Organic-matter additions to soil may also provide nutrients as they decompose, or they may increase the tilth of the soil by amending or modifying the soil structure to promote water infiltration and root penetration. Soil drainage is critical to plant health. The soil's ability to hold water must be balanced with its ability to retain enough oxygen for plant growth. If soil becomes saturated for a prolonged period of time, the oxygen trapped in soil pore space can be depleted rapidly by the plant and soil organisms. When roots cannot get oxygen, the plant's ability to get nutrients and grow is impaired.
Poor drainage causes more problems for landscape plants than any other factor.
Soil Acidity Soil pH, a measure of acidity, has a significant impact on the plant's ability to use nutrients. The scale of pH ranges from 0 to 14. Decay of plant residue, the addition of organic matter, and the widespread use of nitrogen fertilizer also increases soil acidity. Most of North Carolina's landscape plants grow well in soil with a pH range from 6.0 to 7.0. Within this range, the essential nutrients are available to most plants, and soil organisms can carry out their beneficial functions.