Protecting your soil from the wind

By Tim Bartimote – Cropping Officer

To say it has been a tough few years for those in the agriculture industry, is a bit of an understatement. Producers have consistently found themselves in difficult situations where there are long term consequences to each decision they make. Whether it be about retaining and feeding stock or destocking completely or when sowing time comes around, to plant or not to plant, these are the hard questions. One particular question I have been getting of late is in regards to potential methods to protect our main asset; our soil resource, from different forms of erosion while it is in such a vulnerable state.

Many paddocks in the Central West are currently exposed with little to no groundcover. Groundcover is the king at maximising rainfall retention and protecting our soil surface, but what can we do when do not have any?

Wind erosion

Wind erosion is the process of the movement and deposition of soil particles by wind moving at least 20 km/hr. Vulnerable paddocks are generally flat surfaces with little to no groundcover and minimal surrounding windbreaks to reduce wind speed.  Susceptible soils may also exhibit a lack of soil structure and organic matter, which assists in keeping soil particles in heavy ped-like formations. Losing 1 mm of soil means that 10 - 12 tonnes of soil has been lost per hectare. Australian research in the 1970’s found that losing nearly 10 mm of soil could incur a 25% yield loss in the following crop due to a loss in nutrients and organic matter.  As generally these are more concentrated near the soil surface.

Emergency tillage

As I write this article most producers with bare country would have observed wind erosion off their paddocks, if they were susceptible, due to the strong winds we have been experiencing. Research has concluded that soil particles which are 0.8 mm or less are highly likely to blow. This has prompted some producers to undergo emergency tillage. This term encompasses any cultivation that has the aim to roughen the soil surface over the short term in an attempt to reduce wind speed across a paddock. With the main objective to get groundcover back into the system as soon as possible. The idea being that these more stable aggregates will withstand greater exposure to wind for a time while increasing soil surface roughness. To achieve these desired clods, it is crucial that tractor speeds are advised to not exceed 6 km/hr.

If you are observing significant loss to wind erosion and are considering emergency tillage options, I have included some suggestions.

  • The biggest thing to remember is that emergency tillage is a last resort and is a short term solution.
  • By cultivating, particularly when the soil is so dry, you are breaking aggregate stability and as these clods break down over time you could be left with a more susceptible surface then when you started.

Test strips

When introducing roughness to the paddocks put lines perpendicular to the wind direction. Begin by doing test strips in part of the paddock and observe the impact. This will enable you to see if you have produced significant clods and at an adequate depth. Be conservative when implementing emergency tillage. When satisfied with test runs, do a strip of cultivation then leave a gap before doing the next one. This enables you to increase roughness later once your initial ridges have worn down.

How deep to till?

Some research suggests effective tillage depths lie between 4 to 8 inches, while others suggests to the minimum extent necessary to produce clods. The later seems more practical in terms of machinery ware, hardness of the soil and the potential to bring soil issues at depth, such as sodicity which causes soils to be dispersive, to the surface. Greater depths will be more achievable in heavier soils or soils with some moisture.

Machinery

In terms of machinery, I would be hesitant to use a disc implement due to the degree of destruction as opposed to a narrow tyne or even tyne sweeps. A heavy breakout may be required to be able to handle the current soil conditions and achieve the desired depth.  Narrow tynes can be placed roughly 24 inches apart and those with sweeps can be pushed further, up to 48 inches. Discussing the situation with producers, some have found success with chisel ploughs and scarifiers.

Consider soil types

Soil type has a large impact on success. Producing decent sized clods is more achievable in soils with less sand. Operations in sandy soils tend to struggle to produce enough roughness and the roughness produced is generally short lived. Deeper ridges need to be created in sandier soils than other soils types and hence I would normally advise against emergency tillage in these situations. Soil structure in sandy soils is quite fragile and will take a long time to recover from cultivation. So the benefit of the operation does not outweigh the consequences in my opinion.

Landscape considerations

The landscape of the paddock needs to also be considered. Avoid loosening soil on slopes and hilltops due to the risk of exposing country to be more readily washed by intense rainfall events.

Emergency tillage in red country can be particularly hazardous. This soil has the ability to set very hard, and is often compared to setting like concrete. Tillage in these situations often causes extreme damage to machinery, even when hard faced. Again test strips and slow speeds are crucial, due to the high potential to turn these soils into bulldust and make the current situation far worse.

Groundcover is key

The primary consideration when contemplating emergency tillage is that it is not a replacement for groundcover. Establishing groundcover when the break comes will be paramount to protecting our soils, maximising fallow efficiencies and reducing nutrient loss.

Further information

For more information on emergency tillage and wind erosion feel free to contact your local LLS Ag Advisor.

Further Reading:

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