D. Neumaier, D. Lohr, E. Meinken
Different strategies to manage substrate pH during the cultivation of pot plants were evaluated in several experiments. Besides field-proven methods like water quality and nitrogen form or lime suspension more unknown possibilities like sulphur suspension, caustic potash and potassium bicarbonate were tested.
Nitrogen form and water quality only show a mid to long-term effect and the effect is limited by the water and nitrogen demand of the plants. Lime suspension (Ca(OH)2), caustic potash and potassium bicarbonate boost substrate pH rapidly and sulphur causes a strong drop in pH. In these cases the effect is unpredictable and makes a current control of substrate pH necessary. Moreover, the use of lime and sulphur bear the risk of substrate pH layer arrangement and lime deposits on leafs. Caustic potash and potassium bicarbonate feed high amounts of potassium which induce high salt contents. To minimize these risks lime, caustic potash, potassium bicarbonate and sulphur shall be given in specified, small amounts by hand, what makes their use time- and cost-intensive.
Overall the best way to avoid pH problems is an exact crop planning and continuous pH control combined with sophisticated cultural measures, especially the proper choice of water quality and nitrogen form.
Neumaier, D., Lohr, D. and Meinken, E. (2012). AN OVERVIEW OF PH-MANAGEMENT IN SUBSTRATES DURING CULTIVATION OF POT PLANTS. Acta Hortic. 927, 1013-1020
DOI: 10.17660/ActaHortic.2012.927.125
nitrogen form, water quality, lime, sulphur, caustic potash, potassium bicarbonate

Acta Horticulturae