Effect of cassava-sweet potato intercrops patterns and weed control methods on weed suppression.

Abstract

Field trials were conducted to investigate complementary weed control potential of sweet potato on cassava in 2015, 2016 and 2017 cropping seasons at the National Cereal Research Institutes’ farm, (NCRI), Amakama (07˚29′N latitude and 05˚28΄E longitude), South Eastern Nigeria. The study was laid out in a split plot arrangement in a Randomized Complete Block Design (RCBD) with three replicates. The main plots consisted of intercrop patterns which included two populations of sweet potato (10,000 and 20,000 plants ha-1) between rows of cassava, planted at 0, 4 and 8 weeks after planting cassava (WAP), sole cassava (SC) and sole sweet potato (SS), The sub-plots were four weed control treatments viz pre-emergence application of S-metolachlor+atrazine at 1.16+1.48 kg a.i ha-1 alone (P), S-metolachlor+atrazine at 1.16+1.48 kg a.i ha-1 followed by supplementary hoe weeding at 8WAP (PHW1), three hoe weedings at 4, 8 and 12 WAP (3HW) and a weedy check (0W). Results indicated that Cassava intercropped at the same time with sweet potato at 20,000 plant ha-1 (CS200) significantly reduced weed density and dry matter compared with SC which gave the poorest weed control. Weed density and dry matter were higher with cassava+sweet potato introduced at 8 WAP at both populations (CS108 and CS208) comparable to SC. There were statistically significant differences in weed growth between the different weed control methods. PHW1 significantly suppressed weed growth as effectively as 3HW when compared to 0W. The weedy check (0W) and P recorded the poorest weed control and performance of these crops at harvest. Although weed density and drymatter was significantly reduced by CS200 and PHW1 independently, results from this study suggested that CS200 combined PHW1 could provide a sustainable integrated weed management system than sole cassava, introducing the sweet potato at 8 WAP or herbicide treatment alone in the study area.