‘KILMARNOCK’, BOGGABRI, NORTHERN NSW
Commodity: Irrigated and dryland cotton, grains, oilseeds and legumes
Farm area: 4500ha
Rainfall: Long-term average 592mm, range per year 269-1089mm
In the past 9-10 years of rainfall, I’ve noticed that we tend to get more small falls and more large events, but fewer average falls. The problem with the smaller falls, particularly during summer, is the water evaporates almost straight away – even a 10 mm fall. What we have to do is make sure we take advantage of these larger events, which often mean flooding.
Our farm is about 5 kilometres east of a little town called Boggabri, which is between Gunnedah and Narrabri in north-west New South Wales. My father bought the original property in 1965. Since then, he, my brother and I have expanded the property from 400 hectares to 4500 hectares.
Our pillar crop is cotton. 30 years ago, Dad was the first to grow cotton east of Narrabri. In those days it certainly wasn’t considered a cotton-growing area. It was thought to be too cold. Now our irrigated and dryland rotations and crop management decisions generally are targeted toward ensuring the cotton rotation is not disadvantaged in any way.
The varieties grown at the time were a longer season variety, which took longer to grow. If it got too cold near the end of the season, cotton wouldn’t finish. Today we have shorter season varieties, which now suit this area’s climate.
Most years we would plant about 600-800 hectares of irrigated cotton, and about 300-400 hectares of irrigated durum wheat.
We have 1200 hectares of dryland area on which we grow a series of dryland crops in rotation, including cotton, durum wheat, chickpea and canola.
With most of the rest of our land we do some grazing, and my dad runs a small second-cross breeder cattle operation.
In this region we are probably the second largest cotton-producing farm, but not by much. There are quite a few about our size.
We are in a slightly summer-dominant rainfall area. January and February are normally our wettest months. March and April are our driest. During a typical year, we’d get 120 mm from March to the end of November.
The long-term average for Boggabri is 592 mm. For the past 12 years, we’ve had between 413 mm to 900 mm of rainfall per year. If I look at Boggabri’s historical records, it’s ranged from 269 mm to 1089 mm. So, there can be some huge variation.
In the past 4-5 years of rainfall, I’ve noticed that we tend to get more small falls and more large events, but fewer average falls. The problem with the smaller falls, particularly during summer, is the water evaporates almost straight away – even a 10 mm fall.
What we have to do is make sure we take advantage of these larger events, which often mean flooding.
The Namoi River arcs around our property. We’re downstream of the Keepit Dam before the land flattens out into the plains. When the Namoi River or some of its tributaries flood, it floods a fair chunk of our land too.
We haven’t had any event or flood that we haven’t been able to manage, but that doesn’t mean we’re being complacent. We understand the risk of a hundred-year-flood scenario and have worked with the catchment management group and our neighbours to build metre-high flood banks. They are all around the farm to channel floodwaters through the farms and protect the crops.
Climate variability for me is about identifying the risks and then building enough flexibility into our management, rotational and staffing structures. The length of forecasting informs different levels of our decision-making.
The biggest decision we have to make each year is how much cotton we are going to plant. That’s based around water; namely, how much water I have available for irrigation.
Because our biggest decision – how much cotton to plant – is based mainly on available water, in terms of forecasts I want to know when it’s going to rain and how much. When we have an idea of that, I can make planting, harvesting, irrigation and other operational decisions well in advance.
We use seasonal forecasts for strategic decision-making, like setting up long-term crop rotations, or property purchase or sale.
Monthly forecasting informs our tactical decision-making process, like ordering fertiliser or seed so we have it on-farm if a predicted weather event occurs.
Weekly forecasting helps us with operational decision-making, like when to spread fertiliser, or deciding to harvest grain slightly early with a high moisture content and being prepared to dry it rather than risk quality downgrades from a rain event.
We know that forecasts are probabilistic, so we don’t want to plant 100 per cent of our irrigated land to cotton because we want to spread our risk. For instance, in the 2014 season, the Bureau of Meteorology predicted a high probability of greater-than-expected rainfall. So, we decided to plant a higher yielding, less-drought-tolerant dryland cotton.
