Years ago, the farmers use to keep cows in large numbers, which not only would help them earn extra income through dairy farming, but also get cow dung to prepare manure for the field. Greed, uncultivable land under State’s ownership has further caused farmers turn away from the natural manure. Each and every family of farmers generally kept atleast a pair of oxen, cows, buffaloes and calves. However, they have been replaced by tractors and new breeds, which make farmer inevitably depend on chemical fertilisers and help from outside.
Cow dung, a wise choice to enrich soil fertility The Deccan Herald, June 15, 2009 

It is imperative to reduce application of fertilizers as they lead to global warming, organic farming scientist G. Nammalvar has said. It is the third most important cause for global warming after industries and automobile, as nitrogen-based fertilizers enter the atmosphere as nitrous oxide, he said on Monday at a workshop on Technology Transfer and Knowledge Dissemination of Engineering to Agriculturalists in Erode District, organised at Kongu Engineering College.
‘Reduce use of fertilizers’ The Hindu, Chennai, 02 June 2009 ced backup copy