Weed flora dynamics in grain sorghum (Sorghum bicolor L.) crop under Sudanian conditions of Senegal

Abstract

This article presents the dynamics of weed in sorghum crop in Sudanian zone of Senegal. This study was conducted to evaluate the diversity and density of weed flora, discover the chronology of species emerged and evaluate the effect of mineral fertilization on weed dynamics. Permanent rectangles (17/block) were placed randomly in two blocks of 100 square meters one under mineral fertilization, the other in unfertilized conditions. Upon emergence of the crop, weeds were identified periodically (15-20 days), enumerated and eliminated. The flora is composed of 33 species distributed in 28 genera and 9 families. The Shannon and Simpson index indicate that diversity is generally low but higher without fertilization. The number of species recorded under unfertilized conditions was respectively 20 in 2016 and 2017 against 14 and 19 species recorded under fertilized conditions. The results showed that there are more weeds under unfertilized conditions (941 and 2226) compared to fertilized plot (716 and 1973), regardless of the year. The flora is characterized by the dominance of five (5) species which account for 91% of the emergence. Significant correlations between rainfall, the number of rainy days and density were observed but not with diversity. This study should be supplemented by an evaluation of weed seedbank. Knowing seedbank weeds and emerged flora relationship could help to establish predictive models for monitoring the evolution of weed communities.

Keywords: Diversity index, Dynamics, Fertilization, grain Sorghum, Sudanian Zone, Weed Flora