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Regenerative Agriculture Podcast

Apr 13, 2018

In this episode, I had the pleasure of interviewing Dr. Robert Kremer, a microbiology scientist for the USDA who also works as a professor in plant sciences at the University of Missouri. In this episode, we discuss Robert's project with the USDA decomposing weed seeds in soil, native soil microorganisms and microbial interactions, and the implications of AMPA and glyphosate on soil biology. We also discuss Robert's thoughts on the challenge of manganese availability, how growing GMO's impacts soil health, building soil carbon, how to choose soil inoculants and many more fascinating insights from a highly respected soil scientist.



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Episode 1 - Dr. Kremer - Highlights

0:03:00 - What are Robert’s memorable moments leading up to where he is today?

  • Robert was asked by the USDA Agricultural Research Service to look at the possibility of decomposing weed seeds in soil used in microbiological approaches.
  • Robert saw in the 80’s, weed and pest management was mainly chemical based.
  • Through trying natural ways of controlling weeds and attempting to understand what pesticides do, which lead him soil quality/health.


 0:05:50 - Has Robert had success in developing biological controls? Are there tools available for farmers to use today?

  • Robert found it almost impossible to control all weed growth.
  • Modern input based agriculture ecosystems built up many weed seeds in the operations Robert was working on.
  • Robert’s work has helped set the stage for other work that has been done in this area.


0:08:10 - Is Robert aware of any development relevant to fruit and vegetable production systems? Or in areas where ecosystems have longer crop rotation incorporating cover crops? 

  • Agri-Food Canada has contributed to this area
  • However, Robert doesn’t believe there is a lot of development


 0:09:40 - The impact of pesticides?

  • Robert has found some pesticides to be damaging to certain microorganism, while the same pesticides can be stimulating to other microorganisms  
  • Microorganisms were able to adapt to commonly used insecticides and herbicides
  • These compounds were building weed resistance, but also altering the soil microbial community at the same time
  • Finding residual glyphosate in the soil


0:14:40 - How long does Robert find that glyphosate residues are remaining in soil?

  • Plots that had gone a year without RoundUp had as high glyphosate levels as plots that received the glyphosate in the same year, showing there was a carry over of residual glyphosate
  • Robert found it seemed random which plots had high levels of residual glyphosate
  • AMPA can be just as toxic as glyphosate itself
  • Robert was observing 10-50x more AMPA than glyphosate


0:17:40 - What are the implications of high concentrations of AMPA in soil profile?

  • AMPA has very similar effects to glyphosate on soil


0:18:30 - What defines soil quality and health? 

  • Two main indicators: soil organic carbon, and microbial diversity
  • A high proportion of soil organic carbon is active carbon. This is the portion of carbon that supports the microbial community and plant growth protection
  • Diversity in fungi and bacteria

0:25:00 - What can a farmer today do to start measuring these factors?

  • Labs exist that can put together soil assessments
  • Some states have incentives for farmers to do this

0:27:00 - What are the long-term impacts of soil quality/health by compounds such as glyphosate or AMPA? 

  • Robert has noticed glyphosate tends to suppress beneficial groups of bacteria
  • Manganese can become “tied up” because the plant cannot access micronutrients 

0:31:00 - What are the long-term implications of manganese immobility in soil profiles?

  • Shift in microbial diversity.
  • Including cover crops or different crops in rotation can help free up manganese 


0:33:30 - What crops are really effective at having a reducing effect and shifting the availability of manganese in the soil profile?

  • When you have a diversity of cover crops, some will be able to mobilize micronutrients
  • Common example: Buckwheat
  • Sorghum 


0:35:20 - How to GMOs impact soil microbial community

  • Some early GMO soybeans roots seemed to release higher levels of amino acids and soluble carbon, which can attract potential pathogens
  • In some GMO corn varieties, side effect of having more lignin


0:39:10 - What does Robert believe to be true about modern agriculture that many others don’t believe to be true?

  • Depletion of soil organic matter. Robert has seen a drop from 3% organic matter down to around 1%


0:41:00 - How can we regenerate the soluble carbon component in the soil profile?

  • Having a diversity of plants, and having living roots in the soil as long as possible
  • Follow corn or soybean with wheat


0:43:20 - What is a book or resource Robert would recommend to growers?

  • Teaming with Microbes: A Gardener's Guide to the Soil Food Web by Jeff Lowenfels and Wayne Lewis
  • Mycorrhizal Planet by Michael Phillips 


0:45:10 - What is the question Robert wishes John had asked?

  • Robert is often asked about biological products


0:46:00 - What ideas or technologies is Robert really excited about?

  • Lots of classifications of biological productions: Biological stimulants, probiotics, prebiotic
  • Robert has been impressed with what some prebiotics can do
  • Although, some show promising signs but end up not improving total yield 


0:51:30 - Do we have the conditions to give an inoculant or probiotic the opportunity for success?


0:53:40 - What is the one action Robert would recommend that growers should take?

  • Need to keep soil covered, even better to keep living plants on the soil
  • Integrate livestock with crops is a great, but mostly forgotten practice


0:55:00 - What are the economic implications of managing grazing very closely and carefully?

  • Not only benefit for crops, but for the quality of meat as well.
  • We’ve gotten away from what an agricultural ecosystem should be



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Hosted by John Kempf. Co-created & Directed by Geoffrey Shively. Produced by Anna Kempf, Jenna Sodano, and Nathan Harman, and Cody Nesbit.