Controlled-release Fertilizer Placement Affects the Leaching Pattern of Nutrients from Nursery Containers during Irrigation

Abstract

Maximizing nutrient use efficiency while minimizing nutrient leaching and non-point source contributions from containerized crop production systems are goals of researchers and growers. These goals have led to irrigation and crop nutrition management practices that reduce fertilizer and irrigation expenditures and reduce the nutrient load into the environment. However, one area that has received little attention, and may lead to the further refinement of crop management practices, is how dissolved nutrients (solutes) move through a substrate while water is being applied during irrigation. A study was conducted to characterize the effect of a controlled-release fertilizer (CRF) placement method on changes in leachate nutrient concentration throughout an irrigation event and to evaluate these changes at different times throughout a production season. A pine bark:sand (9:1, by volume) substrate was placed in 2.7-L nursery containers (fallow) and was treated with topdressed, incorporated, and dibbled CRF or did not receive CRF. The nutrient leaching pattern was evaluated at 3, 9, and 15 weeks after potting (WAP). Leachate nutrient concentration was the highest in the first 50 mL of effluent and steadily diminished as irrigation continued for the topdressed, incorporated, and the no CRF treatments. Effluent nutrient concentration from containers with dibbled CRF generally increased throughout the first 150 mL of effluent, plateaued briefly, and then diminished. The nutrient load that leached with higher volumes of irrigation water was similar between incorporated and dibbled CRF placements. However, the unique nutrient leaching pattern observed with the dibbled CRF placement method allowed for a lower effluent nutrient load when leaching fractions are low. Dibble may be an advantageous CRF placement method that allows for the conservation of expensive fertilizer resources and mitigates non-point source nutrient contributions by reducing undesired nutrient leaching during irrigation.