Influence of Rate and Placement of Slow-release Fertilizer on Pot Plants of African Violet Grown with Capillary Mat Watering1

Abstract

Ballet African violets (Saintpaulia ionantha Wend. cvs. Ulli and Lisa) were grown in a peat-vermiculite-perlite mix using capillary mat subirrigation in the summer and winter. Rates of 0.9, 1.8, 2.7, and 3.6 kg of Osmocote 14-14-14 (14N-6.1P-11.6K) per m3 of growing medium were either top-dressed, incorporated, or placed in the bottom of the pot. In the summer, maximum dry weight of ‘Lisa’ was produced at the 3.6 kg/m3 rate and for ‘Ulli’ at the 2.7 kg/m3 rate (over all fertilizer placement methods). In winter, the 2.7 kg/m3 rate produced greatest dry weight in both cultivars. Placement method was significant for ‘Lisa’ dry weight and plant quality in summer, with top-dressing or incorporation generally being better than bottom-of-pot placement. Placement method was not significant for ‘Ulli’ in summer or winter for dry weight or quality.