A sufficient and balanced supply of essential nutrients is vital to attain high yield and excellent quality of produce in vegetable and herb production. Soil testing and/or plant tissue testing are routinely used to detect nutrient deficiency or toxicity and derive fertilizer treatment plans to correct nutritional problems. Knowledge about visual symptoms and disorders in vegetables and herbs can help in diagnosing nutrient deficiencies, especially in the absence of soil/plant testing, and can potentially assist in deploying timely treatment to avoid losses in yield and quality of produce. This chapter also elucidates the implications of nutrient mobility in plants and soil. Deficiency symptoms of mobile nutrients are manifested in old and mature leaves, while immobile nutrients affect young groups of leaves and, in some cases, new shoots and fruits; such a distinction can facilitate identifying the deficient nutrient. The mobility of nutrients in the soil is indicative of its dynamics, which is commonly used as a basis to determine the feasibility and success of in-season correction of nutrient deficiency. Correcting a soil-mobile nutrient deficiency for established plants has a higher chance of symptom reversal than correcting a soil-immobile nutrient.