VARIETAL RESPONSE OF SOLE AND COMBINED APPLICATION OF NPK 15-15-15 FERTILIZER ON GROWTH YIELDS OF ROSELLE (Tithonia diversifolia) VARIETIES IN OGBOMOSO, NIGERIA.

Abstract

Roselle (Hibiscus sabdariffa Linn) is regarded as a vegetable, as the calyces are the economic parts commonly utilized for dietary, industrial, medicinal and socio-cultural purposes. However, despite the multipurpose nature of roselle, one of its major production limiting factors in Nigeria is soil fertility. As a result, local farmers opted for rapid nutrients-replenishing means of applying different chemical fertilizers, which had eventually worsened the tropical soil conditions, as manifested through accelerated nutrients depletion and poor general crop performance. Therefore, this research was conducted at the Teaching and Research Farms, Ladoke Akintola University of Technology, Ogbomoso, Oyo state, to evaluate the performance of two varieties of roselle (Green and Red) under percentile proportionate combinations of NPK 15-15-15 fertilizer and Tithonia diversifolia compost, and the control. The experiment involved six (6) treatments namely: F0 (Zero application- control), F1 (100% application of NPK 15-15-15 fertilizer), F2 (Tithonia compost), F3 (75% NPK 15-15-15 fertilizer + 25% Tithonia compost), F4 (50% NPK 15-15-15 fertilizer + 50% Tithonia compost) and F5 (25% NPK 15-15-15 fertilizer + 75% Tithonia compost) were arranged in Completely Randomized
Design (CRD), replicated thrice. Data were collected on growth (plant height, number of leaves, number of branches and stem girth) and yield (fresh and dry weights of calyx, and dry biomass yields) parameters. Data collected were subjected to analysis of variance (ANOVA). Treatment means were separated using Duncan Multiple Range Test at 5% level of probability. The results of pre-cropping soil analyses showed that the soil sample used was texturally sandy loam and slightly acidic with pH (H2O) value of 6.1. Also, the soil was grossly low in major nutrient concentrations N (0.09 %), P (0.42 mg/kg) and K (0.14 mg/kg). Application of different fertilizers significantly (p ≤ 0.05) influenced growth and yield of the two varieties investigated compared to the control. All the treatments applied
significantly improved growth and yield parameters of the two roselle varieties. The Green roselle variety significantly responded better to different fertilizer treatments tested, compared to red roselle variety (VIF4). Generally, the crop yields, irrespective of the variety was significantly enhanced with increasing levels of organic residues from 50 to 100%. However, application of 25% NPK 15-15-15 fertilizer and 75% Tithonia compost significantly improved the growth and yield parameters measured, as well as the nutrient uptakes of roselle. In conclusion, although application of 25% NPK and 75% Tithonia compost significantly improved the performance of green roselle, their values were not significantly different from those obtained from 100% Tithonia compost, therefore application of 25% NPK and 75% Tithonia compost is recommended, in order to: supply adequate nutrients for optimum performance of the green roselle variety and ensure reduction of chemical loads on soils. In addition, application of 100% Tithonia compost is equally recommended for pure organic production of green roselle variety, in the study area.