Chemical and physical properties of pruning waste compost and their seasonal variability

Selected chemical and physical properties of 12 different pruning waste compost (PWC) samples were evaluated to assess their suitability as substrates for ornamental plants. Samples were taken periodically from the same composting facility over 18 months in order to determine if there was any seasonal variability. In addition to the PWC samples, a Canadian Sphagnum peat and a commercial growing medium (CGM) were used as standard materials. With respect to PWC properties, pH values were above 8, significantly higher than the pH of peat and the commercial substrate. All samples showed adequate levels of organic matter and correspondingly high cation-exchange capacity (CEC) values. The C/N ratio varied between 22 and 48, significantly higher than the optimal values of 15-20. Although composts were sampled from piles established in different seasons, no significant differences were found in their chemical properties. However, water retention characteristics were affected by seasonal changes in components entering the facility. Comparing the properties of PWC to those of peat and commercial growing medium, this material appears to be an acceptable component of a substrate for container-grown ornamental plants.     

Substitution of peat for municipal solid waste- and sewage sludge-based composts in nursery growing media: effects on growth and nutrition of the native shrub Pistacia lentiscus L

In this study, the effect of a partial substitution of peat for compost on the growth and nutrition of a native shrub (Pistacia lentiscus L.) was tested. Composts were prepared from pruning and municipal solid wastes or pruning waste and sewage sludge. For preparing growing media each compost was added at a rate of 40%, fresh pine bark at 20% or 40% and peat at 20%, 40% or 60%. Aqueous extracts from the substrates did not impair germination of cress (germination bioassay). In relation to plants growing in peat-based substrate (used as a control), plants of the compost-based substrates reached better growth and nutrition, especially when using the sewage sludge-based compost, and the P uptake was notably enhanced. The concentrations of trace elements were far lower than the ranges considered phytotoxic for vascular plants. Detrimental effect derived from using fresh pine bark was not observed.     

Use of composted sewage sludge in growth media for broccoli

In this study, the use of composted sewage sludge (CSS) as a binary component with peat (P) in growth media for a horticultural crop, broccoli (Brassica oleracea var. Botryti cv. Marathon), was evaluated. Four treatments were established, based on the addition of increasing quantities of composted sewage sludge to peat (0%, 15%, 30% and 50%, v/v). Physical, physico-chemical and chemical analyses of the different mixtures of CSS and P were made. Plant growth, biomass production and macronutrient (N, P, K, Ca, Mg), micronutrient (Fe, Cu, Mn, Zn) and heavy metal (Pb, Ni, Cd, Cr) contents of plants were determined. The addition of CSS to P increased plant nutrient and heavy metal contents of plants and electrical conductivity (EC) and bulk density values of the substrates. The use of CSS did not affect the germination rate, even at 50% compost. For broccoli growth, the highest yield was obtained with the medium prepared by mixing the peat with 30% of compost; however, the mixture with the most sewage sludge compost (50%) had the greatest contents of macro and micronutrients.     

Growth substrates made from duck excreta enriched wood shavings and source-separated municipal solid waste compost and separates: physical and chemical characteristics

Production and use of compost is an effective means to reduce wastes, and offers a large potential as growth substrates and source of nutrients. The objective of this study was to determine the physical and chemical characteristics of duck excreta enriched wood shavings (DMC) and source-separated municipal solid waste (MSW) composts and separates, and to assess the physical characteristics of growth substrates made from these two composts and selected substrates. MSW compost separates were the following sizes: F1 > 4 mm diameter, 2 mm < F2 < 4 mm, 1 mm < F3 < 2 mm and F4 < 1 mm. Growth substrates were prepared by mixing DMC and F2 and F3 MSW separates (M/M ratios). Growth substrates A-E consisted exclusively of 10-60% DMC and 20-60% of MSW separates F2 and F3. Growth substrates F-J, and K-O were the same as substrates A E, with 15% M/M brick fragments or shredded plastic added as porosity agents, respectively. Growth substrates (BE/S) made of black earth (BE) and sandy loam soil (Ls) in a 1:4 (M/M) ratio, commercially available peat substrate (Pr) and an in-house sphagnum peat-based substrate (Gs) were used for comparison. Principal component analysis (PCA) showed that DMC was a better material than MSW with respect to porosity and water field capacity. MSW compost and separates differed by their relatively high levels of water-soluble and HCl-hydrolyzable N and increased advantageous water retention capacity. PCA also showed that substrates A-E exhibited porosity and water field capacity similar to those of Pr. Substrates F-J had porosity and water field capacity similar to those of BE/S, whereas substrates K O were more similar to Pr and to substrates A and B. The presented data indicate that DMC and MSW separates were complementary in providing good physical and chemical characteristics to the growth substrates.     

