The benefits of "ley farming"

 

Two papers demonstrate the benefits of "ley farming" as commonly used in temperate climate organic farming and the negative effects of continuous cropping and synthetic nitrogen on both soil nitrogen and soil organic carbon. This also serves as a reminder about how slow the process of building up soil carbon is, in this case, the ley system took 35 years to increase the SOC from 1.6% to 2.1%. That is 0.5 percentage points over 35 years, or 0.014 of a percentage point per year, which is an annual increase of about 0.9% per year on the original 1.6%. The Paris COP21 initiative, 4 per mille, seeks to increase soil carbon stocks by 0.4% per year https://www.4p1000.org/. Other points to consider are the methane emissions of livestock needed to produce human food from the 3 years of ley and the external environmental costs of fertilisers.


Mulvaney, R. L., S. A. Khan, and T. R. Ellsworth. ‘Synthetic Nitrogen Fertilizers Deplete Soil Nitrogen: A Global Dilemma for Sustainable Cereal Production’. Journal of Environmental Quality 38, no. 6 (December 2009): 2295–2314. https://lnkd.in/dsigMkQ.

Börjesson, Gunnar, Martin A. Bolinder, Holger Kirchmann, and Thomas Kätterer. ‘Organic Carbon Stocks in Topsoil and Subsoil in Long-Term Ley and Cereal Monoculture Rotations’. Biology and Fertility of Soils 54, no. 4 (1 May 2018): 549–58. https://lnkd.in/d23BdAZ.


This diagram I have prepared shows the life experience of a field under conventional no-till with no perennials, vs organic cultivation with 4 years grass. In this paper King et al show the importance of perenniality for building soil carbon, so I wonder which of these systems would sequester more carbon, and ultimately which of them is more regenerative? If you were an earthworm, which life would you choose?

King, Alison E., and Jennifer Blesh. ‘Crop Rotations for Increased Soil Carbon: Perenniality as a Guiding Principle’. Ecological Applications 28, no. 1 (2018): 249–61. https://lnkd.in/ec7vr2g.


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