Water use efficiency of local amaranth as affected by timing and application methods of fertilizer microdosing

Previous studies conducted on fertilizer micro-dosing focused on cereals-based cropping systems and led to promising productivity results. Effort are underway to adapt the technology to other high value crops such as African indigenous leafy vegetables. The recommended hill placement method of application for cereals would not be a viable option with vegetables given their high planting density. To test the potentials of alternative application methods, a field experiment was performed in northern Benin using a randomized complete block design to evaluate the effects of five nitrogen (N) rates (0, 20, 40, 60 and 80 kg N ha(-1), respectively coded N0, N20, N40, N60 and N80), two application dates (0 (d1) and 14 (d2) days after transplanting) and three application methods (broadcast, hill and strip application) on biomass yield and water use efficiency (WUE) of local amaranth. All plots received manure (5 t ha(-1)) during bed preparation except those intended to highest level of N (N80). We found that the broadcast micro-dosing method performed equally, with the strip and hill placement application enabling to save time and labor while guarantying biomass yield and WUE. The early timing of urea application also gave equal performance like the two weeks after transplanting one, giving farmers a considerable slot of time for an effective application. In regards of the application rates, nitrogen application significantly increased biomass yield and WUE. Significantly higher biomass yield and WUE were obtained with N60. Biomass yield for N0, N20, N40 and N60 were 77, 122, 165 and 247% higher than that of N80, respectively. WUE for N0, N20, N40 and N60 were 75, 118, 161 and 236% higher than that of N80, respectively. These results suggested that broadcast micro-dosing, at transplanting of up to two weeks after transplanting, on Local amaranth is a valuable option to increase biomass yield and WUE.