Subsoil Consistence Class. Consistency of the subsoil layer is another important factor in forest soil productivity. The combination of soil-sized particles and the physical and chemical properties of each individual particle type in a given soil determine the soil's consistence class. A layer which restricts the downward penetration of a tree's root system will reduce tree growth in direct relation to the depth of layer. In rare instances, a limiting layer may increase site productivity, such as on sandy soils where the layer may retard leaching of nutrients and increase available moisture.
Southern pines grow over a wide range of soil fertility levels.
Fertilization is normally not recommended early in the rotation except in the case of a critical deficiency of a major nutrient such as phosphorus. A soil test prior to site preparation will alert a landowner to critical deficiencies. Research has shown conflicting results in forest tree response to nitrogen fertilization, particulary early in the rotation. Growth may be suppressed if the fertilizer increases the growth of competing weeds. Best results from early fertilizer use arise in combination with herbicide or mechanical control of competing vegetation.