Abstract: Soil is one of the most important natural resources and medium for plant growth. Anthropogenic interventions such as tillage, irrigation, and fertilizer application can affect the health of the soil. Use of fertilizer nitrogen (N) for crop production influences soil health primarily through changes in organic matter content, microbial life, and acidity in the soil. Soil organic matter (SOM) constitutes the storehouse of soil N. Studies with 15N-labelled fertilizers show that in a cropping season, plants take more N from the soil than from the fertilizer. A large number of long-term field experiments prove that optimum fertilizer N application to crops neither resulted in loss of organic matter nor adversely affected microbial activity in the soil. Fertilizer N, when applied at or below the level at which maximum yields are achieved, resulted in the build-up of SOM and microbial biomass by promoting plant growth and increasing the amount of litter and root biomass added to soil. Only when fertilizer N was applied at rates more than the optimum, increased residual inorganic N accelerated the loss of SOM through its mineralization. Soil microbial life was also adversely affected at very high fertilizers rates. Optimum fertilizer use on agricultural crops reduces soil erosion but repeated application of high fertilizer N doses may lead to soil acidity, a negative soil health trait. Site-specific management strategies based on principles of synchronization of N demand by crops with N supply from all sources including soil and fertilizer could ensure high yields, along with maintenance of soil health. Balanced application of different nutrients and integrated nutrient management based on organic manures and mineral fertilizers also contributed to soil health maintenance and improvement. Thus, fertilizer N, when applied as per the need of the field crops in a balanced proportion with other nutrients and along with organic manures, if available with the farmer, maintains or improves soil health rather than being deleterious.
That was a good read. The associated loss of C from mineralization due to over supplying N is something I’ve come across in other studies but I didn’t expect additional SOC storage as a result of a carefully under-supplied N fertilizer. A comparison study on some of the commonly used fertilizer salts and their effect on soil carbon using these tests would be neat.
Thanks very much for taking the time to read an article from my cache!
There’s a lot of (poor word choice pending…) ‘hype’ around fertilizer salts and their potential impact on the microbial and fungal communities. However, I tend to consider these as smaller part of a larger problem. The acidification effect of N fertilzer use is also nothing to sneeze at and can creep up fast on land mangers.
In my opinion, tillage is really what’s fucking our soils. It decimates the communities that establish and completely alters the oxygenation status of the soil. You get this big boom in mineralization (and a priming effect; Whoo! famers likey!) but it comes at the cost of your SOM/SOC pool. Repeated tillage results in B horizon erosion, as more and more of the subsoil is eventually pulled (admixed) into the topsoil, diluting what organic matter you have, and incorporating less desirable soil parameters (pH, texture). Eventually you get through the B and into the C, which can be even worse in quality.
Don’t get me wrong; salts suck, but they’re somewhat easy to deal with (gypsum, leaching).
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I think a longitudinal study about which fertilizer salts have the greatest positive correlations with increased SOC/SOM would be a boon for large scale operations since it could be a way towards a reduction of inputs all around without losing that plant growth.
I’m right there with you about tillage (This is me) though I think that many folks get up in arms about someone doing an initial till with plans for no till / no dig rather than focusing on repeated tillage as the far worse culprit. It’s not just disrupting those subsoil communities, it’s also oxidizing lots of the stored OM and minerals. This worsens the mixture of less desirable horizons even further, requiring even more chemical intervention. But it’s gotta be mixed back in, and so on and so on.
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Fucking preach. Don’t get me started on cardboard sheet mulching.
Anyway, tillage is ok too in moderation - like if you’re using it to incorporate crop residue.
That last sentence got me thinking about corn/soy rotations (since corn has a ton of residue). Check out this link to a N fixing corn variant that has been cultivated in South America for centuries: link
If it’s worth anything, we sheet mulched with a bunch of cardboard inoculated with Stropharia before piling spring and summer ramial chips along with manures from some nearby horses and our chicken bedding pretty deeply over it. It’s all heavily planted in now as “permanent raised beds” that are more akin to lumpy texture on contour at this stage of development. I think that with a proper plan, it’s a viable part of a toolkit for soil rehabilitation.
Wouldja look at that, I’m already subscribed! (You did it right)
That sounds pretty good, TBH. If I was a plant I would want to grow in your garden.
My point I was poorly trying to make, is that sheet mulch is heralded as some miracle cure, or the only way to remove grass and start a garden when a solid rototilling would do the job as good or better. Since you destroy the sod mat when you till, it’s not a bad way to go for gardening. Further, you mix in the biomass of the mat that way.
Permaculture (though I like to roast them) has some good concepts. I think a lot of it gets taken out of context, though.
For instance, you don’t NEED to do raised beds if your soil is ok and uncontaminated, provided your subsoil is in decent shape/you have enough rooting depth to grow what you want.
On the other side, however, if you have crap soil, absolutely go raised bed. Throw some medium sized woody debris or coarse gravel in the bottom for drainage, and then build your rooting zone out of other organic amendments. Heck. If you want to get fancy you can put sand from a hardware store or garden center in, and then put about 15 cm of shitsmash organic amendments on top provided C:N is ok.
Ugh. You’ve got be blathering again. I honestly could go on forever about soils and how to create suitable growth media. I’m currently designing a trial that looks at using organic amendments to create a growth media on regolith.
And! Alders! Alders are fucking cool! I posted an article way back in the !reclamation@slrpnk.net community about how interesting they are as a pioneer spp.
G A H
Someone stop me!
Come check out my small community over on solarpunk.
!soilscience@slrpnk.net (did I do that right? Did it work?!)
I have a pile of articles I’m slowly posting on there. I also mod !reclamation@slrpnk.net which is more like applied soil science and botany.