Why should more nitrogen fertilizers be applied to the soil in spring and in the first half of summer, and in the second

Why should more nitrogen fertilizers be applied to the soil in spring and in the first half of summer, and in the second half of summer, plants should be fertilized with phosphorus and potassium fertilizers?

Nitrogen is essential for plant growth – this is the so-called “baby” fertilizer. In spring and early summer, the soil is extremely poor in nitrogen (N₂). Later, nodule bacteria settle there, which enrich the soil with nitrogen. By the second half of summer, plants have depleted all phosphorus (P) and potassium (K) from the soil. The reserves of these elements have to be increased with fertilizers. Potassium and phosphorus promote root growth, the formation of fruits and seeds, so they are needed later, and nitrogen will only cause increased shoot growth.