Researchers found extensive regions in which the addition of nitrogen or iron individually resulted in no significant phytoplankton growth over 48 hours. However, the addition of both nitrogen and iron increased concentrations of chlorophyll a by up to approximately 40-fold, led to diatom proliferation, and reduced community diversity. Once nitrogen–iron co-limitation had been alleviated, the addition of cobalt or cobalt-containing vitamin B12 could further enhance chlorophyll a yields by up to threefold. Results suggest that nitrogen–iron co-limitation is pervasive in the ocean, with other micronutrients also approaching co-deficiency. Such multi-nutrient limitations potentially increase phytoplankton community diversity.
Nutrient co-limitation at the boundary of an oceanic gyre
… and that in the short-term carbon through microbial form immobilizes already available N, potentially making less available for plants or loss through leaching.
The belief that adding high-carbon mulch locks up nitrogen may yet have some merit, not necessarily in the mulch, but in the microbes!
Although C input promoted microbial growth and N demand, we did not find indicators of increased N mobilization from SOM polymers, given that none of the soils showed a significant increase in protein depolymerization, and only one soil showed a significant increase in N-targeting enzymes. Instead, our findings suggest that microorganisms immobilized the already available N more efficiently, as indicated by decreased ammonification and inorganic N concentrations. Likewise, although N input stimulated ammonification, we found no significant effect on protein depolymerization. Although our findings do not rule out in general that higher plant-soil C allocation can promote microbial N mining, they suggest that such an effect can be counteracted, at least in the short term, by increased microbial N immobilization, further aggravating plant N limitation.
N-fertilizer, where does it come from?
“The leaf particles act as tiny sponges in soil, soaking up water from large pores to create a micro-habitat perfect for the bacteria that produce nitrous oxide.”
Not as much N2O is produced in areas where smaller pores are present. Small pores, such as in clay soils, hold water more tightly so that it can’t be soaked up by the leaf particles. Without additional moisture, the bacteria aren’t able to produce as much nitrous oxide. Small pores also make it harder for the gas produced to leave the soil before being consumed by other bacteria.
Every time you till, what are you creating? Large pores.
Decomposing leaves are a surprising source of greenhouse gases | MSUToday | Michigan State University
In the image above I’ve basically highlighted the mature dried wheat straw in yellow with a C:N of 80:1 that was first applied to soil. After two weeks the same amount of the green young dry faba bean with a C:N of 20:1 was applied at differing amounts and frequency for two more weeks.
After application of the wheat straw you can see a decline in plant available nitrogen by 75% & phosphorus by 50% in the first two weeks.
After that two week period, adding the equivalent amount of faba bean residue then doubled the original available nitrogen and phosphorus availability, and it seems to me like it may have sustained much higher levels for longer had the study continued. Soil carbon priming in action.
The H1-L4 (High C:N wheat followed by 4 applications of Low C:N faba over two weeks) part of the study however is the most interesting for me. Instead of applying all the faba bean reside in one go, applying it in stages gradually increased (red line) the available N and P. This approach would probably be the most efficient nutrient wise as plant nutrient removal increases as the plant grows, so it makes sense to add the nutrients as it needs them. Plants typically remove nutrients in a sigmoid curve.
Researchers have used nanoparticles to create a a fertilizer that releases nutrients over a week, giving crops more time to absorb them (ACS Nano 2017, DOI: 10.1021/acsnano.6b07781).
They attached urea molecules to nanoparticles of hydroxyapatite, a naturally occurring form of calcium phosphate found in bone meal. Hydroxyapatite is nontoxic and a good source of phosphorous, which plants also need.
In water, the urea-hydroxyapatite combination released nitrogen for about a week, compared with a few minutes for urea by itself. In field trials on rice in Sri Lanka, crop yields increased by 10%, even though the nanofertilizer delivered only half the amount of urea compared with traditional fertilizer.
Slow-release nitrogen fertilizer could increase crop yields | Chemical & Engineering News http://cen.acs.org/articles/95/web/2017/02/Slow-release-nitrogen-fertilizer-increase.html
They should call it UreaCa! Geddit?
Alternately you could just use fresh plant litter or cover crop residues that leach nitrogen over two weeks and also feed soil microbes carbon. Or faba bean that will release it over three years and build soil carbon so eventually you don’t need to add any.
