I ask because I just ran two tests on the area where I recently planted a Chambeyronia macrocarpa. The soil seemed more clayey than in other areas of the garden, which are quite sandy. The results were:

N: little to no trace

P: just the faintest trace, nowhere near the lightest color in the chart

K: very little trace

pH: very little change from the default color value on the test strip which is about a 4.5

This area has been under "black eco mini mulch" for a number of years. Is it possible that the values could be that low? I'm limited in what organics I can mix into the topsoil because we have gopher mesh throughout, under the mulch. I can really only topdress. TIA for any ideas.

Yes soil tests and leaf analysis works. For ph just the standard litmus paper is proven. While iam not familiar with the home soil test kit we get our soil tests done every 3 months, both soil and leaf test! I would recommend a professional company, or contact an agronomist for soil. 

Purchase purchasing a test from a company that is more comprehensive will help you get the big picture.  As it stands, it seems like you just need to throw down some fertilizer. I would recommend organic, personally. 

Before doing anything, perhaps submit your sample to a company for testing and go from there. 

2 hours ago, BayAndroid said:

As it stands, it seems like you just need to throw down some fertilizer. I would recommend organic, personally. 

Oh yeah @BayAndroid I do fertilize a lot, and with this information I probably will more. I use fish emulsion and greensand along with Palmgain, and will expand my use of other organics. 

The reason for a fairly comprehensive test is to check that you don't have problematic conditions which prevents proper growing conditions. If you're on a serpentine belt, for example. There could be some problems with heavy metals. 

Paul, this is an absolutely solid company,

https://www.groworganic.com/products/complete-soil-analysis?_pos=1&_sid=faa19fabc&_ss=r

 

Thanks @Darold Petty, that's what I've been looking for. I found it hard to track down this service at an affordable price. I'll give them a shot.

First, soil tests for nitrogen test for nitrates not urea or ammonium sulfates.  Fertilizers use all three as the urea doesnt rinse so fast like nitrates, or ammonium sulfates.   Typical formulation contain around half of the nitrogen as urea.  Nitrates are very soluble so they are not persistent in soil, water or rain rinses them away, possibly to deeper soil that you are not sampling.  Ammonium sulfates use NH4+ as the nitrogen source, the tests use a NO3- test so you see nothing for ammonium sulfate as well.  

Soil can be heterogeneous, clayish soils will have a different pH/composition vs sandy areas.    Several samples could be used for each area.  The color pH tests are crude, not very accurate.

Color testing can get pale as the test kit ages, the paper strips can get oxidized at some point.  You might be buying  a test kit that is old, sitting in the warehouse or shelf for too long.

If I was to describe concentrations of nutrients in soils it would be like this:  Right after fertilization, nutrients will be on top and drain down into the soil column based on solubility and rinse out over time.  Palm gain uses polymer coating on urea.  The polymer coating pore size is not controlled specifically for each nutrient/micronutrient as in Florikan palm fertilizer(patent), but is other wise similar with osmotically controlled release.  Osmocote is also osmotic in function and uses different thickness coatings on prills to release at different rates in order to get a more consistent timed release. 

Because palm gain uses polymer coated urea, your nitrogen tests will be negative shortly after fertilization as that is when soluble nitrogen(nitrates) they can detect is dissipated but urea remains.  Over time all fertilizers will peak in nutrient soil concentration and then fall off like a sawtooth.  The steepness of the fall off depends on the pore size(Florikan) the thickness of coating of that particular prill(osmocote) and for palm gain I could not find the mechanism other than osmotic polymer coating.  The fastest dissipating nutrients are K, nitrate, then then a slower rate for and urea N.  The problem is to know when each of the nutrients are going low in time so deficiency is minimized. 

Phosphorus is immobile in soils and tends to not be distributed evenly, often being banded in the soil depth.  It does nto rinse away so accumulations ar epossible in ground that has been extensively fertilized.  Phosphate tests will be tougher as it can bind with some substrates and the pH of the soil must be near neutral for it to work.  

Now the soil pH, 4.5 sounds like a bad value, it would cause several deficiencies that should be obvious.  That might convince me to get it tested by a credible lab if another fresh test kit shows the same low pH.

 

My suggestion: get some langbeinite(also called sulpomag, Kmag), it is a crystalline mineral and will dissolve slowly and it adds K, Mg(also soluble) without adding nitrogen (which risks burn) and phosphate accumulation which can limit micronutrient uptake if accumulated phosphate levels are elevated.  You can use the palm gain but augment with the langbeinite(not crushed dust, but coarse) to prevent potassium and to a lesser extent Magnesium deficiency.   And don't worry about the nitrogen test, it doesn't work for urea or ammonium sulfate.  Just add a little fish emulsion(does not burn) between palm gain application.    

Those chem test kits are ballpark measurements and they can become even less accurate if too old(even on the sales shelf).  If you want an accurate measurement get a test done by a lab.  If the lab is any good they will perform an extraction of the soil for quantitive testing.  

On 5/12/2026 at 11:57 PM, Foggy Paul said:

Oh yeah @BayAndroid I do fertilize a lot, and with this information I probably will more. I use fish emulsion and greensand along with Palmgain, and will expand my use of other organics. 

Where do you get greensand? This is difficult to find now.

