Alrightly folks (and Internet).
The assignment doth continue so once more unto the breach, dear friends, once more …
The third thing to chat about soils at Gunyah is erosion.
Sodic soils (which we all know know are caused by too many sodium ions floating around) are also really prone to erosion.
This is because the soil has lost it’s structure and is really dispersive so when it gets wet it will run away easily. This also causes erosion.
Because water cannot infiltrate into sodic soils, the water moves laterally just under the surface, creating drains. These can’t be seen until they collapse into tunnels, and if they keep getting worse they may become erosion gullies (i.e. have a depth of >30cm).
Lastly, sodic soils may lose some topsoil due to dust.
So what did the farmer do?
Well Internet, he basically did the same as for salinity and sodicity; encouraged plant growth through the addition of manure, grazed lightly, and added lime in some places.
Lime is sort of the opposite to gypsum in that it raises pH rather than lowers it. In the case of Gunyah lime was most likely added as the soil was too acidic after years and years of super phosphates being added to perennial crops.
Soil pH is super important in agriculture as crops and pasture take up nutrients best when the pH is about 6.5.
The plants are important as their roots hold the soil and provide protection to it from the eroding powers of wind and rain.
Once you’ve treated your soil with gypsum it will form those nice little peds and all will be well on the farm.
It’s kind of simple, once you think about it carefully!
The craziest thing about all of this is that in the majority of cases it’s cheaper to buy new land than to rehabilitate your own land. So if you have sodic soils just, you know, fence it off and buy some new land. Nuts.
(Also, a really bad philosophy to get into. If we don’t take care of our land it’s not going to take care of us, and where else do you want to grow your food?)
That was the soils part of my assignment.
Stay tuned for when it gets crazy and I compare conventional, organic and time controlled systems in terms of grazing and cropping.
Sustainable agriculture is great!