Dennis B. McConnell

Uses and benefits of MSW compost: A review and an assessment☆

Abstract Soil incorporation of composted municipal solid waste (MSW) usually results in a positive effect on the growth and yield of a wide variety of crops and the restoration of ecologic and economic functions of land. Agricultural uses of MSW have shown promise for a variety of field crops (e.g., maize, sorghum, forage grasses) and vegetables for human consumption (e.g., lettuce, cabbage, beans, potatoes, cucumbers). Responses by plant systems have ranged from none to over a twofold increase in yield. Specific responses are crop and site dependent. In most cases, yields were highest when composts were applied with fertilizer management programs. In some cases, elevated trace metal uptake was noted with lead and boron of greatest concern. Where long-term monitoring has been possible, benefits persist and actually accrue when sound soil/crop management practices are followed. Levels of toxic elements in plants for human consumption are either not well known or thresholds were not reached, as little mention was made in the literature. Container-grown ornamental crops are not for human consumption and this concern does not apply. However, they are high value commodities, and therefore, safe, satisfactory growth is important. Because composts can replace peats and barks which are becoming expensive, this application shows great promise. Silvicultural or forestry applications also represent a nonconsumptive, potentially large use of compost. These uses range from low volume/high value nursery and Christmas tree applications to high volume/low value uses in forest regeneration. Land reclamation whether for minespoil, landfill cover or soil stabilization as in the establishment and rehabilitation of road shoulders represents another potential beneficial use. However, tonnages recycled in this way will be less than in agriculture and silviculture. Compost utilization will occur in response to a number of factors including their benefits to soil-plant systems, especially those having economic value. As important, however, is the realization by policymakers that composting and compost use in agro or natural ecosystems are an integral part of the entire waste management system. Thus, a systems perspective that includes full cost accounting of waste collection, handling, and processing must incorporate marketing, distributing, and recycling in a life cycle analysis that reflects external costs and societal benefits for composting-based solid waste systems to be competitive.

Physical and chemical properties of soils as affected by municipal solid waste compost application

Abstract The organic matter content of composted MSW is high and its addition to soil often improves soil physical and chemical properties and enhances biological activities. Most agricultural benefits from MSW compost application to soil are derived from improved physical properties related to increased organic matter content rather than its value as a fertilizer. Composts provide a stabilized form of organic matter that improves the physical properties of soils by increasing nutrient and water holding capacity, total pore space, aggregate stability, erosion resistance, temperature insulation and decreasing apparent soil density. Application of MSW compost improves the chemical properties by increasing pH (in acid soils), electrical conductivity, cation exchange capacity, and soil nutrient content.

Gibberellic acid affects growth and flowering of Philodendron 'Black Cardinal'

A single foliar spray of gibberellic acid (GA3) at concentrations of 125, 250, 500, or 1,000 mg L−1 induced flowering of Philodendron‘Black Cardinal’ (an interspecific hybrid developed from a series of crosses among P. wendlandii, hastatum, erubescens, imbe, fragrantissimum, and an unnamed species) in approximately 170 d. Percentage of plants induced and mean flower number per plant increased as GA3 concentrations increased. Compared to unsprayed plants, the number of new leaves decreased, petiole lengths of new leaves and length of the largest leaf increased, but leaf width was unaffected among sprayed plants. One hour before the spathe started to unfurl, spadix temperatures increased, and temperatures in the male portion of the spadix rose by 10 °C above ambient as the spathe fully opened. Elevated temperatures were recorded for about two hours and returned to ambient within five hours. Spathes remained open for about five hours. A creamy white spadix with a contrasting burgundy spathe resulted in more aesthetically pleasing plants than with foliage alone. Because of the short period of display, the open spathe would not increase additional ornamental value of Philodendron‘Black Cardinal’ in the marketplace. However, if breeding is the purpose of flowering induction, spathes should be cut away from the spadix to facilitate pollination.

Production and Interior Performances of Tropical Ornamental Foliage Plants Grown in Container Substrates Amended with Composts

Three representative Florida composts were mixed by volume with sphagnum peat and pine bark to formulate 12 container substrates. After physical and chemical characterization, the substrates, along with a control, were used to grow containerized Cordyline terminalis ‘Baby Doll’, Dieffenbachia maculata ‘Camille’, and Dracaena fragans ‘Massangeana’ cane. All substrates were able to produce marketable plants, but only five or seven, depending on plant genus, of the 12 compost-formulated substrates resulted in plants comparable or superior to those of the control substrate. The five also had substrate shrinkage equal to or less than the control. Plants were then moved to an interior evaluation site to determine the suitability of compost-formulated substrates in sustaining foliage plant growth under an interior environment. During a six-month interior evaluation, the plants maintained their aesthetic appearances. Based on plant growth parameters and quality ratings as well as substrate shrinkage both in production and interior evaluation, five of 12 compost-formulated substrates were identified to be equal or superior to the control. This study showed that the three composts, after being appropriately mixed with sphagnum peat and pine bark, can be used as container substrates in every phase of tropical foliage plant production and utilization.

Shoot organogenesis from petiole explants in the aquatic plant Nymphoides indica.

A protocol for rapid shoot organogenesis from petiole explants of the ornamental aquatic plantNymphoides indica L. Thwaites O. Kuntze was developed for use in future mutation breeding and cultivar selection studies. Optimum culture conditions for shoot organogenesis were determined. Effects of factorial combinations of 2-iP, BA or kinetin (0–25 μM) in factorial combination with IAA or NAA (0–25 μM) were examined. On the basis of regeneration frequency (80%) and adventitious shoot number (11.5 shoots per explant), most efficient shoot organogenesis occurred on petiole explants cultured on a basal medium consisting of full-strength MS inorganic salts, 0.56 mM myo-inositol, 1.2 μM thiamine-HCl, 116.8 mM sucrose supplemented with 10 μM BA and 20 μM IAA and solidified with 0.8% TC agar. Formation of adventitious shoots by direct and indirect shoot organogenesis from the same explant was verified by histological sectioning. With the exception of variegated leaf production on a single adventitious shoot produced in the presence of 25 μM kinetin and 15 μM NAA, no visible phenotypic abnormalities were observedin vitro in any of the shoots generated. Solid achlorophyllous adventitious shoots were recovered following culture of this variegated leaf tissue. Plantlets were easily acclimatized toex vitro conditions.

Phytotoxic effects of a short-chain fatty acid on seed germination and root length of Cucumis sativus cv. 'Poinset'.

Many studies indicate short-chain volatile fatty acids, especially acetic acid, are produced during the composting process of organic material. If a compost has not gone through a curing process and matured, its application can result in delay, inhibition or suppression of seed germination and plant growth. The mechanism of these phytotoxic effects has not been well investigated. Some studies have attributed phytotoxic effects to high ionic strength or pH imbalance.Our investigation indicated the inhibitory effect of acetic acid on seed germination and root elongation gave results suggesting a metabolic phenomenon. Further research on specific action of this acid is recommended.