Air Porosity Research Articles

Durability assessment of open-graded friction course using a sustainable polymer

Open-graded friction course (OGFC) asphalt mixture, usually used to construct porous pavements, represents one of the materials supporting low-impact development (LID) philosophy due to its use of coarse aggregate gradation. Using such mixtures brings several benefits related to safety, environment and economy. Alas, coarse, open-graded skeleton of OGFC mixtures is prone to failure, particularly raveling and stripping. Continuous traffic loading and the environmental impacts give hand in hand to further increase the potential for failure, hence higher pavement maintenance and rehabilitation costs. Application of different types of modifiers has proved effective in mitigating failure potential. The most common modifiers are polymers, fibers and anti-stripping agents. Aiming at minimizing the costs and maximizing the lifespan while considering sustainability, the study was to investigate the effect of using a recycled stabilizing material as an asphalt modifier on the performance of OGFC asphalt mixtures. Recycled Low-Density Polyethylene (R-LDP) was adopted in this investigation. Changes in mixture air void, porosity, draindown, permeability, rut depth, moisture damage and abrasion loss were observed to evaluate the effect. Compared with unmodified asphalt samples, R-LDP modification increased mixture air void, porosity and permeability by 15%, 10% and at least 40%, respectively. Also, it noticeably contributed to reducing rut depth, moisture damage and abrasion loss (both unaged and aged) by 31%, 20% and at least 40%, respectively. More significantly, it almost eliminated the draindown problem. Incorporating R-LDP proved effective in upgrading OGFC mixture properties to an acceptable level required by most specifications.

Thermal behaviour of waterproof coated fabrics and identification of chemical groups present in melt-blown polyester non-woven fabrics coated with waterproof acrylic polymer binder

Polyester non-woven fabrics are a good choice for base material in development of engineered waterproof fabrics. They find wide applications in bathroom floor lining, Roof lining, Car floor lining and many such applications. These fabrics not only provide strength and durability to the structure but also enhance the thermal as well as shelf-life of the structure. The presence of Chemical groups like ethylene functional group which is a chemical compound prominently present in polyester and observation of strong peaks of polyester functional groups aids in robust behaviour of the waterproof coated fabrics. These chemical groups present in the waterproof acrylic polymer binder also influences the development of durable fabrics with good hardness values. In this research a waterproof fabric for such applications is developed using a non-woven polyester fabric as the base material and roller coating process. The changes in the surface morphology of the fabrics is recorded and analysed using SEM micrographs. However, the analysis of thermal properties of these coated fabrics using DSC, TG/DTA instruments show melting of the coated material at 375 °C and TGA graphs show degradation of material occurring at 400 °C. The density measurement results show the fabrics ability to achieve lower values when nonwoven fabric layers are doubled which may be due to consumption of less binder and locking of air between layers. The Rockwell hardness results of 31.4 HRB (B scale) for single layer and 68.2 HRB for double layer proves the performance of the coated fabric at par with soft steel. The coated fabrics show zero air porosity when tested under air-permeability tester. The process of roller coating proves to be robust method of application of water proof polymer binder on non-woven fabrics.

Development and Evaluation of Deoiled Seed Cake and Paddy Straw Amended Potting Media for the Cultivation of Tomato and Cucumber

The present study aimed to analyse the potential of six Deoiled cakes (DOCs) (2.5, 5, 7.5 and 10% (v/v)) and Paddy straw (PS) (10% (v/v)) as potting media (PM) amendments and its subsequent effect on the physical and nutritional properties of the PM and plant health. The study focussed on two transplantable horticulture crops, cucumber (Cucumis sativus L.) and tomato (Solanum lycopersicum L.) using coir pith (CP) and vermicompost (VC) as the base material of PM. Among 6 DOCs tested, neem (2.5%) and niger cake (5%) were found to be significant in improving the plant growth of both the crops tested. Further, PS powder amendment to selected PM improved the plant growth, up to 10% (v/v). However, at higher concentrations, PS amendment recorded decreased shoot and root length. Two optimized potting media, DPM-1 (CP + VC + Neem cake + PS:77.5 + 10 + 2.5 + 10% (v/v)) and DPM-2 (CP + VC + Niger cake + PS:75 + 10 + 5 + 10% (v/v)) were evaluated in comparison to peat-based two commercial potting media (CPM-1 and CPM-2). DPM-1 and DPM-2 recorded, bulk density (0.29 and 0.28 g/cm3), water holding capacity (59.87 and 59.02%), and % solid (16.63 and 15.37%), air porosity (23.50 and 25.61%), total porosity (83.37 and 84.63%), Ec (2.64 and 2.76 mS/cm), and pH (6.56 and 6.40), respectively. However, all these parameters were within the recommended range of ideal PM. Tomato and cucumber seedlings were grown in both DPMs showed significant improvement in growth and macro and micronutrients in comparison to CPMs and control.

