This does not mean that the entire soil becomes acidic, just the area around each fertilizer particle or concentration of particles. This acidifying effect is usually of short duration. Phosphates are generally neutral in their effect on soil pH, and potassium carriers are basic. Form of nitrogen. The form of nitrogen applied influences directly the nutrition and growth of the plant.
Most plants seem to prefer the nitrate form.
Nitrate and ammonium are readily absorbed and utilized by plant roots. Under favorable conditions, ammonium nitrogen is converted to the nitrate form by nitrifying bacteria in the soil. Therefore, the ammonium forms are not available as rapidly as the nitrate forms. These high levels may become toxic to plants. Urea is quite soluble and is rapidly broken down to a usable form of nitrogen.