Soils

     The intricate fungi network works with trillions of specialized bacteria to send nutrients to plants roots, which the plants pay for (11-40% of all sugar prodution from photosynthesis).  Myriad creatures, from beetles, worms and insects, to mites to bacteria form an enriched ecosystem.  Farmer Iain Tolhurst in England has become a master of letting  the whole ecosystem boost his crop yields to high levels on “rubble” land without pesticides, herbicides, mineral treatments, animal manure, or any other kind of fertilizer.  Leave low green ground cover on the land 365 days a year.  And much more.

Giga-ton economy for future of farming: “Carbon capture with benefits” (Dean Houton Feb. 27, 2021 seminar)

     Rodlae's Farming Systems Trial, for 23 years since 1981, has shown that soil, under organic agriculture management, can accumulate about 1,000 pounds of carbon per acre foot of soil each year.  This accumulation is equal to about 3,500 pounds of carbon dioxide per acre, taken from the air and sequestered into soil organic matter.  When multiplied over the 160 million acres of corn and soybeans grown nationally, a potential for 580 billion pounds of excess carbon dioxide per year can be sequestered, when farmers transition to organic grain systems.
    Organic grain production systems increase soil carbon 15 to 28%.  Moreover, soil nitrogen in the organic systems increased 8 to 15%.  Decay rates differ for soil organic matter under different management systems.  In the conventional system, the application of soluble nitrogen fertilizers stimulates more rapid and complete decay of organic matter, sending carbon into the atmosphere instead of retaining it in the soil as the organic systems do.
    Soil microbial activity, specifically the work of mychorrhiza fungi, plays an important role in helping conserve and slow down the decay of organic matter.  Mychorriza fungi are more prevalent in the organic farm systems. These fungi work to conserve organic matter by aggregating organic matter with clay and minerals. In soil aggregates, carbon is more resistant to degradation than in free form and therefore more likely to be conserved.
    In conventional and organic farming systems, yields of corn and soybean were not different, except in drought years.  Then, organic systems yielded 25 to 75% more than the conventional system.  The organic yield advantage in drought years is specifically related to the ability of higher-carbon organic soils to capture and deliver more water to crop plants.

This may be our most important way to reduce CO2 levels in the air.

     Holistic Management practices can move 2.5 tonnes of carbon / hectare / year (= 1 ton / acre / year = 0.25 kg / square meter [sq m]) from the air to soils, maybe more, building soil in the process.  This would increase removal almost by another factor of 10, from USDA's 2001 estimates.  Applied to 4 billion hectares of degraded grasslands (rangelands) around the world (about 20% of Earth's land), this would move 10 billion tons (GT) of carbon from air to soils.  Changed grazing practices would do it, rather than changed tillage ones.  10 GT / year removal ~ current world carbon emissions.  The atmosphere holds almost 1,000 GT of CO2.  Thus, Holistic Management applied to the max could cut atmospheric CO2 levels by ~ 4 ppm / year, if we reduce our emissions to zero.
    For perspective, the top foot of 1 square meter of soil weighs 350-500 kg.  Typically, 1% to 12% of that is organic carbon.  So, soils (except deserts, see map at top of page) contain 4 to 60 kg of carbon / sq m.  That includes 8-20 in most of the US, Canada, Russia, Siberia, Europe and China.  That's less than permafrost soils, but more than most tropical rainforests.  In all, Holistic Management practices might increase soil carbon by 1-6% / year (& topsoil mass by 0.05% / year), while tillage changes can increase soil carbon 0.1-0.6% / year.

     However, soil microbes respire carbon to the air faster as soil warms.  This counters moving carbon from air to soils.