Few researches studied the effect of plant extracts on potato growth and yield performance. This study aimed to evaluate the effect of three application frequencies (weekly, bi-weekly, or monthly) of methanol and water extracts from tobacco, wild marigold or garlic at 50 mg mL-1 on potato growth and yield parameters under field conditions over two growing seasons (A and B) in Rwanda. The results revealed that the weekly application of methanol extract from tobacco or wild marigold at 50 mg mL-1 led to a delayed 50% potato sprouting when compared to methanol extract from garlic and water extracts from tobacco, wild marigold or garlic. Furthermore, the weekly application of methanol extract from tobacco showed a delay in 50% flowering similar to positive control (1% Copper oxychloride) than other treatments. The weekly and bi-weekly applications of methanol extract from tobacco or wild marigold at 50 mg mL-1 resulted in higher total yield than controls. No significant effect of growing season was observed in number of days to 50% sprouting and number of main stems per plant. Though, season B led to delayed 50% flowering, taller plants and higher total yield than season A. From this study, it is concluded that weekly or bi-weekly application of methanol extract from tobacco and wild marigold at 50 mg mL-1 can significantly improve potato growth and yield and can be recommended in sustainable horticultural production.
Keywords: Bi-weekly, garlic, monthly, tobacco, weekly, wild marigold