Effect of Different Types of Mulching and Plant Spacing on Weed Control, Canopy Cover and Yield of Sweet Potato (Ipomoea batatas (L.) Lam)

The aim of the study was to determine the effects of mulching, plant spacing and other control measures on effectiveness of weed control, canopy cover and sweet potato yield. The cultivar Blesbok was planted in a randomized complete block design where seven treatments were replicated four times. Field trials were established at the Agricultural Research Council - Roodeplaat Vegetable and Ornamental Plant Institute in Pretoria, South Africa during 2006 and 2007. Seven treatments were applied: 1) HW = Hand weeding, 2) NS = Narrow plant spacing (0.5 m between the rows and 15 cm between plants), 3) CO = Organic mulch (compost), 4) PL = Inorganic mulch (black plastic), 5) E*F = Eptam (EPTC; Thiocarbamate) followed by Fusilate (fluazifop-p-butyl), 6) L*F = Afalon (Linuron) followed by Fusilate (fluazifop-p-butyl), and 7) CN = Control (untreated plot). Organic mulch (compost) was omitted in the second trial as it will be beneficial for both weeds and the crop making it difficult to control the weeds. Instead, grass straws (ST) and newspaper (NP) mulches were added. Narrow row spacing, hand weeding, plastic mulch, and newspaper mulch outperformed the other treatments and obtained more than 90% canopy cover by 5 weeks after planting. Effective reductions in weeds were detected with plastic and newspaper mulched plots and was similar to the hand-weeded treatment, followed by narrow spacing. Plots with newspaper mulch and narrow spacing produced marketable yields similar to the hand-weeded treatment. Inorganic mulching and narrow plant spacing were the most effective weed management treatments. Newspaper mulch seems to be a viable option for small holder farmers to control weeds in sweet potato plantings, eliminating the cost of labour to conduct hand weeding. Compost and grass mulch should not be adopted for weed control since these did not control weeds effectively.