Increasing Crop Yields: What do crop roots do in rhizosphere?

Pro-soil is interested in helping farmers with natural soil nutrition. Our healthy soil products can help increase crop yields as can an increased knowledge about what crop roots do in rhizosphere. Read on to find out more.

What do the roots do in the rhizosphere?

The roots exude water and compounds broadly known as exudates. Root exudates include amino acids, organic acids, carbohydrates, sugars, vitamins, mucilage and proteins. The exudates act as messengers that stimulate biological and physical interactions between roots and soil organisms. They modify the biochemical and physical properties of the

rhizosphere and contribute to root growth and plant survival. However, the fate of the exudates in the rhizosphere and the nature of their reactions in the soil remain poorly understood. The exudates have several functions.

Defend the rhizosphere and root against pathogenic microorganisms.

Root cells are under continual attack from microorganisms and survive by secreting defense proteins and other as yet unknown antimicrobial chemicals. Research has found that exudates in the rhizosphere vary according to the stages of plant growth. For instance, there are more carboxylates and root mucilage at the six leaf stage than earlier.

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Attract and repel particular microbe species and populations.

High levels of moisture and nutrients in the rhizosphere attract much greater numbers of microorganisms than elsewhere in the soil. The composition and pattern of root exudates affect microbial activity and population numbers which, in tum,  affect other soil organisms that share this environment.

Keep the soil around the roots moist.

Research has found that rhizosphere soil is significantly wetter than bulk soil, which protects roots from drying out.  Exudates released from roots at night allow expansion of roots into the soil. When transpiration resumes with daylight, the exudates begin to dry out and adhere to the soil particles in the rhizosphere. As the soil dries and its hydraulic potential decreases, exudates lose water to soil.

Obtain nutrients.

The exudates help roots adsorb and store ions for plant use. For instance, flavonoids in legume roots activate Rhizobium meliloti genes responsible for root modulation that enable the plant roots to obtain nitrogen from the air. Exudates enable the transfer of up to 20% of all photosynthetically fixed carbon to the rhizosphere. Exudates may also be responsible for encouraging vesicular arbuscular mycorrhizae that colonize roots and send out miles of thread-like hyphae into the soil, increasing the surface area and distance covered by the roots and taking up nutrients for the plant.

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Change the chemical properties of the soil around the roots.

The rhizosphere environment generally has a lower pH, lower oxygen and higher carbon dioxide concentrations. However, exudates can make the soil in the rhizosphere more acid or alkaline, depending on nutrients roots are taking from the soil.

For example, when a plant takes up nitrogen as ammonium it releases hydrogen ions which will make the rhizosphere more acid. When a plant takes up nitrogen as nitrate, it releases hydroxyl ions which make the rhizosphere more alkaline. This action doesn’t  usually affect the bulk pH of the soil but is important for the small organisms that live in the rhizosphere because many soil organisms do not move far in the soil.

Stabilize soil aggregates around the roots.

Sticky mucilage secreted from continuously growing root cap cells is believed to alter surrounding soil. Inhibit the growth of competing plant species. Plant roots are in continual communication with surrounding root systems and quickly recognize and prevent the presence of invading roots through chemical messengers. This process is known as allelopathy. In agriculture it can be beneficial when crop plants prevent weeds from growing nearby; or detrimental when the weed plants prevent crops growing.

Our healthy soil products improve soil health by stimulating and feeding native microbial life in the soil which creates a higher yielding crop. To learn more about how you can increase your crop yield, contact us today!