Effects of different sowing date and the combined effects of sowing date and seed rates on the performance of wheat (Triticum aestivum L.)/faba bean (Vicia faba L.) intercropping system

Int. J. Agr. & Agri. R.
stems + leaves <strong>and</strong> pods. The wheat ears were
threshed <strong>and</strong> separated to chaff <strong>and</strong> <strong>seed</strong>s (F.
Walter & H. Wintersteiger K G, Austria). Thereafter,
<strong>the</strong> chaff was added to <strong>the</strong> stem + leaf. The <strong>seed</strong>s
were weighed <strong>and</strong> used to calculate <strong>the</strong> HI for <strong>the</strong>
wheat. Similarly, <strong>the</strong> bean pods were separated into
chaff <strong>and</strong> <strong>seed</strong>s by threshing. The chaff was <strong>the</strong>n
added to stems <strong>and</strong> leaves while <strong>the</strong> <strong>seed</strong>s were used
for calculating <strong>the</strong> HI.
Statistical analyses
In general, data were analysed using GENSTAT
(Genstat 8.1 release, Rothamsted UK). Generally,
<strong>the</strong> following were considered in <strong>the</strong> ANOVA. For
analysing wheat variables, plots with zero wheat
<strong>sowing</strong> treatments were restricted in <strong>the</strong> analyses.
Similarly, in <strong>the</strong> case <strong>of</strong> bean variables, plots with
no bean <strong>sowing</strong> were restricted from <strong>the</strong> analyses to
get <strong>the</strong> sole <strong>and</strong> intercrop values. For <strong>combined</strong>
wheat + bean (henceforth to be referred to as total
intercrop or total) analyses were done mostly with
no restriction. The variables were analysed using
<strong>the</strong> General analysis <strong>of</strong> variance with <strong>the</strong> treatment
structure given as pol (wsr; 3) x (bean/bean <strong>sowing</strong>
<strong>date</strong>). This simply means that <strong>the</strong> bean <strong>sowing</strong> <strong>date</strong>
factor was nested within <strong>the</strong> bean treatment.
However, in this paper <strong>the</strong> mean <strong>effects</strong> <strong>of</strong> wheat
<strong>seed</strong> rate averaged across <strong>the</strong> three beans <strong>sowing</strong>
<strong>date</strong>s for <strong>the</strong> variables assessed are not presented.
Those details are presented in ano<strong>the</strong>r paper being
prepared part <strong>of</strong> three-year field trials that had
yield-density relations as a focus. Similarly, <strong>the</strong>
mean <strong>effects</strong> <strong>of</strong> intercropping averaged across <strong>the</strong>
three bean <strong>sowing</strong> <strong>date</strong>s are detailed in <strong>the</strong> paper
being prepared. Never<strong>the</strong>less, here, an indication <strong>of</strong>
<strong>the</strong> simultaneous <strong>effects</strong> <strong>of</strong> <strong>sowing</strong> <strong>date</strong>s <strong>and</strong> wheat
<strong>seed</strong> rate was given.
Estimates <strong>of</strong> intercrop performance
The performance <strong>of</strong> intercrops compare to <strong>the</strong> sole
crop was evaluated using LER, ATER, CPR, CPRT
<strong>and</strong> MA as described by Willey (1985), Hiebsch <strong>and</strong>
McCollum (1987), Harris et al. (1987), Azam-Ali
<strong>and</strong> Squire (2002) <strong>and</strong> Yahuza (2011c) respectively.
However, here both ATER <strong>and</strong> CPRT were
computed using days (calendar time) <strong>and</strong> degreedays
(<strong>the</strong>rmal time). Wea<strong>the</strong>r data used for
calculating <strong>the</strong> <strong>the</strong>rmal time was obtained from <strong>the</strong>
wea<strong>the</strong>r station at <strong>the</strong> site. Following Harris et al.
(1987), <strong>the</strong> yield per unit area <strong>of</strong> wheat in <strong>the</strong>
intercrop WYi was divided by <strong>the</strong> proportion Piw,
<strong>of</strong> wheat in <strong>the</strong> intercrop to give <strong>the</strong> yield per unit
area sown to wheat. This quantity was <strong>the</strong>n
expressed as a fraction <strong>of</strong> wheat in <strong>the</strong> sole plot,
WYs to give CPR. Similar calculations were also
done for <strong>the</strong> bean, thus allowing <strong>the</strong> total intercrop
CPR to be calculated (Harris et al., 1987). Based on
<strong>the</strong> LER estimates, MA was calculated as described
by Willey (1985). Similarly, based on ATER
estimates MA was calculated as proposed recently
by Yahuza (2011c). Note that although <strong>the</strong> methods
used in calculating <strong>the</strong> MA estimated using ATER
was similar to that used for estimating MA based on
LER estimates, <strong>the</strong> interpretations differ. For <strong>the</strong>
ATER estimates <strong>the</strong> interpretation was in terms <strong>of</strong>
increased intercrop value per unit area x time,
whilst <strong>the</strong> LER estimate was in terms <strong>of</strong> increased
value per unit area only (Yahuza, 2011c).
Results
<strong>Effects</strong> <strong>of</strong> bean <strong>sowing</strong> <strong>date</strong> on <strong>seed</strong> yields
Wheat <strong>seed</strong> yields responded significantly to <strong>the</strong>
effect <strong>of</strong> bean <strong>sowing</strong> <strong>date</strong> (P = 0.002). Averaged
across wsr, wheat sole crop <strong>seed</strong> yield was 423
g/m 2 . Intercropping reduced wheat <strong>seed</strong> yield
significantly <strong>the</strong> early <strong>the</strong> beans were sown. For <strong>the</strong>
intercrops wheat <strong>seed</strong> yields were 136 g/m 2 , 193
g/m 2 <strong>and</strong> 326 g/m 2 for SSWB, SB23DAW <strong>and</strong>
SB37DAW respectively (SED 48.8: DF 30). Note
that compared to <strong>the</strong> sole crop, wheat <strong>seed</strong> yield was
not significantly reduced when bean <strong>sowing</strong> <strong>date</strong>
was delayed by 37 days. There was no significant
response <strong>of</strong> wheat <strong>seed</strong> yields to <strong>the</strong> interactive
<strong>effects</strong> <strong>of</strong> bean <strong>sowing</strong> <strong>date</strong> treatment <strong>and</strong> wheat
<strong>seed</strong> rate detected (P > 0.05).
Averaged across wsr, bean <strong>seed</strong> yield responded
significantly to <strong>the</strong> <strong>effects</strong> <strong>of</strong> bean <strong>sowing</strong> <strong>date</strong>
treatment (P < 0.001). Bean <strong>seed</strong> yields were 477
g/m 2 , 335 g/m 2 <strong>and</strong> 162 g/m 2 for SSWB, SB23DAW
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