Microstructural characterization of vacuum-fried matrices and their influence on starch digestion

Abstract During vacuum frying, starch gelatinization may be limited due to the water boiling point depression, which reduces starch digestibility. In addition, relevant structural changes are induced, which could affect the accessibility of amylolytic enzymes to the site of action. To differentiate the effect of structural changes in the food matrix over the effect of starch gelatinization on starch digestibility, we characterized the microstructure using x-ray micro-computed tomography (micro-CT), confocal laser scanning microscopy (CLSM) and environmental scanning electron microscopy (ESEM), and we also studied the starch in vitro digestibility in two different systems: vacuum (9.9 kPa, Twater-boiling-point = 45 °C) and traditional atmospherically-fried dough (170 °C) with a similar degree of starch gelatinization (60 %). Vacuum-fried matrices had a much higher oil content (∼51.3 % dry basis) than their atmospheric counterparts (∼20.3 % dry basis), as confirmed through micro-CT and CLSM. The quantitative analysis of micro-CT images showed that vacuum-fried samples had less air porosity (36.6 % air-filled pores) than atmospheric fried ones (49 % air-filled pores), whereas, no differences were found with respect to total porosity (p

Vehicular traffic effects on hydraulic properties of a Crosby silt loam under a long-term no-till farming in Central Ohio, USA

Changes in soil properties have been reported under several long-term no-till (NT) studies, however, the magnitude of changes in soil hydraulic properties with the use of new generation heavy machinery under NT farming is not widely documented on a long term basis. Therefore, a site under long-term NT production system was selected, where a known compaction force of 0 Mg axle load (control, C-0), two (C-2) and four (C-4) passages of 2.5 Mg water wagon axle load was applied to cover the entire plot for 20 consecutive years to assess changes in soil hydraulic properties at a site in the Central Ohio, USA. The field was under NT-based corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation since 1997. An additional three plots were established in a natural woodlot (30 m adjacent from the compaction field plots) as the baseline to compare the impact of compaction under a NT managed agricultural soil. Total of 24 (three per treatment for each depth) undisturbed soil cores was collected in November 2016 from 0 to 10 cm and 10 to 20 cm depths by using a hammer based manual core sampler for determination of soil hydraulic properties (soil water retention-SWR, plant available water), and to measure pore size distribution and air porosity. Results revealed that vehicular traffic induced significant changes in SWR at 0 and -6 kPa soil water potential (ψ). A reduction of SWR by 7.9 to 3.2% under C-2, by 6.6 to 0% under C-4 and by 2.4 to 0.8% under C-0 was observed at -6 to -300 kPa compared to that for the wooded soil. The soil under C-4 treatment had the lowest air porosity. Furthermore, the volume of pores with diameter >10 μm under C-4 was reduced by 8.3% compared to C-0 and by 7.6% compared to the wooded soil. Soil water content (transmission, plant available and residual water) followed a trend similar to that of the pore volume distribution for soil subjected to vehicular traffic-induced compaction. The data supports the conclusion that two or four passages of 2.5 Mg axle load of vehicular traffic under NT farming moderately changed SWR, plant available water, pores size distribution and air porosity compared to that of the wooded soil. However, the magnitudes of changes in soil hydraulic properties due to vehicular passages of 2.5 Mg axle load were not consistent under the NT production system. Thus, further monitoring of the impacts of compaction on soil hydraulic properties particularly on some other properties (e.g., water infiltration and air permeability) across the years is needed for better assessment of the relationships between crop production and soil hydraulic properties as well as soil resilience.

