IRRIGATION WATER QUALITY IN CHEWING TOBACCO AREAS OF TAMIL NADU

Abstract

One hundred and thirty nine irrigation water samples collected from 65 chewing tobacco growing villages of Dindigul, Karur, Tirupur, Nagapattanam, Cuddalore and Erode districts of Tamil Nadu were analysed for pH, EC, calcium, magnesium, sodium, carbonates, bicarbonates and chlorides. From the data Residual Sodium Carbonate (RSC) and Sodium Adsorption Ratio (SAR) values were computed and water quality classes were determined. The main source of irrigation in the chewing tobacco growing districts of Tamil Nadu is open wells/ bore wells. Irrigation water samples are alkaline in Dindigul, Karur, Tirupur and Cuddalore districts. In Nagapattanam, 39% of water samples tested were neutral and 61% were alkaline. In Erode district 53% samples were neutral and remaining 47% were alkaline. In Dindigul district, 19% samples for EC were in C2 category, 63% were in C3 category and 18% in C4 category. In Nagapatnam, Cuddalore and Erode district majority samples are in C3category. InKarur and Tirupur districts 100% waters samples were in C2 category. Chlorides in all the irrigation water samples irrespective of the district were high. In Dindigul district, SAR was low (<10) in 82%, medium in 13%, high in 3% and very high in 2% water samples. SAR was low in all the samples of Nagapattanam, Cuddalore, Karur,Tirupur and Erode districts. In Nagapattanam district, RSC was low in 89% samples and medium in 11% samples, while all the samples of Dindigul, Cuddalore, Erode, Tirupur and Karur districts were low in RSC. Majority of irrigation water samples in Dindigul district were in C3S1 water class followed by C2S1. Irrigation waters of Karur and Tirupur districts were in C2S1 category. Majority of water samples in Nagapatnam, Cuddalore and Erode districts were C3S1 category. Irrigation waters of Karur and Tirupur districts can be used safely for irrigation. In Dindigul, Erode, Cuddalore and Nagapatnam districts majority of water samples have EC in the range of 0.75 to 2.25 dS/m and SAR < 10, slight to moderate restrictions need to be imposed by reducing the quantum for irrigation water through scientific irrigation management approaches like drip irrigation to contain the salinity and chloride levels in soil for better management of chewing tobacco.