The 2010 ASHS Annual Conference

Commercially available slow/controlled released fertilizers are increasingly becoming more expensive, and any product that can be cheaper yet effective would be advantageous for the nursery grower. A new type of fertilizer being developed, using advanced granule technology (AGT) could be one such product. However, the nursery industry uses different formulations based on targeted crop species and time of fertilizer application. The objective of this study was to assess different AGT formulations for performance on selected nursery crops in comparison to industry standards at two application timings. Three types of formulations were selected, a 3-4 month, 5-6 month, and 8-9 month, with two application timings, one application starting in the fall, and the other starting in the spring. Fertilizers consisted of 3-, 6- and 9-month formulations of 15-9-12 (15-4-10 actual) Osmocote Plus, 3 month formulation of Harrells 16-6-13 (16-2.6-10.8 actual), 6 month formulation of Harrells 16-6-11 (16-2.6-9.1 actual), 9 month formulation of Harrells 15-6-12 (15-2.6-10 actual), AGT 15-9-12 (15-4-10 actual) 3 month formulation, AGT 15-9-12 (15-4-10 actual) 5 month formulation, and two, 9 month formulations of 15-9-12 (15-4-10 actual), one with monoammonium phosphate (MAP), and the other with triple phosphate [or super phosphate(SP)]. The 3 month formulations and triple phosphate formulations were not used in the fall trials. Test locations included two in Ohio and two in Ontario, Canada. The locations in Ohio were at Klyn Nursery in Perry, Ohio, and Decker's Nursery in Groveport, Ohio. The locations in Ontario were at Willowbrook Nursery in Fenwick, Ontario, and J.C. Bakker Nursery (spring start only at Bakker Nursery) in St. Catharines, Ontario. Species selected for testing consisted of Juniperus scapulorum ‘Wichita Blue, Buxus x‘Green Velvet', and Spirea xbumalda ‘Goldmound' from Willowbrook Nursery, Potentilla fruiticosa, Juniperus chinensis, and Thuja occidentalis from J.C. Bakker Nursery, Fothergilla gardenia, Ilex glabra ‘Shamrock', and Juniperus horizontalis ‘Wiltoni' from Klyn Nursery, Buxus x‘Winter Gem', Spirea xbumalda ‘Goldflame', and Microbiota decussata from Decker's Nursery. None of the fertilizers provided superior growth at all of the nurseries averaged over species, but some fertilizers' performance was based on the species tested. From these studies, it can be concluded that the AGT 9 month super phosphate formulation does provide detrimental effects to some species, especially when incorporated. The other AGT formulations, in most cases, do seem to perform better when topdressed and applied in spring as opposed to fall application and provide similar growth when compared to the industry standards.