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

Table 2

Shoot, root, and tuber growth of Dioscorea spp. as affected by soil type and fertilizers (x: days after planting; y: dry matter in the considered organ; 𝑛∶28 for D. alata, and 𝑛∶24 for D. rotundata).

Soil type	Species	Fertilizer	Growth equations (based on dry weights)
A shoot growth
Forest	D. alata	None	y = −0.3029𝑥^2 + 2.3296x − 1.4887	r = 0.96^a
		Full rate	y = −0.3032𝑥^2 + 2.2935x − 1.1945	r = 0.82
	D. rotundata	None	y = −0.236𝑥^2 + 1.6141x − 1.1447	r = 0.76
		Full rate	y = −0.2635𝑥^2 + 1.858x − 1.4943	r = 0.82
Savanna	D. alata	None	y = −0.1021𝑥^2 + 0.9137x − 0.7546	r = 0.58
		Full rate	y = −0.1415𝑥^2 + 1.2386x − 1.0234	r = 0.70
	D. rotundata	None	y = −0.0916𝑥^2 + 0.6708x − 0.431	r = 0.70
		Full rate	y = −0.2178𝑥^2 + 1.5229x − 1.0748	r = 0.76
B root growth
Forest	D. alata	None	y = −0.0043𝑥^2 + 0.0295x + 0.0219	r = 0.63
		Full rate	y = −0.0027𝑥^2 + 0.0158x + 0.0356	𝑟^2 = 0.67
	D. rotundata	None	y = −0.0022𝑥^2 + 0.0075x + 0.0423	r = 0.67
		Full rate	y = −0.0006𝑥^2 − 0.0095x + 0.0557	r = 0.75
Savanna	D. alata	None	y = −0.0036𝑥^2 + 0.0276 x + 0.0024	r = 0.58
		Full rate	y = −0.0035𝑥^2 + 0.0335x − 0.0096	r = 0.45
	D. rotundata	None	y = −0.0074𝑥^2 + 0.0486x + 0.0048	r = 0.48
		Full rate	y = −0.0042𝑥^2 + 0.0261x + 0.0139	r = 0.54
C tuber growth
Forest	D. alata	None	y = 2.9059Ln(x) − 1.2839	r = 0.83
		Full rate	y = 2.8351Ln(x) − 1.3516	r = 0.79
	D. rotundata	None	y = 1.9668Ln(x) − 0.5224	r = 0.88
		Full rate	y = 2.1574Ln(x) – 0.6713	r = 0.88
Savanna	D. alata	None	y = 1.9881Ln(x) − 0.9843	r = 0.68
		Full rate	y = 2.5169Ln(x) − 1.3072	r = 0.71
	D. rotundata	None	y = 1.0306Ln(x) − 0.3848	r = 0.81
		Full rate	y = 1.4817Ln(x) − 0.4591	r = 0.78

^aCorrelation coefficients based on raw data.