SOIL SCIENCE 109
Homework 2
Spring 1998
The following problem requires that an answer
be determined in each section to determine the liming requirement
of a soil that has a history of extensive ammonical fertilizer
applications.
1. Calculate the equivalent weight of marl that has a
calcium carbonate equivalent of 72%.
2. A 25 g soil sample
was extracted with 300 mL of 2 N KCl after an extraction with
ammonium acetate to yield an NH4+
concentration of 350 ppm. Calculate the cation exchange capacity
of this soil.
3. The filtrate (300
mL) after the ammonium acetate extraction of the above soil
contained 70 ppm Ca++, 25 ppm Mg++, and 60
ppm K+. Calculate the base saturation of this soil.
4. The above soil had
a pH of 5.0. Calculate the amount of marl (from question one)
needed to raise the soil pH to 6.5 and a base saturation of 70 %
for the top 15 cm of a square hectare. Assume a bulk density of
1.2 g cm-3.
5. Calculate the Ca++
saturation of the limed soil assuming that the marl contained
only calcium carbonates as a source of neutralizing equivalents.