- Rhizobium bacteria form a symbiotic relationship with legumes, fixing atmospheric nitrogen into a usable form for the plant. - This nitrogen fixation process is highly energy-intensive, requiring a significant supply of ATP (adenosine triphosphate). - Phosphorus (P) is a key component of ATP and plays a vital role in energy transfer within cells. Adequate phosphorus levels are essential for the metabolic activities of both the host plant and the rhizobia, including nodule formation and the enzymatic processes involved in nitrogen fixation.