In the Sudano-Sahelian zone of West Africa there is potential for
groundnut (Arachis hypogaea L.)
to be grown as a dry-season crop where irrigation is available. However,
there are substantial
variations in the temperatures during the post-rainy season that can be
expected to influence growth
and yield. An experiment at the ICRISAT Sahelian Centre was done in order
to study the effect of
sowing date on phenology, yield and the processes of yield determination
for four groundnut cultivars
under irrigation in the dry seasons of 1990/91 and 1991/92. Starting
on 15 November, eight sowing
dates at 2-weekly intervals were tested. Sowing date significantly affected
phenology (time to
emergence, flowering and maturity) with groundnut sown in November/December
taking the longest
time to reach these phenological stages. November and December sowings
gave the highest pod yield
within each year, despite the lowest crop growth rates (B), and
yield declined progressively as sowing
occurred later (50% decrease by March) despite increasing B. The
observed responses appear to have
been due to the effect of temperature differences during the pod-filling
phase on partitioning.
Partitioning (p) to pods was optimized at c. 30 C, with
some indication of cultivar differences in
partitioning response to temperature. Across all the environments, cultivars
displayed substantial
differences in yield stability. When sown late, yields were low and lines
with high partitioning were
the best. When sown early in the post-rainy season, cultivars with a high
B value were the better
choices. Plant habit differences and B suggest that radiation
interception was a limitation to yield,
particularly when the crops were sown in the cool months of the year. However,
haulm yield and crop
growth rates were not consistently affected by sowing date across the years,
and cultivars
demonstrated different degrees of stability for B. It is concluded
that where pod has a price advantage
over fodder, irrigated groundnut for the dry season should be sown in November
to allow the crop
to develop under the relatively cool temperatures that maximize pod yield.
Further agronomic
research is suggested to maximize B for individual cultivars for
given sowing dates.