determination of exchangeable Al was done
using 5 g of air-dried soil, extracted with 50
mL of 1 M KCl. The mixture was shaken for
30 minutes and filtered using a filter paper
(Whatman No. 42) before determining the
Al by AAS; and (v) extractable Fe was
determined using double acid method. Fe
was extracted using 0.05 M HCl in 0.0125
M H
2
SO
4
. Five g of air-dried soil was mixed
with 25 mL extracting solution, shaken for
15 minutes and centrifuged at 180 rpm.
The supernatant was then filtered through
filter paper (Whatman no 42) and the Fe
was determined using AAS. The analysis
methods are detailed in Carter
et al
. (1993).
Harvesting and Yield Component
Measurements
The crops were harvested on 29
th
August,
2010 and 13
th
February, 2011 for the first
and second seasons, respectively. During
harvest, a quadrate of 25 cm x 25 cm size
was used for sampling the plant parts. The
quadrate was thrown 4 times randomly in
each of the experimental plot. The samples
were taken to the laboratory for yield
components analysis.
The following yield components analysis
were determined: (i) panicle number was
determined by counting all the panicles from
each quadrate sampling and 20 panicles were
selected randomly from each experimental
plot for further yield component analysis;
(ii) panicle length was measured using a
ruler; (iii) determination of spikelet per
panicle was done by threshing the grains
from the samples and unfilled grains were
separated from filled grains using the