For mainland of 1 ha nursery area of 5 gm Picric acid and 25 gm Sodium carbonate are dissolved in 1 litre of water. Filter paper is dipped into it. Then it is air-dried. Then it is cut into 2x20 cm strips. 1gm tuber is crushed in 25 ml water and put into 500 ml conical flask. Strip is hung from the stopper of the flask. Keep it overnight. Colour develops in the paper. Based on intensity of colour, content of HCN can be determined. Strip is cut into pieces and dipped in conical flask with 60 ml water. This is estimated calorimetrically by using green filter (625 nm wave length)