Climatologists contend summer rain is becoming more a proportion of total annual rainfall for much of NSW.
If such trends continue it reinforces the logic of needing to effectively use summer rain in both our cropping and pasture systems.
Pasture that efficiently use summer rain need greater consideration. Fallow management that reliably captures and stores summer rain in a winter cropping system is more critical. And the role of summer crops needs investigating and using far further south. Should these predictions be wrong and average rainfall remains as it has for the last 130 years (the extent of most records) there remains sound logic for effective use of summer rain. Almost all of NSW receives a good portion of its average annual rainfall “out of season”.
The Australian Grains Export Innovation Centre, using Bureau of Meteorology data from more than 8000 stations revised climate maps, moving some zone boundaries 400km. Summer rainfall has increased, with summer dominant and neutral rain zones shifted south.
For most of Australia’s cropping areas efficient rain storage in the summer fallow period is worth an extra 1.0 t/ha cereal grain and more than 0.5 t/ha pulse and canola. Lucerne uses rainfall efficiently in most areas regardless of when it falls and especially over spring, summer and autumn, when winter annual pastures are commonly poor users.
Tropical perennial grasses like premier digit grass offer not only a long-term logical pasture option for areas like northern and central NSW, where they are increasingly being profitably grown, but also southern NSW. These species use soil moisture from mid spring to late autumn. For many environments tropical grasses use moisture when annual winter legumes have hayed off. They also effectively use early autumn rains.
Testimony to the toughness of tropical grasses is a study conducted in the low rainfall Mallee region of southern Australia with less than 300mm average annual rain. Results are published in the CSIRO journal Crop & Pasture Science, 2014, 65, 1033–1043 “Summer-growing perennial grasses are a potential new feed source in low rainfall southern Australia”. The six-year study detailed persistent tropical grasses with production after summer rainfall ranging from 1500-3000 kg/ha peaking at 9000 kg/ha in wetter years.
Next week. Faba been growers must address acid soils carefully.
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or (0428) 752 149.