Plant nutrition, foliar standards, chlorophyll activity and soil nutrient status of two cultivars of Leucospermum cordifolium (Proteaceae)
Two cultivars ('Succession II' and 'Tango') of Leucospermum cordifolium were studied over three years in commercial plantations with optimum yields located on subtropical La Palma Island (Canarian Archipelago). Four foliar samplings were taken per year to determine the evolution of the N, P, and K contents over time and to determine the optimal month for foliar standard sampling. Foliar chlorophyll activity and the foliar standard concentrations of macro- and micronutrients were determined. Soil samples were also taken. Both cultivars developed well in soils with acid and slightly acid pH, low and high organic matter content, and in some cases, high available P concentrations, though Proteaceae is generally considered P sensitive. Chlorophyll activity correlated neither with foliar nutrient levels nor with leaf greenness. The foliar N content reached a maximum of 17.0 g kg-1 in the cultivar 'Succession II' and 17.2 g kg-1 in 'Tango', whereas the maximum P and K levels were lower in 'Tango' than in 'Succession II'. The greatest stability of the concentrations of these nutrients occurred in September; therefore, this month was chosen for performing foliar standard sampling. The standard ranges of N, K, Ca and Mg were higher in 'Succession II', while Fe, Mn, and Zn were higher in 'Tango'. The P and Cu standard ranges were similar in both cultivars.