Why is my soil low in nutrients?

Maynard, MA

I planted lettuce, peas, spinach, carrots, beets, rutabagas, and a few other things in early spring (early April) here in zone 6. Except for the peas and possibly spinach, though, my germination rate wasn't nearly as great as usual--and worse--the plants that did germinate didn't grow much. I kept thinking they would be fine, but after awhile, I got out of my denial and sent out for a soil sample test.

Sure enough, my garden was low on the major nutrients. I'm perplexed about this because I added plenty of aged horse manure, dried blood, wood ash, and bone meal--the same organic amendments I usually add. Could the problem have been that I added them last fall instead of this spring?? (I hadn't been able to garden for a few years and I didn't remember when I used to add amendments.) What could have gone wrong?

Looking forward to your thoughts,

Cherry Grove, OH(Zone 6b)

How did you add the amendments? Did you top dress (did it wash away)? Do you have very sandy soil (did it wash deeper down below the level you tested)?

Everett, WA(Zone 8a)

Sometimes I think that adding organic matter may MAINTAIN mineral content in the soil, as long as you don't grow more plants that you added compost. Intensive c ropping requires intensive fgertilization (just don't go too far overboard if you add chemical fertilzers.)

Compost is mostly organic matter: the nitrogen is very dilute, or even extremely dilute if you added lots of "browns".
If your compst heap got a lot of rain, the soluble goodies may have leached out. Consikder adding it "younger" or less fully dogested to your garden. Some people just tgolp-dress with grass clippings or bury kitchen scraps like composting right in the garden.

That OM is great for the soil tilth and soil life like microbes and worms, abut plants do wnat N, P and K.

I would have thoguht that manure would add enoguh N, but did it have a lot of sawdust? That will activelyh CONSUME N!

If you are growing intensively, it might take a LOT of compost to add as many minerals as you harvest. You might consider adding a measured, minimal amount of chemical fertilizer to bring the soil minerals up to par. Then thinkly about doub ling the amount of compost you add to maintgain that level.

I think that some people add 6" or more of compost per year!

Maynard, MA

"Do you have very sandy soil (did it wash deeper down below the level you tested)?"

Yup, I have sandy soil. Did it wash away the nutrients? I wouldn't have thought so, since we had a very dry winter/early Spring, but you might be onto something.

Cherry Grove, OH(Zone 6b)

My grandmother, who retired to a little bungalow in the Jersey pine barrens, handled sand (I'd say "sandy soil" but really, it was just sand) by putting a layer of mulch under her raised beds. It seemed to hold water and soil additions much better that way. Otherwise water, and the nutrients dissolved in it, would just wash right through.

I deal with hardpan these days, so my sandy soil experiences are a bit old and rusty. I don't know how much water removes what quantity of nutrients from sand, so I can't say if that's what happened to you. I do remember adding a lot of compost to those sandy beds, probably 1/3 of the soil volume of the raised bed.

Grand Saline, TX(Zone 7b)

There have been recent report of people having compost problems because of long term residuals of herbicides used in hay production. Do any of your bean or tomato plant leaves look stunted and, or curled?

Can you supply your test results, including macro, micro nutrients, and Ph?

I have sandy loam and your amendments look much like what I used before testing my soil this year. I've since changed what I was using. But I would like to see what your test says before commenting more.

Anderson, IN(Zone 6a)

It seems like mix, mix and mix some more, with the organic material. Somtimes it seems to go on forever,And then you get to hope to do more when winter passes.

Everett, WA(Zone 8a)

Maybe drape plastic film over the raised bed during heavy rain, at loeast when you don't have crops growing. Reduce the amount of water flowing right through and out of the bed.

Both organic matter and clay help "hold" nutrients in place.

Slow-release fertilizer could help: like do some composting of green-rich stuff like grass clippings or manure, in a layer on top of your bed, or turned into the top 6". As it composts in place, it will release a little N, P and K. If the plant roots grab it before the rains wash it away, it will benefit them some.

Maynard, MA

As I've thought more about the sandy soil question, it makes more and more sense. This is my second season in a new town; hence, my second year with sandy soil. In prior years where I used to live, I had neither-sandy-nor-clay-soil---it was just right. Dumb as it sounds, I hadn't realized that the difference meant that nutrients were held in the soil differently there than here and that therefore, I would have to amend the soil differently.

