Greenhouse experiments were conducted to evaluate main and residual effects of sole and combined applications of ground rock phosphates (GRP) and organic fertilizer, (OF) on maize performance in two Nigerian alfisols. A commercial OF (1.33% P2O5), Ogun RP (31.00% P2O5), Sokoto RP (36.10% P5O2) and mixtures of OF with either ORP or SRP were used as “test” fertilizers while single super phosphate (SSP) was the “standard” P fertilizer. There were 7 fertilizer sources (OF, ORP, SRP, SSP, OF+ORP, OF+SRP and OF+SSP), each applied at 2 levels (25 and 50mg P2O5kg-1). The 14 treatments and the control were replicated 3 times in each of 2 soil types (a medium acid Oxic paleustalf, A, from Zaria and another low acid Typic paleustalf, B, from Ibadan), to give a total of 90 experimental pots arranged in completely randomised design (CRD). In the first cropping, the weakly acid soil, B produced taller maize plants (62.3cm) than the medium acid soil, A (60.3cm) after six weeks of growth. However, plants treated to 50mg P2O5 kg-1 of OM+SRP were the tallest (66.3 cm) while the untreated ones were the shortest (55.1cm). In the second cropping, differences in height between plants given the various fertilizer treatments were recorded as early as the 3rd week of growth but there was no difference due to soil type even after five weeks. There was no difference in forage yield that could be attributed to the various fertilizer treatments in the first cropping. During the 2nd cropping, however, SRP, ORP and OF+ORP (at 25mg P2O5 kg-1) as well as OF (at 50mg P2O5 kg-1) treatments produced higher yields than the control. However, highest P uptake (about 23.5mg pot-1) was recorded by plants grown under the influence of OF and SSP fertilizer mixture, irrespective of the soil type. The lowest Relative Agronomic Efficiency (RAE) values estimated for the test fertilizer materials in the 1st cropping were 81.5 and 117.5% in soils A and B, respectively. The respective values for 2nd cropping were 78.3 and 62.0%. It was clear that the indigenous GRP, OF and their mixtures have great potentials as substitutes for the imported soluble P fertiliser sources in the medium and weakly acid alfisols.
Key Words: Phosphate rocks; organic fertilizer; maize; Nigerian alfisols
Moor J. Agric. Res. Vol.4(1) 2003: 1-7