How big is the difference in fertilizer effect at different application depths?

Crops growing in soil mainly rely on their roots to absorb nutrients, and different crops have different degrees of root development, that is, the depth of root growth differs. Even for the same crop, at different growth stages, the depth at which roots are distributed in the soil layer is also different.

Rational fertilization should place most of the fertilizer in the layer where roots are denser and in the part where root activity is strongest, as this helps crops absorb nutrients. The roots of grain crops such as wheat and rice are mainly distributed within the 0-20 cm soil layer, while the roots of fruit trees such as citrus and apple are mainly distributed at around 40 cm.

Therefore, the same fertilizer should be applied at different depths for different crops. In the early stage of crop growth, roots develop slowly and are mostly distributed in the surface layer, so when applying seed fertilizer, it should be shallower; when the crop grows to the middle stage, the roots grow downward, and when soil nutrients are insufficient, topdressing should be carried out. The depth of topdressing should take into account the depth of crop root distribution, and methods such as furrow application or hole application should be adopted so that the fertilization depth matches the root distribution as much as possible. To meet the crop's nutrient needs throughout the entire growth period, sufficient base fertilizer should be applied before planting in the main layer where roots are distributed (such as 0-20 cm for wheat and rice), so as to meet the crop's fertilizer needs at different developmental stages. Yang Dongwen