Effect of rainfall gradient and previous crop on weed flora diversity in pearl millet (Pennisetum glaucum [L.]) crop under Sudano-sahelian conditions of Senegal

A study was conducted to determine the effect of climate gradient and previous crop on weed flora structure in pearl millet crop. Thus, floristic surveys were carried out during 2016 and 2017 crop years on station in Sahelian, Sudanosahelian and Sudanian zones of Senegal. The results revealed that flora consisted of 81 species distributed in 59 genera and 19 families. Higher number of species were recorded in Sudanian zone (Kolda and Séfa) with respectively 61 and 45 species and the lowest number of species were found at Vélingara in Sudanosahelian zone (28 species) and Sinthiou Malème in sahelian zone (28 species). According to previously crop, the higher number of species was registered in previous fallow (64 species) followed by previous pearl millet (57 species). In previous mucuna and peanut, flora is 14 percent lower than species recorded in previous fallow. Spectrum analysis indicated that the flora is largely dominated by therophytes, which includes 81.5% of the recorded species. It’s presence in pearl millet field was higher in Sahelian zone (93%) followed by Sudanosahelian zone (89%) and Sudanian zone (Kolda and Séfa) with respectively 80 and 84% of recorded species. Domination of therophytes is more accurate in plot with previous fallow (86%) followed by previous millet (82%), previous peanut (81%) and previous mucuna (79%). Also, it was observed a decreasing of perennial species from Sudanian to Sahelian zone.