Compost Mulch Research Articles

Carbon and trace element mobility in an urban soil amended with green waste compost

The amendment of degraded urban soils using recycled organic wastes offers potential improvements to physicochemical status and functionality, but there is a paucity of knowledge on the potential impact on residual contaminants in soil. The aim of this study was to evaluate the mobility of trace metals and arsenic (As) through an urban soil following amendment with green waste compost over an annual cycle. Rhizon soil pore water samplers were inserted into the sides of a soil pit located in a relatively undisturbed urban lawn, which was amended with a surface mulch of green waste compost. Regular sampling and analysis of pore water from the compost and at varying soil depths was carried out, in comparison to an adjacent profile, which had not been amended. Rapid dissociation of As from compost was found following its surface deposition as a mulch. Periods of high rainfall enhanced As mobility through upper soil horizons to deeper technogenic layers with higher pH. Copper (Cu) concentrations in soil beneath compost were substantially elevated and strongly correlated with dissolved organic carbon (DOC) released from compost into pore water. Seasonal biological activity, rather than soluble carbon, determined the patterns of mobility and release of zinc (Zn) in both compost-amended and control soil. Location of more stable concentrations of lead (Pb) at lower depths reflected reduced atmospheric fallout or the composition of the lower strata. Flushes of DOC from compost also enhanced mobility of residual cadmium (Cd) in soil. Amendment of urban soils with green waste compost mulches impacts on residual trace element contaminants and may enhance mobilisation of harmful elements to the wider environment, meaning that caution is needed when applying compost to soils with elevated levels of trace metals.

British Columbia Regional Meeting, 2008

British Columbia Regional Meeting, 2008

Cumulative Sediment, Nitrogen and Phosphorus Losses From Bare and Compost-Amended Fill Slopes

Constructed slopes are often amended with compost in order to reduce erosion and improve vegetation establishment. These composts can contain soluble nutrients which may become a source of pollution to nearby water bodies. This study examined annual sediment and nutrient losses in surface runoff from nine potential types of compost treatments. These included treatments that tested differences between two types of compost (mature and immature) as well as various methods of compost application, including surface blankets and incorporation. Over an entire rain season, there were no significant differences in sediment and nutrient (NO3−, NH4+ and P) losses between the two compost types when they were applied as surface blankets. In treatments where a compost blanket was applied over the top of compost tilled into the soil there was a significant reduction in sediment loss compared to treatments where compost was just tilled into the soil, without a blanket overlay. This treatment reduced sediment loss to a level that was comparable to vegetated treatments. Although this treatment had twice the amount of compost as the treatments with just a surface blanket of compost, it lost less than a fourth as much nitrate in its runoff over the year as either compost type when they were applied as a blanket over bare soil. The greatest sediment loss came from treatments in which compost was tilled into the soil with no additional compost surface blanket. Effects of different treatments were confounded by a gradient in slope hydrology that resulted in a relationship between runoff volume and plot position along the slope. Our statistical analysis took this into account and the data presented represent our attempt to control for this nuisance variable. Our findings suggest that compost can be used as a soil amendment and as an erosion control measure on constructed slopes at a minimal risk of nutrient loss if it is done in the proper manner. We recommend that compost be incorporated into the soil to facilitate greater infiltration and that a blanket of compost or woody mulch be placed over the soil to provide surface erosion protection.

Soil and Redosier Dogwood Response to Incorporated and Surface-applied Compost

Although compost can improve soil properties related to plant growth and water quality, the value of amending landscape beds for trees and shrubs has been questioned. This research assesses short and midterm effects of compost application and bark mulch on soils and plants in landscape beds and compares the effects of compost applied to the surface or incorporated. Trees and shrubs were established in 2001 in a replicated field experiment with the following treatments: 1) unamended control; 2) compost (7.6-cm depth) applied to the surface; 3) 7.6 cm compost incorporated by rototilling to a depth of 20 cm; 4) bark mulch (7.6 cm); 5) compost surface-applied (7.6 cm) + bark mulch (7.6 cm); and 6) compost incorporated + bark mulch. Soil measurements were made one or more times between 2001 and 2007, including bulk density, compaction, infiltration, aggregate stability, soil moisture tension, total carbon (C) and nitrogen (N), nitrate-N, Bray-phosphorus, exchangeable potassium, and pH. Bark and compost mulch depths were determined three times and plant growth measured annually. Half the depth of surface-applied compost and 26% to 41% of the initial soil C increase from incorporated compost remained 5 years after application; and significant changes in bulk density, compaction, infiltration, and nutrients were apparent. Compost incorporation had a greater effect than surface application on soil C, N, and bulk density. Infiltration was similar in incorporated and surface treatments, and nutrient availability was similar except for N. Soil moisture retention was improved with surface-applied compost. Bark had similar effects as surface-applied compost on bulk density, soil moisture retention, and infiltration. During the first 4 years after transplanting, dogwoods in the compost incorporated + bark mulch treatment typically had larger shoot growth indices. By Year 5, treatment no longer influenced shoot growth. Plants in compost-treated plots had darker green leaves. Surface application of compost could provide significant benefits where incorporation is not feasible.

