The Online Gardener's Handbook
Chapter 3: A Word about Soil
Table of Contents
Plants take up their water and nutrients from the soil. For healthy plant growth, therefore, the soil must be adequately supplied with both. A number of nutrients are essential for plant growth, and plants take up these various elements at different rates depending on the stage of growth.
In the spring and summer, when plants are in a vegetative stage, great levels of nitrogen and phosphorus are required. At flowering and fruiting, higher levels of potassium and calcium are needed, and very little nitrogen is absorbed. Perennial plants as well as trees, shrubs and grass will absorb a high amount of nitrogen from the soil and store it both in the roots and crown. This will be used for mobilization in the spring when the rate of growth is very rapid.
Major Nutrients and Micronutrients
Nutrients fall into two categories depending on the amount used by the plant. Major plant nutrients are nitrogen, phosphorus, potassium, calcium, magnesium and sulphur. Of these, nitrogen, phosphorus and potassium are most likely to be deficient in lawn and garden soils. Calcium and magnesium deficiencies are rarely seen except in low pH or sandy soils.
Micronutrients, although required in small quantities, are equally important and essential to plant growth and development. These nutrients include zinc, manganese, iron, copper and boron. Generally, they are not deficient in lawn and garden soils. Depending on the plant species, micronutrient deficiencies may occur in sandy soils, in back-filled areas, or when soils are too alkaline.
Lime-induced iron chlorosis is the most common micronutrient deficiency problem in home gardens, especially with azaleas, rhododendrons, blueberries, Hydrangea macrophylla, and pin oak. Leaves yellow, though the veins remain green; as the problem worsens, leaf tissue becomes almost white, with burning around the edges.
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