Increasing Millet Planting Density with Appropriate Fertilizer to Enhance Productivity and System Resilience in Senegal

Climate forecasts show increased frequency and intensity of drought in the semi-arid regions of west Africa, which negatively impacts food and nutrition security. Developing and improving resilient cropping systems will require adequate varieties with improved agronomic practices. The purpose of the study was to evaluate grain and biomass production of newly released dual-purpose millet varieties under different fertilizer rates and planting densities across the millet-cropping regions of Senegal with different rainfall regimes (Bambey: 600 mm, Boulel: 700 mm, Nioro: 650 mm, and Sinthiou Malème: 800 mm). The experimental design was a split-split-plot with three replicates using one traditional variety (Souna 3) and four dual-purpose varieties (Thialack 2, SL28, SL 169, and SL423) as the main factor; two planting densities (E1: 12,500 seed hills ha−1 and E2: 25,000 seed hills ha−1) as second factor; and eight fertilizer combination as sub-sub-plots. Results showed that variety yield response differed with environments. Regardless of variety, increasing sowing density increased grain yields (1600 kg ha−1 for E2 vs. 1000 kg ha−1 for E1) and fodder yields (4200 kg ha−1 for E2 vs. 3100 kg ha−1 for E1). Fertilizer response differed between environments, but the application of 70N–10P–19K + 2.5 t ha−1 cow manure produced appreciable yields in all the environments. The dual-purpose varieties (SL 28, SL 169, and Thialack 2) sown at E2 produced the best grain and fodder yields. Soil water content was greater for all varieties (Thialack 2: 12.32%; Souna 3: 5.32%; SL28: 6.32%; and SL423: 9.23%) at higher planting density compared with normal density (Thialack 2: 9.25%; Souna 3: 3.21%; SL28: 5.43%; and SL423: 7.47%). The highest agronomic-use efficiency (AEg) of inorganic fertilizer applied was observed at 25,000 seed hill ha−1 and averaged 6.63 kg kg−1 at Boulel, 9.20 kg kg−1 at Sinthiou Malème, 4.67 kg kg−1 at Bambey, and 8.32 at Nioro kg kg−1. The AEg significantly varied among fertilizer combinations, with greatest AEg obtained with 70N–22.5P–22.5K (5.53 kg kg−1) at Boulel and with 95N–17P–27K (4.66 kg kg−1) at Bambey. This study provides crop-management options for millet-cropping systems in the semi-arid regions of west Africa for improving millet productivity while enhancing system resilience through better conservation and utilizing of soil water.