IRRIGATION IMPROVEMENTS
The 200 – 300 mm deep, porous and root-stabilised seedbed created by SC™/BC™ machines absorbs water rapidly and produces large improvements in irrigation efficiency, effectiveness and waterlogging prevention.
Furrow Irrigation
Subbing
The BC™ managed soil, compared to no-till and cultivated soil had:
- Subbing rates 2 times faster in moist soil (@ ~ half field capacity) and 4 times faster in dry soil (@ ~ permanent wilting point);
- Complete and uniform wetting across 2 m wide beds;
- 3 – 4 times more water was stored in the 0-300 mm seedbed at the end of irrigation applications (9 hrs for the moist soil and 8 hrs for the dry soil).
BC™ infiltration contours (mm water) for the moist soil irrigation after 6 h of water application. Bed centre ~ saturated.
NT infiltration contours (mm water) for the moist soil irrigation after 6 h of water application. Bed centres remained effectively dry.
Penetration distance of 20 mm of infiltration that travelled horizontally and vertically in each treatment after 6h of water application in the moist soil irrigation. This raised the water content in the centre of the BC™ beds to field capacity.
Penetration distance of 30 mm of infiltration that travelled horizontally and vertically in each treatment after 4h of water application in the dry soil irrigation. This raised the water content in the centre of the BC™ beds to field capacity.
Water Savings
Because BC™ seedbeds absorb water laterally 2 to 4 times faster and further than NT beds:
- water applications need to be faster and shorter – up to 4 times faster and 4 times shorter than normal;
- moisture deficits need only be based on a depth of only 600 mm, not 1,000 mm, (any excess water above 600 mm depth drains downwards as a matter of course); and
- 20 % to 30 % less water is needed per irrigation.
How to Capture the Irrigation Benefits of BC
Water application rates for BC managed seedbeds are determined by:
- the soil moisture deficit; multiplied by
- the bed width, depth and furrow length (i.e., the volume of soil to be moistened);
- divided by the time for water to reach the centre of beds.
This information allows the optimum application rate to be calculated and, in turn, the diameter of the inflow pipe/siphon, and the height of water in the supply canal required to achieve it.
Soil moisture deficits and time-for-water-to-reach-bed-centres must be observed or measured.
Application rates determined this way ensure water reaches the end of furrows at the same time as it reaches the centre of beds at the top end of the run, and BC™ soil management ensures water is rapidly and uniformly absorbed by beds along the full length of furrows.
This interaction is illustrated below for two moisture deficits, a range of furrow lengths and two pipe diameters.
These data also show larger pipe diameters provide more scope for adjusting application rates for a wide range of soil moisture conditions and furrow lengths.
Irrigation inflow (application rate) and time for water to reach field capacity in bed centres for a range of furrow lengths and two inflow pipe daimeters of 50 mm and 75 mm (horizontal lines), for profile moisture deficits of 10 and 20 per cent.
Surface Drip Irrigation
The 300 mm deep, loose and root-stabilised seedbeds created by SC™/BC™ always overlie naturally consolidated subsoil and this contrast in physical soil conditions produces the same dominant lateral flow with drip irrigation as it does for furrow irrigation, and similarly increases the irrigation efficiency and effectiveness of surface drip irrigation.
Visible surface drip lines allow the SC™/BC™ machines to be inserted into and withdrawn from soil by straddling them during bed and furrow renovation prior to seeding the next crop.
Surface drip infiltration contours (mm) in a well-structured seedbed over a compact subsoil.
Wide lateral spread of wetting from surface driplines in a well-structured soil.This raised the water content in the centre of the DBC™ beds to field capacity.
Limited spread of wetting from drip irrigation in an over-cultivated, poorly structured soil.
Smart siphons® allow easy adjustment of the inflow rates to match soil conditionsThis raised the water content in the centre of the DBC™ beds to field capacity.
Sub-surface Drip Irrigation
SC™/BC™ soil management is NOT recommended for sub-surface drip irrigation. The wings on the SC/BC machines are likely to snag and damage the sub-surface drip lines.
WATERLOGGING IMPROVEMENTS
The 200 – 300 mm deep, loose and root-stabilised seedbed maintained and by SC™/BC™ soil management is naturally waterlog-resilient because of its improved water absorption, drainage and aeration properties.
Well maintained BC beds are able to absorb 150 mm of rain in less than 24 hours and drain and aerate sufficiently to prevent waterlogging.
Permanent waterlogging prevention requires the root zone soil to have a drainage rate of ≥ 30 mm / h and an air-filled porosity ≥ 10%.
IF both these requirements are met by seasonal BC renovation, beds can be as wide as 3m centres and remain permanently effective.
Beds that are NOT regularly loosened by a BC machine consolidate and become ineffective. Once consolidated, beds do not drain and aerate quickly enough (i.e., in < 48 h) to prevent plants from suffering from oxygen depletion, or waterlogging.
ONLY BC™ machines can maintain these soil conditions AND sustainably improve soil structure, fertility and crop production.
Renovation with a BC machine is best done prior to or at seeding each crop to preserve the seedbed’s looseness.
How raised beds work and the soil properties required for them to prevent waterlogging.
Beds being renovated with the prototype BC™ machine on a waterlogged site.