Effect of arbuscular mycorrhizal colonization and two levels of compost supply on nutrient uptake and flowering of pelargonium plants

Two challenges frequently encountered in the production of ornamental plants in organic horticulture are: (1) the rate of mineralization of phosphorus (P) and nitrogen (N) from organic fertilizers can be too slow to meet the high nutrient demand of young plants, and (2) the exclusive use of peat as a substrate for pot-based plant culture is discouraged in organic production systems. In this situation, the use of beneficial soil microorganisms in combination with high quality compost substrates can contribute to adequate plant growth and flower development. In this study, we examined possible alternatives to highly soluble fertilizers and pure peat substrates using pelargonium (Pelargonium peltatum L’Her.) as a test plant. Plants were grown on a peat-based substrate with two rates of compost addition and with and without arbuscular mycorrhizal (AM) fungi. Inoculation with three different commercial AM inocula resulted in colonization rates of up to 36% of the total root length, whereas non-inoculated plants remained free of root colonization. Increasing the rate of compost addition increased shoot dry weight and shoot nutrient concentrations, but the supply of compost did not always completely meet plant nutrient demand. Mycorrhizal colonization increased the number of buds and flowers, as well as shoot P and potassium (K) concentrations, but did not significantly affect shoot dry matter or shoot N concentration. We conclude that addition of compost in combination with mycorrhizal inoculation can improve nutrient status and flower development of plants grown on peat-based substrates.     

Selection of biological control agents against tomato Fusarium wilt and evaluation in greenhouse conditions of two selected agents in three growing media

Two biological control practices are the use of suppressive growing media and the application of biological control agents (BCAs). The goals of this study were: (i) to screen 584 potential BCAs obtained from Fusarium wilt (FW) suppressive growing media; (ii) to evaluate in greenhouse conditions selected BCAs in three growing media with different degrees of suppressiveness of tomato FW. Two isolates selected after screening were identified as Fusarium solani (305) and Streptomyces sp. (A19). Results showed that tomato FW was reduced and total production was improved when both BCAs were applied to a conducive medium (coir fiber). In highly suppressive growing medium (grape marc compost), A19 and 305 inoculations did not improve suppressiveness. In moderately suppressive growing medium (cork compost), only A19 improved this compost to natural grape marc compost suppressiveness level. Therefore, compost suppressiveness of tomato FW depended on the nature of the compost and on the isolates applied.     

Plant response to biochar,compost, and mycorrhizal fungal amendments in post‐mine sandpits

Extreme growing conditions inhibit restoration in sandpit mines. Co‐amendment of soil conditioners such as biochar, compost, and arbuscular mycorrhizal fungi (AMF) may alleviate these stresses and lead to a more successful restoration. We conducted a multiyear restoration experiment in a sandpit in Southern Ontario, Canada, following industrial‐scale grassland restoration protocols. The sandpit substrate was sand with low carbon (C) and nutrients. We tested the effect of biochar, compost, and AMF inoculum in two experiments (plant plugs vs. seed application). In the plant plug trial, we investigated the treatment effects on the growth of eight grassland plant species and colonization of plant roots by AMF over two growing seasons. We found that co‐amending soils with compost plus biochar (20 T/ha + 10 T/ha) was more beneficial than other amendment combinations. Amendments including AMF were not more beneficial to plant growth than those without AMF. In the seed application trial, direct inoculation of AMF in the field combined with high compost addition (20 T/ha or 40 T/ha) resulted in the highest plant cover compared to other treatment combinations. Our results indicate that co‐amending sandpit substrates with biochar, compost, and AMF are practical restoration tools that enhance grassland restoration.     

