One of the goals of sustainable farming systems is to preserve as much land cover as possible - this helps maintain soil structure and protects the soil from erosion. Improving productivity, preserving soil structure and stabilizing fragile soils are some of the desired goals of agriculture. Proper rotations, less tillage, effective use of herbicides, maintenance of cover and careful stock management are part of the management process used to achieve these goals.
Its aim is to create an awareness of the benefits and principles of straw retention - and to outline ways to overcome the problems. It has been compiled from research undertaken by officers of the Plant Industries Division of the Department of Agriculture, Western Australia, with reference to research from Primary Industries, South Australia. Straw handling is part of the total cropping system and must be considered in the management process.
A sign of wind erosion is the windblown appearance of the soil surface and the sandblasting of crops. Cropping the lighter textured soils of Western Australia has made them even more susceptible to wind erosion. Media reports of erosion and dust clouds blowing over populated areas have made society more aware of the erosion problems in rural areas.
The straw forms dams and obstacles to water flowing over the surface of the soil, slowing down the flow of water.
Problems Solutions
Diseases
Weed control
Phytotoxic effect
Nutrient availability
Stubble management
Line intersect method
This amount of straw represents a 2 percent cover (less than 200 kg/ha of straw).
Assessing ground cover by stubble
Pacing the paddock
Pace a paddock and visually count straw at a marked point on the toe of your boots. Step back towards the stake and notice the stumps at the point marked on your boots. If stubble was counted 30 times at the marked points on your boots, then there is 30 percent coverage.
Note: When looking at stubble, do not count small pieces of straw that are unlikely to provide protection to the soil. The amount of stubble you have after harvest can be estimated from grain yield (see Table 3). The grain yield can be used to determine how much surface protection the stubble will provide.
1 t/ha wheat (use a no-till erosion control safe stock – . yield) minus disc implement minus = late enough . which buried cover to prevent. 2 t/ha lupine minus buried with minus for wind erosion = broken down or . yield) tinned implement) removed. The amount of stubble buried depends on the number of tillage passes and the type of implement used.
From these measurements and measurements taken during harvest, it is now possible for you to manage the amount of straw you have from your summer and fall harvest, leaving enough cover to prevent erosion and crop disease. How much you need (page 7) = How much straw you can break or remove safely. Change weed germination; make brome grass less dormant and increase wild radish seed dormancy.
If stubble is incorporated and the soil waterlogged, toxins are leached from decomposing residues. These problems become more common in areas with higher rainfall that have higher stubble levels.
Choices for handling stubble
Note that pasture emergence is not greatly affected at stubble levels required to control wind erosion. Sheep condition will normally deteriorate before stubble levels fall below those levels required to control wind erosion. In cereal/lupine rotations it is best to keep as much stubble as is practical.
Susceptibility of lupine seedlings to sand blast and disease is an example of the economic benefit of stubble retention. In continuous crop rotations there may be times when you need to burn stubble due to the incidence of crop diseases. The rate of disease carryover in straw depends on your locality, crop rotation and straw density.
If your machine cannot handle the stubble level, adjust the stubble to your seeding equipment. By shortening the stubble and spreading it evenly, you will improve stubble handling on all machines. You may need to modify existing machinery or purchase machinery that will be able to process more stubble.
Machines with one or two discs can handle large amounts of stubble without treatment. Shares, disc/tine combinations and wide row spacing are options for better stubble handling. The machines selected must not only be able to handle stubble, but also be compatible with retention systems that do not contain stubble.
If stubble is short and well spread after a normal summer, few problems with cultivation or sowing operations are expected.
Management choices at harvest
The amount of stubble you need to reduce (from Table 5) Removal rate (2 kg/hd/day) x number of days. Chopping and spreading the residue after harvest leaves sufficient soil cover to control erosion, especially in small fields where the residue can easily roll up and be blown away by the wind, providing little protection to the soil. If the stubble is to be grazed, it must be managed in the following way.
In heavy to medium soils, graze shortly after harvest (six to eight weeks). For medium to heavy soils, only graze the post-harvest stubble to get the benefit of pod and leaf material. If there is a lot of stubble, rake and burn the windrow or cold burn the stubble before the season arrives.
Pea stubble is very fragile and rolls up into a heap, providing no protection for the soil.
Breaking down stubble
Removal of stubble
Incorporation of stubble
The ability of the sowing machinery to process stubble cut to 200 mm height and spread evenly. Research has shown that lupine yield is not reduced by wider row spacing, so using wider row spacing can dramatically improve the stubble handling ability of any shrink machine. The average yield from 10 trials comparing row spacing was 1.28 t/ha for a conventional 19 cm row spacing and 1.33 t/ha for double row spacing.
With wide row spacing, the same amounts of seed and fertilizer are used per hectare, so that there is a doubling of seed and fertilizer quantities in each row. This can result in fertilizer toxicity when the fertilizer is sown with the seed – reducing establishment and seedling vigor. Deep banding is one way to avoid the problem of fertilizer toxicity when wide row spacing is used.
Top dressing is a less effective way to apply fertilizer, but can be used in high rainfall areas. The key to a successful farm system for stubble retention using disk implements is to distribute the straw and chaff evenly at harvest. Zero-till single-disc and double-disc designs seem to have good seed placement while leaving most of the stubble on the surface, provided they can penetrate the soil.
Current research and farmer experiences are used to further evaluate and develop crop establishment systems with these machines. These machines are heavily dependent on herbicides for weed control and their effects on soil diseases are unclear. Problems of disc penetration with the culti-bin type disc machine include penetration, incorporation of disease spores, drying of the soil surface and variable seed placement.
Spreading the stubble at harvest will leave an even seed bed, free of straw clumps. Seed placement can be improved by changing the tube placement on culti-trash disc seeders.
Attachments for finishing and levelling the seedbed
Summary
Further reading
