The greenhouse floriculture crop production industry includes such commodities as flowering potted crops, perennials, and annual bedding plants. This sector of the horticultural production industry was valued at $3.94 billion for the top 15 producing states in 2011 (U.S. Department of Agriculture, 2012). Most greenhouse floriculture crops are grown in containers. The container size is dictated by the length of time the crop will be in production and the desired finished plant size. For example, florist potted crops such as cyclamen, poinsettia (Euphorbia pulcherrima), and chrysanthemum (Chrysanthemum ×morifolium) require longer production times to grow to marketability and are typically grown in larger containers than most annual bedding plants.
Petroleum-based plastics (plastic) are the most common materials used to fabricate containers for greenhouse crop production. Plastic is relatively strong, resists mildew and algae growth, and can be molded into a variety of shapes and sizes. However, after use, these containers are typically discarded, and this results in large amounts of waste plastic containers going to landfills. One potential solution to the large amounts of waste plastic greenhouse containers is the use of biocontainers. Biocontainers are generally defined as containers that are not petroleum based and break down quickly when planted into the soil or placed into a compost pile.
Biocontainers are generally categorized as being plantable or compostable (Evans and Hensley, 2004; Evans et al., 2010). Plantable biocontainers are containers that allow plant roots to grow through their walls and may be directly planted into the final container, the field, or the planting bed. Compostable biocontainers cannot be planted into the soil because the roots cannot physically break through the container walls and the biocontainers do not break down quickly enough to allow the plant roots to grow through the container walls. Instead, these containers must be removed before planting but can be placed in a compost pile to decompose in a relatively short time (Mooney, 2009).
There are many types of plantable biocontainers. Composted dairy manure containers are made of compressed composted cow manure held together with a binding agent. Peat containers are made from peat and paper fiber. Paper containers are made from paper pulp with a binder. Rice straw containers are composed of 80% rice straw, 20% coconut fiber, and a proprietary natural adhesive as a binder. Wood fiber containers are composed of 80% cedar fibers, 20% peat, and lime. Coconut fiber containers are made from the medium and long fibers extracted from coconut husks and a binding agent. One type of compostable biocontainer available for greenhouse production is the ricehull container, which is made of ground rice hulls with a binding agent. These containers are available in different sizes and may have solid or slotted walls. Another group of compostable biocontainers are bioplastic containers that are made from a bioplastic derived from polylactic acid or wheat starch, which is then thermoformed into containers.
Differences in growth have been reported for several bedding plant species when grown in biocontainers and compared with growth in plastic containers. Kuehny et al. (2009) evaluated the growth of pansy (Viola ×witrockiana) and petunia (Petunia ×hybrida) in various biocontainers. They found that the leaf area of pansy was highest when grown in wood fiber and coconut fiber containers. For petunia, the highest dry shoot weight and leaf area were found when plants were grown in peat containers. Kuehny et al. (2011) reported results of a biocontainer study on plant growth of impatiens (Impatiens walleriana), vinca (Catharanthus roseus), and geranium (Pelargonium ×hortorum) conducted at three locations. Impatiens shoot growth was similar for all containers, but vinca had higher dry root weight when grown in paper containers than when grown in plastic containers. The paper containers produced the highest geranium dry shoot weights at two locations and at the third location, geranium grown in plastic containers had the highest dry shoot weights. Evans and Hensley (2004) tested feather fiber, peat, and plastic containers under uniform and nonuniform overhead irrigation conditions. Under uniform irrigation conditions, the plants grown in plastic containers had significantly higher dry shoot weights than those grown in feather fiber or peat containers. The plants grown in peat containers had the lowest dry shoot weights. Under nonuniform irrigation, the impatiens and vinca had the highest dry shoot weights in the feather fiber containers, and the plants grown in plastic and peat containers had similar dry shoot weights.
Most of the research conducted on plant growth in biocontainers has been focused on short-term crops, such as annual bedding plants grown using overhead irrigation systems. However, many greenhouse crops are grown as florist potted crops that require longer production times and are often grown on subirrigation systems such as ebb-and-flood benches or flood floors. Therefore, the objective for this research was to evaluate the growth of a long-term greenhouse containerized crop in biodegradable containers compared with a traditional plastic container using a subirrigation system.
Beeks, S.A. 2011 Assessing biodegradable containers for growing long-term greenhouse crops in subirrigation systems. Univ. of Arkansas, Fayetteville, MS Thesis
Evans, M.R. & Hensley, D. 2004 Plant growth in plastic, peat and processed poultry feather fiber growing containers HortScience 39 1012 1014
Evans, M., Taylor, M. & Kuehny, J. 2010 Physical properties of biocontainers for greenhouse crops production HortTechnology 20 549 555
Kuehny, J., Evans, M. & Taylor, M.D. 2009 Assessing biodegradable containers for greenhouse and landscape performance HortScience 44 1148 (abstr.)
Kuehny, J., Taylor, M.D. & Evans, M.R. 2011 Greenhouse and landscape performance of bedding plants in biocontainers HortTechnology 21 155 161
Mooney, B.P. 2009 The second green revolution? Production of plant-based biodegradable plastics Biochem. J. 418 219 232
U.S. Department of Agriculture 2012 Floriculture crops 2011 summary. 17 Jan. 2013. <http://usda01.library.cornell.edu/usda/current/FlorCrop/FlorCrop-05-31-2012.pdf>