Erosion Control Performance of Compost Prepared from Harvested Aquatic Weed

A rainfall simulator was used to measure the ability of compost prepared from harvested aquatic weed (AWC) to reduce runoff and erosion from experimental plots compared with a bare earth control and commercially produced composted mulch and soil conditioners. A 1 in 10 year intensity rainfall event (67 mm hr−1) was applied to each plot for 30 min and runoff water was captured and water volume recorded. Treatment had no effect on the amount or rate of runoff. Water quality samples were collected and analysed for a number of parameters including the concentration of nutrients and total suspended solids (TSS). Load of exported nutrient and sediment (kg ha−1) was also calculated for total runoff. The application of AWC significantly (P<0.05) reduced the export of suspended solids from the plots, relative to the bare earth control by 34%. However, AWC was less effective in reducing nutrient and sediment export compared with the other compost treatments because it contained a smaller proportion (5.5%) of the larger (>15 mm) sized particles, which physically shield the soil surface and help trap entrained soil particles. Assessment of pasture growth and ground cover at 6 and 12 weeks after the rainfall simulations showed that AWC significantly (P<0.05) increased pasture dry matter production and ground cover relative to the bare earth control, which indicates it would be a good medium for pasture establishment, particularly in soils denuded of topsoil. Moreover, applying AWC at a depth of 20 mm supplied an equivalent of 699 and 95 kg TN and TP ha−1, respectively. Over time this should mineralise and provide some benefits with respect to soil fertility and plant nutrition.

Use of Red Clover-Based Green Manure in Leek Cultivation

ABSTRACT In a field experiment with leek, four forms of green manuring with red clover were compared; direct incorporation, biogas residue, compost and green mulch. The application rates were based on concentrations of nitrogen (N) and carbon (C) in the clover roots and shoots in the direct incorporation treatment, and the N-availability. A practically appropriate mulch application rate was included for the green mulch treatment. A mineral fertilizer treatment and an unfertilized control were also included. The criteria compared were; crop yield, crop yield in relation to area of red clover harvested and N-recovery in crop and soil. No differences in leek yield were observed within the treatments with the same amount of N or C added. Leek yield as a function of red clover area harvested was highest in the treatment with the lowest input of biogas residue. The area of red clover needed to produce the same N dose as in the direct incorporation treatment was 10 and 20% greater in the treatments with biogas residue and mulch, respectively, but 50% greater in the compost treatment. The proportion of N supplied with the manure that was taken up by the leek crop or left in the soil profile was around 20% for direct incorporation and application of biogas residue. The lowest fraction of N recovered (4%) was at the lowest dose of green mulch. The amount of mineral N left in the soil profile was highest in the treatment with the highest input of biogas residue, 105 kg ha−1 compared with between 32 and 53 kg ha−1 in the other treatments.