Non-Autoclaved Aerated Concrete Porosity and Factors Affecting it

The total volume of cellular porosity, which comprises pores, interpore partitions, and air-entrained pores, depends on the spatial packing of pores, size distribution, maximum and average size, their shape, and the thickness of interpore partitions. Interpore partitions contain gel and capillary pores, which have a significant impact on the total porosity, thus affecting the operating properties of aerated concrete. This paper presents the calculations of gel, capillary, air, and total porosity in non-autoclaved aerated concrete of average-density grades D100...D1200 for different cement hydration degrees (0.6; 0.8, and 1) and water-cement ratios (0.5; 0.6, and 0.7); calculations use the author-developed methodology. Cement consumption depends on the average-density grade as well as on cement hydration degree. Reducing the latter from 1 to 0.6 in D500 concrete raises cement consumption by 7.4 %; other grades have similar patterns. This is why aerated concrete should be conditioned to maximize the utilization of the binder by enabling its complete hydration. The amount of water in the mixture is what determines the cement consumption and the water-cement ratio, whereby the density of cement dough will not depend on the average-density grade provided that the hydration degree and the WC ratio are constant. The finding is that the ability of cement to form its own pore structure is crucial to D500 and D400 aerated concrete if the mixture has high initial water content.

Studies on Semi-crystalline Poly Lactic Acid (PLA) as a Hydrophobic Coating Material on Kraft Paper for Imparting Barrier Properties in Coated Abrasive Applications

This study investigated and explored the possible use of bio-based Poly lactic acid (PLA) as a barrier coating material on natural Kraft paper to fabricate coated abrasive products and to replace the conventional, non-biodegradable, synthetic polymer based barrier coating materials. PLA was coated on the Kraft paper using a solution coating process. The barrier properties of the PLA-treated Kraft paper were accordingly tested for application as a backing material in coated abrasive products. The concentration of PLA in solution was systematically increased from 5 wt% to 25 wt%. The coating thickness and coating weights were increased quantitatively with increasing solution concentrations. The morphology of the coating was characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), contact angle, and surface roughness measurements. The mechanical properties of the PLA coating applied Kraft paper were quantified by measuring the tensile strength, bursting strength, air porosity and Cobb value in order to find its suitability as coated abrasive product. The thermal analysis carried out using DSC scan indicated the semi-crystalline nature of PLA. The coating’s analysis for air and water resistance indicated that the air and water resistance increased with increase in PLA coating thickness. The data from different studies revealed that the PLA coating with a coating weight of 9 g m−2 appeared to be the most ideal concentration over the untreated or other lower PLA g m−2 treated backing materials and proved to possess superior overall barrier properties that are essentially needed for the fabrication of coated abrasive products.

Is least limiting water range a useful indicator of the impact of tillage management on maize yield?

Tillage management is a key factor driving changes in soil physical properties (SPP) and crop yield around the world. However, there is a lack of knowledge about the relationships between SPP and crop yield. The dynamic of SPP during the growth period is also seldom taken into account to understand suitable soil physical environment for crop growth. Moreover, the crop growth process cannot be explained by an individual SPP substantially. The least limiting water range (LLWR), which integrates soil penetration resistance, air porosity, and soil water potential, may provide a better understanding of soil-crop relationship, especially in regions with limited precipitation. Our objective was to explain how dynamic SPP affected grain yield during the growth period. A long-term field experiment was established in 2003, with continuous spring maize, on sandy loam soil. Seasonal changes of SPP (i.e. bulk density, penetration resistance, porosity, mean weight diameter, LLWR, and plant available water) were determined under reduced tillage with residue incorporated (RT-RI), conventional tillage with residue removal (CT), and no-tillage with residue mulch (NT-RM). The results showed that these SPP were affected by both tillage management and growth stage. Bulk density, porosity, S index, and mean weight diameter were not effective indicators to explain the changes of grain yield under the three tillage managements. The range of LLWR was narrower than plant available water (PAW) during the growth period and more sensitive to assess soil water availability under RT-RI, CT, and NT-RM. NT-RM significantly increased the lower limit of LLWR, which made it more difficult for root water uptake. Hence, RT-RI presented higher corn yield compared to NT-RM, even if the water content remained lower. Redundancy analysis further indicated that maize yield was mainly driven by lower limit of LLWR and penetration resistance. Overall, LLWR was an aggregative indicator including not only soil penetration resistance but also air porosity and soil water potential, which can better explain the change of grain yield under the long-term tillage management in semi-arid region.

