By GRDC Northern Region Panellist Jack Williamson
With autumn now upon us, planning for the 2015 winter cropping season is well underway across Queensland and New South Wales.
Summer rainfall has been patchy across the northern cropping area, prompting a significant variance in sub-soil moisture profiles between farms and even between paddocks.
In the event that planting opportunities do arise, crop performance will be impacted by the adequacy of pre-sowing planning in areas such as fallow weed control, disease risk monitoring, soil moisture testing and soil nutrition testing.
Growers and consultants are acutely aware that management strategies for the likes of weed and disease control can’t simply be considered on a short-term seasonal basis, they need to be planned according to their implications for the farming system as a whole.
With many growers in the north now farming under zero or minimum till systems, effective stubble management is critical to maximising the benefits of improved soil structure, water infiltration, moisture retention and erosion control while controlling the incidence and severity of weeds and disease.
Tactics vary according to growers’ farming systems, past experience and acquired knowledge but there are some general considerations worth keeping in mind, particularly if a strategic cultivation is being considered.
For management of disease carryover it is critical to understand the risk factors associated with individual diseases and the potential impact practices like strategic tillage might have, especially if disease posed a problem in the previous season.
Distribution of infected stubble across an entire bed is highly likely to impact the future incidence of certain diseases while for others, burial and/or stubble decomposition may reduce inoculum levels.
Inter-row sowing can be an effective alternative to cultivation and help growers manage high stubble loads as well as disease issues.
Research backed by the Grains Research and Development Corporation (GRDC) has found that inter-row sowing between the old cereal rows can provide a physical separation between the new plant and the infected stubble, helping manage the build-up of pathogens like crown rot when used as part of a crop rotation strategy.
Crown rot risk should be assessed prior to planting using the the DNA based soil testing service PreDicta B® as it will have important consequences for crop and variety selection as well as paddock management.
It’s also important to remember that disturbance of soil not only affects pathogens but also other soil microbes. Although no-till systems are more conducive to enhancing beneficial soil microbial components that suppress disease, it remains to be seen whether a strategic tillage operation will have sustained impact on the general structure and function of the soil microbial community.
From a weeds management perspective, the main risk from the use of tillage is the potential to move buried weed seeds back to the surface, providing a more favourable environment for germination and/or breaking seed dormancy.
Conversely, a one-off tillage that results in weed seed burial below emergence depths is potentially a useful management tactic for difficult-to-control and herbicide-resistant weeds.
The main message when considering implementing any fallow management or pre-sowing strategy is to weigh up the costs and benefits to the entire farming system. Remember, every action has a consequence so make it a productive and profitable one.
Jack Williamson, GRDC Northern Panellist, Goondiwindi
07 4671 2265, 0438 907 820
Sarah Jeffrey, Senior Consultant Cox Inall Communications