Unfortunately, that rainfall came quite late in the season – 120 mm over 4 days in April – so most of that cotton has struggled and we had to plough some in. Because it’s so wet now, it will be another 3 weeks before we can do some operations we were planning on before the rain.
Because of the uncertainty, I try to make decisions that are not so heavily reliant on, or influenced by, weather forecasts.
We have two sources of water. One is bore water and we have 19 bores across the farm we can access. The other is river water, which we access from the Namoi River. Anything that falls from the sky is extra.
Each year we are allocated a certain volume of water from our bores and the river. So, essentially, we have a ‘bank account’ of water that we can use as we see fit.
Bore water is allocated on an annual basis. On 1 July every year I get my full allocation added to my account. If I haven’t used some of my allocation from the previous year, it gets tacked on top. I can only ever have up to 300 per cent of my allocation in my account. After that, I can’t keep adding more. River water is allocated periodically throughout year, based on how much inflow there is to the dams.
An example of irrigated crop planning was in the 2015 season, where our water balance meant we were only be able to plant 480 hectares of irrigated cotton. That is a bit less than normal because we didn’t have any river water allocated. We relied mostly on bore water in that instance. If rain leads to a whole lot of inflow into the dam in any given year, we can change our planting strategy and plant more cotton.
The cotton decision informs the irrigated grain decision. Wheat generates about $150 per megalitre of water; cotton generates about $500-600. If we have 45-50 per cent of our irrigated land planted with cotton and we have water left over after that, we would then plant irrigated wheat. We don’t want to plant 100 per cent of our irrigated land to cotton because we want to spread our risk.
Given fairly standard dry scenarios in the last 10 years we haven’t had enough water to plant as much cotton as we want, and so haven’t planted very much irrigated wheat this in the last 5 seasons.
If a plant under our irrigation needs water to survive, I have to give it some. Traditional irrigation systems like siphons mean I will apply enough water each irrigation to last the crop about 8-10 days, but with overhead sprinkler systems we only apply enough water for 3-5 days’ crop growth.
We have to order water 3 days in advance so it is here when we need it for irrigating. We usually pump it straight out of the channel onto the fields, so we don’t store the water and risk evaporation. That’s one way we are trying to reduce our water use.
We believe we can irrigate our cotton and wheat even more efficiently by using overhead sprinkler technology instead of flood irrigation, particularly during the early growing season.
When we flood irrigate, we wet soil down to about a metre. A plant that is only 5 centimetres high, only has about 5 centimetres of roots, therefore only needs water down to 50 mm. So rather than waterlog the soil, the lateral overhead sprinklers are able to deliver this precise amount.
As the season progresses, the lateral overhead sprinklers will also allow us to water the crop more consistently and more precisely between any rainfall events we might have.
We have a number of fixed soil-moisture probes throughout our irrigated paddocks. They log soil-moisture measurements every 15 minutes at different levels in the soil down to a metre. They send this information back to our computer in the office, which plots a time-series graph, and we can see how quickly the soil moisture decreases as the plant uses it.
When a plant has taken all the moisture it can from the soil, the drop in moisture per day reduces, so the shape of the curve starts to flatten out. At this point, the plants are under stress. However, we would have irrigated before it hits that period.
When we flood irrigate, it takes 10-12 days for the plant to suck all the moisture out of the soil. When we use overhead sprinklers we are delivering enough water for the plant to survive 3-4 days, so we are irrigating more regularly.
Since we’ve started using overhead sprinklers, we’ve found that the moisture probes aren’t providing us with precise enough data to plot a suitable graph in the shorter time period. So, we trialled newer infra-red heat sensors. Each sensor costs about $1400, so it will be a significant investment for our business. Instead of measuring the moisture available to the plant, these sensors measure the temperature of the canopy. When the temperature rises, the plant uses more water to keep itself cool. We know the millimetres of water it will suck up for every degree increase in temperature, so we can extrapolate when the plant will become stressed and schedule the sprinklers to start irrigating again.
We need to have our soils, particularly on our dryland paddocks, in a condition where they can soak up as much rain as possible when it falls. That’s why we practice zero-till and leave our stubble standing.