Reuse of waste materials as growing media for ornamental plants

The use of different waste materials: pine bark, coconut fibre and sewage sludge as substrates in the production of ornamental plants was studied, with an special interest on the suitability of coconut fibre as growing substrate for conifer plants. The plant species tested were Pinus pinea, Cupressus arizonica and C. sempervirens and the substrate mixtures were: (1) pine bark, (2) pine bark with 15% of sewage sludge compost, (3) pine bark with 30% of sewage sludge compost, (4) coconut fibre, (5) coconut fibre with 15% of sewage sludge compost and (6) coconut fibre with 30% of sewage sludge compost. Substrates were physically and chemically well characterized, and 75-cm plants were grown on them for one year. Plant and substrate status were periodically tested along the experiment. As biosolid recycling is the main objective of the present work, the mixtures with 30% of composted sewage sludge will be the most convenient substrate to use. For C. sempervirens and C. arizonica, a mixture between pine bark or coconut fibre and 30% of biosolid compost in volume gave the best results, but the lower cost of the pine bark than the coconut fibre substrate indicated the use of the PB+30% CSS. For P. pinea the research of new combinations between waste products is recommended to attain better results.     

The Challenge of Peat Substitution in Organic Seedling Production: Optimization of Growing Media Formulation through Mixture Design and Response Surface Analysis

Peat replacement is an increasing demand in containerized and transplant production, due to the environmental constraints associated to peat use. However, despite the wide information concerning the use of alternative materials as substrates, it is very complex to establish the best materials and mixtures. This work evaluates the use of mixture design and surface response methodology in a peat substitution experiment using two alternative materials (green compost and palm fibre trunk waste) for transplant production of tomato (Lycopersicon esculentum Mill.); melon, (Cucumis melo L.); and lettuce (Lactuca sativa L.) in organic farming conditions. In general, the substrates showed suitable properties for their use in seedling production, showing the best plant response the mixture of 20% green compost, 39% palm fibre and 31% peat. The mixture design and applied response surface methodology has shown to be an useful approach to optimize substrate formulations in peat substitution experiments to standardize plant responses.     

Effects of a municipal solid waste compost and mineral fertilization on plant growth in two tropical agricultural soils of Mali

A pot experiment was conducted to compare the effects of compost and mineral fertilization on the growth and chemical composition of ryegrass (Lolium perenne L.) in two Malian agricultural soils (Baguinéda, abbreviated as Bgda, 12 degrees 23' S, 7 degrees 45' W and Gao. 16 degrees 18' N, 0 degrees GM). Treatments included: control, NPK alone, NPK + C25, NPK + C50, NPK + C100, PK + C50, NK + C50, NP + C50, K + C50, P + C50, N + C50 and C50 alone, where NPK represents the non-modified Hoagland's solution (corresponding to 271, 95 and 172 kg/ha of N, P and K respectively) and C25, C50 and C100 the different rates (25, 50 and 100 T/ha) of compost. Compost and mineral fertilization significantly increased dry matter production. The application of 50 T/ha of compost alone increased the dry matter yield by 10% and 17.5% while mineral NPK alone, by 69.7% and 65% for Gao and Bgda soils, respectively. The combination of compost and mineral NPK (NPK + C25 for Gao and NPK + C50 for Bgda) showed the highest crop yields.     

The effects of spent mushroom compost and municipal solid waste compost on Phytophthora drechsleri in vivo and in vitro

Leached spent mushroom compost (SMC), municipal solid waste compost (MSWC) and their extracts, were tested to suppress Phytophthora drechsleri in cucumber plants. The composts were mixed with sand-loam soil in sterile and non-sterile types and were used to assess suppressiveness against P. drechselri in greenhouse experiments. The extracts of composts, in both sterile and non-sterile types, were applied to evaluate their effect in suppression of pathogen in vitro. The results of the experiments showed that all applications rate of non-sterile SMC were significantly effective in the control of the pathogen. However the sterile SMC amendments did not have a positive effect on the pathogen suppression in vitro or in vivo, as it was expected. In greenhouse experiments, both composts were effective in controlling pathogen at the rate of 15%, but the treatments amended with higher rate of MSWC did not show a positive effect. The treatments amended with MSWC (15%) and SMC (25%) showed the most suppressive effect in controlling the pathogen. The extract of leached-SMC could inhibit P. drechselri in petri dish.     

