With daily reports of climate change, involving higher average temperatures, more erratic rainfall, more droughts and floods, maybe changing rainfall patterns, how are farmers to cope?
My approach to climate change predictions is more or less the same management that we currently aim to follow, but at a higher standard, of our cropping and livestock enterprises. What is good for projected climate change is good for management of agriculture should little change be occurring. That doesn't mean ignore these threats of change but embrace greater emphasis on adopting current best management.
Stubble retention in cropping and pasture cover retention were key aspects of the last drought, both for best rainfall capture and soil water storage and for soil erosion prevention. That presents challenges for crops with little stubble left after harvest and can mean attention to crop sequences and ensuring sufficient stubble cover to perhaps provide for soil protection not for just one year but often two years.
Lucerne, an excellent legume for year round production and for building soil nitrogen, in droughts can leave soil bare with poor ability to capture storm rains. Some farmers, supported by research, suggest sowing lucerne with a perennial, including tropical grasses, helps with soil cover and rain capture. Combining lucerne with tropical grasses requires a different sowing strategy including perhaps paired rows and a spring sowing when temperatures suit both species for joint germination.
In previous eras contour banks were valuable for minimising soil erosion on sloping country. With zero or no till farming their significance dropped.
However, they continue to provide extra protection, even with zero till stubble retention, when severe storms occur. Even in our grazing paddocks they warrant periodic maintenance where livestock tracks can develop and are a useful erosion aid.
Plant breeders, with funding from bodies like GRDC and state agencies, place a lot of effort in improving varieties of various crops to better cope with droughts and warmer conditions.
These attributes help regardless of climate change or climate variability. Part of increasing yield ability of recent variety releases, across most crops, is improving ability of them to cope with difficult seasonal conditions.
From a grazing perspective, like many farmers, we are in the process of upgrading water reliability for future lengthy droughts. This has involved cleaning and improving dam capacity, finding and equipping more reliable groundwater, and improving distribution via more troughs. An area has been set aside for a mini feed lot and equipped with feed and water structures. Hay reserves have been improved.
Fallow management, a well established key cropping issue, remains a critical farming aspect, regardless of climate change or climate variability. Except where weeds or self-sown crop are allowed to grow in the early fallow period to provide groundcover when none exists, early fallow weed control is critical. Weeds rapidly use soil water likely needed for the next crop, as well as ties up soil nutrients, especially nitrogen.
Research has established that nitrogen availability for a following crop, can be 40 kg/ha or more down compared to early weed control. Plus that extra stored soil water is on average worth least 1.0 t/ha extra grain yield. Timely weed control can commonly mean an extra couple of herbicide treatments per fallow but that must be costed against lower yield and more nitrogen fertiliser inputs.
Fallow and in-crop weed control strategies are ever increasing aspects of farming, again regardless of climate change or climate variability. Important aspects are not only herbicide choice and agronomic strategies like closer row spacing, varieties with more vigorous seedlings, herbicide group rotation, and strategies like double knock.
One of the most notable soil erosion occurrences, especially wind erosion, in the last drought was where dual purpose crops were grazed out with no groundcover remaining.
Helping to avoid this situation is an upgraded appreciation of feed budgeting, so that stock are removed before critical lack of groundcover occurs.
Next week: Weed issues for 2022
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact (0428) 752 149.
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