"Weird" Science #5: What happened with the nematodes?

This post originally appeared on my personal blog. Ported to Forbidden Questions on 11/21/2011.

I ended my last Weird Science post with two photos: one of a nematode that had been trapped by a fungal hypha, and another of a nematode as it made its way into the stem of a tomato plant, unhindered by fungal hyphae or any other defensive mechanisms. And my last words in the post were these:

"Why wasn't this [second] nematode attacked, and where were the fungal hyphae that killed off the first nematode?"

I promised to answer those questions. And the answers are clear. It has to do with the soil in which the plants were being grown.

In the first photo--the one in which the nematode is trapped by the hypha--the plant was growing (and the fungus and the nematode were living and growing) in healthy soil--soil filled with a huge variety and quantity of protozoa, earthworms, arthropods, algae, bacteria and fungi.

The second photo was taken of a plant that was being grown in typical modern agri-soil--soil that had been tilled and sprayed and treated with pesticides and herbicides and NPK fertilizer and in which, therefore, there was almost none of the microbial life that healthy soil exhibits.

Funny (or maybe not): The use of herbicides and pesticides and NPK (and no other) fertilizers can actually, over time, reduce plants' ability to protect themselves from predators. It can increase plants' susceptibility to disease.

As Elaine Ingham, president of Soil Food Web, Inc., suggests in her Foreword to Teaming with Microbes,

Urban dwellers and other growers have been pouring toxic chemicals on their soils for years, without recognizing that those chemicals harm the very things that make soil healthy. Use of toxics to any extent creates a habitat for the "mafia" of the soil, an urban war zone, by killing off the normal flora and found that compete with the bad guys and keep them under control. . . . If toxic material was applied only once in your life, the bad situation we have today would not have developed, but typically with that first application, thousands of organisms that were beneficial to your plants were killed. A few bad guys were killed as well, but good guys are gone, and they don't come back as fast as the bad guys.

Think about your neighborhood: who would come back faster if your neighborhood was turned into a chemical war zone? Opportunistic marauders and looters, that's who comes back in after disturbances. In the human world, we send in the National Guard to hold the line against criminals. But in soil, the levels of inorganic fertilizers being used, the constant applications of toxic pesticide sprayed, mean the National Guard of the soil has been killed, too. We have to purposefully restore the beneficial biology that has been lost.

--Teaming with Microbes, p. 9