Water Ponding in the Rangelands

Rangelands are used for very diverse purposes and have many associated management issues.

They cover 80% of Australia and comprise diverse ecosystems, such as woodlands, tropical savannah, shrub lands, grasslands and deserts. There are many land uses of rangelands, such as mining, tourism, Indigenous use and agriculture. The semi-arid areas are very important for grazing, and $4.4b is made annually from cattle, and a further $1.1b from sheep and wool.

nsw-map-rangelands-higher-rainfall
The rangelands of NSW cover 60% of the state and are located west of the 500mm per annum rainfall zone. The field preparation for this report was conducted in the area around Trangie and Nyngan. SPicture: R Hacker et al., Best management practices for extensive grazing enterprises, NSW Department of Primary Industries, April 2005. 

 

Introduction

Water ponding was used to reclaim scalded soils at two sites in the Nyngan locality. These sites are now 25 and seven years old and a Landscape Function Analysis was carried out on them to compare functionality and pond age, using a scalded site as a baseline.

Landscape Function Analysis

Landscape function analysis (LFA) is used to assess the functionality of rangelands. It uses visual indicators to give an indicator of 11 physical and biological processes to describe three key soil phenomena, and thus the overall functionality of that landscape (Tongway and Hindley, 2004).

indicators
2 Eleven tests are conducted in order to assess three key soil processes that describe landscape functionality.
Picture: Tongway and Hindley, 2004.

An LFA was carried out on ponded sites in order to determine the effects of water ponding on landscape function in terms of stability, infiltration, nutrient cycling, soil carbon, and soil biomass relative to pond age.

Water ponding

I don’t know about you, but when I hear the word ‘pond’ I think of this:

tumblr_lzhybmvoMG1r9wixeo1_500
Water ponding; less to do with the Ponds, more to do with soil scalds. Picture: Bill Israel.

Water ponding, however, is a practice used to reclaim scalded soils, which we’ve talked about before.

These soils develop due to clearing and overgrazing, causing an excess of sodium ions (i.e. >15%) which creates hard, concrete like surfaces called scalds. Neither water nor roots can penetrate these surfaces, leading to an absence of vascular plants in these areas, which in turn further disrupts the site’s hydrology. At this stage the landscape enters a new stable state that is X to agricultural use. A functional landscape experiences short tortuous flows of water through grass tussocks, whereas a dysfunctional has long straight flows around tussocks which loses resources such as water, soil, and seeds.

water flow
3A functional and dysfunctional landscape. Note the differences in plant cover and resulting water flow.
Picture: Tongway and Hindley, 2004.

Water ponding is a highly successful practice that uses to reclaim these soils, a system that uses 0.4ha horseshoe shaped ponds to hold water and encourage plant growth by holding water on the surface. When a site is identified for water ponding, it is surveyed with a laser leveller in order to find potential positions for pond banks. Ponds are then laid out from the highest point in the scald and overlap like fish scales so water is not lost. They must be no more than 10cm deep or only reeds and rushes will grow, and wave action can destroy the banks. In order to ameliorate wave action, tunnelling, and dispersion there is a heightened buffer section between the banks and the pond. As the system is reliant on rainfall, water ponding may be less effective in times of drought.

Results

Two water ponding sites were visited, one 25 years old and one seven years old. An LFA was carried out in four ponds at each site in order to assess the effect of water ponding on landscape function relative to pond age. This was done by laying down 15m transects at the back of ponds and collecting information on the fore mentioned 11 indicators in the patches (areas of vegetation) and interpatches (clear areas). Soil carbon and biomass were also measured.

biomass
4 Biomass results from the two differently aged pond sites compared to a scalded site. 

Biomass was taken from a 30cm2 plot in the middle of the transect, oven dried and weighed.

carbon
5 Soil carbon results from the two differently aged pond sites compared to a scalded site.
stability
6 Soil stability is a result of LFA. This graph shows the results from the two differently aged pond sites compared to a scalded site.

infiltration

7 Infiltration of water into soil is a result of LFA. This graph shows the results from the two differently aged pond sites compared to a scalded site.
nutcyc
8 Nutrient cycling is a result of LFA. This graph shows the results from the two differently aged pond sites compared to a scalded site.

Discussion

The above results show that water ponding has a positive effect on landscape functionality. In every data set, treated sites performed better than the scalded control. In the case of nutrient cycling and infiltration, this difference was particularly significant. These two factors are both dependant on basal cover, litter origin and surface roughness among other things. The scald does not have these properties as it has no vascular plants and the dispersive soils create a smooth, hard crust that does not allow for the build-up of resources such as seeds, litter and water.

Water ponding allows water to sit on the scalds, which restores the swelling and cracking properties of the duplex soils (Thompson, 2008). Cracks allow windblown seeds to get caught in the micro-topography, as well as allowing water and root penetration of the surface. The seeds can then grow, restoring infiltration and nutrient cycling. This was indicated in the results; stability does not significantly increase with pond age, whereas infiltration and nutrient cycling do, suggesting that stability recovers first and is needed for nutrient cycling and infiltration.

There was no biomass on the scald, and differently aged ponds had similar amounts. This is because total biomass increases and plateaus relatively quickly; it can be up to a 20% increase in the first year.