Soil quality and barley growth as influenced by the land application of two compost types

Agricultural use of organic residues offers an attractive method for their safe disposal and a valuable source of organic amendments and nutrients. A field experiment was conducted to investigate the influences of 0, 25, 50 and 100 t/ha spent mushroom compost (SMC), forced aeration compost (FAC) and inorganic fertilizer on soil properties and yield of barley (Hordeum vulgare). The considered soil properties (0-15 cm), after a growing season, included pH, EC, available P, Kjeldahl N, available cations, DTPA extractable elements, soil OC content, and bulk density and grain yield was also determined. Application of organic materials increased organic status of the soil and nutrient content. The effectiveness of the two composts on improving the productivity of the soil varied. SMC produced strongest correlations between soil nutrient levels and plant yield. Neither compost raised soil copper and zinc to levels that were of concern and high application rates decreased iron content.     

The inorganic component of green roof substrates impacts the growth of Mediterranean plant species as well as the C and N sequestration potential

Extensive green roofs substrates should meet a list of physicochemical and biochemical requirements to be used as a basis for plant growth: high water holding capacity, good aeration, low bulk density, and proper drainage are some of them. In recent years, the impact of different organic matter doses and the substrate depth on the subsequent plant growth have been deeply studied. By contrast, there are not many publications about the effect of the inorganic component of these substrates on plant development and C and N sequestration potential by the green roof system, and even more under semi-arid Mediterranean conditions. Four substrates were made by mixing the same compost, at 10% by volume, with different inorganic materials: CsB (compost, silica sand, and crushed bricks; 1:1:8), CB (compost and crushed bricks; 1:9), CSB (compost, clay-loam soil, and crushed bricks; 1:1:8), and CsS (compost, silica sand, and clay-loam soil; 1:1:8). These were placed, a depth of 10 cm, on “cultivation tables” in an experimental farm located in the SE of Spain. Two native species were sown in each substrate: Lotus creticus and Asteriscus maritimus. Physicochemical, nutritional, and biochemical properties of the substrates as well as the plant development were evaluated during a 10-month experiment. The CsB and CSB mixtures had good physicochemical properties (high porosity and acceptable water holding capacity) although the levels of C, N, and humic substances were higher in the soil-containing substrates than in the CB and CsB mixtures. The hydrolytic enzyme activity was also promoted in these mixtures. The plant growth pattern showed differences regarding the inorganic composition of the substrate; L. creticus had superior development in the CsB substrate and A. maritimus was able to grow in all tested substrate mixtures, although its cover was low, being a more versatile candidate to establish a green roof cover. The greatest C and N sequestration potential was achieved by the CsS mixture, reaching 1.06 kg TC m⁻² of green roof substrate. Therefore, substrate composition impacts the growth of native plant species as well as the C and N sequestration by the green roof system.     

Growth of ornamental plants in two composts prepared from agroindustrial wastes

Two composts prepared from agroindustrial wastes were assayed as substrates: C1 from brewing waste (yeast and malt) plus lemon tree prunings; and C2 from the solid fraction of olive mill wastewater plus olive leaves. Sixteen substrates were prepared by combining each compost with Sphagnum peat or a commercial substrate (CS) in different proportions. The nutrients (N and K) provided by the composts, which acted as slow-release fertilisers, influenced especially the development of calendula, although the physical and physico-chemical properties such as total pore space and electrical conductivity (EC) were also relevant. On the other hand, in the salt-sensitive calceolaria hybrid, EC and chloride concentration were the main factors influencing growth. Adequate substrates for the development of calendula can be prepared by mixing C1 at up to 75% with peat or at up to 50% with CS, and C2 at up to 50% with peat or CS. For calceolaria, the substrate should have a lower proportion of compost, C1 at up to 50% and C2 at up to 25%, both mixed with peat or CS. Therefore, composts of agroindustrial origin such as these can be used as an alternative to peat and CSs for growing ornamental plants. provided the mixture contains at least 25% peat or CS.     

