Wednesday, August 23, 2006

A salty tale

G'day all!

Thanks for all the entries into the 2 year blogiversary contest, the grand prize being something you don't know about yet cos I don't - the winner will get something of their choice. Since I got the date wrong, I'll run it until tomorrow SATURDAY 26 August, 6pm Oz EST.

Tiphanie, who has not made her blogger profile public so I cannot link to her blog, asked if I have any tips for new bloggers.

First hint - make your profile public, Tiphanie, if you want people to find you by following the links in the comments, which is how I find some new blogs.

Tip two - always be true to what you like. That doesn't mean being nasty (or as we say here "slagging on" other people), just letting people know something of what you like and enjoy doing via your blog. If you have some interesting quirks that aren't illegal or immoral, talk about them. It may be that you will find there is a whole group of people who, for example, are addicted to the colour orange, only ever wear orange, drive an orange car, only drink orange Fanta and keep a tank of orange tropical fish.

Tip three - like tip two. Be true to yourself. Blog if you feel like it. Don't blog if you don't. If it isn't fun anymore, don't do it. Blog about things you like. It's your blog.

Because this is my blog, today we have a rant. Yep, another rant. Not much in the way of knitting or spinning pics or tales cos someone forgot to take pics of the dyeing she did. She was a bit het up about doing an "interview" with a temping agency at lunchtime. (It went pretty well I think.)

Australia is an ancient continent. Some of the oldest rocks known on Earth can be found in Western Australia, four billion or so years old. Many of the soils have been here before our species existed. Not all soils, but many. Aborigines came to this land maybe a hundred thousand years ago. They trod fairly soft on the land and didn't do much that whites consider agriculture (though they certainly nurtured their food resources and used fire to their advantage).

So in comes white man. He sees land that can be cleared of the useless (if pretty) scrub and turned into wheat growing areas. Nice productive wheat fields. Mmmmm..... and canola! Canola, the crop of the future!



What the white man doesn't know is that deep in the soil is salt. Salt that has been blown in from the sea over millions of years and washed deep down. The native vegetation is deeprooted and slurps up a lot of water - just one of the local gum tree species is estimated to drink 600L of water a day. Thousands, millions of these trees will keep the water table nice and low and keep the salt deep down where it belongs.


So white man clears the useless scrub and plants nice productive wheat paddocks. He hasn't noticed the salt lakes that pepper the area beyond the fact they are no use for farming. He doesn't realise their implications.

Wheat is not deep-rooted. It has shallow little roots like most annual grasses. It only slurps up a bit of the rain that falls. The rest of the rain (and some years there is precious little of that) soaks through the soil and down into the water table.

Over the years, the water table starts rising. Within 50 years of the land being cleared, farmers notice that parts of their paddocks are no longer growing economically useful plants and the little creeks and water channels don't support plants any longer, or only support samphire and pigface. The water tastes salty.






Places that supported trees now don't, and the trees die.

By the 1970s, whole creekbeds are scouring out - the water table has risen and brought the salt to the surface. Salt is breaking out into paddocks. (This isn't just a problem for the wheat cockies - the cow cockies and sheep cockies face this problem on any land that has been cleared). By the 1980s salt is an acknowledged problem in the wheatbelt. Towns are starting to notice that roadbases are crumbling and foundations of buildings are suffering - salt can be seen encrusting bricks as it creeps up buildings. How to get rid of the salt?


Here's one solution - grade drains along the contour lines of the paddocks. The bloke on the right has been doing this for 30-odd years with good results. The drains pick up the surface run off (rainwater/freshwater) and empty into dams specially constructed so that the water does not seep out of them. This contour drain was set up about 4 or 5 years ago. The paddocks are planted on the contour as well to help reduce soil erosion, and no till/low till methods are being used increasingly too. Soil erosion and salting are the two biggest problems faced by most Australian wheatbelt farmers (apart from the obvious droughts that occur).


See that bare patch in the middle of the canola? That's salted land about 30m downhill of the countour drain. Two years ago an area two or three times the size of that patch would not grow barley, reputed to be one of the most salt tolerant crops we have. Last year barley grew on a fair whack of the area. The salted patch is recovering because the water table is lowering. This year canola, which is renowned for disliking salt, is growing well around the patch, which has shrunk further.

Basically, to stop the water table rising, you need to stop rainwater reaching the subsoil cos it just lifts the water table higher. The higher the water table, the higher the salt. Most farmers won't do the most simple thing to stop rain water recharging (ie water seeping into the soil higher up a slope and lifting the water table further down the slope) cos it means they lose paddock space. That most simple thing is to replant the recharge areas with deeprooted plants. Planting scrub goes against the grain of people who cleared land or whose father or grandfather cleared the land. However, if it was economically useful scrub - eg mallees (gum trees) that can be used for extraction of eucalyptus oil or ornamental flowering plants that can be harvested and used in the floristry trade then farmers might go for it.

Once you drop the water table, the rain that does soak in washes the salt back down. Lowering the water table is key.

We'll see what happens. In the meantime, the salinity problem generated in the paddocks around Merredin is draining into the town, and is already noticeable in the town.

All this because we just didn't know enough about Australian soils and conditions, instead using English methods of cropping.

anon!

2 comments:

  1. Fascinating stuff indeed, at least there are measures to stop or reverse the water table rising, give it a bit longer and there will be no choice but to invest in those measures.

    ReplyDelete
  2. I didn't know any of that - thanks!

    ReplyDelete

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