Research reveals long-term impacts of drought on soils
The visible signs of the heat wave which swept across Europe in the summer of 2003 were above ground; crops lying brown and desiccated in the fields, rivers running dry. However, new research from the German Research Centre for Environment and Health reveals that the drought also led to severe and long lasting damage below ground. Since 1997 Dr Reiner Schroll and his colleagues at the Institute for Soil Ecology have been studying the ability of different soil types to break down herbicides. Until the summer of 2003, one of the soil types had proved to be particularly effective at this; within two months, up to 60 per cent of the herbicide applied to the soil had been broken down by micro-organisms living in the soil. However, after the drought of summer 2003, the ability of the soil to break down the herbicide fell dramatically, particularly in the top few centimetres of the ground. 'Drought and heat led to far-reaching changes in the composition of the microbial community,' explained Schroll. His team found that not only had the total number of micro-organisms in the soil fallen, the species composition had change too. The bacteria which were responsible for breaking down the herbicide had effectively died out in the upper soil layers. Furthermore, the changes have proved to be long-lasting; studies in April 2006 revealed that the soil's ability to break down herbicides was just 15 per cent. 'Our results show how important long-term experiments are,' commented Schroll. 'Only by comparing the break-down capacity over several years were we able to observe the changes.' The findings also have implications for human health; one of the soil types in the study is common in the area around Munich. The researchers are concerned that if the herbicide is not broken down, it will sink down through the soil and eventually get into drinking water. There are potential solutions to the problem. As deeper soil layers are not as severely affected by the drought, ploughing the land could help to mix up the soil and so reintroduce microbes to the upper layers. In cases where the soil microbes have been almost entirely wiped out, targeted application of certain microbial species could be a solution, although this would be expensive and labour intensive.
Countries
Germany