Table 4.

Default and newly parameterized values of average fertilizer recovery efficiency (R_i); physiological efficiency at maximum accumulation of nutrient (a_i) and maximum dilution of nutrient (d_i); and minimum uptake required (r_i) to produce any grain of N, P and K in the above-ground dry matter of maize in the Northern Guinea (NGS), Sudan Savanna (SS) and all (combined data of the two agro-ecological zones).

Coefficients	Nutrients	Default QUEFTS Model (Janssen et al., 1990)	NGS	SS	All
Average fertilizer recovery fraction “Ri”	N	0.50	0.42	0.32	0.40
	P	0.10	0.16	0.08	0.15
	K	0.50	0.54	0.37	0.52
Physiological efficiency at maximum accumulation of the nutrient “ai” (kg grain kg−1 nutrient)	N	30	35	32	35
	P	200	200	164	199
	K	30	25	24	24
Physiological efficiency at maximum dilution of the nutrient “di” (kg grain kg−1 nutrient)	N	70	79	79	79
	P	600	527	528	528
	K	120	117	136	124
Minimum nutrient uptake to produce any grain “ri” (kg ha−1)	N	5.0	4.0	6.1	4.0
	P	0.4	0.5	0.8	0.5
	K	2.0	4.5	7.3	4.5