What came first…?

What came first the chicken or the egg? Err… I mean, the earthworms or the high pH?

Dr. Josef Görres is a smart, funny and kind person that teaches in the Department of Plant and Soil Sciences of the University of Vermont and everyone in there knows he is the expert on worms. He is the kind of professor that if you need to talk about anything, he is the person to go talk to.

The previous week, in the seminar series of the department, he presented us with a paradox. The results he and his collaborators have gathered show that there is a correlation between the presence of earthworms and a high pH* in the soil.

Why do we care? Soil pH is very important for plant growth and nutrient availability for those plants. pH can influence, therefore, what plants can grow in certain soils. Also, the earthworms in the soils of Vermont are not native. All the original ones died in the last glaciation era and the ones we have now have been imported from Europe and Asia by mistakes and by companies that sell them for the use of vermicomposting (composting with worms).

Dr. Görres told us that the presence of earthworms stimulates bacteria (either in the soil or in their own guts) to metabolize ammonia (NH4+), turning it into nitrate (NO3) and, in the process, releasing a proton (H+) into the soil, which for all practical purposes should decrease the pH in the soil. 

Instead, his results show a high pH in those soils. Why?

One theory is that the soils were originally alkaline (high pH) and the earthworms were attracted to these soils for some reason. Another is that fungi or bacteria might use the protons that earthworms release. 

That is what Dr. Görres is trying to find out, but until he and his team give us an answer: who came first? Earthworms or high pH?

Any clues?


*For those needing a reminder on pH, it is the value from 1 to 14 assigned to describe the level of acidity or of alkalinity of a solution. This value is determined with the concentrations of protons (H+) in the solution. A pH of 7 is neutral, while a lower one shows a high contentration of H+ (acid pH). Concentrations of H+ that are very low give a pH number higher than 7 (alkaline pH).

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