Research Problem Statement
Containerized production is the predominate method to produce ornamental nursery crops in the mid-Atlantic. However, soilless substrate used for containerized nursery crop production, when compared to conventional soils, has low water and nutrient holding capacity, and containers have a limited volume from which roots can readily absorb water and nutrients. Consequently, resources (i.e. nutrients and water) are applied in what is believed to be excessive amounts to ensure a fast growing, aesthetically pleasing and saleable crop. As a result, low crop nutrient use efficiency (i.e. applied nutrient utilized by the crop) and subsequent nutrient runoff leads to water quality issues when producing containerized crops.
Agriculture, including the nursery industry, is the leading non-point source of nutrient water pollution in the Chesapeake Bay Watershed; agriculture fertilizer runoff contributes 28% of Chesapeake Bay phosphorus (P) loads (Majsztrik and Lea-Cox, 2013). Phosphorus is of particular concern for water quality, for it is the limiting factor for eutrophication in fresh water systems when in the presence of ≥1.875 mg/L nitrogen (N) (Jørgensen et al., 2001). Thus, when bioavailable P (i.e. orthophosphate) enters surface water, the resulting increased fertility levels accelerate algal growth, which reduces the supply of dissolved oxygen for aquatic biota. Therefore, non-point source phosphorus contributions remain a major concern for the Chesapeake Bay Watershed. As a result, The U.S. Environmental Protection Agency (USEPA) is monitoring agricultural non-point nutrient loads. In Pennsylvania, the Watershed Implementation Plans (WIPs) have increased enforcement and compliance of state requirements for agricultural pollution; in others, implementation of mandatory programs for reduction of agriculture runoff are being considered if reduction requirements are not met (USEPA, 2010). Of the six states and the District of Columbia, which make up the Chesapeake Bay Watershed, Virginia is responsible for the greatest P input reductions by 2025 (USEPA, 2010). By reducing P fertilization levels, the containerized nursery industry would contribute to achieving P runoff reduction goals.