Agri Kultuur March/ Maart 2016 - Page 34

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