Plant and Insect Communications in Biological Cropping Systems with Larry Phelan

This week, I had the pleasure of interviewing Dr. Larry Phelan, a professor at Ohio State University where he heads research programs studying the role of soil communities in plant health and susceptibility to disease and insect pests in biological farming systems. Larry also heads programs researching the identification and behaviors of plant secondary compounds and insect pheromones that affect host finding and other behaviors.

In this episode, Larry and I discuss plant and insect communications, soil communities, and the concept of biological buffering - the capacity of biology in the soil to absorb large amounts of nutrients that are applied and contain those in their cells and release them over a period of time. We also talk about Larry’s new initiatives in the city of Cleveland to incorporate urban agricultural systems. I had a lot of fun with this episode - some of the topics Larry touches on are absolutely fascinating.

 

 

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Episode 8 - Larry Phelan - Highlights

3:10 - What are the memorable moments leading up to where Larry is today?

• Larry was trained as a chemical ecologist - where he would identify pheromones and plant attractants
• As he started talking to organic farmers, he noticed they had fewer issues with insect pests than conventional farmer neighbors

 

5:30 - What were the differences that Larry noticed in organic farming?

• During this time, many organic farmers were doing their own research
• Many organic farmers had animals integrated into their farms
• “If we have healthy soil, then we are going to have a healthy plant, and insects don’t like healthy plants” - Larry was seeing the truth to this and wanted to test
• Larry wanted to figure out if insects could tell a difference between plants from organic farms, and if this was more related to the short-term effects of fertilizer or the long-term effects of mismanaged soil
• The results: Regardless of fertilizer used, the plants growing in soil from the organic farm received few insects eggs

 

9:20 -  Biological Buffering

• With an influx of organic matter, you create a soil community that is beneficial to the plant
• Nutrients absorbed into the soil community are released over time - putting the plants in better nutrient balance
• Plants are almost always limited by nitrogen levels - they’re going to take all they can get and will take more than they can deal with
• Insects are also limited by nitrogen, so plants with excess nitrogen are very nutritious for insects
• No difference in production between organic and conventional farms

 

15:20 - Why can insects not utilize plants as a food source that doesn’t contain as many amino acids

• Free amino acids can short circuit the plant defense system - Insects get these free amino acids they don’t have to break down
• Proteins vary in digestibility in insects

 

18:20 - What had surprised during Larry’s research into all of this?

• 30% ammonia and 70% nitrate resulted in best plant growth
• Where the plant was out of balance, that’s where the insects grew the largest and had the best survivorship
• Survivorship of insects dropped as they approached the 30/70 ammonia/nitrate ratio

 

22:40 - What is some practical advice growers can implement?

• The importance of organic matter added to the soil to sustain a beneficial microbial community
• Important to distinguish between old organic matter and biologically active organic matter - need to focus on active organic matter

 

26:10 - What is the impact of a nitrogen application on soil biological profile? 

• Plants can shut out mycorrhizae and can grow a shallow root system
• When the plant invests in growth above ground, it doesn’t have as effective of a root system to gather water and nutrients
• We don’t want plants to encounter any extremes
• Starter fertilizer isn’t allowing plants to grow resilience they need and can cause plant growth to stall out

 

35:00 - Applying only insoluble start applications

• Resulting in large root systems
• High phosphorus levels without phosphorus application  
• Mineral profiles not very different in organic plants regardless of fertilizer application

 

38:10 - What is something that Larry believes to be true about modern agriculture that is different from mainstream views? 

• The use of soluble fertilizers has been one of the most disruptive practices in mainstream farming
• How different organic farms view what they do - Conventional farmers have a prescriptive approach. Organic farmers had more of a system perspective
• “Tied up” nitrogen isn’t a bad thing - It gives you “money in the bank” in your soil

 

41:30 - What is a resource Larry would recommend?

• Lots of great advances in organic research
• ATTRA
• Natural Resources Conservation Service

 

43:10 - What is a question Larry wishes he was asked?

• Soils in urban centers under vacant lots opening the possibility of urban farming
• Do what degree has the legacy of smokestacks, heavy metals, etc affected soil community. Can these soils be rejuvenated or are these soils effectively lost?
• The influx of organic matter are reducing levels of lead and the bioavailability of the lead - allowing cities to reduce the danger of lead in soil
• Lead is going to be there - need to find a way to bring it out

 

49:20 - Damaging impacts of chronic pesticide use and exposure

 

  

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