Written by Terry Smith
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Best soil testers and meter kits for pH, moisture, and NPK
This article was last updated on April 23rd, 2022 at 6:15 am
If you’re having problems getting things to grow in your garden, don’t hang up your gloves and trowel just yet, as the root of the issue might have nothing to do with your skill or experience as a green thumbed warrior at all – I had some real grief with my lawn once, I scarified and used an aerator which helped, but actually the problem was my soil was somehow acidic! One of the things that new gardeners overlook is the condition of their garden soil – me included, throwing on a lawn weed and feed wasn’t the solution as I first hoped! In fact that lack of understanding resulted in me completely levelling and starting my lawn again! Now, most of us know that in order for our plants, lawns, and crops to thrive, they need the right balance of nutrients. However, how can you be sure what your soil contains? And in what quantities or ratios? This is where the best soil tests come in. To help you along the way we’ve reviewed the best soil meters for ph, NPK, and moisture – learn from my mistakes basically 🙂
The pH balance of your soils is also another factor when it comes to getting things to grow as they should, and some plants will favour different soil conditions to others, but we’ll cover this in more detail later in the article. Adjusting the pH balance and nutrients in your soil isn’t a difficult task, but you need to know what the problem is first before you can improve soil quality, and have a goal in mind. For both of these, a soil tester or meter kit is ideal, telling you exactly what state your soil is in and what it requires in order to turn your barren beds into blooming botanical masterpieces.
Five minutes spent online will show that there are an absolute ton of these testers and kits on the market, and while some are obviously different such as analog and digital products, there are also plenty out there that look identical. To help sort the wheat from the chaff, we have put this article together about the best soil testers and meter kits for pH, NPK, and moisture, giving you a selection of reviews to browse through as well as helping you understand what you need to know about a soil tester. We’ve whittled the list down to the top 6 best soil testers for you:
Best soil testers that can read pH, moisture, and NPK:
Best soil moisture meter for plants: XLUX sol moisture meter – So easy to use it just can’t be ignored – you will have an accurate reading in less than a minute, literally.
Best NPK soil test kit: Luster leaf digital soil testing kit
Best digital pH meter for soil: Sonkir digital soil pH meter – best if you like digital soil testers.
Best soil tester overall: Kensizer 3-in-1 soil tester Best all rounder for pH, moisture, and light – best of the best if you like analog considering it’s three functions.
Best pH test strips for soil: Garden Tutor soil pH strips – there’s nothing more reliable than good old pH strips.
Decent alternative analog moisture meter: Gouevrn soil moisture meter
What you need to know about a soil tester
Although there are quite a few variations, the basic idea is the same- these devices will detect the current condition of your soil, and then let you know what that is. You can then use things like fertiliser, lime, and other products to bring the pH balance to where you need it, and add any nutrients you need.
As mentioned above, there are different types of kits, with some requiring you to take a soil sample and add it to a solution like with the Luster leaf digital soil testing kit, while others, such as the XLUX sol moisture meter, just need you to stake the tester into the ground.
Not all testing kits give you the same information either, but most of them will let you know the pH level and how much of the main three nutrients, aka nitrogen (N), pHospHorus (P), and potassium(K), there is.
Some of the best kits will also give you a reading on the moisture levels and even what contaminants are present in your soil, and while these readings might not be 100% accurate, they are close enough for you to use when altering the state of your soil for the better.
Do I need to test my soil?
I’ve been asked this question so many times over the years, so I’ll give the same answer that I always have and that is-
Unless you want all your growing efforts to be analogous with a spin of the roulette table, you need to test you soil. Pure and simple.
You see, there are quite a few things that affect how well a certain plant or crop grows, and the more you know about these things the better. Makes sense, right? We already talked briefly about pH levels, and NPK, but didn’t really go into detail about it, and while I don’t want to risk droning on, I thought I’d just give a little more info on the three main types of tests you should do on your soil, and also give you a little video to watch on the subject:
pH testing
Testing how acidic or alkaline your soil is, is essential for getting the results you are searching for, and it is not always a case of making sure that the reading you’re getting is neutral (between 6 and 7 on the scale).