The effect of spent mushroom compost on Lecanicillium fungicola in vivo and in vitro

Leached spent mushroom compost (SMC) and its extract were tested to suppress Lecanicillium fungicola in white button mushroom. Sterile and non-sterile mixture of SMC and peat were used to assess suppressiveness against L. fungicola in greenhouse experiments. The extract of SMC was prepared with sterile, non-sterile, filtered, supplied with nystatin, streptomycin and penicillin antibiotics to evaluate their effect in suppression of pathogen in vitro. Isolated bacteria from SMC extract were tested for antagonism rate against Lecanicillium fungicola. The results of the experiments showed that all applications rate of none-sterile SMC were effective in control of pathogen. However, the sterile SMC amendments did not have a positive effect on the pathogen suppression in vitro or in vivo, as was expected. The treatments amended with SMC 100% and 60% showed the most suppressive effect in the control of pathogen. Using of non-sterile SMC 20%, 40%, 60% and peat soil were most effective in mushroom yield. The extract of leached SMC showed inhibition of L. fungicola in petri dishes. Three bacteria isolated from extract, Bacillus subtilis, Bacillus licheniformis and Bacillus amyloliquefacien identified using 16s rRNA, showed an antagonistic effect with the fungal growth.     

Effects of pulp mill solids and three composts on early growth of tomatoes

Compost has been proposed as a means of simultaneously diverting organic materials from landfills while producing a valuable product that improves tilth, organic matter content and nutrient supply of agricultural soils. Composts manufactured from different source materials may have markedly different properties however, even if they meet all regulatory requirements. We compared the capacity of composts made from three different combinations of organic wastes (horse manure and bedding, mink farm wastes, municipal solid waste (MSW) and sewage sludge) along with clarifier solids from a chemo-thermomechanical pulp mill, to enhance the growth of tomato (Lycopersicon esculentum L.) seedlings grown in nutrient-poor organic potting soil. Germination and seedling emergence of tomatoes, cress (Lapidium sativum L.) or radish (Raphanus sativus L.) were tested to assess phytotoxicity of the four amendments. Mink farm compost and horse manure compost stimulated root and shoot growth of tomato seedlings but MSW compost and pulp mill solids were strongly inhibitory. MSW compost and unamended potting soil also inhibited seedling emergence and pulp mill solids produced stunting and deformities in radish and cress seedlings. Both toxic constituents and nutrient imbalances may be responsible for the growth-inhibiting effects of these amendments. Application of pulp mill solids to agricultural soil without composting may lead to deleterious effects on vegetable crops.     

Effects of water additions,chemical amendments,and plants on in situ measures of nutrient bioavailability in calcareous soils of southeastern Utah,USA

Barren, subgrade serpentine substrates are difficult to revegetate due to N, P, and K deficiencies, low Ca:Mg molar ratios, potentially high levels of heavy metals including Ni, Cr, and Co, low organic matter, low CEC, and poor water holding capacity. Several large, bare roadcuts exist in the North Coast Ranges along the west coast of California, USA. Substrate was collected from a large roadcut that has remained barren for more than a decade despite conventional surface amendment with NPK fertilizer and seeding with a mix including nonserpentine grasses and herbs. Although serpentine plant communities have been studied globally in great detail, very little information exists on how to effectively restore these communities after drastic disturbance (removal of topsoil and loss of biological activity). This rhizotron study examined how surface layering and mixing yard waste compost into serpentine substrate affected biomass production, rooting distribution, and tolerance of native, as well as invasive grass species that grow on serpentine. Roots of less serpentine-tolerant species became necrotic upon contact with the serpentine substrate in the layered compost application treatment. The roots of highly serpentine-tolerant species, however, displayed a superior tolerance to the serpentine substrate and were able to grow through its entire depth. Mixing the compost into the serpentine substrate significantly improved the Ca content of the growing medium, allowing the less serpentine-tolerant species to root through the entire depth. Although the compost surface layer treatment promoted growth of the highly serpentine-tolerant species in the serpentine substrate, mixing the compost amendment into the substrate would also permit additional desirable revegetation species to become established.     

