The Biosphere Blog

The History of the Word ‘Humus’ ‘Humus’ to the Romans meant the soil (earth, ground) as a whole. Carl Linnaeus, the inventor of binomial nomenclature, used this word in his system to classify soils as he did plants and animals:… more »

Soil Organic Matter (SOM) ‘Organic’, in science, means nothing more than ‘contains carbon’. It doesn’t imply ‘healthy’ or ‘good for you’ — atrazine is as much ‘organic’ as is glucose.… more »

Last week focused on bulk density as a property of soil, and how lower values were associated with good soil structure and high organic matter content, while higher values were associated with soil compaction. We ended with the note that soils compact… more »

Last week covered pore space, or the holes in soil. This week we look at the opposite of holes — the solids in soil. Pore space is expressed as a percentage of soil volume, while solids are expressed as a mass per volume. This measurement is referred to… more »

We’ve spent quite a few weeks examining soil structure, from soil horizons right down to the level of cations and anions and the role they play. Having zoomed in closer and closer each week on smaller and smaller components, this week we’ll… more »

So far we’ve gone over cations,and exchangeable cations and where there are cations (the positively-charged ions) there will be anions, the negatively-charged ions, because ions come in pairs. Some anions are also soil nutrients — and essential… more »

We’ve gone over quite a few things in this mini-section on soil structure as we zoomed closer and closer in on the structure of soil! I do hope it’s becoming clearer as to why a good soil structure is so important, and how even poor soils… more »

Last week ended with a brief mention of cation exchange being the activity that occurs on the very large surface areas of clay and humus colloids. But before we get to cation exchange, first some very simple chemistry to get up to speed on what a cation… more »

Clay and humus are the two smallest particles in soil, and together they make up the colloidal fraction of soil. A colloid is a particle able to stay suspended in a solution for very long periods of time, without settling to the bottom —you can see this… more »

Last week we covered the five ped types, of which the granular type is the one best for plant growth. This type is synonymous with soils of good fertility, drainage, aeration, friability, and tilth. Not all soils are this good unfortunately, and you may… more »

Last week we looked at soil horizons, the vertical layers that soil forms naturally when undisturbed. This week we’ll zoom in a little closer and look at the soil peds, the natural aggregates of soil within those horizons. A soil ped is an… more »

A few weeks ago you may have gone out and grabbed some soil to have a play with. There’s a good chance that the properties of your particular sample — including its colour, texture, mineral content, structure, and chemistry — will be quite… more »