The invention’s outcome will help in determination of potassium deficiency from the standing crop even if the plant is not showing any visible deficiency symptoms. potassium deficiency levels can be determined at any stage and which will help to prevent its further progress. if on determination, the plant potassium content, is found close to the threshold deficit level or deficient; potash fertilizer which is a readily available form of potassium can be applied to the field crops to recover them from the deficiency and prevent the overall yield losses. . the invention belongs to electrochemical analysis of activity of ions in sample via a potentiometric sensor. this makes it a unique class of chemical sensors that may be very useful in agricultural fields. the sensor is based upon screen printable technology, where a screen printed electrochemical cell is modified using a biomimetic component say; valinomycin- an antibiotic, one of the most potent potassium (k+) ion carrier to function as ion selective electrode. main reason is the ease of use, its speed and the even more important fact that the corresponding ion activity in the actual biological fluid (plant sap) is measured. with time, awareness has settled that it is the ion activity of the free and uncomplexed ion and not the total ion concentration which controls physiological processes. for measuring ion activity in the mentioned plant sap samples, the ion-selective electrodes (ise) are without any competition. the present research is aimed to solve the problem of detection of potassium deficiency prior i.e. early detection to the actual morphological/visible symptoms appears in the crop plants. if the plant potassium deficiency can be determined before the symptoms, then preventive measures can be taken recover the plant health such applying potassium based fertilizer. this will also control the unnecessary usage of fertilizers, improve soil health and reduce water and atmospheric pollution ultimately reducing the cost or expenses of farming.