Diversity and composition of weed species in a continuously grown maize field treated with selected pre-emergence herbicides.

This study analyses the floristic composition of field weeds recorded at the University of Ilorin Teaching and Research Farm (008° 27' 23.9'N and 004° 39' 42.9'E) in the southern Guinea savannah of Nigeria during the 2019 - 2021 growing seasons. The area is characterized by a bimodal rainfall pattern with an average annual rainfall of 1227.85 mm and sandy loam soil (plinthustaffs). The experiment was set up as a randomized complete block design and repeated three times in a field that had been continuously maize-cropped for 10 years. Treatments were preemergence applications of atrazine, metolachlor, and primextra at the rate of 1.5, 2.5, and 3.5 kg a.i.ha-1 and Weedy Check. Maize was sown and maintained using the recommended agronomic practices for ecology. Weed species composition was estimated using four continuous sample quadrats (0.5 m²) at 3, 6, 9, and 12 weeks after sowing. The weed flora consisted of 48% broadleaves, grasses 45%, and 7% sedges. Between 2019 and 2021 there was a gradual shift from the predominant annual broadleaves to induced annual grasses and a reduction in the floristic composition of the weed community by approximately 2 - 28%. Fifteen (15) weed species were predominant and the most stable weed species were Richardia scabra, Digitaria horizontalis and Digitaria sanguinalis. This requires finding an ideal weed control option that controls the negative impact of agricultural weeds on crop after yield while maintaining a diverse weed community. [ABSTRACT FROM AUTHOR]