David Cattanach
Region: Darlington Point, near Coleambally, in south-west New South Wales
Commodity: Wheat, barley and maize
Farming area: 600 hectares
Rainfall: 50–500 mm per year
Email: david.cattanach@bigpond.com
Phone: 02 6954 4685
The biggest issue for me is water, or lack of it. We have only a very small amount of water, so I have to budget how much water I will need to get a crop through to harvest. I also have to decide what crop, or variety of crops, will give me the best return per megalitre of water.
See what David has to say about:
- Using end-of-season weather forecasts
- Budgeting water as an irrigator
- Rethinking sustainable farming practices
- Understanding the benefits of till and no-till
- On-farm green-house gas emissions audit
Using end-of-season weather forecasts
I think there is a reasonable amount of information available that suggests we can expect drier and warmer conditions than we are used to. However, at this stage, the broader community is hanging onto a hope that we might get back to the 1970s/1980s rainfall which may have just been a wet period in history, at best.
In the past I was more interested in what the weather was going to be this week. However, over the past 10 years I have become more interested in what the weather is likely to be at the end of the season, because of limitations on irrigation allocations.
I spend a lot of time looking at what is happening with the weather. I tend to look more at the Indian Ocean, the Indian Ocean Dipole and the La Niña in the Pacific Ocean (Southern Oscillation Index), because these seem to give an indication of longer term weather patterns.
Budgeting water as an irrigator
The biggest issue for me is water, or lack of it. We are in a very low rainfall area and, while most of us are irrigators, we are heavily restricted by what we can extract.
Most farmers around Griffith use surface water. However, there are a small number of us who use groundwater.
Every irrigator has a water entitlement and receives an allocation of that entitlement each year from the government. Since 2000, the average allocation has been around 10–15%. Because I use groundwater my allocation is fixed, and not dependent on rainfall in the catchment.
We have only a very small amount of water, so I have to budget how much water I will need to get a crop through to harvest. I also have to decide what crop, or variety of crops, will give me the best return per megalitre of water.
Because of the increasing variability in rainfall, especially during winter, I have been budgeting to use more water per hectare than I did 20 years ago.
In the past, I would budget to use 2 megalitres per hectare to grow wheat, and about 8–9 megalitres to grow corn. Now, my water budget is 4.5–-5 megalitres for a hectare of wheat and 10 megalitres for corn. Obviously if we get a storm and a decent spell of cool weather, I do not have to use the full amount.
Given the drier conditions, I cannot afford to run short of water because at the moment there is no surplus water to buy from anyone, at any price.
Rethinking sustainable farming practices
We don’t really think a lot about how much farming has changed—we are always adjusting things as time goes on. 30 years ago, after the summer crops, we would plough the ground, knock the beds out and plant wheat conventionally with a combine.
Today, all our cropping is on permanent beds. Once we put the beds into the paddock, we keep them there for several years. This is to reduce soil disturbance and save on fuel.
We are using 2-centimetre guidance systems on the tractors and all our machinery is set up with narrow tyres. The tyres on all the machinery are spaced so that they run only in the furrows and never over the beds. This hopefully improves our soil structure.
We are also looking a lot closer at fertiliser—namely, what we apply, how we apply it, and when we apply it. For us it is all about improving the efficiency and minimising the cost of our inputs.
In terms of harvesting, we harvest and mulch corn. Until last year, I used to burn it and then direct drill into the beds. Now I leave the mulch on the surface and using a disc system to sow through the stubble.
I don’t have hard data yet but some people in the area have tried it as well. We estimate that having the mulch on the surface is saving us 1.5 megalitres of water per hectare from reduced evaporation. I have run the figures past local CSIRO researchers, and they seem to be coming up with a similar figure too.
Understanding the benefits of till and no-till
After I harvest, I decide what I want to do with my stubble. Do I want to leave it standing there to conserve moisture? Or do I want to try and get some of the nutrients back out of it?
After a corn harvest, I preserve the stubble and then plant wheat through it. The stubble helps to conserve water for the wheat to use, which can help increase yields and water efficiency.
However, if I want to put corn back into that paddock, I will bury the stubble. This is because I am more concerned about returning nutrients and carbon to the soil, as well as warming the soil to allow for an early planting.
If we bury the stubble back into soil through no-tillage methods, the nitrogen stored in it can be used by our next crop and would go towards our next harvest. In effect, nitrogen efficiency would be higher than 50% because its effects may be spread over 2, or even 3, harvests.
Our inputs would also be lower because there are already higher-than-normal levels of nitrogen in our soils. Because of this, we have been adjusting our nitrogen inputs across our paddocks. We test nitrogen levels before and during the season.
Since 1991, I have been keeping track of a research project in the Harden area which is looking into the differences between tillage and non-tillage. They are comparing organic carbon levels in minimum-till paddocks and conventional-till paddocks.
In zero-till paddocks, they have been finding a very large pool of labile carbon [soil organic carbon that is available to plants, and which decomposes relatively rapidly] sitting at the surface and reduced levels of more stable carbons (like humus) deep down.
When they looked at conventional-tillage though, they found the opposite—a very small pool of labile carbon on the surface, but increased amounts of carbon stored deep down as humus.
Greater levels of each type of carbon have different benefits for different crops, so you need to bury or retain stubble on the surface for a good reason to get the right results with your method.
On-farm greenhouse gas emissions audit
Between 2001 and 2005, I was involved in a life cycle analysis study to measure the amount of greenhouse gas emissions produced in making corn chips, from seed to shelf.
For my part, I grew corn in the same paddock for 5 years and measured the greenhouse gases emitted from three tillage techniques—mulching and incorporating the stubble; mulching and burning the stubble; and mulching and removing the stubble.
I hooked a laptop up to my tractor and drove up and down a paddock recording all the functions that were associated with producing exhaust fumes—how much fuel the tractor used, how much horsepower it needed to pull machinery, and so on.
When stubble was buried, I only used 36% of available horsepower to pull my machines through the paddock during primary tillage. When I burnt the stubble, I used 56% of available horsepower to pull the machines through. When I removed the stubble, I was not even able to pull the machines through the ground.
Interestingly, the amount of emissions when stubble had been buried was lower than the other 2 strategies.
The life cycle analysis showed that 40% of the total emissions to produce a bag of corn chips were produced on-farm, while 60% were produced off-farm.
People like to point the finger at agriculture, but at least most of our emissions are from biological sources.
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Interview date: 2 June 2010