The fall in air pollution in many parts of the world means that farmers need to carefully measure how much sulphur to apply to the soil using fertilizers such as Polysulphate.
The importance of sulphur to healthy plant growth is well established. Without sulphur, a constituent of all protein and thus an essential nutrient for all plants and animals, growth and productivity are seriously stunted. Farm fields in industrialised parts of the world could rely on the sulphur-containing air pollutants in the atmosphere for the sulphur needed by their crops – pollutants including sulphur dioxide produced as a result of industry, particularly the burning of fossil fuels.
Costs to health outweigh the benefits to soils
The indirect benefit from air pollution of good soil sulphur levels is far outweighed by the cost of air pollution to human health and the wider environment. Worldwide the initiatives to reduce emissions of pollutants, through the use of cleaner energy and less polluting manufacturing processes, mean that sulphur emissions in several parts of the world have already fallen. As a result less sulphur is falling to earth and into soils.
Falling levels of sulphur from air pollution
Air pollution levels are changing in different parts of the world. Across Europe, reveals the European Environment Agency, emissions of sulphur dioxide decreased by 76% between 1990 and 2009.
Past emission trends of sulphur oxides
National emissions reported to the Convention on Long-range Transboundary Air Pollution (LRTAP Convention) provided by European Environment Agency (EEA)
According to the Earth Observatory – which shares discoveries about the environment, earth systems, and climate that emerge from NASA research – the images showing trends of sulphur emission in Asia, the region that now emits the most sulphur dioxide in the world, are interesting. While India saw levels of the gas double between 2005 and 2014, the air over eastern China saw sulphur dioxide decline starting in 2007.
Maps from the NASA Earth Observatory comparing emissions of sulphur dioxide in China during two periods in the first two decades of this century show a steady decline in air pollution which will have resulted in less sulphur reaching the soil.
MULTI-YEAR AVERAGES OF SULFUR DIOXIDE CONCENTRATIONS AS MEASURED BY OMI FOR 2005–2007
Source: NASA Earth Observatory
MULTI-YEAR AVERAGES OF SULFUR DIOXIDE CONCENTRATIONS AS MEASURED BY OMI for 2011–2014
Source: NASA Earth Observatory
Meanwhile in India a 60% increase in sulphur dioxide emissions between 2005 and 2012 is evident in the Earth Observatory maps.
However Indian air pollution – such as the harmful smogs of recent months in Delhi – is not likely to be tolerated long term. As in other parts of the world, anti-pollution policies will be brought in to reduce the emissions and India’s farmers will no longer get their sulphur for free.
Soil testing essential for precision fertilizer use
Farmers worldwide need to know their crops’ nutritional needs. Measurement of available sulphur in the soil is essential. A simple calculation is then required in order to calculate the need for sulphur, and other nutrients, adequately. Polysulphate (the trade name for Polyhalite) is a uniquely balanced fertilizer that is high in sulphate which is internationally admired and relied on to provide what crops need.
The worldwide trend of the reduction in production of sulphur dioxide and pollution of the atmosphere means that the sulphur so important for plant growth is (happily) no longer falling free from the sky. It is also good news that in Polysulphate fertilizer farmers have an effective replacement at the ready.