Plant nutrition is one of the necessary disciplines in the production of crops. The importance of crop nutrition is in increasing the yield and quality of agricultural products. In a simple way, crop nutrition is the study of the absorption and use of nutrients for physiological processes and response to the growth and development of crop plants. One of the main goals of this book is to describe and discuss essential nutrients, their metabolic role and their absorption mechanism in crops, and to explain the basic processes of plant nutrition. Also, this book includes the classification of essential nutrients with emphasis on their role, physiological function, biochemical function and their absorption process through the cell membrane. Among other important points, we can mention the discussion on topics such as: Root structure, absorption of nutrients, their assimilation in cellular levels, diagnosis of nutrient deficiency with different methods, methods to eliminate their deficiency in plants, biochemical and metabolic roles of nutrients.