Biomass yields, radiation interception and radiation use efficiency as influenced by seed rate in a cereal/legume intercropping system

Int. J. Agr. & Agri. R.
otherwise stated, the RUE refers to the efficiency of
conversion of accumulated PAR from sowing until
maturity.
Final biomass yields determination
The above-ground biomass for both wheat and bean
were collected from destructive samples taken from
1m x 0.5m area with a quadrat at maturity. Four
rows were included for sole crop plot and eight for
the intercrops and the plants were cut at the soil
surface. Samples were separated into the
components, weighed, placed in dishes labelled and
packed in ovens and dried at a temperature of 85ºC
for 48 hours. After drying, the samples were
weighed. To get a precise estimate of final BY, the
procedure described by Gooding et al. (2002) was
followed. In Experiments 1 and 2, the assessment
was carried out 293 DAS. On the other hand, in
Experiment 3, the final BY was determined at 152
DAS. Similarly, in Experiments 4 and 5 the final BY
was assessed 287 and 270 DAS respectively. Total
intercrop final BY was calculated simply by adding
wheat intercrop and bean intercrop BYs.
Statistical analyses
In general, data were analysed using GENSTAT
(Genstat 8.1 release, Rothamsted UK). Generally, the
following were considered in the analysis of variance
(ANOVA). For analysing wheat variables, plots with
0-wheat seeds/m 2 were restricted in the analyses.
Similarly, in the case of bean variables, plots with no
bean sowing were restricted from the analyses to get
the sole and intercrop values. For combined wheat +
bean (total intercrop or total) analyses were done
mostly with no restriction. For each of Experiments
1, 2 and 3, the analyses were done using the General
ANOVA. The treatment structure was pol (wsr; 3) x
bean treatment with all interactions. The block
structure was replications/wsr/bean with all
interactions. In Experiment 4 similar procedures
used for Experiments 1, 2 and 3 were employed,
except for the further complication of the BSD factor.
The variables were analysed using the General
ANOVA with the treatment structure given as pol
(wsr; 3) x (bean/BSD). This means that the BSD
factor was nested within the bean treatment. The
block structure was the replications. However, as
stated earlier in this paper means presented are
averages across the three BSD. In Experiment 5, the
analytical procedure differs slightly from that of the
previous experiments because the bean seed rate
(bsr) was also varied. The variables were analysed
using the General ANOVA with the treatment
structure given as pol (wsr; 3) x pol (bsr; 3). The
block structure was the replications.
Regressions mainly using hyperbolic yield-density
equations (Willey and Heath, 1969; Bleasdale, 1984;
Yahuza, 2011a) were performed across wsr
particularly for the wheat SYs where the response to
wsr deviated from linearity. Hence, for all the data
sets for which the regression were performed, the
adjusted R 2 was compared with equation 3 to
determine whether it fitted better when the response
to wsr deviated significantly from linearity.
Y
wsr
a w
b w
3
In equation 3, Y = yield (g/m 2 ), aw and bw are
constants that defines yield per plant in a
competition free environment and maximum yield
potential of the environment respectively (Willey and
Heath, 1969) and wsr refers to the wheat sowing rate
(seeds/m 2 ).
Typically, where equation 3 holds, the responses of
the reciprocals of yield per plant to density is linear
(Bleasdale, 1984) as described by equation 4,
1 / w a b wsr
4
w
w
In equation 4, w = yield per plant, aw and bw are
constants as defined in equation 3.
However, besides applying more complicated
equations other than equation 3 to quantify the BYs,
other simpler or more complicated ones were
applied. In addition, for Experiment 5, the interspecific
yield-density equations (Dolman, 1985; Park
et al., 2002) were applied to quantify the wheat and
total intercrop BYs.
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