Root Systems: Digging Deep to Decipher the Code to Improve Crop Yield

Roots, the foundation of any crop, provide valuable insight into the vitality of plants as well as clues for improving crop yields. Their tangled fibers reveal information related to plant genetics, agronomic practices, disease, nutrient levels, and water availability, transcribed in an earthy code. In fact, the answers to many crop health questions exist below the soil’s surface.

The first fossil records of roots — tiny tendrils captured in stone — date back 430 million years ago, when plants had just emerged from their aqueous habitats and began to grow on land. In need of nutrients and hydration to support their growth, species like ancient clubmosses spouted subterranean systems to hold themselves in place and to mine the soil for resources. The fossil records of these root systems tell a powerful evolutionary story of adaptation and growth, while also providing early evidence of important symbiotic associations.

What can we learn today from examining the roots of live plants? A look below ground can offer clues related to crop health and productivity. Understanding the intricacies of a crop’s root system and structure can help growers improve crop management, work with native microorganisms to enhance nutrient supplies, and ultimately increase yields. Join us on a below-the-surface exploration to decipher these integral systems.

Formation

Not only are roots one of the most essential plant systems, responsible for the acquisition of vital nutrients and water necessary for plant growth, they’re also the first system to develop. As soon as a seed germinates, a tiny sprout, known as radical, ruptures the root sheath and emerges. This radical becomes the plant’s primary root, extending deep into the soil to forage for water and nutrients. After the tap root is established, lateral roots form, followed by rootlets.

Crop vitality is entirely dependent on this sub-surface network. Plants convert energy from sunlight to produce sugar in their leaves that provides the carbon framework for making all the other molecules required for life. Roots are integral to this process. In order to provide more leaves for photosynthesis, plants need roots to forage for water and nutrients. The minerals roots provide are essential for the production of DNA, proteins like chlorophyll, and ATP to fuel the molecular energy system.

Root System Architecture

The structure of a root system is unique and continually changing. Roots can extend deep below the subsoil layers or laterally to form intricate networks. Their architecture is influenced by the plant species, as well as a variety of changing climatic and biological factors, such as soil compaction, surface water scarcity, or irregular distribution of nutrients.

Roots growing in dry soil will bend and grow toward a water source. Roots signal to the rest of the plant when soil water levels drop, and plants use this information to change the architecture of their root systems. Furthermore, there is evidence that when plants detect the presence of nutrients, they allocate more resources to the root system and direct root growth toward nutrient-dense areas. In the case of nutrient deficiency, plants can also use their roots and root exudates to change the chemical environment of the rhizosphere to make nutrients more plant-available or they can recruit the help of microorganisms to bring them more nutrients.

Roots as Indicators

Growers often perform root digs to gather information about the health of their crops. Root analyses can serve as a powerful tool to inform important agricultural decisions. They can be indicators of environmental conditions, pests and disease, and resource deficiencies.

Agronomists recommend unearthing several plants at a time for comparative study. After rinsing the roots to loosen soil particles and eliminate debris, growers can observe the root system in its entirety and make note of patterns related to root growth, depth, and branching.

Here are a few things to look for:

• Color—Depending upon the crop species, roots should be white with soil clinging to a transparent film.
• Length—The depth of root growth can be indicative of water levels. If roots extend far below the surface, they may be seeking water.
• Formation—Zigzag patterns or right angles can reveal compaction issues and may suggest that roots are struggling to push deeper into the soil.
• Nodes— If there is an uneven distribution of nutrients and water, the roots will reflect that in their growth. Nodes can also reveal root responses to fertilizers and irrigation. If a root mass has formed, it can indicate that the crop’s roots have tapped into a nutrient-rich soil area. 
• Damage— Roots can reveal the presence of pests such as rootworms. Discoloration, scarring, or tunneling may appear where rootworms are feeding. When evaluating damage, agronomists recommend inspecting each node for any scarring or pruning. Assess the top three root nodes and assign a damage rating using the 0 – 3 NIS rating scale from Iowa State University.

Root-Fungi Relationships

Below the soil’s surface, thousands of interconnected roots work collaboratively with microbes to capture nutrients and water. Some soil microbes help broker carbon, the building block of soil, while others help fix atmospheric nitrogen. Stimulating these processes can enhance their function and increase the amount of plant-available nutrients in the root zone.

Root exudates contain signaling molecules that aid in the activation of microbes involved in the nutrient cycling process. This is a complex system that plants have evolved over time in which they signal for soil microbes to provide them with bioavailable nutrients in exchange for carbon. Growers today can stimulate this root-microbe interaction with SOURCE, a unique foliar-applied product that facilitates signaling between the plant and native soil microbes.

SOURCE activates both free-living nitrogen-fixing bacteria and phosphate-solubilizing microbes, offering a powerful tool for growers who wish to nourish crops at the root level with plant-available nitrogen and phosphorus without additional fertilizer.

The root-soil interface is an exciting realm in which important biogeochemical processes take place among roots, the chemicals they release, and soil microorganisms. We believe that understanding and harnessing these interactions is key to the future of sustainable food, fuel, and fiber production to support a growing world population.