Saving the Underground Farmers: Soil Ecosystems

Have you ever noticed the earth that you step on?

It is where we get materials essential to our survival. It is soil that supports the growth of plants, the producers of the food chain and the sources of fibre, fodder, and fuel.

At first look, it seems static and lifeless. In fact, soil hosts millions of life forms including bacteria, fungi, insects and other invertebrates, that all interact and perform complex activities. Some of these consume other life forms, others compete for space and resources, and certain organisms form collaborative relationships to access resources.

Underground life forms collectively form the soil biota and continuously re-construct the soil environment. These underground farmers are important to ensure healthy development of a plant, as the roots of the plant are a part of the soil ecosystem.  

The Mutualistic Relationships between Plants, Soil Microbes and Fungi

The underground parts of plants carry out nutrient and water uptake from the soil. The root system of a plant is involved in plant-microbe interaction whereby the plant provides carbons and shelter to the microscopic soil organisms (microbes). The microbes in turn supply minerals and trace elements in a modified form that can be used by the plant.

An example of such interaction is that of legume plants (peas, beans) and nitrogen-fixing bacteria. The bacteria in the soil convert nitrogen from the air into a form that legume roots can absorb from the soil.

Plants also develop symbiotic associations with soil fungi, that is, the relationship benefits both the plants and the fungi. These fungi reside near to or within the root cells of the plants.

Soil fungi use the organic nutrients and sugars that are produced by the plants. In return, they benefit plants by improving the plants’ ability to absorb nutrients and water, and their resistance to unfavourable conditions like pollution and diseases.  

The Alteration of Soil Structure and Composition

Over recent decades, large-scale industrial farming and land conversion have resulted in great change of soil structure and composition. The clearing of trees, shrubs and grasses, the digging and overturning of topsoil using machinery, as well as application of chemical insecticides, herbicides and fertilisers have had disastrous impacts on the underground food web.

The soil environment has become less conducive for the organisms to survive. The soil microbial communities lose connection with plant roots that provide carbons and shelter, and in turn the plants’ capacity for taking up water and nutrients declines. The soil ecosystem is losing its viability and robustness. 

Promoting healthy soil ecosystems

In order to revive the fertility of soil, we need to bring back the carbon to the soil. This is important for ensuring food security and sustainability of agricultural activities.  Here are two ways we can do this:

• Plant different varieties of plants–each plant variety releases a unique set of biological compounds to the surrounding of its root system, and signals different underground microbe community and fungi. The greater the plant variety, the greater the variety in soil microorganisms which improves soil water-retention capacity and nutrient availability.
  Besides soil improvement, more plant varieties result in a greater variety of insects, including predatory insects that feed on pests. The predators help control pest numbers and thus reduce physical damage to the crop plants. 

• Limit the use of chemical fertilizers—The application of NPK fertiliser has to be reduced, so that soil microbial communities have the chance to thrive and re-connect with the plant roots. Instead of relying on chemical input, plants have to derive these essential elements from the underground microbial communities and in return, channel their carbons to the soil. The increase of soil carbon would boost the soil communities, improve nitrogen uptake and also help maintain the structure of soil.  The removal of excess fertiliser reduces the formation of nitrous oxide (a greenhouse gas) in waterlogged or compacted soil.

Summary

If we understand soil and the life it teems with, we can grow healthier plants and do so in a sustainable manner. We can avoid the excessive chemical and water use that is a growing concern.

Plant growth is influenced by the health of the soil and it also influences life around it and beneath it. Having more plants of different varieties helps conserve underground ecosystems. As the soil carbon (provided by plants) increases, the soil microbial community is revived, and the underground farmers can improve the structure and composition of the soil to support more plants.

Reference:

Jones, C. (2018). Light Farming: Restoring carbon, organic nitrogen and biodiversity to agricultural soils . Retrieved from Amazing Carbon Web site: http://amazingcarbon.com/JONES-LightFarmingFINAL(2018).pdf