This helps, particularly during large rainfall events, as it slows the water down and lets it soak in.
This is less of an issue on our irrigated land because that land is set up to have floodwater run over it. In these paddocks, we are able to collect water and recycle it.
Soil moisture is what really informs our dryland operation. Our dryland soils have water-holding capacity of about 260 mm. From past experiences, if we plant without a full profile, we will be lucky to break even.
I would want 200 mm of rain before April if I planned to plant durum or canola. Over the past 4 days [March 2014] we’ve received 100-120 mm of rain. If this continues, then I’ll reconsider planting chickpeas and look at planting the durum or canola. We try to remain flexible in these decisions because ultimately we are trying to make the most dollars out of the season we have been dealt.
In 2017 the cotton industry in conjunction with researchers, Monsanto and the Australian GMO regulator, The Office of the Gene Technology Regulator, brought in an ability for farmers to not pupae bust, or rip the ground post crop, if they had defoliated the crop early enough in the season. Essentially, it was found that if the cotton becomes unattractive to insects before the cold of autumn sets in the moth will move to another local rather than tunnel into the soil for the winter. This has meant we are able to zero-till our irrigated and dryland cotton crops post-harvest through to the following crop, saving moisture that would be lost through aggressive tillage for pupae busting.
This has led to increase in interest in cover cropping post cotton to improve soil biology and soil water holding ability through increased soil carbon levels.
We make most of our variety and crop decisions on gross margin returns. We are looking at what’s working best on average, and then putting that up against whatever constraints we have.
During dry seasons, we tend to plant Siokra 24BRF cotton in our dryland areas. It is a cotton variety known to have a stronger taproot, which will go deeper into the soil.
Last year I planted one field to Sicot 74BRF, which is proportionally higher yielding. I chose it because I thought it would produce a greater yield for the moisture we had and the predicted rainfall. However, it had a much weaker seedling vigour and root system. In the end it proved to be not good enough for this season and we ended up ploughing it in.
When we plant cotton, we like to plant into a seedbed that is 14 °C and increasing in temperature. If our seedbeds are 14 °C but we notice that in 7 days’ time we are expecting 2-3 nights below 6 °C, we would probably hesitate to plant.
It’s important to keep an eye on the minimum temperature forecast at planting and we are very comfortable with the accuracy of the 7-10 day forecasts from the Bureau to make these decisions. We generally don’t need forecasts longer than this to change our timing decisions for planting.
This area will remain very strong in cotton production in the future because it has water security. It doesn’t matter really how dry it is, this farm will always have enough water to grow 500 hectares of cotton because of the bores. Right through the last drought, the cotton production area in this valley barely varied.
I think cotton will also remain profitable in Australia because we produce some of the best quality in the world, and we also produce the highest yields in the world.
I am very confident that cropping will also remain a very big part of this area. We are moving more towards using a rotation of dryland cotton and wheat in our dryland area. Wheat doesn’t make us the same amount of money as cotton, but we really want the zero-till part of wheat as a stubble cover to stop run-off.
When I first read about the MCV Climate Champion program, it struck me as something we were already doing here on our farm and in our area – helping farmers in our region to change practices.
It’s not only changes to the climate that we are trying to get across. It’s what we are doing to manage variability, as opposed to just listening to the forecasts. That’s what I find important. At the end of the day we are trying to do everything better, particularly managing risk.
Interview date: 27 March 2014 – Revisited 29 May 2018
Andrew Watson on his farm Kilmarnock
In 2014, Andrew’s dryland cotton yielded 1.3 bales per hectare and his irrigated cotton yielded 10.4 bales per hectare
Andrew has set his property up to reduce the damage caused by floods and to dictate where the water goes.
Most years, Andrew will plant 600-800 hectares of irrigated cotton – almost 45 per cent of his irrigated land. The rest he will plant to dryland crops.
The first year Andrew used the sprinklers he saved 12 per cent water and generated 17 per cent more yield. Successive years have shown a consistent water saving of around 10% over flood irrigated fields, however yields have remained about on par.
An example of a graph generated from the moisture probes. When the curve starts to flatten, Andrew will start to irrigate.
An infra-red heat sensor