Symbiotic Relationships in Ecology with Don Huber

In this episode, I had the pleasure of interviewing Dr. Don Huber, a leading plant pathologist and Professor Emeritus at Purdue University. We discuss how to manage soil-borne diseases by managing crop rotations, and the management needed to grow 500 hundred bushels corn.

Don shared intriguing observations on how soil-borne disease pathogen populations remain present in the soil constantly and are actually 'beneficial' saprophytic fungi until the right environment is present. Root diseases are a result of the soil environment, not a result of the presence or absence of the organism.

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Related Resources

• Mineral Nutrition and Plant Disease by Lawrence E. Datnoff (Author, Editor), Wade H. Elmer (Editor), Don M. Huber (Editor)
• Marschner's Mineral Nutrition of Higher Plants by Horst Marschner (Author)

Episode 4 - Dun Huber - Highlights

2:40 - What are Don's most memorable moments leading him to where he is?

• Don has fun wherever he is!

3:10 - What has puzzled Don in his research work?

• Studying soil ecology is looking at a black box. Need to slowly build a picture of everything involved.

4:10 - What is something that has surprised Don?

• How seemingly contradictory things all work together, such as a lot of nutrient relationships
• Secondary functions of things like manganese and iron start to come into play
• What are the ecological niches that make the system work?

6:30 - Challenge of manganese availability. What is contributing to that?

• It's a dynamic relationship with soil and fungi.
• Need organisms and nutrients to increase uptake
• Need the bacteria that are responsible for the valiant state - oxidizing groups and reducing groups
• Manganese can be there, but not available for uptake

11:10 - Pathogens dependant on manganese oxidation. Are they directly dependent, or are they producing a manganese-deficient plant?

• Both can be correct. They don't necessarily need the oxidation.
• Enzyme isn't going to work for you without a cofactor

13:50 - How do populations change when you have a crop infection?

• The plant is providing nutrients and resources for the pathogen
• Soil inhabitant vs soil colonizer
• A soil colonizer is an organism that can be provided its nutrient base from a host
• Infection isn't the result of the presence of the pathogen, but the level of plant health and microbial ecology in the rhizosphere

20:20 - What are the tools the growers have available to manage soil ecology most effectively and to develop a disease suppressant soil profile.

• Crop rotation - each crop influences a certain group of organisms in the soil
• Cover cropping
• Time of tillage
• Farming is really managing ecology

28:30 - Is it also possible to use these tools to manage and suppress soil-borne pathogens?

• Definitely!

31:20 - What are some useful crops or cover crops that have a strong disease suppressive effect?

• Depends on disease and overall soil biology
• Perhaps the best crop: Oats!

36:50 - What are the key characteristics shared by disease suppressing crops?

• Boils down to nutrition - may be indirect or direct

39:10 - Can fall tillage application create a rebalancing effect of both reducing organisms as well as oxidizing organisms?.

• Yes! Doesn't have to be every year
• Long term no-tillage can reduce the efficiency of ecology

41:20 - What are the impacts of nitrogen on developing disease suppressive soils?

• Most soil organisms are hungry for 2 things: nitrogen and carbon
• Changes can cause massive stimulation

44:30 - What is the impact of ammonium on an ecosystem with reduced nitrogen

• Tremendous reduction of disease
• Reducing environment creates an increase of manganese availability

46:30: What is the impact of carbon-nitrogen ratio on disease suppressive soils as well as yield?

• Depends on the carbon source
• It's not the carbon to nitrogen ratio, it's the form of nitrogen involved
• Ratio works if working with the same nutrient source

48:30 - Quality/Quantity of photosynthesis - How can we increase quantity of photosynthesis and quantity of root exudates in soil profile.

• Manganese, manganese, iron, sulfur, etc. are essential for photosynthesis
• Mineral nutrient deficiency will reduce overall efficiency.

54:30 - We are not tapping into efficiency of plants by limiting carbon dioxide

55:10 - Increase in photosynthesis producing increased biomass

55:30 - What is the potential for plants to increase their volume of photosynthesis?

• The potential is 100%
• 5-10x depending on what the plant it, starting point, etc.

1:00:30 - What kind of yields did Don achieve during his yield trials? What plant populations were growers using?

• 350+ bushel

1:07:10 - What happened from then, to today when growers are struggling to grow 250 bushel? Why were these not adopted on a broader scale?

• Focus moved to other areas when there was "too much production"
• Requires a long term commitment
• Private company interest is the bottom line
• We forget it's an ecology that needs to be managed

1:11:30 - What is something Don believes to be true about modern agriculture that others do not believe to be true?

• Have to think about entire systems, and not focus on a single piece
• You have to make a few mistakes in order to get there

1:14:00 - What does Don see as the biggest opportunity in agriculture today?

• Reinventing the wheel!
• Getting back to nutrient density
• Eliminating pesticides, especially glyphosate
• Agriculture is the basic infrastructure of society. Recognizing the stewardship we have to the soil

1:18:10 - What are some books or resources Don would recommend?

• Mineral Nutrition and Plant Disease by Lawrence E. Datnoff (Author, Editor), Wade H. Elmer (Editor), Don M. Huber (Editor)
• Marschner's Mineral Nutrition of Higher Plants by Horst Marschner (Author)
• Systems looking at nutrient density

1:22:30 - What is a question Don wishes John had asked him?

• Glyphosate's impact on soil ecology
• Don is excited to see cover crops being used
• Maintaining balance within soil environment
• Supporting the crop with nitrogen

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