Effect of Nitrogen Level on Rate of Decomposition of Plantable Containers in the Landscape

Environmental concerns by consumers and the green industry has increased interest in plantable containers. These containers serve as alternatives to petroleum-based plastic containers due to their ability to eliminate plastic waste and disposal, facilitate efficient planting, and produce marketable plants. Recent research reports alternative containers have provided similar or greater performance of plants grown in these containers. However, little information has been provided about degradation of plantable containers in the landscape.  Factors including pH, nitrogen, soil type, moisture, temperature, and microbial activity can influence biodegradation of plantable containers. It is imperative that these containers break down as claimed because rate of biodegradation can affect plant health and performance. A litterbag study was conducted at two locations at the University of Georgia Griffin Campus (Spalding Co., GA) to evaluate the effect of soil type (Dempsey Farm: sandy clay; pH 5.01; nutrients (mg/kg) Ca=399.0; K=136.2; Mg=85.2; P=5.93, Bledsoe Farm: sandy clay; pH 4.77; nutrients (mg/kg) Ca=230.0; K=135.9; Mg=43.9; Mn=11.6; P=12.3) and nitrogen fertilizer on decomposition of commercially-available containers: coconut coir fiber, processed cow manure, and wood pulp fiber over a six-month growing season. Litter bags filled with three container types were buried at 10 cm soil depth and removed monthly in order to assess container decomposition by measuring container dry weight and carbon-to-nitrogen ratio. Soil type did not significantly impact plantable container decomposition. Container decomposition was significantly influenced by nitrogen fertilizer application at both locations as containers decomposed faster when buried in soil with higher nitrogen content. This suggests that routinely applying nitrogen fertilizer in the landscape bed may increase decomposition of plantable containers.