Abstract:
Evaluation of nutrient status in soil is important for nutritional, environmental, and
economical aspects. The objective of this study was to assess the effectiveness of selected
universal soil extractants (Mehlich 3, 0.02 M SrCl2 and Kelowna) in their extraction
efficiency for the determination of P, NO3
-
and K. The study was conducted using
completely randomized design method in three replications at Haramaya University
Laboratory by collecting four (4) soil samples from Haramaya, Dire Dawa, Babile and
Bako. From the results obtained, Mehlich 3 extraction methods were found to be the most
suitable for the determination of P in neutral and basic soils and Kelowna extraction
method was found to be the most suitable in acidic soils. However, very close correlation
was found between these extractants and conventional soil testing methods. The amounts of
nitrate determined by Kelowna and 0.02 M SrCl2 were higher than the Mehlich 3
extractant used in this study and these extractants were found to be the most suitable ones
for the determination of nitrate in basic soils and also well close correlation were found
between these extractants and conventional soil testing method with (p < 0.05 and r = 0.73) and (p< 0.05 and r = 0.70), respectively. On the other hand, the amount of nitrate
determined by Kelowna showed that it is the most suitable extractant as compared with the
others for basic, acidic and neutral soils and also very close correlation was found
between this extractant and conventional soil testing method with (p<0.05 and r = 0.73 ).
The amounts of K determined by 0.02 M SrCl2, Mehlich 3 and Kelowna were higher in
acidic soil. On the other hand, 0.02 M SrCl2 was found to extract larger amounts of K than
others. Generally, the amounts of exchangeable K determined by ammonium acetate
(NH4OAc) method was significantly correlated to the amounts determined by universal
extractants tested with (p<0.001, r = 0.999). In general, both 0.02 M SrCl2 and Kelowna
can serve as universal extractants for the macronutrients considered in this study.