Heparan sulfate loaded polycaprolactone-hydroxyapatite scaffolds with 3D printing for bone defect repair

With the increasing applications of 3D printing technology in biomedical field, the composition or additives of the related materials has become critical for the next development. In the current study, we have prepared 3D printed polycaprolactone-hydroxyapatite (PCL-HA) porous scaffolds with loaded heparan sulfate (HS), in order to reveal the reparative effect of different concentrations of HS on the healing of bone defects. As a result, the scaffold itself showed sound compression resistance, air porosity and good biocompatibility. From both in vitro and in vivo experiments, the scaffold with low concentration of HS led to positive effects in promoting osteoblast maturation and accelerating bone defect repair. Moreover, scaffold with high concentration of HS showed notable inhibitive effort on the proliferation of osteoblasts, yet it still brought about positive effects in repairing bone defects in organisms. Thus, with good structural properties and biocompatibility, 3D printed PCL-HA-HS composite scaffold can facilitate and accelerate the repairing of biological bone defects, demonstrating as an effective biomaterial for bone defect repair.

Suspended graded-index porous core POF for ultra-flat near-zero dispersion terahertz transmission

Abstract A suspended graded-index porous core polymer optical fiber (POF) for low-dispersion terahertz guidance is proposed. This fiber is consisting of a graded-index porous core, five spoke-like dielectric supporting strips and an outer material ring. The finite element method (FEM) with perfectly matched layer boundary conditions is used to simulate the guiding properties. It is found that by creating artificial graded-index in the porous core, an extremely flat group velocity dispersion (GVD) of 0.14 ± 0.07 ps/(THz·cm) is achieved in the range of 0.71–0.95 THz when fiber core diameter is 432 μm and the air porosity is 44%. Meanwhile, the fiber shows low and flat intermodal dispersion of 0.0152 ± 0.0004 ps/(THz·cm) at 0.8–1 THz under the same conditions. Moreover, other optical parameters of the fiber such as confinement loss (CL), effective material loss (EML) and normalized frequency V are also investigated.

Experimental Study on Pore-Defect by Selective Laser Melting of 316L Stainless Steel

With different process parameters (laser power, scanning speed and scanning distance),the low-time defects of forming part were studied by microscope,including air bubble, pore, micro-crack and macro-crack. The formation mechanism of pore-defect was analyzed. The micro-structure and composition of the pore-defect were studied by means of SEM and EDS. The results showed that the porosity mainly included circular air porosity, irregular process porosity and oxide inclusion.Linear energy density (E=P/v) was introduced as synthetic parameter.According to analysis and test verification, the optimum technological parameters of 316L stainless steel were laser power 190-210KW, laser speed 800-1000mm/s and scanning interval 0.9-0.11mm,and the linear energy density was about 200J/m. There were no cracks, no bubbles, a small amount of porosity, and the product density reached 99.7%.

