The management of a field as a heterogeneous area is now being investigated by many researchers in universities, companies, and research institutions. However, for site-specific application of inputs, it is necessary to develop systems to sense the variation of important properties in real time. Several studies have shown that ion selective electrodes can be used to measure soil nitrates. This work involves an investigation in the use of Ion Selective Field Effect Transistors (ISFETs), to measure soil nitrate levels.