Effect of NPK levels on growth and bulb quality of some geophytes in substrate culture

Abstract

Freesia corms were grown in substrate culture using sand: rice husk-charcoal: coconut fiber at the ratio of 1:1:1. The optimum levels of NPK in the nutrient solution were studied using different combinations of nitrogen at 100 and 200 mg/L, phosphorus at 50 and 100 mg/L combined with potassium at 100, 200 and 300 mg/L. The results showed that the minimum level of NPK at 100:50:200 mg/L was good enough for growing Freesia in substrate culture. Tubers of Gloriosa rothschildiana (10-25 g FW) were grown in substrate culture. The -N, -P, -K, -Mg and -Ca treatments compared with complete nutrient formula were supplied to the tubers. The results showed that nutrient deficiency reduced plant height, number of nodes, tuber fresh weight and tuber length. The optimum level of NPK was further studied by supplying tubers with different combinations of nitrogen at 100, 200 and 300 mg/L , phosphorus at 50 and 100 mg/L combined with potassium at 100, 200 and 300 mg/L. The results showed that the NPK combination at 200:100:200 mg/L was optimal for growing Gloriosa rothschildiana in substrate culture.