Effect of weed management methods and plant spacing on the growth and yield of cassava morphotypes

An integrated weed management study involving crop spacing, cassava variety, and weed control methods for managing M. invisa in cassava farms was conducted at Umudike, Southeastern Nigeria, over two cropping seasons. The experiment employed a split-split plot arrangement in a randomized complete block design with three replications. Main plot treatments consisted of three plant spacings: 1 m × 0.6 m (S1), 1 m × 0.8 m (S2), and 1 m × 1 m (S3). Two cassava varieties with contrasting morphologies were used as sub-plots: sparse branching TME 419 (V1) and profuse branching NR 8082 (V2). Sub-sub-plot treatments included four weed control methods: hoe weeding at 4, 8, and 12 weeks after planting (WAP) (W1); pre-emergence herbicide (Primextra G. 660 SC at 2.5 kg a.i./ha) applied 1 day after planting (DAP) plus hand weeding at 12 and 16 WAP (W2); pre-emergence herbicide plus post-emergence herbicide (Envoke at 7 g a.i./ha) at 8 WAP (W3); and a weedy control (W0). Data were analyzed using ANOVA, and treatment means were separated using LSD at 5% significance level. Results showed that cassava height was not significantly affected by weed control methods or spacing. TME 419 produced thicker stems than NR 8082. Leaf area of TME 419 decreased with reduced spacing, while NR 8082 increased with reduced spacing. Highest fresh root yields were obtained at 1 m × 0.8 m and 1 m × 0.6 m, indicating these spacings are suitable for relatively fertile soils in Southeastern Nigeria.