Reduce traffic to prolong ripping benefits

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Modern large-scale cropping equipment has axle loads similar to road-making equipment and as such can make subsoils as hard as road base

Photo of farm machinery

Modern machinery weights have doubled since the 1980s, resulting in a three fold increase in soil pressure at 40 centimetres. Deep-ripped soils can be re-compacted with a single pass if a controlled-traffic system is not in place. One machinery pass can re-compact susceptible soils to a level at which root growth will be slowed by up to 70 per cent.

PHOTO: GRDC


Impact of one machinery pass on soil compaction to depth (MPa) in ripped (left) and mouldboard (right) soil in Binnu, WA

Figure 1 Impact of one machinery pass on soil compaction to depth (MPa) in ripped (left) and mouldboard ploughed (right) soil in Binnu, WA.

About 80 per cent of compaction occurs with just one machinery pass, making it easy to undo the benefits of deep ripping within just one season if a controlled-traffic system is not implemented.

Figure 1 (right) shows that deep-ripping and mouldboard ploughing have been highly successful at reducing soil compaction at 20 to 30 centimetres from levels at which root growth would be severely restricted (three megapascals (MPa)) down to less than 1MPa.

Soil compaction levels 10 years after deep-ripping (orange line) compared with unripped area and tramlines in Binnu, WA

Figure 2 Soil compaction levels 10 years after deep-ripping (orange line) compared with unripped area and tramlines in Binnu, WA.

However, just one pass of machinery (Figure 1, blue lines) the following season has recompacted the 20 to 30cm of soil up towards 2 to 2.5MPa – a level at which root growth will be slowed by up to 70 per cent and crop access to soil moisture reduced.

With soil compaction now reaching depths that cannot easily be removed (50 to 60cm) and machinery weights increasing every year, it is important to consider preventing compaction rather than curing it.

In sandy soils with less than 15 per cent clay the benefits of deep ripping can last for at least 10 years. However, uncontrolled traffic patterns can quickly remove this benefit, making it important to use controlled-traffic systems to get the full benefits of deep ripping (Figure 2).

More information:

Bindi Isbister,
DAFWA, 08 9956 8532,

bindi.isbister@agric.wa.gov.au

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Double-tyned ripper removes deep compaction

GRDC Project Code DAW00243

Region West