Fertilizer microdosing enhances biomass yield and water use efficiency of African indigenous leafy vegetable

Abstract

ABSTRACT Inadequate nutrition is a limiting factor for African indigenous leafy vegetable (AILV) production. Fertilizer microdosing technology might be a method to increase yields and nutrient use efficiency in AILVs. Field experiments were conducted to determine the effects of fertilizer microdosing on biomass yield and water use efficiency (WUE) of the AILVs: local amaranth (Amaranthus cruentus L.), African eggplant (Solanum macrocarpon L.), and African basil (Ocimum gratissimum L.). Treatments consisted of factorial combinations of five microdosed nitrogen (N) rates and 2 N application dates under fully irrigated (dry season) and supplement irrigated (rainy season) conditions. Under full irrigation, microdosed N rates were 0, 10, 20, or 30 kg∙ha−1 N + 5 t∙ha−1 manure and an additional treatment of 40 kg∙ha−1 N without manure (half recommended rate; HRR). Under supplemented irrigation, microdosed N rates were 0, 20, 40, or 60 kg∙ha−1 N + 5 t∙ha−1 manure and an additional treatment of 80 kg∙ha−1 N without manure (full recommended rate; FRR). Nitrogen application dates were 0 and 14 days after transplanting for both experiments. Biomass yields and WUE of local amaranth and African eggplant under microdosed N level plus manure increased, but not for African basil. Yield and WUE of local amaranth and African eggplant increased with microdosed N combined with manure level up to 40 kg∙ha−1 with little, or no, increase above that. The FRR produced lower yield and WUE compared to any microdosed rate of N combined with manure by 45% for local amaranth, and 30% for African eggplant under full irrigation, and 89% for local amaranth and 18% for African eggplant during the rainy season with supplement irrigation. Time of N application had no effect. The combined microdose application of N of 40 kg∙ha−1 and manure is effective to enhance some African indigenous leafy vegetable yields and water use efficiency while reducing fertilizer input. Further studies are needed at different locations and should include other AILV species to confirm microdosing is efficacious for AILV production.