@Johnny Palmseed I’ve just been getting it from Amazon, for better or worse. There are quite a few types there. I bought this one most recently. Greensand 20 Pounds – Natural Fertilizer for Healthy Soil, Rich in Potassium & Iron, Great for Gardens, Lawns & Growing - Lancaster Agriculture Products https://a.co/d/09vJ2Fc2

18 hours ago, Foggy Paul said:

@Johnny Palmseed I’ve just been getting it from Amazon, for better or worse. There are quite a few types there. I bought this one most recently. Greensand 20 Pounds – Natural Fertilizer for Healthy Soil, Rich in Potassium & Iron, Great for Gardens, Lawns & Growing - Lancaster Agriculture Products https://a.co/d/09vJ2Fc2

Thank you.

Green sand is very high in iron

AI Overview

 

If you are using greensand as a soil amendment, it is a slow-release source of potassium and trace minerals, but it is also very high in iron(12-20%). Over-applying it can lead to toxic iron levels. [1, 2, 3, 4]

 

Iron deficiency ont he other hand is mostly due to high pH soils.  My soil is ~6.5 and iron deficiency is not an issue.

IF you do have soil with an already significant iron level, green sand is not recommended

https://www.smilinggardener.com/collection/major-plant-nutrients/

 

Iron toxicity is more of a problem with continually moist acidic heavily composted soils as the low pH boosts iron availability.  When you add iron to soil the pH of the soil determines the ratio of available(soluble) to non bioavailable(insoluble) iron by chemical reaction.  

IF your newest growth is yellow, its likely an iron deficiency.  However that deficiency is more commonly caused by alkaline pH and not by soil iron levels.

 

I don't add anything with iron except my Florikan controlled release fertilizer which has 2.7% iron 11% total Mg and 12% K.  This is why I use langbeinite,  it can't change long term iron content of the soil as might repeated additions of green sand.  Elevated iron levels can cause stunting of the growth of roots and thus the plant.  Langbeinite doesn't add iron but also adds the appropriate amount of Mg relative. to K as tested in timed release studies.   

 

Green sand will be fine for many gardeners, just make sure you don't have acidic pH, elevated iron in your soil already, and don't add too much.

 

Green sand is 75% the price of langbeinite at amazon with just 1/3rd the potassium and no Mg.  Even if it didnt add the iron I'd go with langbeinite as its cheaper for the K.    Langbeinite is also a natural occurring organic mineral like green sand.  

 

 

@sonoranfans Thanks for the detailed responses, it is much appreciated. I posted a related question in another thread; it went like this: 

I’m bumping this old thread because it covers two things I’m interested in: sandy soil and organic fertilizer. I’ve seen a few recommendations for organic mixes, but they are all pretty costly and come in pretty small bags. 15 lb seems to be the biggest I saw and that much fertilizer wouldn’t last me too long. 

Has anyone made their own mix to approximate say a 4-2-3 ratio from organics available in larger bags? Right now I have Greensand, worm castings and blood meal. I also have liquid fish emulsion. What else do I need? And any suggestions for a proportional mix would be appreciated. 

Do you have thoughts on this? My conditions are sandy, low nutrient soil of uncertain pH, but probably low; thick mulch and gopher mesh everywhere, so I can only topdress; drip irrigation with little to no rain between April and November, although I do hand water frequently, partially to try to dissolve the Palmgain. Thanks for any recommendations.

2 hours ago, Foggy Paul said:

@sonoranfans Thanks for the detailed responses, it is much appreciated. I posted a related question in another thread; it went like this: 

I’m bumping this old thread because it covers two things I’m interested in: sandy soil and organic fertilizer. I’ve seen a few recommendations for organic mixes, but they are all pretty costly and come in pretty small bags. 15 lb seems to be the biggest I saw and that much fertilizer wouldn’t last me too long. 

Has anyone made their own mix to approximate say a 4-2-3 ratio from organics available in larger bags? Right now I have Greensand, worm castings and blood meal. I also have liquid fish emulsion. What else do I need? And any suggestions for a proportional mix would be appreciated. 

Do you have thoughts on this? My conditions are sandy, low nutrient soil of uncertain pH, but probably low; thick mulch and gopher mesh everywhere, so I can only topdress; drip irrigation with little to no rain between April and November, although I do hand water frequently, partially to try to dissolve the Palmgain. Thanks for any recommendations.

If I had sandy soil with low pH and minimal nutrients I would likely amend with organics and langbeinite, not green sand.   I would definitely get a real pH measurement of the soil before deciding whether to add green sand and if I was determined to use it, I would change the soil pH, raise pH to 6-7 or so.  As previously stated green sands high iron levels can be overdone in  moist acidic environments.  The timed release of the iron in green sand is faster in acidic soils as the mostly inactive iron dissolves to active soluble iron in acid pH.  You could use green sand perhaps if you were to make the soil pH neutral or slightly alkaline with crushed dolomite.  The blood meal adds some acidity the worm castings do not, they are neutral, will not change soil pH.    Palm gain has plenty of iron(2.7%), no need to add more in the green sand.    I avoid adding too many ammendments with complex chemistry as you could shift the micro nutrient ratios to a less than optimal formula.  Even if the iron is not at a toxic level, it could limit root growth at lower than toxic levels that typically bronze leaves etc.  Those nutrient ratios are changing over time as less soluble materials are rinsed away from the soil.  Our experiences here are varied due to different soil and conditions which we may or may not understand fully(if we dont test over time).  I learned that the hard way, using lawn lime near my palms, eek!  I thought I was doing them a favor but eh 10:1 Ca:Mg ratio caused a Mg deficiency.  Palms prefer 3:1 as too much Ca competes with Mg for uptake which means Mg deficiency.