Globally, soil quality is diminishing and topsoil is vanishing. A study conducted by researchers from the University of Sydney and presented at the Carbon Farming conference in 2010 found that all the agricultural topsoil on Earth will be gone by 2110, if farming practices do not change.
Factors contributing to soil depletion include overuse of synthetic fertilisers, overuse of ploughing, poor erosion control and climate change including increasing drought. All of these factors are reported to be intensified by global warming and are expected to contribute to a food crisis as the planet’s population continues to grow.
The report highlights that fertile soil is being lost faster than it can be replenished and will eventually lead to the “topsoil bank” becoming empty. Soil mismanagement, over-farming causing erosion, climate change and increasing populations are also to blame for the dramatic global decline in suitable farming soil, scientists said.
An estimated 75 billion tonnes of soil is lost annually with more than 80 per cent of the world’s farming land “moderately or severely eroded”, the Carbon Farming conference heard. The University of Sydney study, presented to the conference, found soil is being lost in China 57 times faster than it can be replaced through natural processes. In Europe that figure is 17 times, in America 10 times while five times as much soil is being lost in Australia and parts of New Zealand.
John Crawford, professor of Sustainable Agriculture at the University of Sydney, who presented the study, said it was unknown how long agricultural topsoil will last.
“It could be as little as 60 years and that is a scary figure because it is not obvious that we have time to reverse decline and still meet future demands for food” he said.
“It is not an exaggeration to say that soil is the most precious resource we have got, and… (we) are not up to the task of securing it for our children never mind our grandchildren.”
Prof Crawford, who is the former chair of the UK Biotechnology and Biological Sciences Research Council’s Agri-Food Committee, said that it can take decades to significantly increase the amount of useful carbon in soil, which helps make it fertile.
The warming trend in New Zealand has led to more moisture loss to the atmosphere from plants because of increased evapotranspiration. This is where plants “breathe out” into the air moisture that is stored in the soil.
The hotter it is, the more moisture plants pump into the atmosphere. These two effects — less rainfall and more water loss from the soil – have resulted in more droughts dramatically affecting agriculture in New Zealand. Liquid fertilisers as part of a fertiliser regime can significantly assist soil and crops in withstanding drought.