Evaluation of Conventional and OMRI-certified Organic Fertilizers, and Their Effect on Soil pH

The rising popularity in the marketplace of certified organic plant materials has extended into the ornamental plant industry, which has created a demand for information on bedding plant production using organic fertilizers. The nitrogen formulation in organic fertilizers tends to be greater in the ammonical form than nitrate, which has the potential to raise the pH of the soil over time. Higher soil pH results in lower availability of various nutrients for a plant. This study was conducted to determine the effects of organic fertilizers on soil pH. This study utilized soil pH, soil EC, plant dry mass and SPAD measurements. This experiment used four different cultivars of petunia in a modified random block design, each cultivar set was divided into four groups for application of four different fertilizers. Two fertilizers were conventional fertilizers, and two were OMRI certified organic fertilizers. The soil pH, soil EC, and plant dry mass were the leading indicators of fertilizer performance.