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ABSTRACT
Ground dolomitic limestone (CaCO3/MgCO3) is used throughout the southeastern United States as a fertilizer amendment to soilless media. In addition to neutralizing media acidity, carbonate-based limestone also provides a source of calcium (Ca) and magnesium (Mg) for growth of many woody ornamental species, among these dwarf nandina. This study was conducted to compare the effects of CaO and CaO/MgO/CaCO3 blends to ground dolomitic limestone on the growth, marketable quality, and foliar nutrition of Nandina domestica ‘Nana Purpurea’ grown in soilless media. Materials were preplant incorporated based on the calcium carbonate equivalence (CCE, or acid-neutralizing equivalence) of ground dolomitic limestone (CCE=63) and plants were arranged in a completely randomized design (CRD). Growth indices (GI) were determined and plants harvested for tissue dry matter weights and foliar nutrient content. Plants amended with CaO, agricultural gypsum (CaSO4ċ2H2O), or pelletized dolomitic limestone, were of similar or better quality than plants amended with ground dolomitic limestone. Greatest nutrient uptake [nitrogen (N), Ca, potassium (K), and phosphorus (P)] was likewise observed for these treatments. All liming materials resulted in higher nutrient uptake compared to the unlimed control and highest foliar Mg was reported for plants amended with ground and pelletized dolomitic limestones. In year 1, plants were of similar quality, with the exception of the Ca(OH)2 treatment, which gave the lowest foliar quality ratings. In year 2, all plants were of marketable quality. Throughout the study, and especially during year 2, many foliar nutrient levels fell below established survey averages for dwarf nandina, illustrating the need to supplement media mixes with additional fertilizers during the growing season. All liming materials raised media pH to within the target range for nursery crops (pH=5.5–6.5) within one month from initial application, but lost their most positive neutralizing effect by the end of the third month. Research conducted indicates that CaO, CaO/MgO/ CaCO3 blends, CaSO4ċ2H2O, or pelletized limestone may serve as suitable alternatives to ground dolomitic limestone for use in soilless media.