Influence of free water on concrete triaxial behavior: The effect of porosity

This work examines the effect of porosity and free water on the behavior of concrete under high confinement. For this purpose, three types of concretes are designed with either low, medium or high porosities but featuring the same aggregate skeleton, yielding: an ordinary referenced concrete (OC), as already characterized in previous studies; a high performance concrete (HPC) with very low capillary porosity; and a low performance concrete (LPC) with the same composition as OC except for a much higher entrained air porosity. The results of triaxial tests, conducted on these three concretes up to a confinement of 600 MPa at both low and high saturation ratios, are presented. The conclusions from past studies on OC are extended herein for the cases of HPC and LPC: the free water quantity exerts a major influence on the concrete strength capacity as well as the volumetric stiffness for all three types of concretes. These results also show that the free water influence on concrete behavior depends on both the amount and nature of this porosity: the effect of modifying the entrained air porosity is much weaker than that of capillary porosity. To better quantify the effect of concrete saturation ratio, results are then completed by triaxial testing performed on OC with intermediate saturation ratios. Lastly, an empirical triaxial failure criterion of concrete, which takes into account the uniaxial strength, porosity and saturation ratio, is proposed; this new criterion accurately reproduces the results presented, as well as, a large database obtained from previous studies.

Colloidal coatings for laser optics

Three-dimensional photonic crystals (PCs) are periodic materials with a modulated refractive index on a length-scale close to the light wavelength. This optical property allows the design of optical components like highly reflective mirrors. Moreover, these structured materials are known to have a high laser-induced damage threshold (LIDT) in the sub-nanosecond range compared with multi-layered dielectric mirrors. This property results from the use of only one high LIDT material (silica). The second material used in the layer stack is air (porosity). This work presents the development of 3D PCs with narrow-sized colloidal silica particles, produced by sol–gel process and deposited with Langmuir–Blodgett technique. Different syntheses routes have been investigated and compared regarding the optical properties of the PCs. Finally, a numerical modeling based on an ideal opal network with and without defect is used to support the experimental results.

Improving the Filling System for a Defect Free Casting: A Review

Abstract With the evolution of modern technologies, now a day’s, it is very convenient to find out the primary causes of casting defects. Before going to actual practice, the flow behaviour can be simulated with the help of computer and input parameters can be optimized for obtaining defect free castings. The major defects in casting leading to early failure are due to air porosity and surface turbulence caused by the flow velocity and nature of flow of molten metal. Thus, it is needed to modify the gating system to get the optimised velocity and no surface fluctuations. In this review article, the flow behaviour of some improved gating systems such as submerged gating, uphill filling and trident gating systems have been reviewed and they were found to be turbulent free and the defects due to the surface turbulence have been considerably reduced.

Optimum Range on Soil Physical Indicators Under Plastic Film House

The water and nutrients in the soil can be absorbed by the crop root. The soil physical properties affect the growth and penetration of crop root. The objectives of this study were to determine soil physical indicators that could inhibit the crop growth under plastic film house, and to establish the appropriate soil physical criterion depending on crop types. The soil physical (including effective rhizosphere, soil three phase, and bulk density) and chemical (including pH, EC, organic matter content, and available phosphate) properties were investigated in the mainly cultivated area for greenhouse crops including lettuce, strawberry, cucumber, tomato, oriental melon, and water melon from 2015 to 2017. For plastic film house, soil physical indicators were commonly chosen as bulk density, air porosity, and effective root depth. The optimum ranges for plastic film house soil were as follows; deeper than 50 cm for effective root depth, less than 1.5 Mg m-3 for bulk density and more than 10% gas phase. The optimum range of soil physical indicators for crops cultivated greenhouse. Greenhouse crops Effective root depth (cm) Bulk density (Mg m-3) Gas phase (%) Lettuce, Strawberry, Cucumber, Tomato, Oriental melon, Watermelon above 50 below 1.5 above 10

Enhancing Micro-CT methods to quantify oil content and porosity in starch-gluten matrices

X-ray micro-computed tomography (micro-CT) is a non-destructive method to study internal structures based on the differences in the strength of x-ray attenuation within a scanned material. In the field of food science, distinguishing certain components represents a challenge as food ingredients have low x-ray attenuation. The objective of this study was to explore the potential application of different agents to enhance x-ray attenuation in fried starch-gluten products, quantify oil content and air porosity, and analyze its microstructure using micro-CT. Control dough, dough stained with a Lugol solution (0.1% (w/w)) or with a BaCl2 solution (0.5% (w/w)), and samples fried in oil stained with Nile Red (0.05 g/L) or stained with Lugol solution and fried in Nile Red were examined. All agents studied improved x-ray attenuation in fried dough. Quantitative analysis of micro-CT images showed that samples attenuated with Nile Red exhibited the smaller standard deviation in oil content and air porosity. These results did not show significant differences with those determined by means of traditional analytical methods.

