AGRI NEWS - A handful of soil seems to be just that: a handful of soil.

But it is not so, says Pieter Swanepoel, scientist at Outeniqua Research farm near George.

Healthy soil contains of microbes that are essential to healthy growth of crops. Soil depleted of nutrients as a result of continuous planting by a single crop, can be revitalised by adding organic matter.

"The advantages of soil organic matter are almost limitless," says Swanepoel.




Benefits of a healthy soil

• Biological activity of soil is increased. Soil is a living entity and without the biological component the soil will not be able to perform normal functions, namely to provide plants with nutrients;
•  Healthy soil provides a steady supply of nutrients and water to the microbes and plants;
• Evaporation of water from the soil is decreased;
•  Infiltration rate and water holding capacity is increased;
• Structural characteristics of the soil are advanced, which will prevent compaction, crusting and erosion;
• Poisons and toxins such as herbicides, insecticides and fungicides are deactivated and absorbed;
• Soil temperature is regulated; and
• Carbon is sequestered, which in turn may have an positive impact on global warming.

According to Swanepoel there is a positive message for the farmer in this. "Some features of soil are relatively easy to change or manipulate, such as the chemical characteristics. However, most of the physical characteristics - such as soil type, depth and texture - are difficult, or even impossible to change."

Therefore attentions should be paid to characteristics that can be improved by manipulation, while characteristics which are less easy to manipulate, should be preserved.

"Increasing soil organic matter is critical to convert degraded soil into healthy soil, or enhance already healthy soils. Soil orga-nic matter is necessary to maintain life in the soil - bacteria and plants directly require soil orga-nic matter as a nutrient source."

Apart from this beneficial effect, soil organic matter also influences almost all physical, chemical and biological characteristics of soil which has an indirect effect on plant production.

"Soil organic matter is even critical to limit damage from pathogens and pests," Swanepoel acclaims.

These are a few approaches to be followed to increase soil organic matter:

• Amend the soil with organic matter (compost, manure, mul-ches, green manure, legumes, crop residues or other organic mate-rials);
• Use diverse sources of organic matter to supply various nutrient groups;
• Adapt to a no-till system or at least minimum tillage.
• Adopt conservative fertilisation practices - maintain the fertility status of the soil (soil pH, macro- and micronutrients);
• Include legumes into the planted pasture and rotational systems;
• Grow cover crops or living mulches in applicable systems;
• Adopt rotations that allow high amounts of residues left after harvesting; and
• Prevent salinisation of soil.

"Unfortunately there is no quick and easy and quick way to build soil organic matter. Management has to be adapted and prolonged and one has to have patience and perseverance," says Swanepoel.

Pieter Swanepoel is a scientist at the Western Cape Department of Agriculture working on pastures and soil quality. He is currently conducting his PhD on soil quality of pastures in the southern Cape. He will be one of the keynote speakers during the Agri Herold Agricultural Festival which takes place from 29 August to 1 September.

ARTICLE: TISHA STEYN