The Effect of Minjingu Phosphate Rock and Triple Superphosphate on Soil Phosphorus Fractions and Maize Yield in Western Kenya

Table 6

Sequentially extractable soil P fractions (mg kg⁻¹) at Khwisero in the season.

Treatment	Resin-Pi	NaHCO3-Pi	NaOH-Pi	HCl-Pi	NaHCO3-Po	NaOH-Po	Sum of fractions
(1) Control	13	10	85	10	59	297	474
(2) Tithonia	15	13	85	11	72	284	480
(3) TSP + urea (50 kg P ha^−1)	15	12	106	10	63	295	501
(4) TSP + tithonia (50 kg P ha^−1)	17	12	103	10	58	298	498
(5) MPR + urea (50 kg P ha^−1)	17	10	101	10	54	307	499
(6) MPR + tithonia (50 kg P ha^−1)	20	15	93	13	60	283	484
(7) TSP + urea (250 kg P ha^−1)	46	30	158	13	76	288	611
(8) TSP + tithonia (250 kg P ha^−1)	59	38	165	12	78	300	652
(9) MPR + urea (250 kg P ha^−1)	46	23	134	20	62	293	578
(10) MPR + tithonia (250 kg P ha^−1)	44	24	145	24	67	323	641
s.e.d.	6.5	3.2	13	2.1	NS	NS	25
CV	8	10	12	10	8	11	9

TSP: triple superphosphate; MPR: Minjingu phosphate rock; s.e.d.: standard error of difference between means; CV: coefficient of variance.