Improving rock phosphate availability through feeding, mixing and processing with composting manure

The objective of this study was to improve the availability of phosphorus (P) from rock phosphate (RP) through feeding, mixing and composting manure. The experiment was conducted as a 3 x 2 split-plot design. Manure was collected from 12 Boran steers (200+/-4.5 kg live weight) fed a basal diet of Napier grass (Pennisetum purpureum) at 2.5% body weight on a dry matter (DM) basis. The main plot treatments were (i) manure from steers supplemented with 113 g Busumbu rock phosphate (BRP) per day (FBRP), (ii) manure from steers not supplemented with BRP, feces mixed with 113 g BRP per day (MBRP) and (iii) manure from steers not supplemented with BRP and feces not mixed with BRP (CONT). The sub-plots comprised composting the manure either (i) mixed with 440 g of wheat (Triticum aestivum L.) straw per kg fresh feces (WS) or (ii) without straw (WOS). The manure was composted in 200 L plastic bins for 90 days. After 90 days, P availability was evaluated (i) by aerobic laboratory incubation at 25 degrees C for 1, 2, 4, 8, 12, and 16 weeks and (ii) by greenhouse agronomic evaluation study using maize (Zea Mays L.) as the test crop in either a humic Nitosol or an Andosol. In the laboratory incubation study, resin P was higher (p<0.05) for the WS compost than for the WOS compost; values were higher (p<0.05) for the Andosol than for Nitosol and followed the order of FBRP-WS, Andosol>FBRP-WS, Nitosol>MBRP-WS, Andosol>MBRP-WS, Nitosol>FBRP-WOS, Andosol>FBRP-WOS, Nitosol. In the greenhouse evaluation, maize crops in the WS compost had higher (p<0.05) biomass yield than the reference fertilizer, triple super phosphate, (173% versus 196%; Andosol and Nitosol, respectively). The biomass yield and P uptake relative agronomic effectiveness (RAE) for WS compost was also higher (p<0.05) than that of WOS compost (184 versus 3+/-0.8 and 242 versus 162+/-0.2, WS and WOS, biomass yield and P uptake, respectively). Nitosol biomass yield and P uptake RAE were also higher (p<0.05) than for the Andosol (99 versus 88+/-0.8 and 332 versus 72+/-0.2, Nitosol and Andosol, biomass yield and P uptake, respectively). The results show that P-enriched composting in the presence of wheat straw significantly increased P availability and increased plant growth. However, in terms of plant growth, there was no additional benefit of first feeding the RP to steers before composting the manure because most of the RP fed seem to have been utilized by the animal.     

Assessment of suitability and suppressiveness of on-farm green compost as a substitute of peat in the production of lavender plants

Suppression of root rot diseases of ornamental plants is a potential benefit of formulating soilless container media with compost. A green compost (green nursery compost, GNC), obtained by a circular-economy approach from residues of pruning of woody plants and grass clippings during the nursery activities was analysed for its suppressiveness of root rot diseases using lavender. To this end, a bioassay was develop by formulating potting mixes containing GNC with two rates of peat substitution (25% and 50%) and infested with the root rot pathogens Sclerotinia sclerotiorum, Rhizoctonia solani and Phytophthora nicotianae. Contrasting results were obtained by using both substrates with a significant reduction of root rot by S. sclerotiorum, no effect on the containment of that by P. nicotianae, and an increase of symptoms caused by R. solani. The specific suppressiveness observed may be attributed to the colonisation of compost by specific groups of antagonistic microorganisms. This hypothesis was investigated by the analysis of culturable fungal community, which resulted in the isolation of Trichoderma harzianum and T. atroviride as preponderant fungal species. Trichoderma representative isolates exerted in vitro antagonistic activities against the target pathogens with varying efficiencies indicating the employment of multiple complementary mechanisms, which may have contributed to the observed specific suppressiveness. Both substrates containing GNC resulted suitable for nursery cultivation of lavender, showing a growth performance similar to that obtained with peat-based substrate. Present results indicate that on-farm compost is a suitable component of mixed-peat substrates capable to support plant growth and provide specific disease suppression.