Practices to avoid when furrow sowing:
- Top-dressing all fertilisers before seeding with points or blades. The fertiliser can be lockedup in thrown ridges and less available in dry seasons.
- Using simazine-diflufenican mixtures post emergence on lupins. Metribuzin/ diflufenican causes less crop damage.
- Using shallow duplex soils which are prone to waterlogging, especially on the south coast of Western Australia.
A furrow is a groove or corrugation in the surface of water repellent soil that allows sowing onto moisture and water harvesting. Sand and clods can be thrown (for example, by points and blades) or pushed (for example, by discs and presswheels) to form a furrow.
Firming sand at the furrow base with a light presswheel will improve water retention and nutrient uptake by the crop. A thin band of surfactant sprayed in the base of the furrow will further improve soil wetting, especially in relatively dry and more repellent conditions.
This is an excellent technique for improving pasture establishment, but caution is needed to achieve the best formulation for cropping. Furrow sowing can be done after cultivation, in a direct drill, no-till *(narrow points or blades) or zero till ( single, double or triple disc openers) system.
No-till and zero till methods make smaller furrows and retain more soil cover than direct drill methods which can have higher erosion risks on water repellent sands.
The benefits of furrow sowing:
Sowing seed onto moisture:
Zones of dry sand frequently occur in water repellent top soil, while the lower topsoil or shallow subsoil is often more consistently wet. Furrowing can place seed in or close to moist sand (see Figure 2) without making the seed depth too great.
Level sowing to the same depth may make the seed too deep from a level soil surface. Deeper furrows will allow sowing onto deeper moisture, but extra care is needed to avoid the greater erosion risks which can occur as more loose sand is moved.
Figure 2. Level and furrow sowing before, during or after rain; note the difference between the two
techniques when sowing onto moisture after rain and drying
Water harvesting:
Water often sheds from the upper parts of the soil surface of water repellent soils. Wider furrows will harvest more water (see Figure 1), but the furrow does not need to be deep. More water will be harvested from standing stubble than from flattened stubble.
Grading topsoil into ridges:
Forming a furrow with a narrow point or blade point throws topsoil aside to form a ridge (Figure 3). The ridge can contain nutrients and weed seeds and also herbicides, fertilisers and plant pathogens.
Some of this material can be within a dry ridge centre. Weeds and pathogens may have less opportunity to affect the crop when concentrated in ridges, especially if the ridges of water repellent sand remain dry after autumn rains.
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