 Carbon and Nitrogen Release from Legume Crop Residues for Three Subsequent Crops
Abstract | Digital Library https://dl.sciencesocieties.org/publications/sssaj/abstracts/79/6/1650
 Formation of soil organic matter via biochemical and physical pathways of litter mass loss : Nature Geoscience : Nature Research http://www.nature.com/ngeo/journal/v8/n10/full/ngeo2520.html
Wood chips are fantastic, but with come some caveats like mentioned. A high C:N in any mulch actually has a negative priming effect on soil carbon, and soil carbon is needed to build microbial communities that fix nitrogen, adding these mulches to low carbon soils can initially slow the process, this is the reason some wood chip or even straw mulch soils can take a while to become productive soils, especially in drier climates where they take longer to biodegrade. It’s only when the C:N of the material biodegrades to about 50:1 that positive priming of soil carbon occurs. In low carbon soils you’re better off putting down compost first before a mulch.
When put on too thick the existing soil can also become deprived of air or saturated with moisture which slows the microbes that perform the nitrification process which happens for the most part in the top 10-15cm of soil. 10 cm of mulch is enough to keep moisture levels high, more doesn’t seem to help much there. Some mulches are also allelopathic and impede microbial communities and plant growth. Allelopathy can often be broken down by composting first, like in those piles the road crew made.
The priming process can be sped up by adding a carbon source like glucose that plants normally feed microbes, or with nitrogen for example from chicken manure. I’d rather add a liquid carbon that microbes can use to replicate themselves immediately rather than nitrogen, as carbon-13 labelling studies have shown that adding nitrogen can mean plants allocate less below-ground carbon for the soil microbes that fix nitrogen. I read one study that showed soil carbon was correlated with 86% of all soil nitrogen in forest ecosystems. You eventually get lots of useful soil carbon and other goodies from wood chips! Eventually…
Awesome to see Jagganath on the land growing again and the Cinghiale (Wild hogs) prevention he’s had to implement to get a keyhole garden going.
In the video he talks about creating another follow up video to discuss solving his nutrient deficient lettuce problems on degraded land, however I wanted to address that here as it sparked a few thoughts and searches while watching.
For my lettuce I’ve currently been soaking straw in mixtures like the Amrut Jal that Jagganath mentions (I use my guinea pig instead of cow) and it has worked well.
Straw alone initially has a slight negative priming effect as Huw found in the following video.
Straw has a C:N of about 80:1 and needs to be brought down to 50:1 or less either naturally or through intervention before the soil carbon building begins and microbes can use that carbon to fix nitrogen.
The figure shows the priming effect of different organic matter C:N ratios, and depending on your environment, reading along the bottom you want to be on the right side of the pink line in the short-term where positive priming occurs, and left of it in the green area for long-term when considering for mulch temperature and moisture management, as well as slow nutrient release. In the blue, carbon mineralization is likely to be limited.
Priming patterns resulting from different glucose and ammonium inputs to incubations of wood litter (a), leaf litter (b), as well as Oa horizon organic soil (c) and mineral-soil A horizon (d) from a subtropical forest.
One of the other figures in the priming paper that I found most interesting, was this one.
Based on it I just calculated that at least 10 grams of glucose (sugar, molasses etc) to 1 kg of dry straw is needed to prime it, 40 grams (two tablespoons) will accelerate it and so should 2 grams or more of ammonium, which is about 200 ml of human urine.
Guess what I’m making tomorrow and soaking some straw in?
Permie Flix’s Max Prime (+15) Recipe:
- 4 mL (1 teaspoon) of sugar (unsulfured molasses etc)
- 200 mL of urine
- 800 mL of water
My 1L concoction would do about 100 grams of straw. Or if scaled up to a larger 1oL soaking 1kg would be possible.
Permie Flix’s 10 L Max Prime (+15) Recipe:
- 40 mL of sugar (2 tablespoons)
- 2.0 L urine
- 8 L water
Soaking overnight with a weight on top should be enough.
A 20 kg bale? That’s:
- 800 mL of sugar
- 40 L urine
- 160 L water
That’s a lot of piss. I measured mine and I get maybe 800 mL. That’s 50 piss stops or about a month.
For my experiment I only have enough aged urine for my 10L bucket… 🙂
I expect Max Prime would work wonders to kickstart small size heartwood chips and anything with a C:N less than 300:1, while Base Prime (cutting the sugar by a quarter) would be good for less than 150:1 or ramial (branch) chipped wood.
One of the other added benefits if you choose your glucose (sugar) source carefully, is that it can be high in potassium, which fungi love. The low phosphorus in urine is also good for fungi too. Adding manure or high phosphorus material however will upset the fungi, and it’s fungi you want to encourage long-term with a continuous supply of carbon.
 Carbon and nitrogen additions induce distinct priming effects along an organic-matter decay continuum https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4726261/
Note to self: Don’t calculate at 4AM.
“According to a recent article at Grist”
While I can’t tell if David is being sarcastic about the recent part of the Grist article since it’s from 2010, I totally agree with what he says and quotes.
