Nodulation Differences Between Organic and Conventional Systems

Nodulation Differences Between Organic and Conventional Systems
Dr. Kris Nichols, Chief Scientist, Dr. Emmanuel Omondi, Research Director – Farming Systems Trial, Jeff Moyer, Executive Director, and Ross Duffield, Farm Manager

Rodale Institute’s Farming Systems Trial (FST) has been comparing organic and conventional management systems since 1981. Nodules in roots from soybean plants in the manure-based organic system were compared to roots from the conventional system. Legume plants, such as soybeans, have nodules on their roots where rhizobium bacteria convert atmospheric nitrogen (N2 gas) into plant-available nitrate-nitrogen. The energy needed to do this process comes from photosynthesis where sunlight energy is stored in the bonds of simple sugars. Because excess amounts of nitrate-nitrogen are present in the conventionally-managed field due to the addition of synthetic fertilizers, plants do not allocate energy into forming fine roots to access more nitrogen from the soil profile and nodulation is concentrated around the tap root so the rhizobium bacteria are only feeding each individual plant (Figure 1), but in the organic manure system, more fine roots are developed and nodules are found throughout the fine roots (Figure 2). Greater amounts of fine roots assist the plant in obtaining a variety of nutrients from the soil profile and nodules on these fine roots will help distribute nitrogen throughout the soil profile for subsequent crops.

Figure 1. Soybean plants grown in the conventional system have few fine roots, and the nodules are concentrated on the tap root. Photo taken on 9/3/2015.


Figure 2. Soybean plants grown in the organic system have far more fine roots and root nodules. Nodules are distributed on the tap root as well as lateral roots and root hairs. Photo taken on 9/3/2015.

6 Responses to “Nodulation Differences Between Organic and Conventional Systems”

  1. Herwig Opdebeeck

    Dear…(sorry but I could not find the name of the author of the article):
    Please don’t let a couple of photos but only science, robust scientific methods and results published in peer-reviewed and renowned journals decide about the outcome of a trial, were it only in respect for the farmers, organic, conventional or those in between.

    All the best,

    • Rodale Institute

      Hi Herwig, thank you for reaching out. I understand your concern. However, this is not finalized, published research results. These nodulations are more of an observation made between the two different systems.

  2. Herwig Opdebeeck

    To the president of the Rodale Institute:

    Yesterday I wrote a comment on above article but neither did I receive a reply nor did my comment appear below that article.
    I don’t think that it is a healthy and sustainable strategy to select only the positive, the thumbs-up sort of comments. I would be very much disappointed if your Institute would appear adopting “conventional” strategies such as those used by the tobacco industry or by companies such as Monsanto i.e. only publish what fits your positions.
    A reply would be very much appreciated in order for me to know your institute’s policy regarding openness and objectivity.
    Herwig Opdebeeck

    • Rodale Institute

      Hello  Herwig, 
      I apologize for not approving your comment sooner. All of our comments are reviewed and approved once a week. To encourage a healthy dialogue on our posts we allow all comments, that are not offensive nor threatening, to be approved for the site. Since your comment was neither of these, we are in the process of approving your previous comment.
      The mission of the Rodale Institute, for the past 70 years, has been to improve the health and well-being of people and the planet through organic leadership. Rodale Institute has been researching the best practices of organic agriculture and sharing our findings with farmers and scientists throughout the world, advocating for policies that support organic farmers, and educating consumers about how going organic is the healthiest option. In reference to the nodulation article you commented on, please visit This section will delve into the scientific results of our Farming Systems Trial, America’s longest running, side-by-side comparison of both organic and conventional agriculture. I hope this answers your questions and if not, please let us know how we might be able to help you find the information you are seeking. Thank you for your concern and passion for organic agriculture! I hope you have a wonderful day!

  3. Jukka

    I agree with the writers. The pfotos are good.
    I have seen this type of differences in legumes many times on practical level.
    There is more modules in roots of organic legumes and more dense root system.
    The reasons for the differences may be:
    -different nitrogen fertilisation and mineral nitrogen level in the soil
    -herbicides may disturb the fotosyntesis for 2-3 weeks after application – and disturb nodulation
    -organic compounds like amino acids may have influence
    -differences in energy status of the plant
    -better aerated soil in organic fields

    It´s good to get peer-reviewed results from this topic.

  4. Dr. Emmanuel Omondi

    A lot of research has been done on this topic already and have established that organic farming practices increase nodulation in leguminous crops. The photos and report in this article are observational and just highlights what has already bee established, but is probably not common knowledge. A few resources that reports these differences include the following: 1)Kontapoulou et al., 2015; Effects of organic farming practices and salinity on yield and greenhouse gas emissions from a common bean crop available at; 2) Yan et al., 2014. Abundance and Diversity of Soybean-Nodulating Rhizobia in Black Soil Are Impacted by Land Use and Crop Management. Available at; 3) Bot and Benites, 2005. The Importance of Soil Organic Matter.


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