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.
Hello everyone! I’m taking part in a weekly writing challenge to shake it up. Check it out:
It is night, and raining. A YOUNG WOMAN sits at a computer, headphones in, typing with one hand. Her chin is resting in the other. The audience can hear the tinny sound of electro-house music and the clattering of keys. Enter THE BOYFRIEND. She doesn’t notice. He taps her gently on the shoulder.
YOUNG WOMAN: (startled) Gah! Dude, you scared me.
THE BOYFRIEND: You’re still here how I left you this morning! What have you been up to all day?
She takes out her earphones and turns to face him, excited.
YOUNG WOMAN: Soils! Soils are amazing. Well, goats and soils. See, they had too many woody weeds, then they put goats on it to make it better, but the goats messed it up, so now the soil is unhappy because there isn’t any clay and so there’s a film and basically it’s all just terrible.
THE BOYFRIEND removes his jacket, sits down in the armchair next to the desk and looks at her intently. He likes hearing about what she’s learning.
THE BOYFRIEND: (patiently) … Right. And what are woody weeds?
YOUNG WOMAN: (impatiently) They’re woody shrubs that grow in the Australian rangelands and are unpalatable to stock. The rangelands are, like, 80% of Australia, but this case study is from the semi-arid region between Broken Hill and Cobar, in the south-west corner of New South Wales.
THE BOYFRIEND: So where do the goats come in?
YOUNG WOMAN: Well, removing woody weeds mechanically or chemically is really expensive, and they tried burning it but it doesn’t always work. That’s one of the main maxims in Australian geography; if there’s a problem, set fire to it and ask questions later.
THE BOYFRIEND: (laughing) So they put goats in? Where did they get the goats from?
YOUNG WOMAN: That’s the beauty of it, see. You just fence off a whole lot of feral goats that are out there anyway, and the expense of the fence is offset by the profit made from the goats. There’s a growing market for goat in Australia, especially goat that’s Halal. The goats start off eating all the yummy things, like the forbes and perennial grasses, but then they go on and eat the woody weeds. Unpalatable doesn’t worry goats!
THE BOYFRIEND: Forbes? Isn’t that a town in central New South Wales? And how does this relate to soils being unhappy?
YOUNG WOMAN: Yeah, it is a town too, but forbes is another name for ‘herb’, something that’s not a grass or a shrub but is still a little plant. So they put in heaps of goats. Like, heaps. Out there the stocking rate is 0.3 DSE per hectare, which means that for every hectare you should only have 0.3 of a dry sheep equivalent. This is the amount of resources needed to support a ewe that doesn’t have a lamb. A cow is equal to about 15 DSE, a pony or light horse has a DSE of 10, and so on. So this place is at 0.3/ha, and they go and put in 4 goats on every hectare! This is so they can really eat the weeds down, put that many goats puts pressure on the soil. See, the soil is usually alumino-silicate aggregates coated by clay, yeah? But the goats grind it all together and the clay comes off. You following?
THE BOYFRIEND: Yep. The area has a DSE of 0.3/ha, but you run it at about 4/ha and the clay gets rubbed off the soil particles. What happens then?
YOUNG WOMAN: Well, usually the water would just infiltrate into the soil and there’s basically no run-off at all. No erosion or anything, just lots of water for the plants, but because the clay has come off the soil it forms a film on the surface and the water can’t infiltrate into the soil. There’s lots of run-off which causes erosion, and the plants can’t access the water.
THE BOYFRIEND taps his nose thoughtfully.
THE BOYFRIEND: Hmm, doesn’t sound too good. Anything else?
YOUNG WOMAN: Yeah, dust. Because the soil is made so unstable by the goats they lose massive amounts of topsoil via wind erosion. This is a serious problem in Australia and is very costly, both environmentally and economically.
THE BOYFRIEND: So … goats solve one problem but create a few more?
YOUNG WOMAN: (sadly) Pretty much. If you can figure out how to solve the woody weeds problem they’ll basically make you Australian of the Year and you’ll be a gazillionaire.
THE BOYFRIEND: That’s a shame, goats are otherwise so cool.
YOUNG WOMAN: (excited, looking to a future of solving problems with goats) Yeah, geography is awesome!
So that was my night last night. More or less a true story.