Ernest Dube, Willem Kilian, Ben van Rensburg,Manus van der Merwe,
Dawie du Plessis, Elsa van der Merwe and Hesta Hatting
ARC-Small Grain Institute, Bethlehem
Photo supplied
I
n 2015, South Africa experienced its worst drought in 30
years due to the ‘El Niño’ effect. A combination of low
rainfall and incessant heat dried up
dams early on many farms in the
KwaZulu-Natal, Free State, Mpumalanga and Limpopo Provinces. Temperatures were higher than normal
during the entire wheat growth
period, especially in the warmer
northern areas and KwaZulu-Natal.
Many irrigation wheat farmers did
not have enough water to meet the
high evaporative demand. Figure 1
is temperature data from Groblersdal, showing that temperatures were at least 3°C higher than
normal from June to October. Heat
stress can have significant effects
on grain yield of wheat. It causes
premature leaf senescence, tiller
abortion, a reduction in number of
seeds per ear, reduced duration of
Figure 1: Average monthly temperatures in Groblersdal during 2015
grain fill and reduced grain size.
There is scientific data which
shows that a 3-5% (±190 kg/ha)
reduction in grain yield of wheat
can occur for every 1°C increase in
average temperature above 15°C.
The 2015 National Irrigation Wheat
Cultivar Evaluation Program was
however conducted successfully.
There were 23 entries that were
supplied by the major breeding
companies of South Africa, namely