Optimizing NPK fertilizer requirements for Jatropha zeyheri tea under greenhouse conditions

Abstract

Jatropha zeyheri is an indigenous crop to South Africa, which contains tea brewing and medicinal properties commonly utilized by local communities in rural areas of South Africa. Domestication and commercialization of indigenous herbal teas have gained popularity in recent years however, domestication of J. zeyheri will require optimum NPK fertilizer mixture to improve the yield and quality. Therefore, the study was intended to determine whether different fertilizer application rates will optimize yield parameters of J. zeyheri tea under greenhouse conditions. At two-leaf stage, J. zeyheri seedlings were transplanted into 25 cm diameter plastic pots. Each pot was filled with heated-pasteurised sandy soil and Hygromix at 3:1 (v/v) ratio and placed in a spacing of 0.30 m × 0.30 m inter-and intra-row spacing. Six treatments constituting NPK fertilizer rates (0, 2, 4, 8, 16 and 32 g) were arranged in a randomized complete block design, with five replications. Treatments were initiated a week after transplanting, and 130 days after that, treatments had highly significant effects on chlorophyll content, leaf width and dry root mass, contributing 70, 78 and 62% in total treatment variation (TTV), respectively. In contrast, vine length, stem diameter and leaf length were significant, contributing 47, 60 and 49% in TTV, respectively. However, treatments had no significant effects on normalized difference vegetation index, number of leaves and dry shoot mass. Jatropha zeyheri plant variables exhibited positive quadratic relations with increasing fertilizer levels. Fertilizer requirements for J. zeyheri were optimized at 3.34 g fertilizer/plant, which translates to 33 kg NPK fertilizer/ha for 10 000 plants of J. zeyheri. In conclusion, J. zeyheri appears to qualify as a low-input tea crop.