Soil carbon increased over time and in comparison to the scalded site. Soil carbon helps to restore functionality by ameliorating soil structure and available nutrients (CSIRO, 20011).

Conclusion

It can be seen from the results that water ponding is successful in reclaiming scalded soils for use. Functionality of landscapes was seen to increase with age, but not significantly in regards to stability. It can also be concluded that, despite it’s irrelevance to agriculture, Amy and Rory’s story is wonderful and that the Last Centurion and the Girl Who Waited are heart warming in their (literally) undying love for each other.

rory
He waited 2000 years for a woman who ripped Time apart for him, but can he reclaim a scalded soil?

Grazing on Struggle Street: Conventional

Morning Internet! 

cat
Internet is totally ready for some science. PHOTO: cutespaw.com

My assignment is still lurking around in the shadows of my Wednesday, so here we go, back into my developing field report.

So this morning we’re going to talk about grazing, specifically we’ll be talking about the merits of conventional versus organic versus time controlled grazing. I then have to decide which is the most sustainable, economically and environmentally, and then justify that decision. 

Oxton Park, Buronga and Tulgani: Discuss the advantages and disadvantages of these various agricultural practices, and therefore which is the most sustainable (both environmentally and economically).

So grazing. Yeah. 

Conventional Grazing

We saw a conventional grazing system at Oxton Park. It’s an 8000 ha property with 200 ha set aside for grazing.

They had their soils classed and they have classes 1 – 5. Soil classing works like this; hazards are used to assess capability; the potential consequences of a hazard and the likelihood that that consequence will be realised. The LSC is based on the most limiting hazard. Soil classes go from 1-8. You can do anything you like with 1 but 8 is rubbish country. The assessment scheme is the major tool to assess the sustainability of land management practices. It follows on from one made for the Central West of NSW in 2008 (which was itself based on the US Dept of Ag scheme from the early 1950s).  A Land and Soil Capability (LSC) assessment scheme is most suitable for broad scale assessment of land capability particularly for low intensity dry land agriculture-less so for high intensity use or irrigation. 

classes
Class 7 isn’t great at all, class 4 is good for grazing class 2 is beautiful. PHOTO: NSW Office of Environment and Heritage.

So they graze on class 5. They crop for four years on classes 2 – 4 then graze for 15. This very long term thinking is in place as the farm is not a family farm but a business. They are playing with huge amounts of money and every paddock has a plan for it; they know what they will be doing there every year for about the next 20 years. 

They run about 30 000 merino, mostly for superfine wool. 16 000 are pure merinos and 6000 are a quicker growing crossbreed that they use for meat, which is now worth more than wool. The meat sheep are exported if they’re more than 11 months old. 

bigmerino
The Big Merino in Goulburn, NSW. Legit. PHOTO: weekendnotes.com
merino
Merions, man. Note the wrinkly neck, their most recognisable feature. PHOTO: farmadvisor.com.au

 

Wait, what’s superfine wool? How is it different to normal wool?

Good question Internet. Superfine wool is 18-19 microns thick, which is the diameter of the wool. Wool is also measured on it’s tensile strength, but the diameter is the most important factor and is dependant on the sheep’s age, breed, health and so on. Merinos are known for their superfine wool, which is used in thermal and luxury products. 

icebreaker-clothing
Clothes made from superfine wool are really soft, warm and dry quickly, so they don’t get smelly. These properties make them ideal sports clothes. PHOTO: gearforgirls.co.uk

They shear every ten months, generally in April and January. You need about 70mm of wool to make it worthwhile and you shouldn’t shear them in winter (really?!) or when they’re lambing. 

This way of raising sheep is very high input, both in terms of money and time. You have to drench them and crutch them; you have to shear them, you have to move them from one paddock to the next. 

The advantage is that you get a consistently high quality product, but the disadvantages are that if you run out of money or inputs the system will collapse. Also, because they’re grazing their sheep on class 5 land, it is reasonable to expect that the sheep’s diet isn’t great as the pasture in those paddocks may not be very varied. If this system was hit by a serious drought the farm would probably be fine financially but it’s anyone’s guess how the land would go after being managed to produce meat and wool rather than to produce pasture with the sheep as by products. 

So what’s your conclusion?

Well Internet, it’s probably only sustainable financially as long as you have enough money to put into it and aren’t hit by a big drought; it’s very dependant on inputs. Environmentally it’s probably not that resilient, although good on them for understanding their soils and utilising them correctly. 

Tune in next time for the same again, but with organic grazing!

Soils on Struggle Street Part Two

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.

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.

peds1
Peds! Look at all that soil structure! PHOTO: R. Patterson.

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!

Weekly Writing Challenge: Dialogue. About goats.

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.

grassland
What Australian grasslands of that area are meant to look like. There’s a overstory of trees and an understory of grasses and forbes and nothing else.
woody weeds
An area over run with woody weeds; the middle story. Note the absence of an understory.

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?

clay runoff
Soil particles are covered in clay (happy soil), but then goats come in and rub it off. The clay forms a film on the surface when it rains, and water can’t get in (sad soil).

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.

apocalypse
Sydney Harbour in the 2009 Australian dust storm. I was 16 at the time and it felt like the apocalypse had come.

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.

goats3
Goats are awesome.
goat1
What a cutie!

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