The costs of producing ornamental plant species vary among alternative nursery production systems because of differences in planting procedures, growing practices (fertilizing, irrigating, pruning, etc.), and harvesting activities. Common systems used in the green industry currently include field-grown and container methods, as well as PIP systems that are a hybrid of the previous two methods. Each of these systems offer distinct advantages relative to the other systems, but there are inherent trade-offs and concessions that nursery operators make when selecting their preferred method of production.
PIP nursery production is a modified container production system used extensively in the south and increasingly in the midwest. Plastic nursery pots are set in the ground and liner pots of the same size containing the plants are inserted, making a double pot system that prevents rooting out into the soil. The pots are recessed in the ground, preventing blow over and protecting the roots from extreme temperatures, negating the need for extra winter protection. The liner pots get pulled and sold with the plant; the outside socket pots are then replanted with a new crop. The end product, a plant grown in a pine bark substrate in a large pot, is easier to handle and plant than a BNB plant.
Compared with field-grown trees, PIP requires more labor and greater investment costs at planting, but provides labor, equipment, or both savings at harvest, saves valuable topsoil, and provides a supply of fresh trees for market all season. In some parts of the country, growers have even stated that production time has also been reduced with the use of PIP.
Each of these nursery production systems also vary in terms of their environmental impacts, which are becoming increasingly important to consumers in the green industry marketplace (Hall et al., 2010; Yue et al., 2010, 2011). Although it is widely recognized that green industry products increase the function and aesthetics of the built environment and improve the quality of life of individuals in those environments, they also provide valuable ecosystem services such as sequestering carbon and elevating O2 in the environment. However, the choice of inputs used during the production of those plants in the nursery and those used while performing related maintenance services while in the landscape will determine the degree of sustainability of the green industry (Marble et al., 2011; Prior et al., 2011).
Ingram and Hall have been exploring the carbon footprint and variable cost structure of selected nursery species (Hall and Ingram, 2014, 2015; Ingram, 2012, 2013; Ingram and Hall, 2014a, 2014b) but to date have not compared the results of alternative production systems on the same plant species of the same salable size. Given that the production protocols are now available for BNB and PIP production of similarly sized Acer rubrum ‘October Glory’ shade trees, the objective of this study was to compare the two systems to ascertain the cost and GWP differences between them.
Specifically, this analysis examines the differences in shrink (sometimes referred to as dumpage or scrap); the impacts of differing lengths of production cycles; the effects of differences in cultural practices (e.g., pruning, fertilization, etc.); PIP container costs vs. supplies for prepping BNB trees (e.g., BNB materials); differences in planting costs (e.g., smaller liner used in field production and grown for more years while the PIP model system requires a large liner but grown in less time); and transportation cost differences (e.g., weight and number of plants on a truck, as well as loading and unloading time and equipment use comparisons).
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