Dissolved organic nitrogen distribution in differently fertilized paddy soil profiles: Implications for its potential loss

Dissolved organic nitrogen (DON) is recognized as an important nitrogen (N) pool in soil N cycling, but its role in the N cycling of paddy soils, which are intensively fertilized, is not fully predicted. In this study, we investigated DON in flooded layer and soil solution along soil profiles with suction cups in fertilized paddy fields. The DON concentration showed a relative decrease in the deeper layer of paddy soil, while free amino acid N (FAA-N) exhibited a drastic increase along with nutrient profiles of soil. In the upper layer (0–20 cm), DON accounted for 54–64% of total dissolved N (TDN), but this value increased up to 63–97% in the deeper layer (40–60 cm). Low concentrations (9.6–15.0 μg L−1) of FAA-N and low percentage of FAA-N/DON (0.1–0.2%) were observed in the upper layer, but higher concentrations (111–307 μg L−1) and increased percentage (8–36%) were examined in the deeper layer. The high percentage of DON/TDN indicated that DON was the predominant N pool in the deeper layer. Concentrations of DON were significantly and positively correlated with organic matter, total N, and electrical conductivity (EC), while negatively related to soil pH. Additionally, capillary porosity, air porosity, bulk density and particle density were also found to be significantly associated with DON. We suggest the DON and FAA in the paddy field could be an important source for N leaching, which is most strongly related with soil nutrient profiles and physical properties. It is estimated that a total loss of 4.0 kg N ha−1 yr−1 is potentially linked to DON in the paddy field, which implied that ca. 3.35% of the applied N fertilizers could be lost via DON.

Oxygenation of Irrigation Water during Propagation and Container Production of Bedding Plants

Oxygen supply to the root zone is essential for healthy plant growth, and one technology that can potentially supply additional oxygen is the injection of purified oxygen (oxygenation) into irrigation water. The objective was to evaluate whether oxygenation of irrigation water affected plant growth and substrate dissolved oxygen (DO) levels during mist propagation of unrooted cuttings and subsequent growth in containers. Dissolved oxygen measured at source tanks for ambient tap water (averaging 7.1 mg·L−1) or oxygenated tap water (31.1 mg·L−1) was pumped through fine (69 µm) mist nozzles for propagation of Calibrachoa ×hybrid ‘Aloha Kona Dark Red’ and Lobelia erinus ‘Bella Aqua’. There were no measured differences in root length or root dry mass for Calibrachoa and Lobelia propagated using oxygenated water compared with ambient water because DO of ambient or oxygenated water reached ≈100% oxygen saturation in water (8.7 mg·L−1) after passing through mist nozzles. To evaluate subsequent growth without the effect on DO of fine emitters, rooted cuttings of these two plant species and Pelargonium ×hortorum ‘Patriot Red’ were grown in 10.2-cm diameter pots. The plants were irrigated with either ambient (6.0 mg·L−1) or oxygenated (27.7 mg·L−1) nutrient solutions, delivered by top watering or subirrigation when the substrate dried to ≈45% of container capacity (CC), measured gravimetrically. Oxygenated water did not enhance root or shoot growth compared with ambient water for the three bedding plants. In addition, Pelargonium growth was not enhanced when irrigated at high moisture level (maintained at 80% CC) with oxygenated water compared with ambient water. In container substrate without plants, it was possible to increase DO of the substrate solution by 68% when a high volume of oxygenated water (200% container volume or 850 mL) was applied by top watering because existing substrate solution was displaced. In contrast, when containers were subirrigated at 45% CC, the smaller 180-mL volume of oxygenated water was absorbed by the substrate and did not increase DO compared with ambient water. Overall, irrigating with oxygenated water did not enhance root or plant growth of three bedding plants grown in porous, peat-based substrate. To increase oxygen supply to roots in container production, growers should focus on having adequate air porosity in substrate and avoiding overwatering.

