The Nitrogen Solution with Dr. Christine Jones (Part 3/4)

April 13th 2021

Dr. Christine Jones discusses the Nitrogen problem we face in conventional agriculture. She also answers audience questions for practical applications on how to change.

There have been over 200 scientific articles published from the Jena Biodiversity Experiment.

One of the findings from the Jena research was that high plant diversity with no added N was just as productive as low plant diversity with 200 kgN/ha/yr (roughly equivalent to 200 lbN/acre/yr). Here is the article and the link ......

Weigelt, A., Weisser, W. W., Buchmann, N. and Scherer-Lorenzen, M. (2009). Biodiversity for multifunctional grasslands: equal productivity in high-diversity low-input and low-diversity high-input systems. Biogeosciences, 6: 1695-1706, doi:10.5194/bg-6-1695-2009

https://www.biogeosciences.net/6/1695/2009/bg-6-1695-2009.pdf

The four functional groups used in the Jena Biodiversity Experiment are described in detail in the following publication ...

https://www.sciencedirect.com/science/article/pii/S1439179116300913

If you click on the above link it will take you to the on-line version, from which you can download the PDF for free.

The article describes the criteria for selecting the four functional groups and provides the names of the plant families to which each of the 60 species belong.

There were 16 plant families used in the Jena Biodiversity Experiment (Apiaceae, Asteraceae, Brassicaceae, Campanulaceae, Dipsacaceae, Fabaceae, Geraniaceae, Juncaceae, Lamiaceae, Plantaginaceae, Poaceae, Polygonaceae, Primulaceae, Ranunculaceae, Rosaceae, Rubiaceae).

The Jena folks put together a great little video, only 8.55 mins .... definitely worth a look.

https://www.youtube.com/watch?v=j3SvG2nBCTM

In summary, plant diversity increased microbial diversity, resulting in increased soil carbon, which in turn improved soil health, increased productivity, enhanced the availability of nitrogen and phosphorus (and a whole heap of other plant nutrients) and improved soil water-holding capacity.

An important point to emerge from the Jena Biodiversity Experiment was that plant diversity significantly increased root exudation which in turn supported greater microbial biomass, particularly soil fungi. See for example the excellent article by Nico Eisenhauer et al.

Eisenhauer, N., Lanoue, A., Strecker, T., Scheu, S., Steinauer, K., Thakur, M.P. and Mommer, L. (2017). Root biomass and exudates link plant diversity with soil bacterial and fungal biomass. Nature Scientific Reports 7: 44641. doi:10.1038/srep44641

You can download the PDF from the link below .....

https://www.nature.com/articles/srep44641

And here's a link to the relationship between plant species richness and the sequestration of soil carbon, which is what I'll be talking about next week.

https://www.nature.com/articles/ncomms7707

From what I see around the world, functional diversity in annual covers and companions seems to require a minimum of four plant families.

During my presentation I also mentioned an excellent piece of Irish research from Thomas Moloney's PhD (Teagasc was the lead agency)

A mix of perennial ryegrass, timothy, red clover, plantain and chicory receiving no inorganic N fertiliser matched the annual yield achieved by perennial ryegrass receiving up to 360 kg N/ha per year (equivalent to 780kg urea/ha/yr).

See ........
http://archive.sciendo.com/IJAFR/ijafr.2020.59.issue-1/ijafr-2020-0002/ijafr-2020-0002.pdf

I've pasted Part c) of Figure 2 below.


Figure 2. Annual DM yield of (c) PRG, Mix 1 and Mix 2 at inorganic nitrogen rates of 0, 120, 240 and 360 kg/ha per year. All values are averaged across the Early, Middle and Late harvest schedules. PRG = perennial ryegrass; Mix 1 = PRG, timothy, red clover and white clover; Mix 2 = PRG, timothy, red clover, plantain and chicory.

As you can see from the above figure, Mix 2 (perennial ryegrass, timothy, red clover, plantain and chicory) out-yielded perennial ryegrass at all rates of N.

Or to put that another way, ryegrass required over 200 kgN/ha to produce what Mix 2 could produce with no added N.

Mix 2 was four plant families (four functional groups).

On the subject of diverse pastures, there was a great little video released last month, featuring Irish dairy farmer James Foley ... (only 4 mins). Check out the glossy coats on the cows!!

https://www.youtube.com/watch?v=_Z4VP_pOO7M

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