How Do Different Kinds of Water & Soil Affect the Way Plants Grow?

Water Quality

• For plant irrigation, the level of salts present in the water is the primary concern surrounding water quality. Salts found in irrigation water pull water from the plant, causing effects similar to drought or root damage. Reactions in the soil can also cause an abundance of chloride ions, which can cause toxicity in some plants, or tie up nutrients plants need to take from the soil. High levels of dissolved minerals, like boron, in water can also cause toxicity in plants.

Soil Texture

• Soil texture describes the amount of clay, silt and sand present in a soil. Each of these 3 particle types has a different size, with clay being the smallest -- a single particle visible only under an electron microscope -- and sand the largest. Likewise, the spaces between soil particles, called pores, are tiny in predominantly clay soils and large in predominantly sand soils.

  Soil texture impacts plant growth indirectly by affecting the availability of water, nutrients and the ease with which plant roots penetrate the soil. Large pore spaces found in soils with a large amount of sand allow water to drain through quickly, taking with it soluble nutrients. Plants in these soils typically experience drought and deficiency symptoms faster than plants in other soils. The pores in clay soils, on the other hand, drain with difficulty. Plants in clay soils often have trouble obtaining enough oxygen for their roots. Clay soils are also liable to become compacted, making root penetration difficult and stunting growth. (See References 4)

Soil Fertility

• Soil fertility refers to the availability of nutrients in the soil. Plants take at least 13 mineral nutrients from the soil in amounts ranging from large -- like nitrogen or potassium -- to minute. Deficiencies can stunt growth, cause deformities or restrict flower and fruit production. Excesses can cause a flush of growth -- in the case of nutrients like nitrogen or phosphorus -- or cause toxicities that threaten plant health.

  Other chemical properties of soils are linked to fertility. Soil pH affects the availability of certain nutrients, with some nutrients becoming unavailable or toxic at very low or very high soil pH. Soil texture can also affect how susceptible nutrients become to washing away with water.

Organic Matter

• Healthy soils also consist of about 5 percent organic matter, materials that once belonged to living plants and animals. Soils high in organic matter tend to cause soil particles to clump, allowing excess water to drain away while the soil holds onto enough water for the plant to use. Likewise, organic matter helps the soil to retain nutrients. Larger clumps of soil particles versus many tiny individual particles makes the soil looser, easier to work and more readily penetrated by plant roots.

  Organic matter in soil also attracts soil organisms ranging from microscopic -- bacteria and fungi, for example -- to macroscopic, like earthworms. These helpful organisms release nutrients from organic material in the soil, nourishing the plant. They also create an environment hostile to microbial pathogens and reduce the incidence of disease.