Substrate pH influences nutrient availability. When substrate pH rises or falls below the optimal species-specific range, nutrient deficiency or toxicity symptoms can develop. Sampling plant leaf tissue for nutrient analysis will aid in identifying nutritional symptomology and determining the appropriate corrective procedure.
In floriculture, high-quality crops are those free of pests and diseases; the plant is proportional to the container size; foliage is blemish free and colorful for foliage crops; and are budding and flowering. These characteristics influence the overall aesthetic appeal, marketability and profitability of a crop. However, during production, nutritional disorders such as deficiencies and toxicities can occur affecting crop growth and development and thus, the aesthetic appeal and value.
Nutritional deficiencies and/or toxicities can develop as a result of environmental, physiological, mechanical, chemical, and/or cultural factors. The most common factor inducing nutritional deficiencies and/or toxicities is substrate pH drift. When substrate pH rises above a species-specific optimal pH, nutrients such as P, Fe, Mn, B, Zn, and Cu become less available for update and plant develop deficiency symptoms. When substrate pH falls below a species-specific optimal pH, Ca and Mg become less available for uptake resulting in deficiency symptoms. Furthermore, at low substrate pH, Fe, Mn, B, Zn, and Cu are more available for uptake and lower, matured leaves can develop toxicity symptoms. To best identify nutrient disorders or to determine the nutrient status of a crop, growers should 1) perform in-house nutritional testing of the substrate pH and soluble salts [referred to as electrical conductivity (EC)] by conducting either a 1:2 Dilution, Saturated Media Extraction (SME), or PourThru; and 2) sample leaf tissue for nutrient analysis.