Field dissipation kinetics of atrazine in soil and post-harvest residues in winter maize crop under subtropical conditions

The growing awareness of environmental and health problems due to increased use of pesticides has led to the implementation of various monitoring programmes. Thus, to monitor residues in crops, dissipation studies were conducted of atrazine in the soil of winter maize in field conditions under the subtropical climatic zone of the Tarai region of India. A maize field was treated with atrazine at 2.0 and 4.0kg a.i. ha(-1) as pre-emergent herbicide. The degradation pattern of atrazine indicated correspondence to monophasic first-order kinetics in soils. The persistence of atrazine in soil was more in higher rate (135 days) compared with lower (100 days) application rate. The half-life values calculated to be 16.4 and 20.8 days at lower and higher application rate, respectively. Detector response was linear within 0.01-1.0 mu gmL(-1) concentration range at per cent relative standard deviation 2.07%. The instrument limit of detection was 1ngmL(-1) and limit of quantification for soil, straw and cobs 0.005, 0.007 and 0.006 mu gg(-1), respectively. The average recoveries of atrazine from soil, cobs and straw samples were found between 86.8-90.0%, 88.0-91.6% and 93.2-95.6%, respectively. At both the application rates, no residues have been observed in soil, maize cobs (seeds) and straw at the time of harvest.