Effect Of Population Density Of Sweet Potato And Cropping System On The Yield Of Sweet Potato-Soybean Intercrop In The Southern Guinea Savannah Agro-Ecological Zone Of Nigeria

Sweet potato has become an attractive crop among farmers due to its high productivity, universal uses, calorie content and good taste. It tolerates adverse environmental conditions such as drought, low soil fertility and it require very little labor and care compared to other crops (Abdissa, 2011). It is one of the cheapest potential sources of vitamin A to alleviate problem of night blindness and infant mortality (Terefe and Geleta, 1994; Korieocha et al., 2009). Researchers revealed sweet potato as a weapon against diabetes as a result of its low glycemic index (Bradley, 2009; Zakir et al., 2008). It serves as cover crop which prevent run off, therefore controlling erosion in farmers plots (Janssens, 2001). The crop has a short duration (3-4 mouths) and could be cropped more than once in the year (Nwauzoe et al., 2006) and once fully established, it suppresses weeds and reduces cost of production compared to cassava and yam (Chukwu, 2001; Abstract: The effect of population density of sweet potato and cropping system on the yield of sweet potato intercropped with soybean was studied; the objectives were to determine the effect of population density on the growth, yield and yield components and to investigate possible differences in the response of the two crops to various population densities and cropping system. Field experiments were conducted at the University of Agriculture teaching and research farm during 2011 and 2012 cropping seasons in a split plot laid out in a randomized complete block design replicated three times. Three population levels (50,000plants/ha; 33,333plants/ha and 25,000plants/ha) and two cropping systems (sole and intercropping) were used. Result showed that in sweet potato, number of branches, vine length and leaf area were significantly (P<0.05) influenced by intercropping. Number of branches increased with decreased in population density, population density one (50.000plants/ha) significantly differed from population densities two and three (33,333 plants/ha and 25,000 plants/ha). Yield and yield components of sweet potato (excerpt root length and harvest index) were significantly influenced by cropping system; there was 47.04% and 56.46% reduction in net yield in 2011 and 2012 in intercropping. Significant effect of population density was only observed on number of roots per plant, unmarketable root number and net yield. There was decreased in net yield and unmarketable root number as population density was decreased. Result on soybean showed that all parameters excerpt number of pods per plant and net yield were not significantly affected by cropping system. Soybean number of pods per plant and net yield were significantly (P>0.05) higher in sole cropping than intercropping. Population density had no significant effect on any soybean parameters observed. Land Equivalent Ratio (LER) values irrespective of the population density tested were greater than unity (LER>1.0). Higher LER values of 1.46 and 1.48 were obtained at 33,333 plants /ha. Competitive Ratio (CR) values of intercropped soybean were higher than its associated crop, for sweet potato, higher CR values of 0.56 and 0.70 were obtained from population density of 25,000 plants /ha.