Abstract
Two field experiments were
undertaken with three sowing dates (28 of December, 28 of January and 24
of March) under irrigated conditions and three sowing dates (June 19,
July 19 and August 19) under rain-fed conditions. Two levels of NPK (no
fertiliser and fertiliser: 120 kg N ha-1, 90 kg P2O5 ha-1 and 60 kg K2O
ha-1) and two maize varieties were used in a split plot design with four
replications on a Gleyic Lixisol (Silitic) in the Northern Region of
Ghana. Highest yield was obtained for SD3 and the lowest SD2 compared to
SD1.
Biomass and harvest index was highest for SD1 followed by
SD3 and SD2 respectively. The results from this study suggest that air
temperatures (>35° C) at anthesis decrease grain number per cob and
grain yield under irrigated and rain-fed conditions. Analysis of
fertilised and unfertilised plots revealed that the negative heat stress
effect around anthesis on the number of grains per cob and grain yield
was only significant in unfertilised plots. Sowing date had no
significant interaction with maize variety. However, fertiliser
application dampened the negative effect of heat stress and increased
water use efficiency by 2.3 times. Comparing the SIMPLACE model output
to the observed field data, the duration of development phases were
predicted with acceptable accuracy among the three sowing dates.
The
heat stress component of SIMPLACE gave a good prediction for yield
under heat stress when no other stress (water, nutrients) occurred. The
estimations of the final yield showed an over estimation when the model
was run with no heat stress condition in the rainy season experiment in
particular under nutrient stress.
Under changing climate, the
impact of heat stress on maize yield can be minimised by sowing late in
March for the dry season or in June for the rainy season to avoid the
combined effect of heat stress and terminal drought. However, the use of
NPK fertiliser can help to reduce the effect of heat stress.
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