….It comes as a surprise to many to learn that over 95 percent of life on land resides in soil and that most of the energy for this amazing world beneath our feet is derived from plant carbon. Exudates from living roots are the most energy-rich of these carbon sources. In exchange for ‘liquid carbon,’ microbes in the vicinity of plant roots — and microbes linked to plants via networks of beneficial fungi — increase the availability of the minerals and trace elements required to maintain the health and vitality of their hosts (1,2).
Microbial activity also drives the process of aggregation, enhancing soil structural stability, aeration, infiltration and water-holding capacity. All living things — above and below ground — benefit when the plant-microbe bridge is functioning effectively….Over the last 150 years, many of the world’s prime agricultural soils have lost between 30 and 75 percent of their carbon, adding billions of tons of CO2 to the atmosphere (3)….
….PRINCIPLES FOR SOIL RESTORATION
- Green is good — and year-round green is even better. Every year, photosynthesis draws down hundreds of billions of tonnes of CO2 from the atmosphere. The impact of this drawdown was dramatically illustrated in a stunning visualization released by NASA in 2014 (8). The movement of carbon from the atmosphere to soil — via green plants — represents the most powerful tool we have at our disposal for the restoration of soil function and reduction in atmospheric levels of CO2….
- Microbes Matter. A healthy agricultural system is one that supports all forms of life. All too often, many of the life-forms in soil have been considered dispensable. Or more correctly, have not been considered at all. The significance of the plant-microbe bridge in transferring and stabilizing carbon in soil is becoming increasingly recognized, with the soil microbiome heralded as the next frontier in soils research….
- Diversity is Indispensable. Every plant exudes its own unique blend of sugars, enzymes, phenols, amino acids, nucleic acids, auxins, gibberellins and other biological compounds, many of which act as signals to soil microbes. Root exudates vary continuously over time, depending on the plant’s immediate requirements. The greater the diversity of plants; the greater the diversity of microbes and the more robust the soil ecosystem….
- Limit Chemical Use. The mineral cycle improves significantly when soils are alive. It has been shown, for example, that mycorrhizal fungi can supply up to 90 percent of plants’ N and P requirements. In addition to including companions and multi-species covers in crop rotations, maintaining a living soil often requires that rates of high-analysis synthetic fertilizer and other chemicals be reduced to enable microbes to do what microbes do best….
- Avoid Aggressive Tillage. Tillage may provide an apparent quick-fix to soil problems created by lack of deep-rooted living cover, but repeated and/or aggressive tillage increases the susceptibility of the soil to erosion, depletes soil carbon and organic nitrogen, rapidly mineralizes soil nutrients (resulting in a short-term flush but long-term depletion) and is highly detrimental to beneficial soil-building microbes such as mycorrhizal fungi and keystone invertebrates such as earthworms….
…It is not so much a matter of how much carbon can be sequestered by any particular method in any particular place, but rather, how many soils are sequestering carbon. If all agricultural, garden and public lands were a net sink for carbon we could easily drawdown sufficient CO2 to counter emissions from the burning of fossil fuels.
Everyone benefits when soils are a net carbon sink. Through our food choices and farming and gardening practices we all have the opportunity to influence how soil is managed. Profitable agriculture, nutrient-dense food, clean water and vibrant communities can be ours … if that is what we choose.