If it remains relatively dry in any given area over the summer/autumn fallow, many farmers will mainly opt for low-cost wheat, barley, triticale or oat production this coming season.
While everyone appreciates risks associated with cereals without being an integrated part of rotations involving pulses and canola, if fallows have little water reserves logically low-cost cereal production is a sensible strategy.
However, a few management options can help reduce the risk of these succumbing to high-risk disease and other possible yield constraints.
Crown rot, take-all, common root rot, root lesion nematodes Pratylenchus thornei (Pt) and Pratylenchus neglectus (Pn), cereal cyst nematodes, stem, leaf and stripe rust, soil acidity, Septoria tritici and yellow leaf spot are all diseases, pests and conditions for example that can drastically impact on wheat yield.
Variety choice can commonly reduce the impact of these risks, with greater emphasis placed on the most likely of these factors.
One important aid to selecting strategies to combat some of these risks is the soil and stubble DNA test, Predicta B.
It is readily commercially available, backed by good science (much of it funded by GRDC) and is capable of providing good guides to risks such as nematodes, crown rot, yellow leaf spot, take-all, common root rot and long fallow disorder.
NSW DPI's Winter Crop Variety Sowing Guide provides variety ratings, including all cereals, against major growing risk factors.
For example, if crown rot is anticipated as a problem in wheat, varieties like Reliant, Spitfire, Mitch and Sunguard have the best, but nowhere near perfect tolerance rating.
Durum wheat varieties are especially susceptible.
Barley varieties are mainly rated poorly but their common rapid ripening sometimes masks major crown rot disease.
Oat varieties have good tolerance to crown rot but triticale's are rated susceptible.
Pt and Pn nematodes can cause big yield losses and can be detected in the Predicta B DNA soil and stubble test.
Some wheat varieties have good tolerance to Pt. Varieties like Kiora, Burke, Livingston, Flanker, Gauntlet, Lancer, Reliant, Mace, Mitch, Sunguard, Sunmate, Suntop and Wallup have a moderate or better rating.
A number of barley varieties also have good Pt tolerance
A number of wheat varieties have good tolerance to Pn, as do several barley varieties.
Most triticale varieties have good Pn tolerance and the disease has not been noted as a significant issue in oats.
Yellow leaf spot can also be detected in straw samples as part of Predicta B analysis.
Take-all is also often a serious root rot disease with little known variety tolerance, but at least it is important to know if it is a likely issue.
Stem leaf and stripe rust can each be major wheat yield reduction factors but these are air borne spread diseases not detected by sampling.
If a variety is being grown with poor tolerance to one of the rusts, a backup fungicide strategy is sound business, with timely detection as part of the control strategy.
Phosphorus fertiliser is an important part of cropping if significant soil deficiency exists.
Sometimes soil tests identify good carryover from previous applications to failed crops (not cut for hay) and sometimes reduced fertiliser rates are feasible if tests indicate optimum levels.
If soil water is low it can be feasible to restrict high nitrogen rates until the season breaks properly apply post-emergent up to at least the end of tillering.
While liming is an integral part of many farms, research has identified acid soil layers because of insufficient mixing, and also subsoil layers can be acid and hard to rectify.
Choosing acid tolerant varieties is therefore still sound practise where such risks are likely.
While a cost it is important to control fallow weeds after any rain event likely to strike weeds.
Timely spraying is cheaper and generally more effective.
Part of in-crop weed control is sowing at the earlier end of a sowing window.
More vigorous the crop, and the earlier it gets away (within a variety's sowing window), the more competitive it is.
Details of Predicta B services are available at www.crownanalytical.com.au
Accredited agronomists are generally available to undertake paddock sampling.
Next week: Upgrading introduced and native grass pastures.
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact (0428) 752 149.
