Fertilizer concentration affects growth and nutrient composition of subirrigated pansies

Ebb-and-flow irrigation is an economically attractive subirrigation method that reduces labor costs and eliminates runoff from greenhouses. The effects of fertilizer concentration on growth of subirrigated pansy (Viola xwittrockiana Gam.) and the leachate electrical conductivity (EC) and pH were quantified, using two growing media. Leachate EC increased as the EC of the fertilizer solution increased from 0.6 to 3.6 dS.m(-1) (70 to 530 mg.L-1 N). The leachate EC was fairly constant over time when the EC of the fertilizer solution was 0.6 dS.m(-1), while it increased throughout the experiment at higher fertilizer concentrations. MetroMix 300 leachate consistently had a higher EC than did MetroMix 500. Leachate pH of both growling media was similar throughout the growing season. The pH decreased over time and was lower with higher fertilizer concentrations. Optimal pi ant growth occurred with a fertilizer EC of 1.2 or 1.8 dS.m(-1), and a leachate EC between 1.5 and 4 dS.m(-1). Increasing the concentration of the fertilizer solution resulted in increased shoot tissue levels of P and Mn and decreased tissue levels of K, Mg, and Na. The results of this study indicate that pansy is not very sensitive to the EC of the growing medium and can be grown successfully in a closed subirrigation system.