Growth and Yield Response of Improved Sweet Potato Cultivars to Intercropping with Hybrid Maize and Inorganic Fertilizers

Abstract

A field study was conducted in 2018 to determine the growth and yield response of improved sweet potato cultivars to intercropping with hybrid maize and inorganic fertilizer application using a randomized complete block design in a split-plot arrangement and three replications. Maize was intercropped with NASPOT 1, NASPOT 8 and NASPOT 11 potato cultivars. Sole crops and the potato/maize intercrops were fertilized with graded levels of N, P and K comprising a control without fertilizer, 40-20-30, 80-40-60, 120-60-90 and 160-80-120 kg/ha of N-P-K. Vine lengths, and numbers of vine branches and leaves of potato plants under intercropping were higher (<I>P</I> < .05) than those of plants under sole cropping system. In both systems, NPK fertilizer application didn’t (<I>P</I> >.05) affect the vine lengths and numbers of vine branches compared to the control. But numbers of vine branches of plants under sole cropping for all the fertilizer treatments were higher (<I>P</I> < .0001) than those of plants under intercropping system. Generally, NPK application in the sole potato cropping significantly (<I>P</I> =.02) affected the leaf numbers, and the fertilized potato plants had greater (<I>P</I> < .05) leaf numbers than the control. In both systems, NASPOT 11 produced the highest tuber yield, followed by NASPOT 8. Tuber yields were better (<I>P</I> < .01) under sole cropping (43.36 MT/ha) than under intercropping (33.35 MT/ha). Maize grain yields were also better (<I>P</I> < .0001) under sole cropping than under intercropping. But grain yields from all the fertilized intercrops were greater (<I>P</I> < .05) than those of their corresponding control treatments. In all the intercrops, the land equivalent ratios (LERs) were greater than unity indicating yield advantage of intercropping over sole cropping. It was concluded that applying 120-60-90 kg/ha of N-P-K into the potato/maize intercrops results in better tuber yields compared to the unfertilized control. Also, N-P-K application in quantities greater than 40-20-30 kg/ha does not lead to significant differences in tuber yields between the potato/maize intercropping and sole potato cropping systems indicating that inter-specific competition for nutrients in the intercrops is eliminated by the fertilizer. In addition, the application of 80-120 kg N/ha, 40-60 kg P/ha and 60-90 kg K/ha in the intercrops results in better intercrop performance as revealed by higher LERs indicating that improved potato cultivars and hybrid maize are compatible for intercropping. Therefore, farmers can intercrop improved sweet potato cultivars with hybrid maize and apply 120-60-90 kg/ha of N, P and K in the intercrops to maximize yields.