RA 00015.pdf - OAR@ICRISAT

3000
2000
1000
0
M
F
V,F,M
V,F
V V V
Synergistic effect of
steps in combination
Sum of yield increases
from single
steps
Three Three T w o steps
steps steps in in
singly combination c o m b i n a t i o n
Figure 77. Sorghum yield increases from improved
variety ( V ) , fertilization (F),
and soil and crop management (M)
singly and in combination over traditional
technology, ICRISAT Center,
1976.
any two of the factors were combined; however,
the magnitude of this effect was far less. Similar
synergistic effects were observed in maize yields
in North Carolina (Krantz and Chandler 1975),
and in wheat yields in India (Krantz et al. 197S)
when all major "steps" were combined in a
production system.
Yields of the ratoon crop were very low
compared to that of the main crop, due to poor
ratoonability and heavy attack of shoot fly. Total
yields and net benefits are given for ratoon crop
as Well as the main crop (Table 60). However, no
attempt can be made to make either agronomic
or economic interpretation of treatment effects
upon the ratoon crop because of the poor
F
V,M
M
F,M
M
F
ratoonability. In cooperation with the breeders it
is planned to screen a large number of genotypes
for ratoonability. The factors affecting
ratoonability are also being investigated so as to
capitalize on this method of double-cropping. As
soon as good ratoonability can be achieved,
treatment effects can be reliably interpreted and
proper conclusions drawn.
The sorghum fodder yield of PJ8K was nearly
double that of CSH-6. In contrast, the harvest
index of the PJ8K variety was very low (7 to 24)
compared to CSH-6 which ranged from 26 to 49.
Maize/pigeonpea intercrop in Verttsols. The
treatments and yields of maize and pigeonpea in
a Vertisol are shown in Table 61. No water was
applied to the maize crop or the main pigeonpea
crop and Treatments 9 and 10 were considered as
additional replications of 4 and 8, respectively.
As in the case of sorghum, maize yields were
significantly increased due to improved fertilization,
but improved variety or improved soil
and crop management as a single factor did not
increase yields significantly. However, with improved
fertilization, the improved maize variety
gave a highly significant response to management.
These results again demonstrate the positive
synergistic effect of one improved practice
upon another.
In the case of pigeonpea, however, the story is
quite different. Relatively little synergistic effect
can be observed. This is believed to be due to the
fact that the improved variety was not responsive
to fertilizer and was not appreciably better than
the traditional variety. Also the general yield
level of this and all other pigeonpea experiments
at ICRISAT Center was much lower in 1976 than
in 1975, probably because of the September and
October drought. The drought occurred during
the critical flowering period after the removal of
the competing cereal intercrop. However, improved
soil and crop management, which included
closer row spacing on pigeonpea, gave
consistent and significant increases. In both
varieties, there was also a significant yield increase
in the pigeonpea ratoon crop due to a 5-
cm water application immediately after harvest
of the main crop. Since this is the first season in
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