Abstract:
Soil acidity is the most serious challenges to agricultural production and productivity
worldwide in general, and developing countries in particular. Liming is a common
agricultural practice worldwide, which is used for increasing the productivity of acidic soils.
Liming reduces aluminum toxicity, increases the soil pH up to values where the availability of
Al decreases; and the bioavailability of essential nutrients, such as phosphorous is enhanced.
In this study, three buffer methods for determining the lime requirements, namely, the
Shoemaker - McLean - Pratt single buffer (SMP-SB); Shoemaker - McLean - Pratt double
buffer (SMP-DB) and new Woodruff buffer methods were evaluated. These buffer methods
were evaluated using Ca(OH)2-titration to a pH of 6.5; and CaCO3-incubation to a pH of 6.0
and 5.5 as a reference pH because they are reliable and were often used as a calibration for
buffer methods. In this study a total of 24 soil samples representing the major agricultural
acid soils in Nedjo district were considered. The lime requirement needed for adjusting the
pH to 6.5, 6.0 and 5.5 were correlated with the amounts of exchangeable aluminum (r =
0.80), exchangeable acidity (r = 0.82), Organic carbon (r= -70) and soil pH (r= -0.97). The
study revealed that the SMP-DB is the best method for determining the lime requirement for
the Nedjo district acid soils. The SMP-DB method gave the highest correlation coefficient
values (r=0.98) with the reference pH, the least variations from the ideal lines. The sensitivity
of the SMP-DB method was comparable for soils of high (>5.88 t/ha) and low (<5.88 t/ha)
lime requirements, while the sensitivity of SMP-SB and New Woodruff methods were poor for
soils of low and high lime requirements. Pot experiment in lath-house the highest plant height,
spike length and biomass were obtained at pH 5.99 and 6.14 in Vertic Luvisols and Rhodic
Nitisols, respectively; while the biomass yield of wheat was declining at pH levels beyond
these. Since it might not be necessary to lime these soils to pH levels higher than 6.0. Hence,
to ameliorate the soil over there, the SMP-DB method is recommended.
