seed separator; (iv) percentage of filled
spikelet was calculated using a formula
(filled spikelet per panicle/total spikelet per
panicle) x 100; and (v) 1000 grain weight.
Grain yield was determined from all plants
from a 25 m
2
site (except border plants) in
each experimental plot.
Plant Tissue Analyses
The upper part of the plants was oven-dried
at 65ºC for three days. The samples were
ground using a stainless steel grinder and
passed through a 1-mm sieve. The samples
(0.25 g) were then digested by wet-ashing
using 1:1 ratio H
2
SO
4
-H
2
O
2
on a block
digester at 350ºC. The digested solutions
were filtered through Whatman filter paper
No. 42 and made up to 100 mL volume
with distilled water. The concentrations of
calcium (Ca), magnesium (Mg), aluminum
(Al) and iron (Fe) were measured using
Perkin-Elmer AAnalyst 400 AAS. Nitrogen
(N) and potassium (K) were measured using
Lachat QuickChem® FIA+ 8000 Series auto
analyzer (AA).
Analysis of Water from the Field Plots
Water was collected from each of the
experimental plots. The samples were taken
every week for the first 5 weeks, followed
by every 2 weeks until harvest. For the first
season, the sampling started at 14 DAS due
to dry conditions on the field at 7 DAS,
while for the second season, the sampling
was stopped at 77 DAS when the paddy field
dried up. After filtering the samples, pH was
determined using Sartorius pH meter PB-11
Al and Fe concentrations were determined
using Perkin-Elmer AAnalyst 400 AAS.
Statistical Analysis
Data from the experiment were analyzed
statistically using analysis of variance
(ANOVA), and least significant difference
(LSD) test was employed to determine the
mean differences between the treatments.
The statistical package used was SAS v9.1
software.