Effects of ground cover (straw and compost) on the abundance of natural enemies and soil macro invertebrates in vineyards

Abstract1 Herbicides are commonly applied under grapevines in Australia to remove weeds and thereby to avoid water loss through transpiration.2 Interest in sustainability promotes a reduction in chemical inputs, including herbicides, leading to trials with surface mulches to suppress weeds.3 Surface mulches may also influence the abundance of a range of invertebrates. Potentially, an increase in natural enemies will contribute to pest control and encourage a reduction in pesticide application.4 We used three trapping methods and direct soil sampling to assess invertebrates at ground level, in the canopy and in the soil to determine the influence of mulch on natural enemies, potential pests and soil macroinvertebrates, including earthworms.5 Collections sorted to family demonstrated that the addition of straw or compost mulches increased natural enemies collected with pitfall traps and soil organisms. However, there was no clear indication of the overall superiority of either mulch.6 Abundance of ground beetles, parasitoid Hymenoptera and spiders collected with pitfall traps were increased by the addition of mulches. In the canopy, predatory and parasitic Diptera and predatory Hemiptera increased after mulching.7 Earthworms collected by hand sorting soil increased with straw mulching.8 No influence on pests was detected. Although Lepidoptera and Sigmurethra, collected in pitfall traps, increased with straw mulching, neither included pest species.9 The results are discussed with reference to the potential economic impact of mulches.

Evaluation of Revegetation from Blanket Applied Composts on a Highway Construction Site

Compost has been evaluated as a stormwater best management practice for erosion control, but site revegetation is the ultimate goal of most stormwater plans. In this study, three different composts applied as a surface layer or mulch at two depths of 5 and 10 cm were compared with topsoil and subsoil as a medium for crop growth and weed suppression during revegetation of a highway right-of-way. Compost was shown to be as effective as topsoil and subsoil controls for crop growth, while significantly reducing growth of weed species. There were no significant differences between 5- and 10-cm depths of composts, indicating that the shallower depth would be adequate for establishing a cover crop and achieving weed suppression. Compost mulches offer promising opportunities for crop and weed management during revegetation of roadsides and other disturbed landscapes.

Removal of added nitrate in cotton burr compost, mulch compost, and peat: Mechanisms and potential use for groundwater nitrate remediation

We conducted batch tests on the nature of removal of added nitrate in cotton burr compost, mulch compost, and sphagnum peat that may be potentially used in a permeable reactive barrier (PRB) for groundwater nitrate remediation. A rigorous steam autoclaving protocol (121 °C for 2 h each day for three consecutive days) for the cotton burr compost and autoclaving of all labware and the nitrate working solutions resulted in drastically different results compared to the non-autoclaved treatment. In the non-autoclaved cotton burr compost, added nitrate at 20 mg N l −1 decreased rapidly and was not detected after 3 d; whereas, the autoclaved cotton burr compost showed persistent nitrate above 15.5 mg N l −1 even after 10 d, which is comparable with nitrate concentrations above 17.6 mg N l −1 in a treatment using NaN 3 at 1000 mg l −1. Dewaxed cotton burr compost showed decreased nitrate reduction compared to the pristine cotton burr compost. No nitrate reduction was detected in the dewaxed sphagnum peat. It is concluded that nitrate removal in the organic media is controlled by microbiologically mediated processes. The use of readily available cotton burr and mulch composts may offer a cost-effective method of nitrate removal from contaminated groundwater.

Composted Yard Waste Affects Soil Displacement and Roadside Vegetation

The benefits of composted yard waste applied as a mulch were demonstrated in a field study at two locations and supporting greenhouse research. Compost was applied to eroded roadside slopes of about 12° and 27° to determine the influence on soil displacement and establishment and/or enhancement of permanent roadside vegetation. Treatments consisted of compost rates of 5 cm and planted with asiastic jasmine (Trachelopermum asiaticum), 5 and 10 cm, seeded with 110 or 220 kg·ha–1 80:20 bahiagrass (Paspalum notatum Flugge): bermudagrass (Cynodon dactylon L.) seed mix by weight, straw erosion control mats, and bahiagrass sod. Compost treatments effectively controlled soil displacement regardless of compost rate or seeding with turfgrass at both locations. Effects on roadside vegetation and visual quality varied with location. Asiatic jasmine did not establish at either site. Compost mulch applications increased total vegetation, turfgrass density, and quality at the site with 27° slope and 4% initial soil organic matter content, but resulted in a decline in cover at the site with a 12° slope and &lt;1% organic matter content. Compost mulch can effectively prevent soil displacement from roadside slopes, but may not promote establishment or enhancement of permanent vegetative cover.

Are decomposition and N release from organic mulches determined mainly by their chemical composition?

