Certified Crop Advisor Practice Exam 2025 – Complete Study Resource

The correct answer highlights nitrogen as the nutrient most often linked to deficiencies observed in younger leaves of a crop. Nitrogen is a crucial macronutrient that plays a pivotal role in plant growth and development, primarily because it is a key component of amino acids, proteins, and nucleic acids. It is also a significant part of chlorophyll, which is essential for photosynthesis.

When a plant experiences nitrogen deficiency, the younger leaves tend to exhibit symptoms like chlorosis (yellowing) first, as the plant reallocates nitrogen from older leaves to support the growth of younger, developing tissues. This is a typical response, as nitrogen mobility within the plant allows it to prioritize its newer growth, leading to visible nutrient stress in the leaves that are still developing.

Other nutrients such as potassium, magnesium, and calcium have different mobility characteristics and often exhibit deficiency symptoms in older leaves before impacting younger leaves. For example, potassium is vital for overall plant health and is more likely to cause necrosis at the leaf tips and margins, while magnesium deficiency tends to show itself as interveinal chlorosis in older leaves due to magnesium’s immobility. Calcium, on the other hand, is needed for cell wall structure and is typically associated with issues in younger tissues