EFFECT OF POPULATION DENSITY OF SWEET POTATO ON THE YIELD OF MAIZE-SWEET POTATO INTERCROP FOR WEEDS SUPPRESSION IN SOUTHERN GUINEA SAVANNAH NIGERIA

ABSTRACT Maize–sweet potato intercropping often results in weed suppression and increased crop productivity. This study was designed to determine the appropriate planting time and optimal density of sweet potato in a maize-sweet potato intercropping system that will minimize weed infestation and improve yield of the component crops in a drought-prone southern Guinea savanna of Nigeria. The experiment was laid as a randomized complete block design with a split-plot arrangement and 3 replications in 2018 and 2019 growing seasons. The main plots were planting time (May, June and July) while the sub-plots consisted of 3 maize-sweet potato intercropping populations(maize at 53,333 plants/ha + 33,333 plants/ha of sweet potato, maize at 53,333 plants/ha + 66,666 plants/ha of sweet potato and maize at 53,333 plants/ha +99,999plants/ha of sweet potato), sole maize at 53,333 plants/ha and sole sweet potato at 33,333 plants/ha. The results revealed that, 7 weed species were the most prevalent and there was inconsistent effect of planting date on weed flushes while weed smothering efficiency of intercropping was between 31 to 49 % and 48 to 73% for weed density and weed biomass, respectively. Intercropping resulted in land equivalent ratios (LER) of 1.29 to 1.74 while the competitive ability of maize was increased with an increase in sweet potato density. Planting in the month of June had significantly higher tuber yield of 9.56 t/ha of sweet potato and maize grain yield of 3.28 t/ha while intercropping 33,333 plants/ha of sweet potato (1 vine of sweet potato planted at 0.40m apart on the ridge and 0.75m between ridges) and maize at 53,333 plants/ha (0.25m x 0.75m) gave an intercrop yield of 7.32 t/ha tubers and 3.46 t/ha grain yield with highest LER of 1.74, a net profit of ₦566,435.00 and benefit cost ratio of 1.44 was relatively similar to sole sweet potato. Therefore, the above intercropping pattern established in the month of June will minimize weed infestation and improve productivity of maize and sweet potato in the southern Guinea savanna of Nigeria.