Optimal proportions between N, S and P and between K, Ca and Mg in the fertilization of roselle (Hibiscus sabdariffa L.)
Keywords:Roselle, Fibre crop, Vegetable crop, Systematic variants, Vegetative development, Generative development
AbstractA fertilization experiment on a green and a red variety of Hibiscus sabdariffa L. was carried out in glasshouses, July-December 1984, based on the method of systematic variants as proposed by Homes and Van Schoor (1969), which makes it possible to calculate optimal proportions between quantities of fertilizer elements given to the plant. Optima were calculated for N, Sand P, and K, Ca and Mg, respectively. For the vegetative development (leaves, stem) of the plant N, S, and Pare all needed in the same proportion. The same applies for K, Ca and Mg when the plant is cultivated for the stem (fibres). For leaf production more Mg and less K are needed. For reproduction the green variety still needs a 1:1:1 balanced cation and anion fertilization. The red variety needs more P than N (N:S:P, 1:1.4:1.6) and more Mg than K (K:Ca:Mg, 1: 1. 75:2.25). As the experiment was carried out on a poor river sand containing no minerals, one should take the amount of elements already present in a soil into account when giving a fertilization based on the proposed proportions.