The influence of chemical composition on the decomposition and N release rates from samples of 11 organic mulches enclosed in nylon mesh bags was assessed under field conditions at the University of California, Riverside. Time was adjusted by temperature and the cumulative temperature-adjusted days (tad) were used to model the pattern of the decay and N release. The chemical composition of the mulches significantly affected their decay. In descending order of significance, the concentration of the polar extractable carbon fraction ( C P) and the acid insoluble fraction ( C AI) were significantly correlated with decomposition during the year of study. Correlation was positive with C P and N and negative with C AI (mostly lignin). The C P was selected as the best predictor for mulch decomposition during the early and intermediate phases of this process (36 and 195 tad), but C AI was selected as the best variable for predicting the fraction of the initial mulch mass remaining at the end of the study (397 tad). N was immobilized, as indicated by temporary increases in N masses in mulches above initial conditions, in shredded redwood, pine trimmings and in two of three compost mulches. Immobilization was most pronounced during the first 36 tad of the study, with a maximum rate that varied from 6 to 11.5% above the initial N concentrations. At the end of the study N releases ranged from 97% of initial N (grass clippings) to only 8% (one of the composts.) The C P was selected as the best predictor for N remaining in the four sampling dates (397 tad) and explained from 52 to 68% of the variation in N release as a percentage of initial N content.

Estimation of oxygen concentration in the soil gas phase beneath compost mulch by means of a simple method

A simple method for measuring oxygen level in the root zone of plants growing in non-saturated humidity conditions is presented. The oxygen concentration of soil air under layers of compost mulch was measured using galvanic oxygen sensors mounted in diffusion chambers and the results were compared with infrared gas analyses of soil air samples. Two trials showed that a moderate (5–10 cm) layer of compost mulch has no major effect on the oxygen level in soil under dry conditions, while a 15-cm mulch layer results in an oxygen depletion of short duration. In wet conditions, oxygen depletion under even a 5-cm layer of compost mulch results in a significant lowering of the oxygen level in soil and lasts for days in conditions of much precipitation. Root functions can be negatively affected at <10% oxygen concentration of the soil air. Compost mulch can decrease oxygen concentrations to well below this critical level in wet or poorly drained soils and thereby contribute to the stress load of urban trees. The use of galvanic oxygen sensors proved to be a simple and low-cost method for measuring soil-air oxygen.

(415) Evaluation of Weed Control Practices in an Organic Bell Pepper Production System

A 2-yearfield study in Lexington, Ky., evaluated the use of mulches in two organic production systems for bell peppers. Two planting strategies, flat ground and plastic-covered raised beds, and five weed control practices, straw mulch, compost mulch, wood chip mulch, corn gluten, and “living mulch” clover were tested. In 2003, the mulches were applied at planting, while in 2004, shallow soil cultivation was used for 6 weeks prior to mulch application. In 2003, the experimental field had been under a winter wheat cover crop; in 2004, the field had been cover cropped for more than a year prior to planting with sudex/cowpea (Summer 2003) and rye/hairy vetch (Winter/Spring 2004). Bell pepper yields in both bed treatments were very low in 2003 due to extensive weed competition. In 2004, plastic-covered raised beds coupled with mulching in-between beds resulted in significantly higher yields than the peppers grown on flat ground. These yields were as high as yields from a conventional pepper trial conducted on the same farm. Compost mulch, continuous cultivation, and wood chip mulch provided excellent weed control in 2004. Straw mulch was variable in its weed control efficacy; corn gluten and “living mulch” clover were ineffective.

Pest management benefits of compost mulch in apple orchards

The effect of compost application on weed, fungal, and insect pest management in apple orchards was investigated from 1999 to 2001. Composted poultry manure was applied in June 1999 to half of two small research orchards which had previously received little or no management. The compost provided weed control for 1 year after application. There was no effect of compost on apple scab (Venturia inaequalis) infection. In a laboratory experiment, growth of the brown rot fungus (Monilinia fructicola) was significantly slower on a compost substrate than a sterilized compost substrate. The compost significantly affected arthropod abundance during two years after application, with more predators and fewer herbivores in the compost treated plots. Populations of spotted tentiform leafminer ( Phyllonorycter blancardella) and migrating woolly apple aphid (Eriosoma lanigerum) nymphs were reduced in the compost plots. This study showed that the use of compost in an orchard ecosystem is beneficial to management of weed, fungal, and insect pests. The use of compost as a mulch in orchard ecosystems should be encouraged as a sustainable management practice because of a potential to reduce pesticide use. Published by Elsevier B.V.

