Growth and Nutrient Use Efficiencies of Yams (Dioscorea spp.) Grown in Two Contrasting Soils of West Africa

Table 3

Impact of soil type and fertilizers on tuber yields and harvest index (HI) of Dioscorea spp.

Soil type	Species	Fertilizer	Yield (t fresh matter/ha)	Harvest indices
Forest	D. alata	None	28	0.96
		Full rate	35 (25%)**	0.93
	D. rotundata	None	13	0.99
		Full rate	15 (15%)**	0.96
			P values
	Species		< 0.0001	0.0399
	Fertilizer		0.1764	0.0263
	Species × fertilizer		0.4376	0.8682
Savanna	D. alata	None	17	0.88
		Full rate	29 (71%)**	0.90
	D. rotundata	None	8	0.93
		Full rate	11 (38%)**	0.97
			P values
	Species		0.0037	0.0135
	Fertilizer		0.0981	0.1598
	Species × fertilizer		0.2458	0.6461
SE mean (𝑛=32)			3.5	0.17

**Numbers in parenthesis indicate the increase/reduction in tuber yield in relation to the nonfertilized plots.