Decorative values and the nutritional status of some Magnolia species under the climatic conditions of Lublin (Poland). Part II. Evaluation of the nutritional status of the plants

The present study was conducted on six Magnolia species in the period 2006-2008 in the Botanical Garden of the Maria Curie-Skłodowska University in Lublin. The soil and leaves from the locations of the following species of Magnolia were subjected to evaluation: cucumber tree (Magnolia acuminata L.), Kobushi magnolia (Magnolia kobus DC), purple lily magnolia (Magnolia liliiflora L.), Japanese willow-leaf magnolia (Magnolia salicifolia Siebold et Zucc. Maxim.), saucer magnolia (Magnolia x soulangiana Soul.-Bod.), and umbrella magnolia (Magnolia tripetala L.). The studied plants were planted during the period 1968-1989 on grey-brown podzolic soil derived from loess. The significantly lowest content of phosphorus, potassium and magnesium as well as the lowest pH were recorded in the soil from the location occupied by the purple lily magnolia (M. liliiflora). The other sites were characterized by an optimal range of pH, high soil phosphorus and magnesium availability as well as medium potassium availability. An optimal content of nitrogen and calcium was found in the leaves of the cucumber tree (M. acuminata), of phosphorus and magnesium in the leaves of the Kobushi magnolia (M. kobus), and of potassium in the leaves of the Japanese willow-leaf magnolia (M. salicifolia). A low content of nitrogen and calcium was shown in the leaves of the purple lily magnolia (M. liliiflora), of phosphorus in the leaves of the saucer magnolia (M. x soulangiana), and of potassium in the indicator parts of the cucumber tree (M. acuminata). The study found that among the studied species the cucumber tree (M. acuminata) could be a good biostabilizer of nitrogen, while the Kobushi magnolia (M. kobus) a good biostabilizer of phosphorus and magnesium. In spite of significant differences in soil nutrient availability and clear variations in macronutrient contents in the indicator parts of the investigated plants, no visual symptoms of nutrient deficit were found in the Magnolia species under study.