Effect of slow release fertilizers on container-grown woody plants

Slow-Release Fertilizers (SRF) Silvamix Forte and Silvagen were tested in two-year experiments with container-grown woody plants (Pyracantha coccinea, Thuja occidentalis). Several fertilizing systems were compared: preplant application of SRF into substrate as the sole nutrient source for a two-year period, preplant application of SRF and soluble fertilizer (PG Mix), and preplant application of SRF and soluble fertilizer together with additional fertilizing by solution of nitrogen fertilizer during both growing periods. A system with controlled-release fertilizer (CRF) Osmocote 5-6 was chosen as a control variant; it was incorporated into substrate before planting in the first year and top-dressed in the second year. CRF Plantacote 6M (mixed into substrate before planting and top-dressed in the second year) and Osmocote 16-18 applied only before planting were tested, too. The experiments showed that SRF Silvamix Forte and Silvagen give results comparable with CFR provided that they were incorporated together with soluble fertilizer dose and plants were fertilized by solution of nitrogen fertilizer during both growing periods.