Composted biogas residue and spent mushroom substrate as a growth medium for tomato and pepper seedlings

A composted material derived from biogas production residues, spent mushroom substrate (SMS) and pig manure was evaluated as a partial or total replacement for peat in growth medium for tomato and pepper seedlings. Five different substrates were tested: T1, compost + perlite (5:1, v:v); T2, compost + peat + perlite (4:1:1, v:v:v); T3, compost + peat + perlite (2.5:2.5:1, v:v:v); T4, compost + peat + perlite (1:4:1, v:v:v); and CK, a commercial peat + perlite (5:1, v:v). The physical-chemical characteristics of the various media were analyzed, and the germination rate and morphological growth were also measured. Real-time Quantitative PCR (qPCR) was used to quantify Fusarium concentrations. The addition of compost to peat-based growth medium increased the pH, electrical conductivity, air porosity, bulk density, and nutrition (NPK), and decreased the water holding capacity and total porosity. The use of compost did not affect the percent germination at day 15 of the tomato and pepper seedlings. The addition of compost resulted in better or comparable seedling quality compared with CK and fertilized CK. The best growth parameters were seen in tomato and pepper seedlings grown in T1 and T2, with higher morphological growth in comparison with CK and fertilized CK. However, T2 showed the highest Fusarium concentration compared to compost and all growth media. Fusarium concentrations in T1, T3, and T4 did not differ significantly from those in CK for tomato seedlings, and those in T1 and T4 were also similar to those in CK for pepper seedlings. The results suggest that biogas residues and SMS compost is a good alternative to peat, allowing 100% replacement, and that 20–50% replacement produces tomato and pepper seedlings with higher morphological growth and lower Fusarium concentrations.

Short-term improvement of soil biological activity in biochar-amended organic greenhouse tomato crops

Several studies have shown that adding biochar as soil amendment to agricultural land can increase the sustainability and productivity of cropping systems by sequestrating C from the atmosphere into the soil, by minimizing the emission of greenhouse gases (GHG), by improving soil properties and soil fertility via its effects on porosity, particle aggregation, soil structure, water and nutrients retention, and by improving microbial activity and plant health. Thus, we tested the hypothesis that biochar amendment to different types of soil enhances soil microbial activity, mycorrhizal colonization, plant nutrient availability, plant growth, productivity and reduces GHG when fertilizers are applied monthly or bi-monthly. The experiment consisted of 36 experimental units (e.u.) randomized in a complete block design with 3 replicates. The following organic soils were investigated: 1) a loam, 2) a sandy loam, 3) a sandy soil, 4) a muck soil, 5) a reconstituted organic soil with 40% air porosity and 6) a peat soil amended with sawdust. Half of the e.u. were amended with 10-20% (v/v) biochar (balsam fir + white and black spruces). Tomato plants 'Trust' were cultivated during three growing seasons (February/May to October 2012, 2013, and 2014). The crop was fertilized at 4-week (May to July) and 2-week (August to October) intervals using certified organic amendments. Irrigation was controlled for each soil based on the matric potential measured at 15-cm depth. Effluents from each container were collected and their nutrient content analyzed. Regardless the type of soil, our results showed that biochar amendment increased soil microbial activity expressed by the hydrolysis of fluorescein (FDA) by 14-27% (2013) and 26-41% (2014), and led to lower (~16%, 2012-13) and greater soil CO2 efflux (~11 and 21% when fertilizers were provided at 4- and 2-week intervals, respectively). No significant effect of biochar on root colonisation by mycorrhizae was observed. However, adding biochar to organic soils reduced by 30% (10% v/v) and 50% (20% v/v) the earthworm population. Soils amended with biochar had higher soil mineral content (NO3, P, K, Mg, Fe, Cu, Mn), except for Ca which concentration was equal to control soils and NH4 and Zn which were lower. Biochar amendment reduced by 30% (10% v/v) to 50% (20% v/v) the NO3 content in the leachate. Plant growth, crop yield and leaf mineral content were not influenced by biochar amendment. In conclusion, biochar amendment to different organic soils increased soil biological activity and N retention resulting in lower N leaching and improved crop system sustainability, which might in the long term have beneficial effects on crop performance.