Negligible nitrate contamination in groundwater
Intensive cultivation and use of chemical fertilisers had not resulted in groundwater samples being contaminated with nitrates in Coimbatore district, a study by the Tamil Nadu Agricultural University (TNAU) has confirmed.The reason was that farmers applied only optimal or sub-optimal dose of recommended chemical fertilisers. This resulted in negligible losses of nitrate through leaching, it said.Water samples with nitrate content of more than 10 PPM (parts per million) were considered hazardous to human and animal health, Dr S Natarajan, director, Soil and Crop Management studies (SCMS), who carried out the study, said.It was known that apart from manure and fertilisers, other industrial and anthropogenic activities can cause nitrate pollution in aquifers. These include direct point sources like transfer of pollutants from municipal industrial liquid waste disposal sites and from municipal and household hazardous and refuse disposal sites.
Diffuse agricultural sources like washoff and soil erosion from agricultural land carrying materials in agricultural use - mainly fertilisers, herbicides and pesticides and diffuse urban sources like run off from city streets, from horticultural, gardening and commercial activities in the urban environment and from industrial sites and storage areas, also contribute to the contamination, the study said.