Your suggestions are all very helpful. Thank you!!!

Fortunately, it is not too late for me to add blood meal, bone meal, and muriate of potash before transplanting warm-weather plants like tomatoes, melons, etc. But what to do about the plants that are already planted but not growing well? I can't dig them up to mix in amendments. Should I try a liquid fertilizer? I've never used one before. Does anyone know of any organic liquid fertilizers that are up to the job? I have Neptune's Harvest here, though I wonder if it's too weak for my purposes?

Anderson, IN(Zone 6a)

Maybe a job for compost tea? Start lightly till you get the amount to mix with water .

Everett, WA(Zone 8a)

If the bed gets most of its water from a hose, just water less at any one time. Less run-off, less leaching.

If you're willing to use chemical fertilizer to rescue plants in sandy beds, foliar spraying with soluble products like Miracle Gro is always a quick fix. But I consider that an expensive way to fertilize bulk soil.

I use whatever balanced fertilizer-in-a-bag is cheap, and just use it sparingly until the plants turn greener. That way, I might be under-fertilizing but I'm NOT over-fertilizing.

Did your soil test say you were much lower in one thing thasn the others? Look for something with that number higher. You mentioned Potash, for K. There are several chemical fertilizers that are all-phosphate. My own limited experience is that more unimproved are poor in organics and nitrogen first and foremost.

Many stores look at you funny if you ask for ammonium nitrate or urea - I guess they can turned into explosives. But farmers use those for fast, cheap Nitrogen. I think you have to be extra-careful to avoid excess urea - the plants won't explode, but some urea breakdown product 'burns' plants in lower concentrations than other fertilizer breakdown products. When I could buy urea, I didn't obsess on that: I just used very small amounts frequently.

And since you're now cursed and blessed with snady soil, any excess will wash away in the first heavy rain.


If you have compost already composted, or coffee grounds, top dress with it and let rain and worms carry nutrients down to the root zone. Microbes will turn it into minerals plants can take up.

Mulch with grass clippings, though some say to keep it an inch away from plant stems. It wsill contribute some nutrients.

Manure, as long as it's not too fresh and hot, could be broken up and used as a top-dressing, but they say not to let it touch plant stems. Like, put down a layer between rows.

I don't know if compost tea is like manure tea, but if you go that route, I think it benefits from brewing as aerobically as possible. But if your plants are really hungry, they may need heavier feeding than moderate amounts of weak tea will provide. Maybe partly-composted "manure soup" would be more satisfying, but again, hot manure on the stems may not be a great thing.

And not everyone likes the idea of manure with their veggies ...

Cherry Grove, OH(Zone 6b)

As much as I like organic solutions, a bit of Miracle Gro might be good advice.
I also completely agree that top dressing and mulching are a good idea to "save" the already planted veggies.

Another thought is to plant some Fava beans. They are tall, 4-6 feet, so plant on the North side of your vegetables. Use soybean inoculant on the seeds. The Fava's deep (2-3 feet) dense roots fix nitrogen and they later rot in the soil adding water and nutrient holding organic matter deep down. I always start a new bed off on it's first year with a very dense planting of Favas. They break up clay, improve sand and are "nature's little miracle" for a gardener with difficult soil. At the end of the season till the tops in, or just leave on top. In hot weather they usually won't go to seed, but if they do, they are quite tasty. You can eat then like green beans, shelled beans or dried beans. The leaves are also edible, tasty, and nutritious if you enjoy salads or cooked greens. Fertilizer, mulch, soil amendment and a tasty veggy. What's not to love?

Murphysboro, IL(Zone 6b)

Did your soil test report a cation exchange capacity (CEC)? And is it low? If your soil is high in sand and low in clay, the CEC is probably low. Clay particles (some types, not all) and humus hold on to positively charged nutrient ions much better than sand particles, so as others have mentioned, nutrients wash out of sandy soil easily. Humus is what you need -- not just mulch or partially composted stuff. The best way to improve humus is by getting some hot composting going and adding that to the garden after it is very very well composted.

