Taking Care of Topsoil
The issue?
Loss of topsoil has significant economic and environmental impacts, which means increased need for good cultivation techniques and farmer awareness of the importance of soil conservation.
Positioned in the path of the Roaring Forties means it's no surprise that Southland experiences more than its fair share of strong winds. During cultivation of paddocks in readiness for next season's crop or pasture, you'll see enormous amounts of topsoil being picked up and carried off by the accompanying winds. Historically, Southland has experienced its fair share of wind events, but it seems that recently, the wind is getting stronger and it's arriving earlier in the season.
Early in November 2004, an Environment Southland staff member noticed a huge amount of topsoil from cultivated paddocks blowing and forming adust cloudat Garston and around other nearby northern Southland areas.
So what can I do?
One of the most effective tools available for minimising soil loss through wind erosion is shelter. The other is of course maintaining good vegetative cover, which in turn holds and protects bare soil.
The time of greatest risk is when this protective plant cover is lost through cultivation, whether for pasture renewal or crop establishment. But even with well-established shelterbelts protecting paddocks, wind erosion can still occur because of inappropriate cultivation techniques.
Farmers in wind prone areas and with lighter soils should look at their cultivation techniques and employ cultivation practices which maintain maximum vegetative cover on the soil surface and encourage moisture retention in soils. The aim should be to produce an uneven soil surface in as 'rough' a condition as practicable and restrict the cultivation period to a minimum timeframe.
The use of the chisel plough or grubbers is recommended as these give a fine deep working while still retaining a cloddy surface. Top-working implements, discing and rolling can create a fine seedbed prone to wind erosion even in well-sheltered situations.
Cultivating and sowing at right angles to the prevailing wind and ridging is also recommended as it presents an uneven surface, which will minimise soil blow.
Winter-feed paddocks can be different as the top few centimetres of soil has often been 'puddled' by stock in wet conditions and is therefore very prone to wind erosion once it has dried out. This is because this top layer of soil has lost all its structure and can lift from the paddock very easily. Turning this type of ground over as soon as soil conditions permit in the early spring will minimise the risk of losing this fine layer to the north-westerly wind.
Environment Southland Land Sustainability staff are happy to come and demonstrate techniques for monitoring changes in soil conditions using the Visual Soil Assessment [VSA]. Adopting appropriate good soil management practices will keep your soil in healthy condition and ensure your most valuable asset isn't blown over the fence to your neighbour's place or into our riverbeds.
Environment Southland is the brand name of Southland Regional Council.