Characterization of weed flora in a cassava crop in Tabasco

Abstract

Objective: To evaluate the effect of the incorporation of Crotalaria juncea L. as green manure on the weed community in a cassava crop in Tabasco. Design/methodology/approach: The study was carried out in the Experimental Field of Colegio de Postgraduados, Campus Tabasco (18º01' N and 93º03' W). The samplings were made on four dates: 1) at the planting of crotalaria (12/03/2018); 2) at flowering (31/01/2019); 3) 20 days after incorporation (22/02/2019); 4) at cassava harvest (25/04/2019), using metal squares 50 x 50 cm. Two planting densities, 50 and 80 cm (16,600 and 10,375 plants ha-1), two doses of NPK fertilization (160-40-80 and 00-40-80+GM), and a control were tested. The name of the species, number of individuals and coverage (percentage) were recorded to calculate the richness (S), Shannon diversity (H') and uniformity (E) indices, and the importance value index (IVI). Results: The weed community consisted of 32 species, 28 genera and 16 families, of which the best represented are: Convolvulaceae, Asteraceae, Cyperaceae and Poaceae. The most frequently recorded species are Lindernia crustacea, Ludwigia octovalvis, and Ageratum houstonianum. The diversity indices reflected a poor community, especially with GM treatments; diversity ranged from low to medium and uniformity from medium to high. The importance of the families was more related to the environmental conditions than to the treatments; Cyperaceae were more important in the rainy season and Asteraceae in the dry season. L. crustacea appeared throughout the cycle. Limitations/implications: It is advisable to extend the investigation period. Findings/conclusions: The weed flora consisted of 32 species; the Convolvulaceae family was the most diverse and L. crustacea was the most recorded species during the cycle. The diversity indices reflected a poor community. The importance of the families was related to environmental conditions, where Cyperaceae stood out in the rainy season and Asteraceae in the dry season