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Corn+Soybean Digest

Roots of Plant Health | Root Physiology Tools, Agronomic Basics Aim to Reduce Stress, Boost Yields

TAGS: Corn


If you lack focus below the soil, on your crop root environment, then these critical plant pathways won't efficiently transport water and nutrients into place for top yields. To build healthy roots, start with the basics, suggests Bruce Potter, integrated pest management specialist, University of Minnesota Southwest Research and Outreach Center.

"You don't need any magic or added products," he says. "Most of what you need to improve root health are simply good agronomic practices. Proper seedbed preparation, residue management, adequate nutrients, the correct hybrid or variety selection, seed placement and good drainage are the fundamentals. If you're not doing the basics right, there's no point in fine-tuning other things."

Bob Nielsen, Extension agronomist, Purdue University, adds managing compaction to that list. "Avoiding or mitigating compaction is first on my list," he says. "With corn-on-corn, starter fertilizer is also key. Long term, anything you can do to improve drainage helps root growth."

Potter is confident that most growers understand the fundamentals. Following them in a time-stressed spring or fall is often the biggest challenge. Another problem is recognizing the challenges a particular field or farm presents and finding the appropriate response. A perennial pest problem such as soybean cyst nematode (SCN) is a good example of this.

"Crop rotation and selecting varieties with good sources of SCN resistance can help manage the problem," Potter says. "Doing so goes a long way to managing brown stem rot (BSR) and sudden death syndrome (SDS) as well as moisture stress. The nematode impedes root function with direct damage and has all these other interactions."

While insecticide and fungicide seed protection have become common, they can't replace the basic agronomics. "Seed treatments don't cover environmental problems resulting late season pathogens such as we saw in southwest Minnesota this year," says Potter. "While the industry is working on adding different fungicides, and crop breeders are getting better at incorporating different types of resistance, they attempt to save yield, not increase it, and there is usually a cost of some sort."

Covering the basics allows a grower to work at increasing yield, not simply saving it, Potter says. Like Nielsen, he points to drainage as key to root health. "With the drier soils this season, they haven't had diseases nibbling away at them."

One way to reduce potential crop root diseases every year is to enhance microbial diversity in the soil, suggests Tom Kaspar, plant physiologist, USDA-ARS. Like Nielsen and Potter, he emphasizes drainage, pointing to anaerobic conditions in flooded soils known to kill off beneficial microbes and fungi. He endorses cover crops for the same reason; they have a positive impact on drainage, create channels for root pathways and enhance soil aggregation for improved structure, aeration and drainage.

"In corn and soybeans, you can see the roots follow old root channels or earthworm channels into greater depths in the soil," says Kaspar. "When you get below the tilled layer or the top 12 in., most of your roots will be in these old channels, depending on the soil type. By planting cover crops, you increase the number of channels, and different cover crops have different impacts. Radish and other Brassicas with a strong tap root have a better ability to get through compacted soil layers."

Eileen Kladivko, agronomy professor, Purdue University, endorses any practice that builds soil organic matter, such as reduced tillage and cover crops. "We can't do anything about the soil's inherent capability," she says. "However, we can improve and manage the properties the best we can. The more organic matter, the higher the productivity will be on any given soil. Cover crops put more organic matter back in the soils, exude carbon compounds and feed soil biota, aggregating the soil and improve its physical structure.”

Biological activity necessary

Providing year-round biological activity is one of the lesser-recognized benefits of cover crops, but may be important for root health as a disease preventative. It's a good example of where basic agronomics and new knowledge meet.

"If you reduce microbial diversity, certain crop diseases become more prevalent, says Kaspar. “This is an emerging field with new techniques available to study it."

Palle Pedersen, seed care technical asset lead, Syngenta, welcomes those new tools. New root-scanning technology and software, and water and soil conductivity sensors measure root branching and area, making it easier and faster to evaluate roots and their environments.

“Root physiology is an untapped area," says Pedersen. "We are looking at root systems to maximize a crop's genetic potential. They are so much greater than what farm yields are today."

While much of that potential is related to moisture and nutrient uptake, it’s the underground biological life and interaction with the plant and disease and insect pests that Pedersen is exploring. "These below-ground complexes, from wireworms and grubs to SCN and Fusarium, influence the root system and can stress it, preventing it developing as it should," he says. "A strong and healthy root system is really important to increased productivity and faster and more consistent yields year to year."

Pedersen and his associates see traits and improved seed treatments with longer residual effects as important tools to improve health and reduce stresses on the root system. "There are very complex interactions between soil types, soil texture, compaction, genetics and all the biotic stresses," says Pedersen. "We have more tools to address these interactions than ever before."


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