Carbon sequestration via rotational grazing

When it comes to grazing, there are a few ways in which it can be done:

Continuous grazing; Rotational grazing; Strip grazing; Mob grazing; Creep grazing; Forward grazing; Multi-species grazing

Today’s focus will be on rotational grazing, and how it can contribute to sequestering carbon in the soil.  

What is Rotational grazing?

The whole pasture is divided in smaller paddocks, and the animals are moved through these paddocks in a planned sequence.  Each paddock is grazed for a short period of time ( a day is very common but no more than 5 days), depending on the size of the paddocks, time of the year, and size of the grazing herd. This allows ample resting periods for the vegetation in the paddocks that are not being grazed, and gives it time to regrow properly, with increased nutrient content, and deeper root system.
Among the many benefits of rotational grazing is the fact that abundant perennial vegetation helps sequester carbon from the atmosphere in the soil.

What is Soil Carbon Sequestration?

Soil carbon sequestration is a process in which CO2 is removed from the atmosphere and stored in the soil carbon pool. This process is primarily mediated by plants through photosynthesis, with carbon stored in the form of SOC.
The carbon captured via soil carbon sequestration can be released if the soils are disturbed, and that’s why it’s so important that we switch from frequent tillage and annual crops to perennial crops and minimal disturbance of the soil.

Here are a few examples of research that has been done in this field.

Dr. Jason Rowntree of Michigan State University conducted an LCA (Life  Cycle Assessment)  of Multi-species pasture rotation (MSPR) on a farm in Southern US. Their conclusion:

             “The 20-year MSPR chronosequence of soil C and other soil health indicators shows dramatic improvement since establishment, sequestering an average of 2.29 Mg C ha−1 yr−1. Incorporation of soil C sequestration into the
                LCA reduced net GHG emissions of the MSPR by 80%, resulting in a footprint 66% lower than COM.”

               https://www.frontiersin.org/articles/10.3389/fsufs.2020.544984/full


Here is an article from Progressive Forage magazine, describing “how to enhance your soil carbon storage”:

              https://www.progressiveforage.com/forage-types/grasses-and-grazing/enhancing-your-carbon-soil-storage

This paper published in the Journal of Animal Science states:

             “With appropriate management of grazing enterprises, soil function can be regenerated to improve essential ecosystem services and farm profitability. Affected ecosystem services include carbon sequestration, water
               infiltration, soil fertility, nutrient cycling, soil formation, biodiversity, wildlife habitat, and increased ecosystem stability and resilience.”
                                                                   W R Teague, FORAGES AND PASTURES ... Journal of Animal Science, Volume 96, Issue 4, April 2018, Pages 1519–1530, https://doi.org/10.1093/jas/skx060


In this meta-analysis and review paper written by Viglizzo and Ricard in 2019: “results show that grazing lands generate C surpluses that could not only offset rural emissions, but could also partially or totally offset the emissions of non-rural sectors. The potential of grazing lands to sequester and store soil C should be reconsidered in order to improve assessments in future GHG inventory reports.”

              https://www.sciencedirect.com/science/article/abs/pii/S0048969719301470?via%3Dihub

On a different note, ranchers in Montana can now get paid to sequester carbon using rotational grazing practices:

              https://www.agriculture.com/news/livestock/montana-ranchers-can-now-get-paid-to-sequester-carbon-using-rotational-grazing

There's more in this article (referenced above) about carbon in soil: https://www.frontiersin.org/articles/10.3389/fclim.2019.00008/full

Globally, soils contain about 1,500 Gt of organic carbon (C)1 to 1 m depth and 2,400 GtC to 2 m depth (Batjes, 1996). Thus, the total size of the soil carbon reservoir exceeds the total mass of carbon in vegetation and atmosphere combined.  

And here's the part about grazing, from the same paper:

Most agricultural soils (both mineral and organic) are depleted in C relative to the native ecosystems from which they were derived, due to reduced net primary production and export of harvested biomass—which reduce C inputs to soil; nutrient depletion, intensive soil disturbance, and soil erosion are other contributing factors to soil C depletion (Paustian et al., 1997). Most cropland mineral soils have lost 30–50% of the C stocks in top soil layers (0–30 cm) relative to their native condition (Davidson and Ackerman, 1993). In contrast, grassland soils managed for grazing may or may not have suffered similar C losses relative to their native state, depending on how they have been managed. Grasslands that have been overgrazed and poorly managed are likely significantly depleted in soil C, whereas well-managed grasslands may have C stocks equal to or exceeding their original native condition (Conant et al., 2016).

Here's another good research article on how grassland management impacts soil carbon: https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/eap.1473

improved grazing management, fertilization, sowing legumes and improved grass species, irrigation, and conversion from cultivation all tend to lead to increased soil C, at rates ranging from 0.105 to more than 1 Mg C·ha−1·yr−1.

The world's grazing lands are a key element of livestock production systems globally (Bouwman et al. 2005, Erb et al. 2016) providing livelihoods for about 1B of the world's poorest people and one-third of global protein intake (Steinfeld et al. 2006). Here we build on recent regional syntheses (Wang et al. 2011) and studies of particular aspects of grazing land management (e.g., McSherry and Ritchie 2013) to produce an up-to-date, comprehensive source of information on how land management and conversion to grasslands affect this important resource. This new synthesis can undergird global estimates of grassland soil C stocks and changes, which are an essential basis for policy and market decisions on grassland C stock management.

What unit of measure is an Mg? A milligram??? Lol? I’m hoping it’s a million grams aka a thousand kilogram aka a metric ton.  Otherwise if it’s a milligram per hectare per year, I’m selling the farm 😏.