NPK values

[imafan26]

I was looking through some posts on the forum. There were some questions regarding the meaning of NPK values.

Homemade Compost NPK= Nitrogen 0.5% Phos 0.27% Potassium 0.87%

NPK values are not the whole story with compost. There is very little NPK value in compost. What compost does do is add and support the soil food web---microorganisms, earthworms and other biota creating a living soil.

Compost contains micronutrients, increases soil tilth, water holding capacity and drainage.

To get good compost what goes in matters. Compost buffers the pH of the soil over time, but compost can vary in pH 6.0-8.5 depending on whether alkaline (comphrey,chicken manure) or acidic materials (pine) are used. Compost naturally cycles through different pH values starting acidic and gradually becoming more alkaline as compost bacteria changes and compost nears the finish.

The mere presence of nutrients in the soil is not enough. Nutrients must be available to the plants. Soil pH matters. Nutrients become more or less available at different levels of pH. All life survives optimally within a narrow pH range.

Most fruits and vegetables prefer a pH range of 6.0 to 7.0 or slightly acidic. There are acid loving plants blueberries, rhodedendron, gardenia, potatoes that like pH 4.3-5.5 and alkaline plants cabbages, baby's breath that like pH above 7.5. Most plants will not grow with a pH less than 3.0 or greater than 9.0.

Below are links expanding on different NPK, Soil and compost topics.

http://www.allotment.org.uk/grow-your-o ... of-manures
http://www.extsoilcrop.colostate.edu/So ... ost_pH.pdf
http://www.composting101.com/using-compost.html
http://soils.usda.gov/sqi/concepts/soil ... d_web.html
http://extension.missouri.edu/p/MG4

[rainbowgardener]

We have had this discussion before about the fertility value of compost. I agree the usefulness of compost is a lot about adding life to the soil from earthworms down to bacteria and fungi and adding tilth, etc. NPK values of compost range around 1-1-1 to 2-2-2. That doesn't sound like a lot compared to synthetics with values like 20-20-20. However, the synthetics have to be used in relatively tiny amounts or they will burn the plants and poison the soil with salt build up. Compost is used in shovels full. More can be added any time and it just keeps breaking down and adding to the soil. In the long run, I think as well as adding to the life of the soil, you are adding MORE fertility with compost.

[toxcrusadr]

Completely agree with all of that.

[imafan26]

I went and read back a few pages and this topic has been discussed in bits and pieces here and there. Since, it has been covered to your satisfaction. Nuff said. I would lock this post down but I don't know how

[rainbowgardener]

Mods have to do that.

Keeping track of stuff here got a lot harder because Search the Forum doesn't work very well any more and mostly will only pull very new and very old stuff.

It used to be I could do a quick search and post all the relevant links, so we could keep everything connected. Then reading one thread would give you links to all the other threads about the topic, if you were interested. Can't really do that any more...

Sorry, I didn't mean to sound harsh. You gave lots of good info and helpful links. I was only reacting to these few words out of everything you said:

" There is very little NPK value in compost."

That was meant to be the context for what I said about shovels-full etc. But everything else you said was spot on.

[imafan26]

No offense taken rainbow. I have also noticed that I was having problems using the search function, but I thought I was not doing it right.

[Susan W]

Thanks for bringing this topic back out again, especially this time of year as we are looking to freshen and amend the beds and start new ones. It is easy to figure if one puts in compost, worm stuff and other additives all will be well. For some plants yes, but not for all. The next thing to figure is if one needs to add and N,P or K for particular plants or beds. For example a flower bed a wee bit different from the herb bed!

[rainbowgardener]

Flower bed is different from herb bed and needs a different nutrient mix to promote blooming. But perhaps because I am a lazy gardener, I just figure if I provide good enriched soil, the plants will take what they need from it. Works for me. Besides, I tend to have flowers, herbs, veggies all mixed together, so it would be hard to provide specific nutrients for each.

What do you actually do differently between flower beds and herb beds?

[Susan W]

Of course a good base soil is best for all plants. I try to go more lean for most herbs, basil excluded. I have been lazy about feeding the flowers, and it shows! (rather doesn't show with weak blooming!). For basil and other fast growing I try to fish every 1-2 weeks (cup of fish emulsion/5 gal bucket water). I am telling myself now in Jan when chilly to feed the perennials and other flowers. For me that means working in some Flower-tone (Epsoma) when cleaning up in spring -March-April, and adding more to zinnias and other bloomers when they are planted.

[mywebinfo]

Correct me if I am wrong but I read somewhere the rotting wood chips (no walnut)draws out nitrogen and should not be used as direct mulch around veggies etc. However, I was using it for some years around my flowers to help keep weeds down and they seemed to like it. At least they did well and look very healthy.

I was wondering if the article I read(have no idea where it is) could have been wrong. Does anyone know about rotting wood?

[applestar]

Composting Wood Chips thread -- currently bwing discussed here
http://helpfulgardener.com/forum/viewtopic.php?t=50316

[rainbowgardener]

Correct me if I am wrong but I read somewhere the rotting wood chips (no walnut)draws out nitrogen and should not be used as direct mulch around veggies etc. However, I was using it for some years around my flowers to help keep weeds down and they seemed to like it. At least they did well and look very healthy.

I was wondering if the article I read(have no idea where it is) could have been wrong. Does anyone know about rotting wood?

that's apparently a bit controversial. we've been having a whole big discussion of it here:

http://www.helpfulgardener.com/forum/v ... highlight=

What I have always believed is that if you bury your wood chips, they will tie up Nitrogen from the soil in the process of breaking down. That does not apply to wood chips just sitting on top of the soil as mulch. Some people are disputing whether even buried wood chips actually sequester N. I guess I need to do some more research.

[toxcrusadr]

Short version: Wood can deplete nitrogen in the soil it's touching, so if it's tilled in, it can temporarily deplete nitrogen in the root zone. Used as a mulch, it only affects the very top of the soil, AND there is atmospheric nitrogen available as well. That's why wood mulch doesn't harm plants.

[ElizabethB]

Any vegetive matter - wood, leaves, grass, kitchen waste will initially deplete nitrogen. That is why I keep a compost pile instead of adding green matter directly to my soil. Since I do square foot gardening my soil requirements have to be monitored closely. My lovely compost is the best additive - as long as I can keep the fire ants out of it.

Oh well - good luck.

[toxcrusadr]

Looks like Rainbow and I were posting at the same time. I am not necessarily wedded to the idea that tilled-in chips will deplete nitrogen, certainly never tried it so it's 'conventional wisdom' as far as I'm concerned. Sounds like we are all pretty much in agreement that mulching does not, though.