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On Earth Day we Recognize Soil

On 22 April we recognized Earth Day which aims to bring urgent change to the way we interact with our planet. Most of the discussions around our planet have focused on climate change and carbon emissions, but one of the most important topics is Soil Conservation.

All life on land depends on soil. Without it, plants and microorganisms wouldn’t grow, and then animals wouldn’t have anything to eat. But what is soil anyway? Soil is composed of clay, sand, silt, organic matter, air, water and biology. Each of the items interact and produce certain systems which allow life to live off soil.

However, there is an agricultural practice called Tillage, where large tractors are used to break up the soil to loosen it and remove weeds. Most commercial monoculture farms use this practice to solve problems that occur on those types of farms. However, this technique is extremely damaging to soils. This is one of the worst practices we do and may have caused the largest damage to earth out of anything else. To understand why, we need to understand how the soil works:

One of the most important components in soil is air. Air is needed in the soil for microorganisms to break down organic material. Usually, the biology in the soil (E.g. worms, frogs, beetles) will aerate the soil to levels which are in balance with the particular soil system. But when we till, we cause excessive air to enter the soil, which accelerates oxidation of organic matter (releases as CO2), much faster than any natural rate. In fact, since the dawn of agriculture, the world’s soils have lost 133bn tonnes of carbon. Several years of continuous tilling without replacing the organic matter, will quickly deplete the organic matter in the soil.

The organic matter is the food source for biology. The organic matter contains protein (from animals), chitin (from invertebrates), lignin (from wood) and cellulose (from leaves) which soil biota use to make sugars for cell functioning. With the loss of organic matter due to unnatural aeration, the biology quickly dies out.

With no soil biology, crop residues do not get taken into the soil, but rather lie on surface and dry out. This is what motivates farmers to think that they should turn the residues under the soil, forming a vicious cycle.

The turning motion also breaks up the soil into very small pieces, which seals any pores in the soil, preventing rainwater from infiltrating. This results in water flowing rapidly off the farm when it rains, and carrying away the rich top soil. Soil in South Africa is lost at a rate of 4.8 ton/ha/yr and it is only replaced at a rate of 0.15 ton/ha/yr, which means that at some time in the future we will have no soil left to farm.

A solution is to conserve our soil using practices like Conservation Agriculture, where we minimize disturbances to the soil and we put back carbon into the soil through composting and mulching. It aims to maintain the health of biology in the soil, which in turn leads to healthier crops.

To learn more about conservation agriculture, visit

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