Impact of Air Pollution on Maize Production in the Sasolburg Area , South Africa

Previous studies have shown that air pollution has an effect on maize production and can also influence yield. Since the pollution load at Sasolburg exceeds certain air quality standards, it is identified as a ‘hot spot’ and is therefore a perfect region to conduct studies regarding the impact of air pollution on maize production. The Northern Free State region is well known for its high maize production and residents of towns up to 50 km away from Sasolburg indicated that they can smell the fumes of the Sasolburg industries. This study included status of maize production over the past 5 years by visiting farmers every 25 km from Sasolburg, for 100 km. Thus, 4 sampling points of 25 km intervals have been visited. Farmers were asked to fill in questionnaires and provide information related to air pollution and maize production. This was done in three different directions from Sasolburg. It is expected that maize yield near Sasolburg will be less than yield far from Sasolburg if pollution influence maize production. Average maize production by the Free State province as well as individual farmers, and other published and unpublished data which were used, concluded that maize production is in fact, influenced by the air pollution from Sasolburg, low income residents burning coal and other substances in the Sasolburg region. The research also indicated that new technology and techniques make it possible for farmers to maximize maize yield and still, year by year, increase the maize production on their farms. South Africa is able to adapt and work around the air pollution problem, but will enter a downwards maize production curve when the original pollution problem is not addressed. It is therefore recommended that the problem of air pollution in the Sasolburg region be solved, rather than adapting to the circumstances with new agricultural technologies. This study has contributed to maize production, air pollution influences on maize yield and farmer awareness in the Sasolburg region and nearby towns.


Introduction
Global near-surface concentrations of ozone in the northern hemisphere have risen from between 10 and 20 parts per billion (ppb) at the beginning of the twentieth century to values between 20 and 40 ppb in recent times (Van Tienhoven et al., 2006).Ozone is the most prevalent and damaging air pollutant to which plants are exposed in many parts of Europe, North and Central America and the Far East.About 3 billion dollars' worth in losses have occurred in the USA due to the impacts of ozone on crops (Adams et al., 1988;Holmes, 1994).Ozone may affect crops in yield or quality reductions, as well as physical effects such as leaf spotting (Ollerenshaw et al., 1999;Fumagalli et al., 2001;Fuhrer & Booker, 2003).Many researches of the impact of ozone and other pollutants have been conducted in Europe and North America, but very little research has been carried out in Africa.
South Africa is the biggest maize producers in Southern Africa and agriculture is important for export and subsistence (Holmes, 1994).Maize is a staple crop and is not particularly sensitive to ozone (Marenco et al., 1990).However, some studies show decreasing relative yield parameters with exposure to high ozone concentrations (Mulchi et al., 1995;Rudorff et al., 1996).Over rural parts in Southern Africa surface ozone varies between 20 and 40 ppb (Annegarn et al., 1996).At Cape point, South Africa, an unpolluted background measuring station, the ozone is 22 ppb.At Elandsfontein and Verkykerkop, located in an industrialised mining region, maximum hourly means of 76.8 and 110 ppb ozone were measured respectively (Kirkman et al., 2000).4 the average maize production in the Free State for 2009 was 4.7 tons/ha and all the farmers in the different direction had a lower maize production than the total Free State average, except for Famers HP3 (4.8 tons/ha) and HP4 (4.9 tons/ha) whose production was higher.In 2010, the average maize production for the province was 4.4 tons/ha and therefore only farmers PV1 (3.7 tons/ha); P V 2 (4.2 tons/ha); KK1 (3.8 tons/ha) and PV3 (4.3 tons/ha) had a lower maize production than the average production of the Free State province.Only farmers P V 1 ( 4 .0 t o n s / h a ) and HP1 (3.3 tons/ha) had a lower maize production than the average maize production (4.3 tons/ha) of the province in 2011.3 the average maize production over the past 5 years is increasing with distance from Sasolburg and thus resulting in low yields in maize production near source of pollution.According to Arnold (2012) ozone pollution generated in each of the Northern Hemisphere's major industrialised regions (Europe, North America and South East Asia) has damaged six important agricultural crops (wheat, maize, soybean, cotton, potato and rice) not only locally, but also by travelling many thousands of kilometers.Of the yield losses to Europe caused by ozone, pollution originating from North America is responsible for a 1.2 million ton annual loss of wheat (Arnold 2012).This is the biggest intercontinental ozone-related impact on any food crop and is in line with table 3 results.These findings from Arnold ( 2012) also demonstrated that air pollution plays a significant role in reducing global crop productivity and show that the negative impacts of air pollution on crops may have to be addressed at an international level rather than through local air quality policies alone (Arnold, 2012).According to Table 4 the average maize production increases with distance from Sasolburg as results of air pollution.This situation is similar to another study conducted in India by Mukherjee (1999), who emphasised that air pollution is linked to industrial estates in the nearby towns of Ballavgarh and Faridabad and is factory related.The industrial belts of these two towns are close to the villages and smoke and other pollutants from the factories pollutes the air and settle on crops and thus affecting yields.Several studies have also shown that the yield growth rates of some key staple crops have been stagnant or declining over the last few decades in many parts of the world as results of air pollution (Tilman et al., 2001;World Bank 2009;Rogerson, 2000).South Africa can therefore benefit directly from these studies with respect to new technology, improved farming methods and equipment, improved maize seeds, improved transport methods.The data in the Heilbron-Petrus Steyn area corresponds directly with each other (Table 5).It is clear that the farmers closest to Sasolburg (HP1) has 1.4 tons/ha lower maize production than the farmer furthest form Sasolburg (HP4) in the same rainfall region.It is also clear that the farmers furthest from Sasolburg have a higher average maize production over the past 5 years than the farmers closest to Sasolburg.According to Emberson (2012) air pollution impacts on crops has to be taken more seriously as a threat to food security.Air quality should be recognized as a determinant of future crop supply given the sizeable yield losses of staple crops caused by surface ozone, coupled with the challenges facing the ability to be food secure in the coming decades.

Conclusion
Since the Vaal triangle is classified as a pollution hotspot, and from all the above data which includes the gas submissions by Sasol in Sasolburg, soil analysis by Nieuwoudt et al. (2009), average maize production as well as individual farmers, and other published and unpublished data, it can be concluded that maize production is, in fact, influenced by the air pollution from Sasol and low income residents burning coal and other substances in the Sasolburg region.However, the data also indicates that new technology and techniques make it possible for farmers to maximize maize yield and still, year by year, increase the maize production on their farms.The greatest concern in the coming decades should be the impact of air pollution on food production in the developing countries.

Recommendation
There is a need, in particular, for an objective assessment to identify the regions and pollutants of greatest concern; improved rural monitoring of pollutant concentrations; evaluation of the pollutant sensitivity of local crops and cultivars; and field experiments to quantify impacts of air pollution.A great contribution could be made to these needs by the governments and scientists of developed countries where impacts of air pollution are of less immediate relevance for the welfare of the population.It is therefore recommended that the problem of pollution in the Sasolburg region is solved, rather than adapting to the circumstances with new agricultural technology. Figu

Figure 4 .
Figure 4. Average Maize Production in Free State Province, Source: Authors

Table 5 .
Farmers Maize Production (Heilbron and Petrus Steyn Area) Source: Authors