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Furrow Sowing Often Worsens Water Repellence

22 August 2011

AUSTRALIA - New research findings confirm grower observations that Western Australia's most common seeding technique - furrow sowing using knife points and press wheels - often exacerbates water repellence on sandplain soils.

This was one of the messages delivered to growers at a recent soil amelioration bus tour at Badgingarra.

The tour was organised by the West Midlands Group with support from the National Adaptation and Mitigation Initiative (NAMI) project, supported locally by the Birchip Cropping Group, and funded by the Grains Research and Development Corporation (GRDC) and the Department of Agriculture, Fisheries and Forestry (DAFF).

Department of Agriculture and Food Western Australia (DAFWA) researcher Stephen Davies, who conducts GRDC-funded non-wetting soils research, said furrow sowing had historically been introduced to improve crop establishment by directing or ‘harvesting’ water from the ridges to the base of the furrow where the seed and fertiliser was placed.

“But recent evidence shows this technique can in some circumstances actually cause water repellent soil to become concentrated with the seed and fertiliser in the base of the furrow,” he said.

“This may be a result of the flow of dry, water repellent soil around the knife point and into the slot ahead of the closer plate and press wheel.

“For example, on water repellent gravel at Badgingarra, the average volumetric moisture content in the base of the furrow on June 24 was just 2.2 per cent compared with 4.8 per cent in the ridge when seeded with knife points.

“Interestingly, in adjacent furrows created using a seeder with winged points, the soil moisture in the furrow was 4.2 per cent compared with 2.6 per cent in the ridge.”

DAFWA researcher Stephen Davies explains a newly established soil amelioration and nutrition trial to growers.

Dr Davies said the problem might be alleviated by modifying the knife point seeding system to minimise the flow of water repellent soil behind the knife point, using an in-furrow banded wetting agent, and seeding after sufficient rain.

“However, these ideas still need further research and testing,” he said.

Dr Davies also warned growers to take steps to reduce the risk of soil erosion caused by strong winds on exposed soils following soil amelioration techniques such as mouldboard ploughing or spading.

“In areas including Badgingarra, strong pre-frontal winds resulted in significant wind erosion problems this year,” he said.

Dr Davies said growers could reduce the risk of mouldboard ploughing or spading causing damage by:

    • Only mouldboard ploughing or spading wet soil and to seed as soon as possible after using these techniques;

    • Only sowing cereals in the year the soil has been mouldboard ploughed or spaded as cereals have greater capacity than canola and lupins to recover from sandblasting;

    • Not creating a very smooth soil surface when rolling or firming the soil after mouldboard ploughing, as this increases the erosion risk;

    • Not grazing stubbles in the first summer after mouldboard ploughing or spading.

    • Taking extra care where there is fine sand with few coarse sand particles and little clay content, such as those soils found on the South Coast, as these soils may be particularly vulnerable to wind erosion;

    • Considering the option of mouldboard ploughing or spading in a green manure crop or pasture in spring when the soil is wet and winds are reduced, then seeding a cereal cover crop or summer crop.
Dr Davies said new trial results confirmed that mouldboard ploughing and spading continued to improve crop establishment the year after the techniques were used.

“A number of the farmer demonstration sites established in 2010 were sown to lupins this year and, in general, lupin establishment improved significantly compared with unsuccessful furrow sowing with knife points,” he said.

“This result is encouraging because, although often successful, mouldboard ploughing and rotary spading are expensive and irreversible.”

Dr Davies said that while there was a lot of interest in mouldboard ploughing and spading – with at least 9000ha in WA being mouldboard ploughed this year – growers should also consider using less risky, simpler soil amelioration techniques.

West Midlands Group executive officer Hellene McTaggart said a key message to growers on the bus tour was to be aware of the risks associated with soil amelioration and to use techniques at the correct time.

She said the effects of a range of soil amelioration techniques used on-farm were inspected, including mouldboard ploughing, spading, offset discs, surfactants and claying.

The 33 tour participants visited the Badgingarra properties of Andrew Kenny, Colin McAlpine, David Paish and Jeff Fordham.

Trials on Mr Fordham’s property include a new GRDC supported trial investigating the effect of soil amelioration on crop nutrition.


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