Phytosociological characteristics of the predominant weeds in calabar as influenced by cassava density and soil solarization duration

Abstract

Field experiments were conducted in the 2019 and 2020 early cropping seasons in the Teaching and Research Farm, Department of Crop Science Teaching and Research Farm, University of Calabar, to identify the predominant weeds and assess their responses to cassava population density integrated with pre-planting soil solarization duration. The experiment was a factorial combination of three crop densities of cassava: 17,778 plants ha-1 (0.75 m x 0.75 m), 13,333 plants ha^-1 (0.75 m x 1 m) and 10,000 plants ha^-1 (1 m x 1 m) and four pre-planting soil solarization durations (0, 4, 7 and 10 weeks), laid out in randomized complete block design (RCBD) with three replications. Data were collected on the phytosociological characteristics at four weeks intervals up to the 20th week. The relative density, frequency and abundance of the weed species varied across treatments in both years. C. bicolor consistently had the highest relative important value index reaching up to 57.2 % in the plot treated with 17,778 cassava plants ha-1 integrated with pre-planting soil solarization for 10 weeks, followed by P. maximum, A. compressus and C. dactylon in that order. Aspillia bussei, A. conyzoides, P. amarus and T. rhomboidea had zero percent important value index when soil solarization duration of 10 weeks was integrated with crop density of either 17,778 plants ha^-1 or 13,333 plants ha-1 of cassava. The important value index of C. bicolor consistently increased as cassava density and solarization duration increased, while those of the other weed species tended to decline. The integration of cassava density at 17,778 plants ha^-1 with soil solarization duration of 10 weeks effectively controlled most of the weed species in the area except C. bicolor and could be recommended for effective weed suppression.