Hill placement of manure and fertilizer micro-dosing improves yield and water use efficiency in the Sahelian low input millet-based cropping system
tInadequate nutrient supply and insufficient rainfall are the most important limiting factors for crop pro-duction in the Sahelian agro-ecological zones. Targeted technology application may help to improvethe efficient use of limited nutrient and water resources. The objective of this study was to determinethe optimal combination of fertilizer micro-dosing and manure application rates for improved milletyield and enhanced water use efficiency in low input millet-based cropping system. A two-year fieldexperiment was conducted at a research station in Niger using a randomized complete block designwith three replications. The treatments consisted of the factorial combination of: (i) two fertilizer micro-dosing options (20 kg ha−1of diammonium phosphate (DAP) and 60 kg ha−1of NPK corresponding to2 g hill−1of DAP and 6 g hill−1of NPK, respectively), (ii) cattle manure at four application rates (0 kg ha−1,1000 kg ha−1, 2000 kg ha−1, 3000 kg ha−1) and (iii) two methods of manure application (broadcasting andhill placement). Millet grain yields under fertilizer micro-dosing combined with manure was increasedon average by 59%, 83% and 113% for 1000 kg ha−1, 2000 kg ha−1and 3000 kg ha−1, respectively com-pared with fertilizer micro-dosing alone. Combined applications of manure and fertilizer micro-dosingincreased water use efficiency significantly. Hill placement of manure increased total dry matter on aver-age by 23% and water use efficiency by 35% relative to manure broadcasting. The total root length densitywas increased by 66% and 42% in hill placement of manure at 25 cm and 50 cm, respectively, from the hillcentre compared with manure broadcast. These results indicate that millet production with the fertil-izer micro-dosing technology can be improved further by hill-placement of manure. The combination of2000 kg ha−1of manure and 20 kg DAP ha−1hill-placed were most promising for increasing millet yieldand the efficient use of limited nutrients and water in Sahelian millet based systems. There is need fortesting this technology further together with farmers to valuate its effectiveness.