I have recently purchased a piece of land that I am preparing to plant this coming season. To start with I conducted a 100ha-grid soil survey with interesting results.
The piece can be broken into three land use sections. First off, there is a small section of natural pasture or veld.
This is a snapshot of what the soil should look like chemically and, unsurprisingly, there is no acidity. The calcium magnesium and potassium levels are fairly high though.
The phosphorus level is very low, which is typical of our well-weathered soils.
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The next section had been used as a hay field with a planted pasture. Here the acidity is very high and cations, particularly calcium magnesium and potassium, are very low, as is phosphorus.
Years of hay cutting has effectively exported these elements and the acidity can be explained by this export of cations, as well as the overuse of nitrogen fertilisers.
The third section is existing maize land and here things are much more in line for crop production. There is less acidity, probably from liming, higher levels of cations, also from liming and because less is exported as grain.
Phosphorus and potassium levels are also higher, probably from fertilisation. Through strategic liming and fertilisation, these areas can all be corrected.
The challenge is to use this information as a case study to not allow the soil to degrade again. I intend to spread lime and plough this in. I see it as a necessary evil, but in the future I plan to no-till this field.
I also intend to plant cover crops during the winter fallow period. This no-till, cover crop combination will greatly improve the organic matter in the soil. The cover crops will mop up any unused nitrogen fertiliser, which will help to prevent acidification.
All this is going to improve crop yields, which will be exported from the field. I believe through good carbon management and responsible fertilisation, we can export bountiful crops, sustainably, for a very long time.
Bruce Shepherd farms in KwaZulu-Natal, South Africa. He plants 320ha of rain-fed summer crops. He also runs 2,200 weaner oxen on pastures, finishing them in a feedlot with maize grown on the farm.