Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2006
Publication Date: 6/1/2007
Citation: Million, J., Yeager, T., Albano, J.P. 2007. Effects of Container Spacing Practice and Fertilizer Placement on Runoff from Overhead-Irrigated Sweet Viburnum. Journal of Environmental Horticulture. 25(2):61-72. Interpretive Summary: Information on how grower implemented management practices affect the volume and nutrient levels of runoff water is needed to improve irrigation and fertilizer efficiency while minimizing environmental impacts. Runoff, defined here as water that leaches (i.e. drains) from containers plus water that directly lands on the growing bed was studied using sweet viburnum grown in 1 gallon containers for a period of twenty weeks. Treatments consisted on the placement of controlled release fertilizer (CRF), either applied directy to the growing media surface of incorporated (i.e., mixed) into the growing media prior to planting; and plant spacing, either spaced at planting or spaced later in the study (non-spaced plants are typically pot-touching-pot). Irrigation-type was overhead. Spacing containers at planting reduced plant growth most likely due to a small plant canopy to shade the container surface from direct exposure to the sun, resulting in higher growing media temperature. Spacing, however, had no effect on nutrient runoff. Applying CRF to the growing media surface resulted in lower levels of both N and P that leached from containers. Half of the nitrogen, phosphorous, and potassium contained in the CRF was released within the first six weeks of the study. This information may be useful for assessing environmental impacts as well as for planning on-site recycling and water treatment systems.
Technical Abstract: Information on how management practices affect runoff volume and nutrient content is needed to improve irrigation and fertilizer efficiency while minimizing environmental impacts. Runoff (leachate plus un-intercepted irrigation and rain) was collected weekly for 20 weeks during production of a 2.7-L (trade #1) sweet viburnum crop fertilized with a resin-coated controlled-release fertilizer (Osmocote® 18N-2.6P-10K 8-9-month release) and overhead-irrigated with water at 1 cm.d-1. Treatments were a factorial arrangement of two container spacing practices [spaced at planting (SP) or spaced midseason (SM)] and two fertilizer placement methods [incorporation (INC) or surface-applied (SA)]. Runoff volume averaged 80 L.m-2 or 66% of irrigation plus rain and was 9% higher for SP than SM with the increases only observed during the first half of the season. Spacing containers at planting reduced plant growth 37% but had little effect on runoff nutrient losses (per container basis) despite increased substrate temperatures. Fertilizer placement had no effect on plant growth but SA reduced N and P losses (per container basis) 31 and 35%, respectively, compared to SM. One-half of the total amounts of N, P, and K in runoff were recovered 2, 6 and 4 weeks after planting, respectively, indicating rapid release of CRF in this study. Season-averaged flow-weighted concentrations in runoff were 2.9-7.5 mg.L-1 nitrate-N, 0.46-1.16 mg.L-1 orthophosphate-P, and 5.3-10.3 mg.L-1 K. Cumulative nutrient loads in runoff were 4.6-11.1 g.m-2 N, 0.48-1.25 g.m-2 P, and 5.8-10.1 g.m-2 K. This information may be useful for assessing environmental impacts as well as for planning on-site recycling and water treatment systems.