Gainesville, FL(Zone 8b)

Quote from ShaynaPearl :
Sure enough, my garden was low on the major nutrients. I'm perplexed about this because I added plenty of aged horse manure, dried blood, wood ash, and bone meal--the same organic amendments I usually add. Could the problem have been that I added them last fall instead of this spring?? (I hadn't been able to garden for a few years and I didn't remember when I used to add amendments.) What could have gone wrong?

You don't say who did your test. Unless you paid for it, most extension services only estimate nitrogen content. It costs quite a bit to actually run a complete, accurate test because of the different forms of nitrogen that can be present in most soils. That said, in a warm soil or a loose sandy soil, or in gardens that get a lot of rain or irrigation, the nitrogen can disappear quickly regardless of the source.

The same is true of manures. In most cases it is the bedding that lasts the longest (especially if it is wood-based and coarse), and that can actually end up robbing nitrogen from the soil (by microorganisms breaking down the carbon). It needs to be added every growing season unless the soil is naturally very rich.

Most forms of potassium are quickly leached out of soils by irrigation and rain. The types that aren't (greensand, certain rock dusts) are very slowly available to plants and may become deficient. If the sample is prepared using a simple water extract (the most common way to test for potassium), those forms will not show up.

The same may be true for phosphorus. Bone meal breaks down slowly. Labs test for available phosphorus, and as with the other elements the type of test performed will determine whether that form is measured correctly. See http://www.ipm.iastate.edu/ipm/icm/2000/9-18-2000/availablep.html.

It sounds like you are adding what you should, but nitrogen and most potassium sources have to be added more frequently to make certain they are available when the plants need them. One of the main reasons organic amendments are chosen over industrial chemicals is that they supply nutrients gradually over the growing season. Depending on the methods used to test the soil, they may not be getting measured. Most likely the poor growth was due to insufficient nitrogen. Since nitrogen is the key element taken up by plants (more than 10 times as much as potassium), low nitrogen alone could account for poor growth. You should always add a source close to planting time, and consider side-dressing fast-growing plants during the growing season.


Shawnee Mission, KS(Zone 6a)

My brother lives in an area that has sandy soil. He put all his veggies in cattle watering troughs filled with compost. He also spreads compost on his lawn every year in order to get grass.

You might also read about Findhorn (Scotland) as they are a self-sustaining community that started with sandy soil. What I remember from the book is lots of compost including cow manure was added every year.

Murfreesboro, TN(Zone 7a)

I live in the high desert, and it is pure sand here - except for my garden plot. I have been adding the composted bedding of 2 dozen chickens to it for the last 4 or 5 years (that's a LOT of chickie poo!), and the sand and the desert just gobble up the nutrients. The first few years, you couldn't even tell I added compost and "bought dirt" to my raised beds at a ratio of 1 part compost, 1 part dirt, 2 parts sand both years. I had to add time released chemical fertilizer in order to get anything to survive. After I got my chickies, I slowly weaned myself off of the chemicals and added nothing but composted chickie poo bedding to both the raised beds and in ground beds. Finally, after 4 or 5 years, the sand in my garden has organic matter, holds water well (grows weeds galore!), and is purely organic. And, of course, I'm moving this year... to start over with clay in Tennessee...

Maynard, MA

Quote from ssipes :
Did your soil test report a cation exchange capacity (CEC)? And is it low?

CEC= 5.9 meq/100g. Yup, that's low. I just added all the fully composted compost I had, which will get me through this year, but I'll a ton more in the future.

Everett, WA(Zone 8a)

I wonder if there isn't some method of reducing your leaching. Something like "He put all his veggies in cattle watering troughs filled with compost".

Maybe put down a floor of heavy plastic film under your bed, and carefully reducing the amount of water it gets. The organic matter will still be digested very fast, but soluble minerals would mostly just leach down to the plastic, where roots might still reach them.

If the floor sloped to one side, all your fertilizer runoff would end up there, and you might find that spot to be fertile.

Slow-decomposing organics might help. Wood does need some pre-composting with nitrogen so it doesn't srteal N from your plants. Conifer bark takes around 3 years to break down in some soils and climates - maybe it would last 2 years for you!

