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

In flooded soils, the conditions create an environment that increases the mobility of certain nutrients due to reduced oxygen levels and changes in chemical forms. Manganese, in particular, becomes more soluble and mobile in waterlogged conditions, which enhances its availability to plants.

In contrast, in upland soils, where there is better drainage and higher oxygen levels, manganese can form insoluble compounds that restrict its movement and availability to crops. The presence of water in flooded soils can also lead to the reduction of manganese oxides to more soluble forms, further contributing to its increased mobility compared to upland soils.

While iron and zinc may also see changes in their mobility in flooded conditions, manganese's significant increase in solubility under anaerobic conditions specifically highlights its distinction as a nutrient that is more mobile in flooded soils. Potassium, on the other hand, generally remains relatively stable in its availability regardless of soil moisture conditions.