Phosphorus is an essential nutrient for the growth and development of vegetables, but it is also one of the most immobile nutrients in the soil. This means that once it is added to the soil, it can't move around easily. Over-fertilizing with phosphorus can lead to build-up in the soil and cause imbalances in the soil, which can negatively impact the growth of your vegetables. It is important to only supply phosphorus when necessary, as determined by soil testing, to support healthy growth without causing imbalances in the soil.