is mainly due to fertilizer leaching. Compost amendment can increase soils’ organic substances and thus promote denitrification in intensively cultivated soils. In this study, two agricultural plots located in the Padana plain (Ferrara, Italy) were monitored and modeled for a period of 2.7 years. One plot was initially amended with 30 t/ha of compost, not tilled, and amended with standard fertilization practices, while the other one was run with standard fertilization and tillage practices. Monitoring was performed continuously via soil water probes (matric potential) and discontinuously via auger core profiles (major nitrogen species) before and after each cropping season. A HYDRUS-1D numerical model was calibrated and validated versus observed matric potential and nitrate, ammonium, and bromide (used as tracers). Model performance was judged satisfactory and the results provided insights on water and nitrogen balances for the two different agricultural practices tested here. While water balance and retention time in the vadose zone were similar in the two plots, nitrate leaching was less pronounced in the plot amended with compost due to a higher denitrification rate. This study provides clear evidence that compost addition and no-tillage (conservation agriculture) can diminish nitrate leaching to groundwater, with respect to standard agricultural practices.