Effect of Phosphorus Applied as a Controlled-release Fertilizer or Soluble Fertilizer to a Container Nursery Crop

Abstract

Thirty commercially propagated bareroot cuttings and 30 cuttings with growing medium around the roots of Halwards' Silver Spiraea were fertilized with various phosphorus fertilizers to determine the effect of fertilizer type on P leaching and on plant quality. The following treatments were applied: 1) 100% controlled-release fertilizer (CRF) consisting of 22N–6P–14K; 2) 50% CRF consisting of 22N–3P–14K plus 50% soluble fertilizer (SF) consisting of 0N–46P–0K, triple superphosphate (TSP); and 3) 100% SF consisting of 22N–0P–14K plus TSP (0N–46P–0K). There was a significant plant by fertilizer interaction for leachate P content. Cuttings with medium and bareroot cuttings receiving 100% SF had a higher concentration of P in leachate; while the cuttings with medium receiving 100% CRF and 50%CRF/50%SF had lowest P concentration in leachate. Plants grown with 50%CRF/50%SF had larger root dry masses compared to the plants grown in 100% CRF and 100% SF. Plants grown in 100% CRF had the smallest stem dry masses compared to the other fertilizer treatments. Plants containing 100% CRF had a lower P concentration in the stems compared to plants containing 100% SF and 50% CRF/50% SF.