Yield response of African leafy vegetables to combined manure and urea microdosing in West Africa

Description of the subject. Fertilizers microdosing was tested for African leafy vegetables (ALVs) production to reduce the high rates of fertilizers usually applied to their production in West Africa. Objectives. This study aims to (i) evaluate the response of three ALVs (Amaranthus cruentus L., Solanum macrocarpon L. and Ocimum gratissimum L.) to cattle manure combined with urea-N microdosing and application timing and (ii) assess their partial factor productivity. Method. On-station trials were carried out over three growing seasons (2015 to 2017) in Northern Benin. Urea-N rates of 0, 10, 20, 30, 40 and 60 kg urea-N·ha-1 combined with 5 t·ha-1 of cattle manure (M5N0, M5N10, M5N20, M5N30, M5N40 and M5N60, respectively) and sole application as control (40 (M0N40) and 80 kg urea-N·ha-1 (M0N80)) and two urea-N application timings (T1 = 0 and T2 = 14 days after transplanting) were tested in a randomized complete block design with four replications. Results. The M5N60 treatment resulted in the highest A. cruentus fresh yield and improved leaf yield by 90 and 151% compared to M5N0, and the average of the two no-manure input treatments M0N40 and M0N80, respectively, while M5N40 treatment improved S. macrocarpon fresh yield the best by 23% compared to M5N0. For O. gratissimum, no significant difference was found between urea-N microdose rates. Besides, urea fertilizer application timing affected neither fresh yields nor partial factor productivity for any studied ALVs species. Conclusions. Reduced combination of urea-N and cattle manure is a promising nutrient management practice for ALVs production in West Africa as it improved yields while saving fertilizer for smallholder vegetable farmers.