Australia's climate has always been prone to variability

Australia's climate has always been prone to variability


Cropping
Tropical grass (Jan 4, 2019) responding to mid-summer light rain events during the drought. Pasture types able to use moisture, whenever it falls, an important part of coping with climate variability or climate change.

Tropical grass (Jan 4, 2019) responding to mid-summer light rain events during the drought. Pasture types able to use moisture, whenever it falls, an important part of coping with climate variability or climate change.

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Both for temperature and rainfall it seems to me a fair assumption that enormous variability has always been the story.

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A close study of rainfall records (up to 140 years for some districts) for any area indicates enormous rainfall variability within a year, from year-to-year and even from one group of years (for example a decade) to the next.

Temperature records are far sparser and for many areas don't go back that many years. Both for temperature and rainfall it seems to me a fair assumption that enormous variability has always been the story.

To me, advice about crop, pasture and soil management issues will be much the same regardless of whether we are experiencing climate change, climate variability, or a combination of the two.

READ MORE FROM BOB FREEBAIRN:

Zero till farming combined with stubble retention, has almost universally been adopted by farmers over the last 40 years and is an example of better managing climate change or climate variability.

Practices that improve conservation of fallow moisture are widely known and used by most farmers. Conserving stubble and replacing cultivation with timely herbicide applications to control weeds, commonly conserves 25-50mm more moisture for a winter crop compared with a cultivated fallow.

Tram-lining, moisture seeking sowing, better rotations and using fertilisers like nitrogen strategically during the growing season, are technologies widely used by farmers that better suit erratic rainfall patterns.

Zero till farming combined with stubble retention, has almost universally been adopted by farmers over the last 40 years and is an example of better managing climate change or climate variability. - Bob Freebairn

Characteristics of crop varieties have been changing subtlety for years. Pre-breeding research is deliberately chasing and finding genes, for example with improved heat tolerance and improved tolerance to drought. These genes are entering breeding programs with some variety releases already containing the newly identified traits.

While varieties with "winter habit" have been used for many years (example Windebri, released in 1959) more are being released that help extend their suitability across NSW, as well as their dual-purpose role. Winter crops with "winter habit" suit more flexible sowing, with heading date similar for sowing over two to three months.

Varieties released with a low "cold" requirement tend to suit warmer western areas (but not north western ones, as there is commonly not enough "cold" to precipitate the reproductive phase in sufficient time).

Varieties with moderate "winter habit" tend to suit slopes areas, while those with high "winter habit" best suit colder areas. If temperatures continue to warm over winter a variety currently suited to a given area, for example the slopes, may well better suit a tablelands area.

A good canola crop in a drought year like 2018 largely accounted for by efficient storage of soil moisture over the fallow period.

A good canola crop in a drought year like 2018 largely accounted for by efficient storage of soil moisture over the fallow period.

Perennial pasture type is the biggest aspect of change I feel that suits both projected climate change or just climate variability. Perennials combining long term persistence with improved ability to respond to rain whenever it falls better suits many if not most variable rainfall areas (most of NSW) than current temperate perennials.

Tropical grasses, in conjunction with legumes already perform this role on many farms as far west as Nyngan and Nymagee. They are grown as far south as Koorawatha (between Cowra and Young) and many centres in between with suitability for far wider use.

Even without "climate change, which some are predicting will see more summer rain and less autumn winter and spring rain in southern areas, tropical grasses have an important role. They can use rain that commonly is regarded as "out of season", between mid-spring and mid-autumn.

Commonly temperate perennials, especially out of their favoured higher rainfall environments, and winter legumes, poorly use such rains, even though these can be more than 50 per cent of annual precipitation.

Lucerne also has an increasing role in variable rainfall environments and except for the coldest areas responds to rain whenever it falls. While lucerne has its issues, such as requiring periodic replanting, bloat, low ground cover in dry times, it does build soil nitrogen, can be very productive and fits in well in many cropping rotations.

A lot of winter legumes such as sub clover do not have the ability to use a later than expected spring rain event should it follow a dry/warm, dry/late winter, early spring (a common occurrence). Early maturing varieties of species like serradella and biserrula are better able to re-fire should rain fall after such a dry period.

Next week: Strategy to address acidity through the soil profile.

  • Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact (0428) 752 149.
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