Each cell contained a peat/perlite (70/30) substrate and the trays were stood in a mist propagation unit. The mist supplied either a complete water-soluble fertiliser containing macroand micro-nutrients or just the micro-nutrients alone.
Treatment began immediately and after seven days one half of the trays in each treatment were transferred to the other treatment. Similar transfers were performed after 14 days so as to create a total of eight treatment combinations. From now on, the fertilisers were applied twice each week and by hand.
After 21 days, cuttings that had received the complete fertiliser for the first seven days of propagation were heavier than those that had not. Furthermore, cuttings that received the complete fertiliser for all 21 days were heavier, taller and had more leaves than any other cuttings.
It was evidently beneficial to supply a complete fertiliser to unrooted cuttings from their very first day under mist, which implies that nutrients could be taken up before roots were initiated.
Dr Ken Cockshull, Associate Fellow, Warwick Crop Centre, University of Warwick
Timing of Macronutrient Supply During Cutting Propagation of Petunia by Santos, Fisher, Yeager, Simonne, Carter and Argo (2011). HortScience 46 (3): 475-480. Members of the ISHS can view HortScience from the website www.ishs.org