Linda Benedict, Kuehny, Jeff S.
Biocontainers provide the ornamental plant industry with an opportunity to improve the level of adoption of sustainable products and practices. However, many factors must be considered before using these containers for ornamental production and transplanting into the landscape.
Most containerized ornamental crops are commonly grown in plastic containers, which present a significant disposal issue for the horticulture industry as well as for consumers and landscapers. Biocontainers are an alternative to plastic. They generally are made from a variety of organic components that decompose when placed in a composting facility or planted in the soil. One group of biocontainers decomposes slowly or is designed to be removed before planting and composted. The second group is designed to be planted directly into the landscape or the final container and decomposes quickly.
Some of the concerns with biocontainers are that the strength and rigidity vary. Strength is important because containers that tear or break during handling and shipping result in the loss of saleable product. Water use is an important property of biocontainers because some allow more or less water to evaporate from the surface walls of the container. Finally, the ability of transplantable containers to decompose in the soil is important to landscape establishment.
Limited research has been conducted on these properties of biocontainers, and thus a comprehensive study using a wide variety of biodegradable containers to test performance in greenhouse production and in the landscape was conducted at three locations: the LSU AgCenter
Burden Center in Baton Rouge, La., the University of Arkansas in Fayetteville, Ark., and Longwood Gardens in Kennett Square, Penn.
Eight biocontainers and two typical plastic containers were tested for physical characteristics, as well as their effect on plant growth and development during greenhouse production and in the landscape. The biocontainers produced solely for production included:
The plantable biocontainers included:
Measurements of the physical properties were conducted at the University of Arkansas. For the production-only containers, plastic had the highest wall
strength followed by paper containers. Coco fiber and rice hull containers had higher dry strength than OP47, Fertilpot, CowPot, Jiffypot and Straw Pot containers
containers. Wet strength, which is important when shipping live plants, was adequate for all containers except Fertilpot, Jiffypot and CowPot. Thus, the containers that do not have to be removed for planting may require a little extra care in production, shipping and handling.
In the second part of this study conducted at Burden Center and Longwood Gardens, the containers were filled with a standard growing substrate, planted with vinca transplants and placed in a greenhouse. During greenhouse production, the plastic, Fertilpot and Kord containers produced the largest plants, while Coir containers produced the smallest plants. However, all plants were of marketable quality at finish. Water was poured through each pot, and the accumulated leachates were tested at finish with a pH of approximately 6, which was similar for all containers.
The greatest water loss was from the Jiffypot, Fertilpot, Straw Pot and Coir containers followed by CowPot and Kord. Irrigation frequency also was recorded during greenhouse production where similar results were found. When growing plants in these types of plantable containers, one will have to consider increased irrigation frequency in both the greenhouse and retail environments. The least water loss was from the nonplantable rice hull, OP47 and plastic containers.
The third study was conducted in the landscape with vinca from all containers transplanted into the landscape after six weeks of greenhouse growth. After being planted for seven weeks, plants grown in the Fertilpot, CowPot, Straw Pot and Kord containers were somewhat larger than plants grown in the other containers. However, plants grown in all
containers were of acceptable quality. The CowPot had the greatest degradation in the landscape ( greater than 45 percent) while the Jiffypot and Straw Pot containers had the next greatest percent degradation at approximately 10 percent. Differences in decomposition rates are likely due to the difference in materials used to make the containers. Those composed of high-cellulose materials, such as CowPots, had higher rates of decomposition than those containing high amounts of lignin or other difficult-to-decompose components such as coco fiber. Additionally, nitrogen in the dairy manure used to produce the CowPot containers may have stimulated the activity of microorganisms and subsequent decomposition rates.
Container strength, biodegradability, water use and greenhouse performance varied among the different types of biocontainers tested. Fertilpot, Jiffypot and CowPot containers had wet strengths low enough to make handling difficult and had higher water requirements. These biocontainers, however, were some of the fastest to decompose in the landscape. Depending upon the geographic location, crop, management conditions and post-production handling, different properties would be more or less important.
Greenhouse growers wanting to improve sustainability by switching to biocontainers will need to evaluate which properties are the most significant and choose a biocontainer that best fits their production techniques, resources and end users. In general, all biodegradable containers tested in this study would serve as suitable replacements for petroleum-based plastic containers in the greenhouse and landscape.
Acknowledgment: Louisiana Nursery and Landscape Association and the Baton Rouge Landscape Association for support; Jiffy Group International, ITML Horticultural Products Inc., Fertil USA, Summit Plastic Co., Ivy Acres, and CowPots Manufacturing for providing containers; Scotts Co. for providing fertilizer and Sun Gro for providing substrate.