Evaluation of Wollastonite As a Silicon Source for Production of Sunflower, Poster Board #175

Silicon-accumulating plant species may benefit from supplemental silicon application during production with stronger stems and disease resistance. A greenhouse experiment was conducted to compare two methods of silicon supplementation: a weekly drench with a solution of 20.8% Si0₂ from potassium silicate (AgSil 25^TM) and pre-plant incorporation of 50.1% Si0₂ from the dry powder wollastonite (Vansil W-10^TM) at both a low and high rate (1.5 and 3 g Vansil per liter of substrate) into a peat-based mix. A control with no Si was also included. Growth of Helianthus annuus ‘Ring of Fire’ plants was evaluated at mid- and end-crop. The weekly silicon drench resulted in the shortest plants. Compared to the untreated control, the wollastonite and AgSil treatments all resulted in increased silicon concentrations in the substrate and plant tissue. The silicon level in the substrate and resulting silicon tissue concentrations were comparable between the low rate of wollastonite and the weekly AgSil drench. The high rate of wollastonite provided the highest silicon level in the substrate when compared to any other treatment, and tissue Si was comparable to the AgSil drench. Both wollastonite rates resulted in a higher substrate pH than the untreated control or AgSil drench. Therefore, horticultural substrate manufacturers and crop producers may reduce the amount of lime when wollastonite is incorporated pre-plant into peat-based substrates. Pre-plant incorporation of wollastonite shows promise as a less labor-intensive means to provide silicon to crops that accumulate it during production.