(3) What are the main things that plant roots must obtain from the soil?
Author: Theresa Lynn Ford
Created: Friday, 3/25/2005 3:02 PM

(3) What are the main things that plant roots must obtain from the soil?

Soil provides plant roots with air, water, nutrients, and a firm foundation to hold and support the plant. Soil's structure and texture, made of different size particles of sand, silt, and clay, supports the plant and dictate the aeration, water drainage, and nutrient holding capacity.

Wright mentions that the plants need the mineral nutrients phosphate, potassium, calcium, and other ions. The minerals plants get from soil are mainly recycled from the detritus, with supplemental minerals from the slow breakdown of rocks. Soil also needs the correct pH and salinity for the type plants growing in it. (Wright, p. 212)

Commercial fertilizers (synthesized or organic) are generally marked with three main nutrients. For example, my African violet "food" is labeled 8-14-9. These numbers refer to the percentage of nitrogen, phosphate, and soluble potash, respectively. The side of the bottle additionally lists iron, manganese, and zinc. Because different plants have different mineral needs, my generic indoor plant food spikes are 6-12-6, with added magnesium, boron, copper, iron, manganese, and zinc.

An interesting way to look at the things soil provides is to consider what must be "replaced" if soil is not used, as is the case with a hydroponic garden. A hydroponic garden is a soil-less garden where plants are fed by a nutrient solution. There has to be a foundation to support the plant roots that provides water and nutrient retention, while allowing aeration, water drainage, and adequate nutrients. There also has to be adequate space for the plant roots to grow. A hydroponic fertilizer has different minerals and mineral amounts in it to compensate for ones normally found in soil. Hydroponic fertilizers (synthesized or organic) should not be used on plants living in soil because it will over-fertilize (burn) them, and soil fertilizers should not be used in a hydroponic garden. My hydroponic garden was using a 9-30-12 hydroponic fertilizer. Just as in soil, the correct pH has to be maintained. Special attention also needs to be taken to maintain the solution temperature and evaporation.

Thus, soil provides plant roots with air, water, nutrients, and a hospitable (pH, temperature, drainage, and room to grow) foundation to hold and support the plant.


Wright, R. (2005). Environmental Science, Ninth Edition. New Jersey: Pearson Prentice Hall.

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