Maynard, MA

[quote="RickCorey_WA"] Slow-decomposing organics might help. Wood does need some pre-composting with nitrogen so it doesn't srteal N from your plants. Conifer bark takes around 3 years to break down in some soils and climates - maybe it would last 2 years for you![/quote

You mean, mix the wood chips in with the soil so that they absorb water rather than having the water leach? And the wood chips won't absorb nutrients themselves? If so, that might work, since I have a huge pile of chips from a blue spruce that got hit in last fall's tornado.

Everett, WA(Zone 8a)

>> You mean, mix the wood chips in with the soil so that they absorb water rather than having the water leach?

That's what I was thinking.

Wood will use up nitrogen unless you compost it first with some source of nitrogen. It will absorb nitrogen from your compost heap, so maybe you should start throwing grass clippings or coffee grounds or manure on top of those chips. And I imagine that bigger wood chips would need longer to "reach nitrogen equilibrium" than sawdust would.

As the wood chips break down the rest of the way, they will be spongy, and then fibrous, and then humus. All of those stages would hold some water, which I think is the basic problem with sand. It's like trying to grow in a bag of marbles.

Even if the wood gets somehwat fungusy, the fun gus will hold water and nutrients better than sand!

One possible concern: I've read that black walnut is "bad" for plants. I don't recall reading that about blue spruce, but then I know little about spruce. And I stick with bark ever since I bought a lot of a cheap "soil conditioner" that was mostly wood chips. It was very full of fungus and just wierd fgor a year, until it broke down. That was a cold, soggy, airless pure clay bed, the opposite of your situation. So I wouldn't assume my "fungus" experience would repeat for you.

Here's another thought: Google "hugelkultur sandy soil". That's where people make a big pile of wood (limbs and even trunks) as a foundation for a bed. They put compost o0r soil on top to give the plants something to work with, but excpect the wood to break down into a huge, water-retaining sponge. I guess they don't have a problem with fungus or nitrogen depletion! Probably the fact that wood is buried fairly deeply in big chunks, instead of mixed with the soil as chips or sawdust, helps.

Grand Saline, TX(Zone 7b)

I'm trying hugelkultur on my sandy soil next year, and think it would be a very good idea for you to look into as well. If your sand is like mine there is really very little of value in it. I've been using compost, bone meal wood ash for the last four years in my raised beds. Things would grow, but some didn't thrive. My soil test proved I wasn't getting enough added.

I needed,
primary macro (N-P-K),
secondary macro (Ca-S-Mg)

Nitrogen, I get from turned crops, alfalfa pellets, raw compost, it doesn't take much to get a plants started. I use fish emulsion once blooming starts. Most fruiting plants use less then 20% of their N requirement before fruit set. Rapid growth from N should be avoided in the early stages to prevent disease and insect pressure. As stated before, it sounds like yours was leached away or used up by carbon.

I'm using Dolomitic lime, for Ca and Mg, raises Ph.

Sulfur, seems counter intuitive for acidic soil, but in small amounts helps solubilize Ca along with humus and microbial action.

Phosphate, I used Calphos which is a soft rock phosphate (Ca-P) that is immediately available to plants. I'm building reserves with rock phosphate (not the same as SOFT rock phosphate) I also use chicken manure.

Potash, I'm using 0-0-60 along with K-mag 0-0-22 (which has sulfur, Mg, K) building reserves with greensand, rock dusts and minerals.

Compost has very little Ca in it. I don't see anything that your adding now that would give you enough Ca to support strong growth. Bonemeal, maybe, but it's slow, it would be best if you have multiple Ca compounds for the soil/plants to work with. Calcium is essential for plant and microbial life. Most soils have plenty of calcium and it's just tied up, sandy soil usually doesn't have it to begin with.

Can you post your test results, please?

Maynard, MA

The results are on a pdf so it's hard to copy the whole thing, but here are the highlights:

Soil pH=6.8
organic matter=3.9% (desirable range=4%-8%)

Cation Exch Cap: 5.9 meq/100g

Since the test, I added several bushels of cow manure, lots of compost, and bone meal.

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