CARBON and NITROGEN copyright 2021-22 rob dixon dba OK.O.S 1
There is a carbon (C) flow linking the Air and Soil and all life.
There is a nitrogen (N) flow that connects Microbes with Plants, Animals & People.
These two elemental streams inter-act constantly with each other. The carbon to nitrogen ratio (C/N ratio) controls key processes in capturing carbon from the air and storing it in the soil.
In agriculture, carbon and nitrogen move from the Air through the Plants to the soil Microbes. Carbon then can get gassed off to the Air again or, stored in the soil as humus. Livestock and humans dip into these elemental streams of C and N too (think forages and concentrates; sugars and proteins).
Carbon capture farming means using the plants and microbes to pull carbon from the air and store it over the long term, in the soil, as humus. We do not fully understand these invisible and mysterious forces. Some things are clear, though.
Too much carbon without enough nitrogen, and the microbes just gas off carbon into the atmosphere. Too much nitrogen without enough carbon and the excess nitrogen just flows into the surrounding water flow. Each part of soil organic matter has around 10 parts of carbon (C) for every 1 part of nitrogen (N). This gives a C/N ratio of 10.
Organic farming is obsessed with CARBON, as measured by % Organic Matter.
Industrial farming is obsessed with NITROGEN as measured by Available N.
As noted above, both are needed to capture carbon from the air and store it as stable humus in the soil.
Nitrogen does many things, but for crops it is associated with GROWTH, like leaves. Big yields are linked to lots of nitrogen.
Carbon is the building block of life but in agriculture, it is ENERGY and storage, with roots. Plants share carbon with microbes through roots. Roots are made of carbon and become food for microbes to create trapped-carbon, as humus.
Carbon is used to assess the soil health as measured through % organic matter (OM). But it can take years for changes in farming practices to show up as changes in OM. Nitrogen can also be used to asses soil health since available nitrogen generally increases along with increasing OM and aggregation. Changes in available Nitrogen respond much faster to changes in farming practices.
CARBON and NITROGEN copyright 2021 rob dixon dba OK.O.S 2
Building healthy soil requires balancing the C and N needs of the microbes and plants and humus forming processes . These three interact with each other in complex ways that can create conflicts and cross-purposes eg. microbes tie up scarce nitrogen for crops. Regenerative (carbon-capture) farmers and ranchers use animal manure (composted) along with multi-species forage crop mixes to provide the soil microbes with the carbon (C) and nitrogen (N) they need. Industrial farmers get N from petroleum-based fertilizers but these provide no C for the soil life.
Grain farmers use nitrogen balances to target commercial yields.
Vegetable growers and organic farmers generally do not use nitrogen balances.
Perhaps they should and they could profit from managing nutrients organically ie. using materials approved for organic certification.
It takes careful use of N to get yields while building organic matter at the same time.
What has the biggest impact on the flow of carbon and nitrogen to crop plants?
Tillage has a big impact on how carbon and nitrogen get used by crops. Carbon will gas off from tilled fields as the microbes are stimulated to break down organic matter. Cultivation can also destroy the soil aggregates which are at the heart of healthy soil (stable large and small pore space structure). Aggregation increases available nitrogen. Scientists study the pore space structure of soil, as aggregation.
Summerfallow is the most destructive type of tillage. Roto-tilling inverts the soil layers and disrupts the fungal networks linking plants. Slowing down the speed of equipment and tilling in just the top 3 inches (~1 cm) helps reduce the most destructive effects of tillage. This is a step towards no tillage. Let your crop rotations with plant roots, do the tillage.
Many believe livestock are a major cause of the climate-crisis and that reducing livestock numbers and eating less meat would be good for human and planetary health. Is this true? The livestock sector in Canada does emit 60 mega-tons (Mt) of CO2 eq. each year. Alberta is 34.1% of the livestock sector and so produces about a third of emissions. Most of this is from cattle belching methane, which has Carbon (C) in it. Nitrogen (N) comes off of manure piles, as nitrous oxide, into the air.
CARBON and NITROGEN copyright 2021 rob dixon dba OK.O.S 3
Young people, and others; have good reason to be concerned about livestock emissions. Can anything be done?
Can livestock carbon emissions be reduced? How can cattle help capture carbon? Lots can be done eg. compost manure to reduce nitrous oxide gassing off from manure piles.
Planting carbon capture habitat enhancements along farm and ranch hedgerows and riparian buffers could have a huge impact, far beyond the small areas involved (Smukler, 2019).
Dr. Lal, director of the Carbon Sequestration center in the USA Mid-West, says
under ideal conditions a mid-west farm can sequester (capture) 1,000 pounds (lbs) of carbon (C) per acre per year (2020 CivilEats interview July 15 Virginia Gewin).
On the Prairies, Canadian agriculture is capturing around 97kg of C per hectare per year (around 97 pounds per acre, too), most of this from no-till. Much more could be done with habitat enhancement along hedgerows and in riparian buffer areas. (Smukler ,2019; Mullinix et al, 2018) Hay land, pasture and rangeland will probably be capturing more carbon then this, perhaps as much as 0.89 Mg of C per hectare (ha) per year (yr)(Smukler 2019). That is around 784 lbs of C per acre per year, according to my math. Is this enough to off-set the emissions from livestock? How much can be done to reduce emissions eg. composting manure?
What is needed to get yields while building healthy soil at the same time? Our company uses research to blend the organic obsession with CARBON (as % organic matter) with the industrial fixation on NITROGEN (as Availabe N). Field-ready information helps farmers and ranchers use carbon-capture farming on their land.