#soil

Chromatography of soil sample, a low-tech method for assessing soil composition and health. Source: Eugenio Gras / Milkwood

Chromatography of a soil sample, a low-tech method for assessing soil composition and health, including microbial population.
Source: Eugenio Gras / Milkwood

When we think of healthy soil, we usually think of pH levels, mineral content, and availability of water. When we think of biodiversity, we think of animals and plants.

And then there’s soil biodiversity. One tonne of soil can harbor up to 25% of its weight in living microorganisms. And it is this group of life that is responsible for the nutrient exchange of the soil, its carbon and nitrogen content, its structure.

Microcoleus vaginatus, one of the soil-dwelling microbes examined in the study

A recently published study published in Science suggests that soil-dwelling microbes may be temperature dependent, and that their composition in a given soil may change with rising temperatures. Microbes that currently enrich soils in temperate regions could find themselves competing against arid-climate microbes.

This could in turn, of course, affect soil health as much as drought or other climate change impact. The question as to just how microbe migration might impact larger environments remains open.

Simplified Soil Food Web, showing bacteria and microorganisms at the 2nd trophic level.
Source: European Soil Portal

Science study – Temperature Drives the Continental-Scale Distribution of Key Microbes in Topsoil Communities by F. Garcia-Pichel, V. Loza, Y. Marusenko, P. Mateo, R.M. Potrafka

Scientific American post/podcast – Climate Change Alters Soil Bacteria Distribution

Clay soil
Image via: Gardening Made Easy

When summer comes to my neck of the woods (which this year is looking less and less likely with every passing week of rain, but that’s another issue), the kiln of July and August bake the heavy clay soil of my garden to a hard surface that rivals a brick for impenetrability. Woe is me if I haven’t loosened and treated the soil around plants beforehand, or done my weeding. Whatever is in the ground will be encased until the next rains.

If you don’t get your fingers out into the dirt on a regular basis, you might not know just how different soil can be from place to place. Oh, we know about the chalky soil of the Champagne region, or the depleted soil of dustbowls, but soil is alive, both literally and figuratively. It’s alive, it develops, it changes, if affects the life in it and on it. It is a non-renewable resource.

The first ever Soil Atlas of Africa has been published, compiled by an international team of soil experts and edited by the European Union. It has some amazing images.

One of the soil maps in the Soil Atlas of Africa Source: European Commission – European Soil Portal

According to the release web page:

“Healthy and fertile soils are the cornerstones of food security, key environmental services, social cohesion and the economies of most African countries. Unfortunately, soil in Africa tends only to reach public awareness when it fails – often with catastrophic consequences (…)

In addition to providing the medium for food, fodder and fuel wood production (around 98% of the calories consumed in Africa are derived from the soil), soil controls the recycling of nitrogen, phosphorus, carbon and other nutrients. Soil reduces the risk of floods and protects underground water supplies. Soil organic matter can store more than ten times its weight of water while the soils of Africa store about 200 Gt of organic carbon – about 2.5 times the amount contained in plants.”

The web site offers free downloads. Gorgeous images, and an insightful education into the true, often neglected value that soil represents, even if you don’t live in Africa.

The Guardian article – Africa’s soil diversity mapped for the first time by Ben Appiah

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Microbe Migration

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