Fertilizer Source and Irrigation Depth Affect Nutrient Leaching During Coleus Container Production

Abstract Nutrient leaching during nursery container production can have negative effects on plant growth and the environment. The objective of this study was to evaluate effects of fertilizer source at two irrigation depths on nutrient leaching during coleus [Plectranthus scutellarioides (L.) Codd] ‘Solar Sunrise' container production to develop best management practices. Coleus received no fertilizer, a controlled-release fertilizer (CRF), or a water-soluble fertilizer (WSF) applied at 0.30 kg N and P per m3 (0.02 lb per ft3) and were irrigated at 1.9 or 3.8 cm.day−1 (0.7 or 1.5 in.day−1) for 56 days after planting (DAP). Leachate was analyzed every 7 DAP for inorganic N and dissolved total P (DTP). At 56 DAP, root biomass, leaf quality, and plant growth index were similar between CRF and WSF treatments at both irrigation depths. Highest inorganic N and DTP losses occurred within 21 DAP. Application of WSF resulted in higher cumulative N and DTP losses compared to CRF applications. Coleus irrigated at 3.8 cm.day−1 and fertilized with WSF resulted in higher DTP losses compared to CRF applications regardless of irrigation depth. Reducing irrigation reduced inorganic N leaching for each fertilizer source. Application of CRF provided consistent growth while curbing nutrient losses across both irrigation depths compared to WSF. Index words: controlled-release fertilizer, water-soluble fertilizer, nursery producers, best management practices. Chemicals used in this study: Micronutrients mix (Micromax®); controlled-release fertilizer (Osmocote® Classic); water-soluble fertilizer (Grower's Special). Species used in this study: Coleus [Plectranthus scutellarioides (L.) Codd] ‘Solar Sunrise'.