Which of the following nutrients absorbes both positive and negative forms?

Nitrogen is a nutrient that absorbs both positive and negative forms.
Nitrate is the form of nitrogen most used by plants for growth and development. Nitrate is the form that can most easily be lost to groundwater. Ammonium taken in by plants is used directly in proteins.
Plants absorb nitrogen from the soil as both NH₄⁺ and NO₃^- ions, but because nitrification is so pervasive in agricultural soils, most of the nitrogen is taken up as nitrate.