Which nitrogen source typically has the quickest plant uptake?

Ammonium nitrate is known for its rapid plant uptake due to its nitrogen content in both ammonium and nitrate forms. When applied to the soil, ammonium nitrate can dissolve quickly, making nitrogen readily available for plants almost immediately after application. The ammonium portion is taken up directly by plant roots, while the nitrate form is quickly available for absorption as well, due to its high solubility in water. This dual availability allows plants to access nitrogen efficiently during critical growth phases.

In contrast, the other choices typically involve slower release mechanisms or require microbial activity for conversion into forms usable by plants. For instance, natural organics often need time to decompose, and ureaform materials require enzymatic breakdown to become available. Potassium nitrate, while also providing a readily available source of nitrogen and potassium, does not reach the same level of quick uptake by plants as ammonium nitrate because its uptake is dependent on specific soil conditions. Therefore, ammonium nitrate stands out for its immediate nitrogen availability and rapid plant uptake.