Assessing soil nutrient change under long-term application of mineral fertilizer micro-dosing to pearl millet [Pennisetum glaucum (L.) R. Br.] on a sahelian sandy soil

Abstract

In the Sahel, mineral fertilizer micro-dosing technique is known for its benefits to providehigher nutrient uptake and higher crop yields. A study was set up at ICRISAT research stationat Sadoré in Niger, which aims at evaluating the sustainability of the technology in the longterm with emphasis on soil nutrients dynamics. The study has started since 2008 and waslaid-out in a randomized complete block design that involved two pearl millet varieties, threeplanting densities, and four nutrients management options. For this study, a sub-set of thetreatments from this long-term experiment was used. The nutrient management factor,which includes 4 levels was considered. The most important findings obtained indicated thatthe change in soil nutrient was markedly different on the planting hills and that frombetween hill. The change in soil $pH-H_2O$ values on the planting was -7.06 % for the controlplots and -9.57 % for the plots applied with NPK. The total nitrogen content has dropped inthe two different plots. The amplitude of drop has lowered with the application of NPKmicro-dosing on the planting hills with respectively -5.11 % and -12.45 % in the control plotsand the micro-dose plots. Positive change in available P was significantly observed (P≤0.05)in soil between hill with 1.08% in the control plots and 15.97 % in the amended plots. Bothgrain yield and total dry matter showed similar trend in which decreased yield was obviousover the time. In 2008, an average grain yield of 732 kg. ha-1 and 989 kg. $ha^{-1}$ was obtainedrespectively for the control plots and 6g per hill of NPK plots. Whereas in 2016, 146 kg. $ha^{-1}$and 218 kg. $ha^{-1}$ were produced respectively for the control plots and the mineral fertilizermicro-dosing plots. These findings indicated that in the Sahel low-input based milletcropping systems, for the mineral fertilizer micro-dosing technology to be sustainable in thelong term, the improvement and maintenance of soil fertility should be considered as thecornerstone.