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Soil Matters!

2015/3/22 — 8:30

By Kristian Johnson. A graduate of Johns Hopkins University, Kristian is preparing for a career in agriculture and forestry. He is currently undertaking an internship at Wildroots Organic Farm. His goal is to help conserve forests through sustainable farming practices.

In Hong Kong, it’s easy to forgive the impression that we have transitioned to a post-soil society, where with enough concrete and wifi all of our needs can be met. We aren’t there yet and never will be, as soil is an irresistibly efficient way of providing nutrients for food crops to grow. It is the most valuable asset of a farm. Before we get the chance to finally appreciate soil, it may soon disappear. Agronomists predict that within 60 years global soil systems will be irreparably degraded.

Soil is a simple word that describes a complex ecosystem consisting of five essential components. Much of soil is a combination of minerals essential for plant health. Organic matter is made up of plant and animal remains that have been broken down by microorganisms, such as fungi and bacteria. Microorganisms are nature’s diligent nutrient recyclers. Soil needs to be loose to allow gases (oxygen, carbon dioxide) that are essential to the life processes of microorganisms and roots to circulate. Finally, water dissolves and transports nutrients to plant roots. Ideally, all five components are present in relative abundance. Soil composition and quality can vary widely, which is why organic farmers add compost and organic fertilisers to soil.

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It may be tempting to grow crops without soil by using water-based hydroponic systems. These systems however have significant drawbacks. First, they can only provide for a fraction of our food needs. They are unable to grow large quantities grain such as rice, wheat, soya and corn that account for 60% of our diet (much of this is fed to the animals we eat). Second, they are capital and energy intensive, making them uneconomical except in circumstances where there is an abundance of both and a shortage of arable land (such as the Middle East).

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In contrast, the vast majority of farmers are armed simply with a handful of seeds, a hoe, and a patch of earth. Even without additional inputs, healthy soil can contain many of the nutrients a plant needs to grow (such as calcium, magnesium, iron, potassium, zinc, sulfur, copper, maganese). Humans also require these minerals but do not have the capacity to absorb them directly from the soil. Instead, we rely on plants to process the laundry list of minerals and repackage them into edible leaves, roots, seeds and fruits. It follows that the health of the soil dictates the amount of nutrients we derive from the plants we eat.

A thriving soil ecosystem means healthy, nutritious crops and a productive farm. Maintenance of a farm’s soil however is often neglected. For example, many farmers in colder climates leave their fields bare over the winter. Unprotected from the elements, the topsoil erodes, severely reducing the amount of organic matter and microorganisms. Conventional farmers also use synthetic fertilisers that pollute the soil with caustic salts, killing microorganisms and ultimately disrupting the ability of crops to absorb nutrients.

Worldwide, 70% of topsoil is severely degraded. In China 19.4% of soil is contaminated with heavy metals from industrial pollution. Organic matter is being lost 40 times faster than it is being added. In Hong Kong, misguided government policy is irreversibly damaging valuable soil through rampant development. Construction causes soil compaction that destroys its agricultural value. Food waste is thrown food into landfills instead of recycled into valuable plant nutrients and organic matter.

The destruction of this crucial resource is not inevitable. We can choose to:

  • Compost food waste to increase organic matter in the soil
  • Support eco-friendly local farms by buying their produce
  • Enforce zoning laws by reporting illegal construction and waste dumping
  • Lobby the government to end the import of unsafe vegetables grown with excessive synthetic fertilisers and pesticides that damage the soil

原刊於 Go Green 網頁

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