In his latest newsletter on climate and agricultural conditions, Johan van den Berg of Santam Agriculture says some relief for winter grains are expected but that crop damages have already occurred. Neutral conditions of El Niño Southern Oscillation (ENSO) are likely to dominate the summer.
Current climate conditions
Conditions for winter grain production deteriorated in the Western Cape after a relatively favourable first part the season. September is the most crucial month for winter crop production due to the growth stage sensitivity of winter crops and the high evaporative demand following warmer conditions.
Winter grain crops in the summer rainfall area, especially the dry land wheat crop in the Free State, still look promising provided rain falls within the next two to three weeks.
Intense drought conditions still remain very prominent in large parts of Southern Africa. Namibia, the western parts of North West, most of the Northern Cape, the central to southern parts of the Eastern Cape, the north-eastern and north-western parts of the Western Cape, as well as parts of Limpopo, are in the grip of a severe drought with less than 50% of the long-term average rainfall that occurred throughout the 2018/19 season (1 July 2018 to 30 June 2019). Very little or no rain also occurred in July, August and September 2019.
The surface water situation is, however, relatively favourable for most of the large storage dams in the country with the exception of the Vaal Dam and dams in the Eastern Cape and Karoo.
El Niño and Indian Ocean
All Niño-regions are now indicating non-El Niño trends with both the Niño-1+2 and Niño-3 regions already on the border or in La Niña-type of territory. The important Niño-3,4 area was about 0,3˚C cooler in mid-September, which is also the lowest recorded temperature in the past 12 months. It must be remembered that there are also short-term developments taking place.
Most of the forecasts remain positive for 2019/20 points to the replacement of El Niño conditions with neutral conditions.
Warming of the western Indian Ocean resulted in the development of a positive Indian Ocean Dipole (IOD) Index. Forecasts, however, are showing a weakening towards November.
Expected rainfall and temperature conditions
The development of a positive IOD over the next few months can have a negative effect on the probabilities for rain in spring and early summer. The outlook that favours a more neutral state of ENSO can favour mid-to late-summer rainfall.
Short-term forecasts indicate some rain towards the last part of September and first part of October over the central to southern and south-eastern parts of the country. However, it is more from a winter rainfall system (cold front associated) than from a summer rainfall system. It is possible that some light rainfall may occur over the very drought-stricken southern parts of the Northern Cape and Eastern Cape before the end of September.
With a negative signal from the Indian Ocean and a neutral signal from the Niño-areas, the best chances for rain are towards the second part of the season. Some rain may occur in October and November but it will probably not be enough to break the drought. However, it could enable summer grain farmers to plant within the optimum planting window.
Winter rainfall areas
An approaching frontal system will result in some rain from about 21 to 24 September which will benefit winter grain areas. Some rain is also possible in the last few days of September and first few days of October, especially towards the Southern Cape. This rain can help to stabilise the deteriorating condition of grain crops.
It is likely that very little rainfall will occur in the next months resulting in a possible late start of the summer rainfall season of 2019/20. Significant rain is not expected before the middle of November in the central to northern parts and even later for the southern parts.
Summary and conclusions
Rainfall conditions for the winter rainfall region deteriorated and damage is being done to the winter grain crop. Relief is expected with some rain possible over most of the southern parts of the country in the period 21 to 24 September.
Neutral conditions of ENSO are more likely to dominate the rest of the summer season. This can positively affect the summer rainfall area. However, the Indian Ocean conditions are less favourable but will become more neutral which will contribute to improved rainfall conditions in the summer rainfall area. – Santam Agriculture