Habitat manipulation of the apple orchard floor to increase ground-dwelling predators and predation of Cydia pomonella (L.) (Lepidoptera: Tortricidae)

Abstract Augmenting generalist predator populations in new apple ( Malus domestica Bork) plantings could potentially aid in the establishment of balanced orchard ecosystems that are less susceptible to pest outbreaks. Habitat can be an important factor in retaining predators in a system and can affect predator efficiency. We investigated the potential of increasing a complex of generalist ground-dwelling predators and enhancing biological control in a young ‘Golden Delicious’ apple orchard through ground habitat manipulation. We modified the orchard floor with four comparative habitat treatments: (1) detritus-rich compost mulch layer, (2) detritus-free synthetic mulch layer, (3) herbicide-treated vegetation thatch, and (4) bare soil with vegetation hand-removed. Relative abundances of predators and alternative prey in the habitats were measured with pitfall trapping throughout the growing season. Predation was measured using sentinel Cydia pomonella larvae and directly observed in night experiments. Throughout the season, the compost mulch treatment consistently supported significantly greater densities of alternative prey resources for predators, and generalist predators were more abundant in the compost mulch than the other habitats. Predator complex abundance was positively correlated with increasing alternative prey availability in the compost mulch habitat. However, predation of C. pomonella was significantly lower in the compost mulch than in the herbicide-treated thatch habitat. Our study revealed that a prey-rich organic mulch can enhance ground-foraging generalist predators on the orchard floor, but habitat structure may be more important than alternative prey for predation of C. pomonella .

Mulching with compost improves growth of blue spruce in Christmas tree plantations

Compost derived from source-separated organic household waste was used in a blue spruce (Picea pungens var. glauca) Christmas tree plantation as a mulch in tree rows in a 3–year trial. The amounts, which were applied at the start of the experiment, were 29 t ha –1 (treatment 1) and 58 t ha –1 (treatment 2; dry matter), corresponding to 3 and 6 combined annual compost applications, respectively. The compost mulch reduced the shoot growth of the 6-year-old blue spruce trees in the first year after compost application by 6% and 8% in treatment 1 and 2, respectively. In the second year, growth was enhanced for 8% and 5% in treatment 1 and 2, respectively. The growth enhancement was well proportioned and characterized by increases in both shoot growth and the number of lateral buds. In the third year, shoot growth was no longer significantly different from the untreated control. The soil contents of plant-available nitrogen and potassium, pH and electrical conductivity increased significantly through the compost application. The slightly increased water content of the soil positively influenced tree growth at this dry and sandy site.

Engineered bioretention for removal of nitrate from stormwater runoff.

A bioretention unit is a simple, plant- and soil-based, low-impact treatment and infiltration facility for treating stormwater runoff in developed areas. Nitrate, however, is not attenuated in conventional bioretention facilities. Thus, this study systematically evaluated a reengineered concept of bioretention for nitrate removal via microbial denitrification, which incorporates a continuously submerged anoxic zone with an overdrain. Experimental studies were performed in four phases. In the first two phases, column studies demonstrated that, overall, newspaper is the best solid-phase electron-donor substrate for denitrification out of the set studied (alfalfa, leaf mulch compost, newspaper, sawdust, wheat straw, wood chips, and elemental sulfur) based on superior nitrate removal and effluent water quality. The nitrate loading and hydraulic loading studies in the second phase provided design information. In the third phase, system viability after 30- and 84-day dormant periods was evaluated in column studies, demonstrating that newspaper-supported biological denitrification should be effective under conditions of intermittent loadings. Finally, in the fourth phase, pilot-scale bioretention studies demonstrated the effectiveness of the proposed design, showing nitrate plus nitrite mass removals of up to 80%. These results indicate that engineered bioretention for the removal of nitrogen from stormwater runoff has the potential for successful application as an urban stormwater treatment practice.

