More natural ways of sequestering carbon
SIR, – I was disappointed with the attitude expressed in ‘Agrecalc answering your questions on carbon’ (January 28 issue of The Scottish Farmer) towards sequestering carbon on a longterm basis in pastures and arable fields.
Gabe Brown, in Bismarck, North Dakota, in about 2019 pulled over 100 soil cores across 600 acres of his farm and found well aggregated soil down to four feet. I believe that this was conducted on fields that were cropped.
In about 1994, the organic matter for his soil was 1.7% in the upper few inches of his soil. Now he has well aggregated soil to at least four feet that most famers would love to have in the top six inches of their soil. Well aggregated soil has good organic matter content. [Reference video Gabe Brown ‘Keynote at Farming For The Future 2020’ at 1 hour 9 minutes].
Gabe also reported in his video presentation to the Midwest Soil Health Summit 2021 (at 36 minutes), that on farms using adaptive multi paddock grazing over five years in five different states in the US, there was a significant increase in soil organic matter measured down to three feet in six-inch increments, compared to rotational and continuous grazing.
The most dramatic differences occurred in the lower two feet, showing an increase of about 1.5% to 2% in soil organic matter compared to the rotational and continuous grazing fields.
The difference was less in the top foot.
I believe the increase in soil organic matter in the lower two feet adds to the long-term sequestration of carbon and thus CO2 as the soil at these depths are unlikely to be disturbed.
In the video ‘FY22 Grazing Forum 7 Dr Christine Jones Carbon Farming’ [five minutes 30 seconds], Dr Christine Jones said that on March 14, 2019, the first Australian farmer was paid for carbon sequestration under an Australian government programme.
In 2019, he sequestered 11.2 tonnes CO2 e/ha over 12 months. In 2020, he sequestered 13.7 tonnes CO2e/ha over 12 months. “The largest increases were observed in the 30-100 cm increment.” This was on pasture into which multiseed mixes had been planted [in ‘A world first for soil carbon in Australia’ video].
Watch the whole of the above videos to get a better understanding of the possibilities.
Research done about 90 years ago in Germany, as reported in Andre Voisin’s ‘Better grassland sward’, points to the potential for significant storage of carbon below the top 10cm of a grass sward.
A growing number of arable and stock farmers, horticulturists, and market gardeners in Scotland and around the world are focused on increasing carbon in their soils to increase soil fertility, improve nutrient quality of crops and forages and thus improve the nutrient quality of grazed animals.
This I believe results in food for humans of higher nutrient density leading to improved health. These improved soils require no chemical fertilisers, little if any herbicides, fungicides, or pesticides. They have increased water holding capacity. reducing water run-off and retaining more moisture in the soil during droughts.
A big barrier is how to manage the transition while still ‘putting food on the table’. I believe the principles, as advocated by Gabe Brown, are applicable worldwide, but each farmer must develop their own techniques to apply on their farm. This is not something that can be directed from the top as each farm is unique, but SRUC could play an important role in facilitating knowledge transfer amongst farmers.
My vision is that we will ultimately have profitable agricultural businesses and improved employment opportunities in the rural communities which have been left behind.
By the way, this will also meet the climate change goal of sequestering CO2 without the expense of huge specific projects to sequester CO2. It also can lead to the greening of many semiarid and desert areas around the world.