Use of Plastic Trays to Reduce Irrigation Demand of Biocontainers

Biocontainers have been successfully marketed as sustainable alternatives to petroleum-based containers in greenhouse production. Despite this appeal, past research has shown that biocontainers, especially those constructed from more porous plant materials (e.g., peat and wood fiber), tend to require more frequent watering than conventional plastic products. However, no research to date has investigated how the use of a plastic filling/carry tray (commonly used facilitate production using small diameter containers) influences water demand in biocontainer production. This project evaluated plant growth and water consumption for 10 different containers (a plastic control and nine biocontainer alternatives) used to grow a short-term greenhouse crop (Vinca minor) at three different greenhouse sites in Fayetteville, AR; Lexington, KY;and Crystal Springs, MS. Containers were either left exposed or surrounded by an excised filling/carry tray pocket for the duration of the five-week study. Results indicate that both container type (P < 0.0001, all sites) and the absence/presence of a tray (P < 0.0001, AR; P = 0.0093, KY; P = 0.0023, MS) influence total water consumption. Trays generally reduced watering demand (up to 40% for straw pots); however, the benefit offered by the addition of a tray was not as significant for the more impervious containers made of plastic, bioplastic, and pressed rice hulls. In contrast with water use, growth responses (i.e. leaf area, dry shoot weight, and dry root weight) generally did not differ among the treatment combinations (with the exception of leaf area at the Arkansas site), indicating that water consumption was driven largely by the treatment combinations and was not confounded by differences in growth. We conclude that filling/carry trays can be an effective means of managing the overall sustainability of greenhouse production when using more porous biocontainers, especially if water use is a key concern. Additionally, past research may overestimate differences in watering demand in production systems where plastic filling/shuttle trays are used.