Effects of Initial Site Treatments on Early Growth and Three‐Year Survival of Idaho Fescue

AbstractPrairies in the Pacific Northwest have been actively restored for over a decade. Competition from non‐native woody and herbaceous species has been presumed to be a major cause for the failure of restoration projects. In this research, plugs of the native prairie bunchgrass, Festuca idahoensis Elmer var. roemeri (Pavlick), were grown from seed in a nursery and transplanted into a grassland site dominated by non‐native pasture grasses. The growth of the plants was followed for three years, and biomass of all volunteer plants was measured. Before planting, five treatments were applied to the plots: removal of vegetation by burning, removal of vegetation by an herbicide‐and‐till procedure, soil impoverishment by removal of organic matter, fertilizer application, and compost mulch application. Initial growth of Idaho fescue plugs was greatest with fertilizer and compost mulch. Plants grown in mulched plots were also able to photosynthesize later into the dry summer season. After the first year, plots initially fertilized or composted had the lowest survival rate of Idaho fescue. Impoverished and herbicide‐and‐till plots had the greatest 3‐year survival. Mulched plots supported the greatest weed growth after three years. Stressful environments give a competitive advantage to Idaho fescue in prairie restoration projects. As weedy species increase, growth and survival of Idaho fescue decreases.

Immature Compost Suppresses Weed Growth Under Greenhouse Conditions

The influence of immature municipal solid waste-biosolids composts on emergence and mean days to emergence (MDE) of several weed species was evaluated in a pot trial under greenhouse conditions. The experiment consisted of placing a 7.5 cm deep layer of three-day-old immature compost, a mature and stable compost, an artificial medium or control sand as a mulch on ivyleaf morning glory seeds. Immature three-day-old compost decreased percentage emergence, shoot and root dry weight, and increased MDE of ivyleaf morning glory. In an experiment with eight-week-old immature compost utilizing mulching depths of 2.5, 5, 7.5, 10 cm and the untreated control on seeds of three weed species, common purslane did not emerge under any of the immature compost treatments. The MDE of ivyleaf morning glory and barnyard grass increased linearly as immature compost depths increased. Next, eight economically important weed species were sown in pots with either mature or immature (eight-week-old) compost utilizing mulching depths of 2.5 and 10 cm, in addition to an untreated control. Control pots yielded higher percentages of emergence than compost treatments for all species evaluated. Common purslane, large crabgrass, pig-weed, Florida beggarweed, and dichondra did not emerge through a 10-cm deep layer of mature compost mulch, or 2.5 or 10 cm deep layer of immature mulch. Significant compost maturity/depth interactions were observed for percent emergence on common purslane, ground cherry, large crabgrass, Florida beggarweed, and ivyleaf morning glory. A thinner layer was required to suppress germination using immature eight-week-old compost as compared to mature and stable compost. Immature (three-day or eight-week-old) compost containing acetic acid concentrations of 2474 and 1776 mg.kg−1 respectively reduced percentage emergence of several economically important weed species. These studies suggest that immature composts can be used to control weeds under conditions where spatial separation is maintained between the crop and the compost and phytotoxic fermentation products do not affect the health of the mulched plants and where odors associated with such partially stabilized products do not pose problems.

Use of fabric and compost mulches for vegetable production in a low tillage, permanent bed system: Effects on crop yield and labor

AbstractWe tested the usefulness of mulching with polypropylene landscape fabric and compost as alternatives to bare soil for growing red cabbage and watermelon. Polypropylene landscape fabric has features similar to the polyethylene film that is popular for commercial vegetable production, but its durability permits multi-year use, which would reduce excessive waste produced from the typical single-season use of polyethylene film. On the other hand, compost used as mulch enhances soil development while providing weed suppression and water retention, among other benefits. Yields of red cabbage and watermelon were measured for 3 years in plots receiving either 10 cm compost, landscape fabric, or no mulch. Labor associated with crop production and weed suppression was measured as time spent on each task. Cabbage yields over 3 years followed the treatment order of compost &gt; no mulch &gt; fabric, while for melon yields it was compost &gt; fabric &gt; no mulch. Total labor required over 3 years for both crops, according to treatments, was fabric &gt; compost &gt; no mulch. However, labor for the fabric-treated plots dropped sharply after the first year, because fabric was left in place after initial placement. Labor for unmulched cabbage plots increased over time due to weeding and transplanting; labor for unmulched and compost-mulched melon plots increased for the same reasons. Compost provided the highest crop yields with a moderate labor investment. Surface-applied compost substantially increased underlying soil nutrient levels. The study indicates that polypropylene landscape fabric may be a potential alternative to the more traditional polyethylene film for permanent beds in vegetable production.