Certified Crop Advisor Practice Exam

Which nutrient is most commonly associated with a deficiency in younger leaves of a crop?

1. Nitrogen

2. Potassium

3. Magnesium

4. Calcium

The correct answer is: Nitrogen

A deficiency in nitrogen is most commonly observed in the younger leaves of a crop because nitrogen is a vital component of chlorophyll, the pigment responsible for photosynthesis. As crops grow, nitrogen is preferentially allocated to new growth, which includes younger leaves. When there is an insufficient supply of nitrogen, these younger leaves exhibit symptoms of deficiency, such as yellowing, which is referred to as chlorosis. In contrast, other nutrients like potassium, magnesium, and calcium tend to affect older leaves first or have a more uniform distribution throughout the plant. Potassium deficiency often shows up as marginal leaf burn, while magnesium deficiency typically presents with interveinal chlorosis starting in older leaves. Calcium deficiencies frequently lead to issues in new growth and structural integrity, but the symptoms manifest differently, typically in younger tissues but not as prominently as nitrogen. Thus, nitrogen deficiency is distinctly characterized by its impact on the younger leaves of a crop.