Background: Sweet basil (Ocimum basilicum L.) is one of the most economically important aromatic herbs of the Lamiaceae family. The plant is used in complementary and alternative medicine in different cultures worldwide. However, its productivity is generally low due to low soil fertility as an important constrain and there poor information on the type and rates of fertilizers applied.
Objective: Therefore, the present study was carried out in experimental gardens at Waja Kero Kebele, Sodo Zuria district, Wolaita Zone, southern Ethiopia to evaluate the effect of blended NPS and potassium fertilizer rates, and to assess their cost and benefit at different application rates.
Methods: The treatments were composed of four rates of blended NPS (0.50, 100 and 150 kg NPS ha-1) and four rates of potassium (0, 35.5, 71, and 106.5 kg K ha-1) fertilizers, plus 100 kg Urea ha-1 applied to all plots equally. The experiment was laid out as a Randomized Complete Block Design (RCBD) in a 4 x 5 factorial arrangement repeated three times. Widely used sweet basil variety Nantes was used as a test crop.
Result: The Analysis of Variance (ANOVA) revealed that the main effects of blended NPS and potassium fertilizers influenced significantly (P<0.05) plant height, number of leaves, shoot fresh and dry weight, root length, diameter, fresh weight, dry matter, total root yield, and marketable root yield. The highest marketable root yields were obtained in response to the application of 100 kg blended NPS ha-1 and 106.5 kg K ha-1 provided 21.46 t/ha. On the other hand, the lowest marketable yield of 12.82t ha-1 was obtained in response to an unfertilized plant. The partial budget analysis revealed that the application of 100 kg ha-1 blended NPS and 106.5 kg K ha-1 resulted in the net benefits of 115485.2 ETB ha-1 with 59% net income over control treatment. This treatment was initiated to optimum sweet basil root production and economic returns in the study area.
Conclusion: Furthermore, the yield of sweet basil at sodo zuria can be increased by combined application of 100 kg NPS with 106.5 kg K/ha. Whereas the highest net return however was obtained from sweet basil plants supplied above mentioned treatment when compared with all other treatments. To formulate sounded recommendation however, it is advised to repeat the same experiment on other areas of the woreda.