Exponential increase of publications related to soil water repellency

Soil water repellency is much more wide-spread than formerly thought. During the last decades, it has been a topic of study for soil scientists and hydrologists in at least 21 States of the USA, in Canada, Australia, New Zealand, Mexico, Colombia, Chile, Congo, Nepal, India, Hong Kong, Taiwan, China, Ecuador, Venezuela, Brazil, Mali, Japan, Israel, Turkey, Egypt, South Africa, Germany, The Netherlands, Spain, Portugal, United Kingdom, Denmark, Sweden, Finland, Poland, Slovakia, Russia, France, Italy, and Greece. Although, water repellent soils already have been indicated at the end of the nineteenth century, they have been discovered and studied in most countries in the last decades. Water repellency is most common in sandy soils with grass cover and in nature reserves, but has also been observed in loam, heavy clay, peat, and volcanic ash soils. From 1940 to 1970 research was focussed on identifying vegetation types responsible for inducing water repellency and on developing techniques to quantify the degree of water repellency. Of special interest has been the effects of wildfire on the development of soil water repellency and its consequences for soil erosion. Due to increasing concern over the threat to surface and groundwater posed by the use of agrichemicals and organic fertilisers, studies on water repellent soils have also been focused on its typical flow behavior with runoff and the existence of preferential flow paths. Since the end of the 1950s, wetting agents and clay amendments have been studied to ameliorate water repellent soils. Since 1883, more than 1200 articles related to soil water repellency have been published in journals, reports, and theses. An exponential increase in number of publications started in 1960, resulting in an average of 200 publications per 5 years.