Certified Crop Advisor Practice Exam

Which of the following nutrients is more mobile in a flooded soil than in an upland soil?

1. Zinc

2. Nitrogen

3. Manganese

4. Phosphorus

The correct answer is: Manganese

In flooded soils, the waterlogged conditions create an anaerobic environment that significantly influences the mobility of nutrients. Manganese is one nutrient that becomes more mobile under flooded conditions due to its chemical transformations in the soil. When soils are flooded, the reduction potential decreases, altering the oxidation state of manganese. In this reduced state, manganese is solubilized and can more readily migrate within the soil compared to oxidized conditions found in upland soils. This increased solubility allows manganese to be more accessible to plant roots, thereby enhancing its availability in flooded conditions. In contrast, zinc tends to become less mobile in flooded conditions due to the formation of insoluble compounds. Nitrogen, while it can be somewhat mobile in the form of nitrate, does not exhibit the same level of increased mobility as manganese in flooded conditions, especially since much of it can be lost through denitrification. Phosphorus mobility is also reduced in anaerobic conditions due to its tendency to bond with iron and aluminum oxides, forming insoluble complexes. Thus, manganese stands out as the nutrient whose mobility is notably enhanced in flooded soils compared to upland soils.