Our first thought when we hear “soil” is the black topsoil we stir around (or did) with steel and diesel fuel to kill weeds and whip the soil into shape to receive seed. With the adoption of zero till we rarely see the topsoil now, but that black layer is still the concept of soil for many.
To really understand a soil we must examine the entire soil profile that extends far below the top few inches or feet. In the last column we looked at the soil zones across the Prairies. Let us now look at what is underneath the topsoil and what it means to our management of Mother Earth.
The soil layers are called horizons and the four photos with captions tells the story.
A Horizon: This is the topsoil and the leached layer that can occur just below the topsoil.
B Horizon: This is the transition layer, and is often referred to as upper subsoil. It contains clay and other things that have been washed out of the topsoil over the past 10,000 years.
C Horizon: This is the true subsoil or the original material Mother Earth had at her disposal. All of our soils had lime (calcium carbonate) present when deposited by glaciers or melt waters 10,000 years ago. Water passing through a soil for 10,000 years removes lime from upper horizons and deposits it in the Cca (lime accumulation) layer. Put another way, the depth to lime is the 10,000-year record of the amount of water that has passed through a soil.
J.L.(Les)Henryisaformerprofessorand extensionspecialistattheUniversityof Saskatchewan.HefarmsatDundurn,Sask. Healsorecentlyfinishedasecondprintingof “Henry’sHandbookofSoilandWater,”abook thatmixesthebasicsandpracticalaspects ofsoil,fertilizerandfarming.Leswillcover theshippingandGSTforGrainewsreaders. Simplysendachequefor$50toHenry Perspectives,143TuckerCres,Saskatoon, Sask.,S7H3H7,andhewilldispatchasigned bookpost-haste.