Smart Agrometer is a smart plant diagnostic handheld device developed by Lithuanian company UAB “Žemdirbi? konsultacijos”, designed to determine the nutritional status of plants and help farmers make more accurate fertilization decisions during plant vegetation. It uses a spectrometer (light reflection analysis) and cloud technology to provide real-time insights into plant nutrient deficiencies. The device determines not only the deficiency of major nutrients, but also micronutrients in plants. Unlike laboratory tests, Smart Agrometer provides data immediately, allowing for quick decisions on plant fertilization. Developed algorithms determine which major and micronutrients plants lack. After performing plant measurements in the field with Smart Agrometer, it is possible to diagnose the deficiency of an element that limits crop growth. The results are immediately visible on the user portal.