The relationship between brays p 1 modified sodium bi carbonate new mehlich and ammonium fluoride hydro fluoride extractants for phosphorus in savannah soils of western nigeria
Ayodele, O.; Agboola, A.
Fertilizer Research 2(2): 89-100
1981
Accession: 006749424
Sixty surface (0-15 cm) soil samples and 20 field sites with different cropping histories were selected from the major soil types of the western Nigeria basement complex savannah. Available P was evaluated with 6 different extractants, i.e., Bray's P1, 0.1 N AHDF [ammonium hydrogen bifluoride] (pH 4.1-4.3), 0.1 N AHDF (pH 5.0), 0.05 N AHDF (pH 7.0), New Mehlich and modified Olsen's 0.5 M NaHCO3 (pH 8.5). The highest amount of P was extracted by 0.1 N AHDF (pH 4.1-4.3), while 0.05 N AHDF (pH 7.0) extracted the lowest. In the greenhouse, the New Mehlich extractant had the best correlation with P uptake (r = 0.95, P < 0.001), which was not different from Bray's P1, 0.1 N (pH 4.1-4.3), 0.1 N AHDF (pH 5.0) and modified 0.5 M NaHCO3 extractants. Field experiments in the various locations showed a significant correlation between relative maize yield and soil tests. The 0.5 M NaHCO3 had the highest correlation (r = 0.70, P < 0.01) while 0.1 N AHDF (pH 4.1-4.3) had the lowest (r = 0.53, P < 0.05). All extractants seem to extract the same forms of P. Although Fe-P contributes the highest amount of active P extracted with the Chang and Jackson procedure, its utilization by the crop seems to be relatively lower than the other P forms. The 0.1 N AHDF (pH 4.1-4.3) extracted 38% of this active P form while Bray's P1, New Mehlich, 0.1 N AHDF (pH 5.0), modified 0.5 M NaHCO3 and 0.05 N AHDF (pH 7.0) extracted 29, 27, 22, 21 and 7%, respectively. Any of the following 4 extractants, namely New Mehlich, 0.5 M NaHCO3, 0.1 N ADHF (pH 5.0) and Bray's P1, could be adopted for routine soil testing for P in the savannah zone of western Nigeria.