What Affects Greenhouse Media pH?
• Media components contribute significantly to pH. Organic materials are generally more acidic than inorganic materials. Peat moss is commonly used for acidic media. • Irrigation water quality. Alkalinity (bicarbonates) increase pH. Remember that a water pH of 7.0 can be more alkaline than water with a pH of 8.0. • Lime. Commonly incorporated into many greenhouse media to increase pH or stabilize pH under conditions that favor a pH reduction. • Acid injection into irrigation water. • Crop being grown. • Fertilizer type used. Fertilizers with nitrate forms of nitrogen increase pH over time. Fertilizers with ammonium and urea forms of nitrogen gradually decrease pH over time. Increase Media pH during Greenhouse Crop Production • Eliminate acid injection into irrigation water. • Use an alkaline-reaction fertilizer type. • Add potassium bicarbonate at the rate of 13.5 oz per 1,000 gallons of irrigation water. This also supplies 40 ppm potassium. Use in cases of low water alkalinity (bicarb
