Is your soil healthy?

Healthy soil has certain biological, chemical and physical components that interact and will influence one another, says Dr Pieter Swanepoel, a soil quality, plant and pasture scientist at the Western Cape department of agriculture.

Good ground cover has prevented soil erosion on this steep hillside, despite heavy rain in the summer. Ground cover has been retained after the planter has passed over the land.
Photo: Marius Swart

Chemically healthy soil will have sufficient, but not excess, nutrients and will be free from harmful chemicals.

Physically healthy soil will have good tilth, sufficient depth and adequate water storage capacity and drainage.

Biologically healthy soil will have:

  • low populations of plant disease/ parasitic organisms;
  • high populations of beneficial organisms;
  • a resistance to being degraded; 
  • resilience (an ability to recover quickly from adverse events).

READ MORE: Doing the tango with no-till in Argentina

Ongoing

Enhancing soil health is a continuing journey, says Barry Fisher, a soil health specialist at the US department of agriculture, who recently visited the Western Cape.

“We had to break away from conservation tillage, because its emphasis was on tillage and not on conservation,” he explains. “But quality no-till, which implies more than no-tillage, can reduce soil disturbance. It requires new management practices, including an adaptation of nutrient management.”

Farmers till their soils to break it up to allow for moisture penetration. However, it’s been proven that no-till soils hold more water and nutrients after rain.

“In contrast to South Africa’s variety of soils and climate zones, it’s relatively easy to be a good crop farmer in America. I was humbled by what I saw on the Western Cape farms that we visited,” says Barry.

“I’m hesitant to make any recommendations to these farmers, apart from saying that they should keep on the path of less soil disturbance, crop diversity, and monitoring pests and diseases so that they use pesticides only when needed. In other words, let nature do as much as it can and avoid practices which will allow pests to build up resistance. Although we’ve been on a degrading path in the US for a long time, we’ve come to realise that the fat of the land won’t last forever.”

Techniques

Briefly, the three most important soil building approaches are:

  • Minimising the disruption and destruction of the soil’s structure, composition and natural biodiversity by employing no-till practices and chemical weed control;
  • Maximising biodiversity by adopting a diverse programme of crop rotation that includes establishing legumes; and 
  • Mulching to decrease evaporation, cool the soil, protect the soil against erosion and create a habitat suitable for soil organisms.

READ MORE: Working with sandy soil

“Other soil building practices include the judicious use of chemical and organic fertilisers, bio-fumigation, improved drainage, terracing, contouring, residue management and farming system to match the soil, climate and chosen cultivars,” adds Peter Greeff, technical and sales manager at fertiliser production and distribution company DASA.

Read more about strategies to enhance soil health in FW, 29 August, 2014.