ABSTRACT

This research was designed to evaluate on-farm orange-fleshed sweet potato variety response to time of planting and NPK (15:15:15) compound fertilizer; and the effect of sweet potato variety and pro-vitamin A maize spatial arrangement on productivity and economic returns of the intercropping systems. The planting time experiment was a split-split plot laid out in a randomized complete block design with three replications. The main plot treatments were two mid season planting dates of mid May or early July and late season plantings of mid or late August. The sub plot treatments were three NPK (15:15:15) fertilizer rates (0,200 and 400kg/ha), while the sub-sub plot treatments were three orange-fleshed sweetpotato varieties (Umuspo1, Umuspo3 and Umuspo4). The experimental design for sweetpotato and maize intercrop studies was a randomized complete block design (RCBD) with three replications. The treatments were fifteen and comprised sole Umuspo1, sole Umuspo3 and sole Umuspo4, sole maize at spatial arrangements of 1x1m,4 plants/stand,1x0.5m 2plants/stand and 1x0.25m 1 plant/stand, and Umuspo1, Umuspo3 and Umuspo4 mixed with maize at the three spatial arrangements. Results indicated that planting in mid May or early July resulted in significantly more branches, greater leaf area index, higher number of storage roots per plant, root weight per plant and higher storage root yield than planting in August. NPK fertilizer application at 400kg/ha significantly increased storage root yield while Umuspo1 and Umuspo3 had comparable shoot and storage root yields but significantly higher values than Umuspo4 in 2020. Maize seed yield was not significantly influenced by intercropping, sweetpotato variety and maize spatial arrangement, while sole Umuspo3 sweetpotato had comparable root yield with Umuspo3 intercropped Umuspo3 and sole Umuspo1 but significantly higher yield than Umuspo4 in both cropping systems and Umuspo1 intercrop irrespective of maize spatial arrangement. The highest LER, ATER and LEC were obtained from all the sweetpotato varieties intercropped with maize at 1x1m, 4 plants/stand spacing pattern, but the highest profit (net monetary returns) was from Umuspo3 orange-fleshed sweetpotato mixed with maize at 1x0.5m spacing 2 plants/stand spatial arrangement. Based on the results, it is recommended that Umuspo1 and Umuspo3 orange-fleshed sweetpotato be planted in mid-May to early July and NPK fertilizer applied at 400kg/ha for high root yield. Intercropping Umuspo3 variety with maize at 1x0.5m spacing 2 plants/ stand arrangement resulted in good use of land and the highest profit, and is recommended to give farmers meaningful yield gains and profit from the two nutritious crops, having diets rich in vitamin A.