Take a flexible approach to managing stubble to ensure you do not compromise on the big things: weeds, diseases, pests and timeliness.
There is no perfect stubble-management strategy for every paddock. Crop rotations, weeds, disease, pests, stubble load, harvest and sowing machinery and the desired level of cover will largely dictate how stubble should be managed.
Planning and management start before harvest and continue through the fallow to sowing. To assist growers with developing a plan for each paddock, the GRDC’s Stubble Initiative has developed a series of questions for growers to consider (above).
Estimate the stubble load in each paddock before harvest to select the best management practices. Wheat stubble loads are usually 1.5 to two times the grain yield, while canola is about three times the grain yield. Stubble loads greater than four tonnes per hectare need careful planning and management from harvest onwards.
Crops can be successfully established in stubble loads of up to 6t/ha with tyne seeders with good planning (smash and spread straw, sow at 15 degrees to previous year’s crop or use coulters). Sowing into stubble loads greater than 8t/ha will need careful post-harvest management for success with tyne seeders, or, alternatively, sown with a disc seeder.
Stubble height and spread pattern across the swath are the first considerations for harvest. Ideal cutting height will vary according to crop type and yield, next season’s crop and capability of seeding equipment. Other considerations are risk of weather damage at harvest (speed of operations) and impact on fallow spraying. Harvesting high or with a stripper front is the quickest and most efficient method of producing the least residue, which may need to be threshed, chopped or spread (see Profitable header set-up).
Tall standing stubble is better suited to disc-seeding operations, or where post-harvest operations such as grazing,
mulching, incorporation, baling or burning are planned. For tyne seeding systems, harvesting low and ensuring straw length is reduced by smashing and spreading evenly across the swath width is important to avoid large mounds, potential blockages at sowing, poor crop emergence and nitrogen tie-up.
If harvest weed-seed control is necessary, harvesting low is essential to maximise seed capture. Seed capture is not effective if weed seeds mature and scatter before the crop matures. Narrow windrow burning for canola stubble or lower-yielding cereal stubbles is effective provided there is a minimum of 20t/ha of dry matter in the row. Chaff decks, which drop chaff and weed seeds on tramlines while spreading smashed straw over the entire swath, chaff carts or the Integrated Harrington Seed Destructor may be better suited to higher cereal stubble loads.
Crop sequence is very important, especially in high stubble loads. Canola can struggle to establish in heavy cereal stubble, whereas faba beans and other grain legumes are better able to emerge through heavy stubbles and will assist in stubble decomposition.
Where sclerotonia risk is low, a double break, such as sowing canola into a less antagonistic legume stubble, is profitable and provides effective weed management.
GRDC Research Codes BWD00024, CSP00186, CWF00018, EPF00001, CSP00174, MFM00006, RPI00009, YCR00003
Tony Swan, CSIRO
02 6246 5142