Comparative Effect of Poultry and Swine Manures on the Performance of White Guinea Yam (Dioscorea rotundata Poir) in an Ultisols Environment

White Guinea yam (Dioscorea rotundata Poir) is an important staple food in a number of African countries, including Nigeria and Ghana. However, the tuber yield in these areas is below its potential yield. The most probably constraint to low tuber yield is the low soil nutrient status. A field trial was conducted at the Experimental Farm of the Department of Crop Science, Faculty of Agriculture, University of Benin, Benin City, Nigeria, between April and November 2016 and 2017, to evaluate the effect of poultry and swine manures on the growth and tuber yield of white Guinea yam (D. rotundata) in an ultisols environment. The trial was laid out in a 2 × 3 split plot arrangement fitted into randomized complete block design with three replicates. The main plots were organic fertilizers (poultry and swine manures) and the sub-plots were represented by three rates (0, 300 and 450 kg N ha-1) of application. Data collection on growth characters were on vine length (cm), vine girth (cm), number of nodes, number of leaves and leaf area index. At harvest, tuber length (cm), tuber girth (cm), number of tubers per plant, tuber weight and tuber yield (t ha-1) were also evaluated. The results showed that growth and yield variables varied significantly (p < 0.05) with organic fertilizer types and application rates. Poultry manure treated plants produced higher (p < 0.05) number of nodes and leaves than swine manure treated plants. Application rates of 300 and 450 kg N ha-1 of poultry manure significantly increased vine length, vine girth, number of nodes and leaves as well as leaf area index. Tuber weight and yield were higher in plants treated with poultry manure with the application rates of 300 and 450 kg N ha-1 performed better than control in 2016, while the application rate of 300 kg N ha-1 had the highest tuber weight and yield in 2017. Application rates of 300 and 450 kg N ha-1 performed better than the control (0 kg N ha-1) in 2016. However, in 2017, application rate of 300 kg Nha-1 had the highest tuber weight and yield. The present study suggests that poultry manure at application rate of 300 kg N ha-1 could be adopted by white Guinea yam farmers for high productivity of the crop under intense and continuous cropping in humid ultisols environment.