Phosphorus status of some Ethiopian soils. III. Evaluation of soil test methods for available phosphorus
Keywords:Ethiopian soils, Available P, Plant responses
AbstractEight chemical methods were employed for estimating the available P in 32 Ethiopian soils using phasey bean (Macroptilium lathyroides c.v. Murray) as a test crop grown in small pots in a glasshouse and the soil test values then correlated with plant characteristics. Olsen's method gave the highest correlation with percentage yield and P uptake in all three cuts and also was the most reliable giving 97% correct predictions. Warren and Cooke, and Truog methods were the next most useful methods. The critical levels of available soil P for the three methods below which response to P fertilizer would be expected on the soils were 8.5, 48 and 215 ppm P, respectively. The Egner method was the least useful of all the methods for estimating available P from the soils. Olsen, Warren and Cooke, Truog methods are tentatively recommended for use in routine analysis for P in Ethiopian soils until regional field experiments are established to define the superior chemical methods.