Surface application of synthetic nitrogen alone has been shown to deplete the surface layer of organic carbon and increase the amount of dissolved organic carbon. This then leaches into the lower layer and initially increases C mineralization there. As a result there is then less carbon in the surface layer for microbes to use and to bind nitrogen from air and so more fertilizer is then needed, leading to even more leaching over time and the creation of the more-on farmer.
Now there are studies showing that if synthetic nitrogen is added in moderation with organic matter that it can actually increase carbon mineralization, I just can’t find where I filed them. 🙂 What really matters is the form of organic matter added.
Recent studies[2,3] indicate a C:N of 100:1 or less is good for carbon mineralization depending on the clay in your soil, with between 11:1 and 50:1 being near ideal for priming in lab conditions. Split the difference and you get 30:1 which is often recommended for compost piles for microbes to break them down, not a coincidence!
Responses of priming of organic matter (OM) decomposition to OM C:N ratios (horizontal axis) and labile C:N ratios (vertical axis).
This contour figure was made based on all priming results of four OM forms from Fig. 2, using C:N ratios in OMs as x-axis, C:N ratios in the labile inputs as y-axis, and all priming data as z (color) axis. Priming effects vary strongly among substrates along the white dashed line, where labile carbon inputs are high and nitrogen is low. Priming effects do not vary strongly among substrates along the black dashed line where labile carbon is low and nitrogen is high. The dashed pink line indicates the substrate C:N threshold ratio where priming changes from negative to positive.
Ramial(small branch) chipped wood tends to be at the upper end of the region between 30:1 and 170:1 and can be a good choice long-term. However getting the C:N down should build soil faster. Chopping and dropping is one approach. Growing and harvesting cover crops before grazing and trampling them in with animals like Gabe Brown does would be another.
There are also mechanical versions like those used in biodynamics and regenerative practice. Hand operated versions of the latter are also possible.
Growing lawn grass and leaving any mower clippings can even build soil carbon. However it may take 30 years to raise Total SOC levels by 1% doing it this way…
However in cases where you’re adding heartwood chips like many Back to Eden peeps, then nitrogen addition may help, I believe this is why many like Mr. Back to Eden himself Paul Gautschi has found that high nitrogen chicken manure helps.
Another example would be after forest fire or biochar creation where you have a lot of carbon but are nitrogen, phosphorus and sulfur limited as these tend to boil off at fire temperatures.
In the comments on David’s post Bob also mentions the N impact on ectomycorrhizal fungi.
I found a carbon-13 labelled study that seems to suggest that by adding nitrate in the form of calcium nitrate, that trees significantly reduce below-ground C allocation, probably because the trees are getting their nitrates from the fertilizer and don’t need the microbes to fix the nitrates for them. As a knock on effect the fungi also reduce their C allocation to soil biota by 60%, likely because fungi need continuous carbon input to grow and fruit and can only afford to give up so much. This all suggests that nitrate addition short-circuits the carbon-nitrogen cycle when it doesn’t increase below-ground plant C allocation. Those papers Bob quotes suggests the effect is not limited to nitrate but also ammonium further up the nitrogen cycle.
I’ve also read that the symbiosis between legumes and their rhizobia breaks down with use of nitrogen fertilizer. And that there’s a consistent change in soil microbial communities with additions of N and P.
If N doesn’t do it, I’m wondering what will actually increase below-ground C allocation to build soils fast… any suggestions? [Other than legumes or perennials with long thin roots]
Off to Google Scholar I go…
 Carbon mineralization in response to nitrogen and litter addition in surface and subsoils in an agroecosystem http://www.tandfonline.com/doi/abs/10.1080/03650340.2016.1145792
 Is the fate of glucose-derived carbon more strongly driven by nutrient availability, soil texture, or microbial biomass size? http://www.sciencedirect.com/science/article/pii/S0038071716302103
 Carbon and nitrogen additions induce distinct priming effects along an organic-matter decay continuum, Figure 5 doi: 10.1038/srep19865 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4726261/figure/f5/
 Quantification of effects of season and nitrogen supply on tree below-ground carbon transfer to ectomycorrhizal fungi and other soil organisms in a boreal pine forest – Högberg – 2010 – New Phytologist – Wiley Online Library http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2010.03274.x/full
 Long-term nitrogen fertilizer use disrupts plant-microbe mutualisms http://www.rdmag.com/news/2015/02/long-term-nitrogen-fertilizer-use-disrupts-plant-microbe-mutualisms
 Consistent responses of soil microbial communities to elevated N & P nutrient inputs in grasslands across the globe PNAS | Mobile http://m.pnas.org/content/112/35/10967.abstract
 Turfgrass Selection and Grass Clippings Management Influence Soil Carbon and Nitrogen Dynamics https://dl.sciencesocieties.org/publications/aj/abstracts/0/0/agronj2016.05.0307