While it is generally the case that plants and crops do well in a neutral soil condition, you will a get much better response if you tailor the soil’s pH to the liking of what you are trying to grow. For example, potatoes’ perfect soil pH is between 4.8 and 6, whereas some fruits, such as plums, prefer the soil being closer to the other end of the scale and even as high as pH8.
The two examples we just gave are just the tip of the iceberg, and you should definitely look into the optimal growing conditions for the things you are planting, and then use a testing kit- them Sonkir digital soil pH meter for example, to see if your soil’s pH is in the required range. Trust me, it will make a huge difference.
Macronutrient testing
Look on most fertiliser packaging and you’ll see the letters NPK and usually some kind of ratio too, such as 7-7-7, and this tells you the ratio of Nitrogen, pHospHorus, and potassium that the product contains.
These three macronutrients are essential for plant growth, and each has a part to play in the process. For example, nitrogen helps with photosynthesis where energy is taken from the sunlight, pHospHorus affects the development and growth of roots and can impact flowering and fruit yields. Then there is potassium which helps the plants internal systems, such as pHotosynthesis and cell development, keep ticking along like they should.
Testing your soil’s macronutrient levels will give you a better idea of which fertiliser products to use, as you can buy the ones with the NPK ratio to suit your needs. Again though, do some research and find out what kind of soil is best for certain types of plants and you will be rewarded for your efforts.
Not all soil testers will be able to give you NPK readings, and the ones that do usually need you to mix some soil in a solution before testing it. This is the case with the Luster leaf kit we review a little later in this article.
Micronutrient testing
As important as getting the right NPK balance right is, those three nutrients aren’t the only things that your plants need to thrive. In fact, there are all kinds of other micronutrients that play an important role in plant and soil health, such as magnesium, zinc, calcium, and iron to name but a few.
Again, the key is the correct balance and to ensure you have that means testing the soil. I have to say though, that finding a testing kit that will give you an accurate reading of micronutrients isn’t an easy task at all, and most kits will focus mainly on pH, moisture, and NPK.
The following clip goes into more detail about both macro and micro nutrients, so take a look:
Which type of soil testing kit should I buy?
There are a few options available to people wanting to test their soil, and just giving a simple answer to the question “which soil tester is the best?” just isn’t possible as there are variables that come into play.
Some testers are more accurate, some give faster results, and others are the simplest to use. In the end, we figured it’s best to just describe the different types here for you and let you decide for yourself.
Digital soil tester
One of the easiest soil testers to use, digital soil testers are a good choice for people new to measuring soil pH levels, or for those who just want a quick reading. They can also be reused again and again, as long as you keep them clean and stored properly.
They aren’t usually thought of as great measuring devices for macro and micronutrients though, and you will more than likely have to buy batteries to power the tester. However, there are some very practical digital soil testers that you can simply stick into the ground and get a very accurate pH reading, and this makes them popular with beginners.
Recently there have been some new digital products that work with your smartpHone via Bluetooth, and also some other electric testers that are multi-functioning and claim to measure pH, NPK, and moisture. In my experience though, it is hard to find one tester that can accurately measure all those different kinds of things without it costing a lot of money.
Strip test soil pH kits
Strip test kits should be pretty familiar to you, as I’m sure you remember doing the exact same thing in your high school science class back in the day. The only difference here is that you mix some of your garden soil with a solution before dipping the strips in there.
The results usually come in less than a minute when using strip tests, and this is definitely the case with the Garden Tutor soil pH strips, but you will have to compare the colour of the strip on the provided chart and work out the pH level from there. Obviously, this isn’t as accurate as a digital tester, and the chance of human error is higher too. On the plus side, they are usually inexpensive tests to buy and you can measure multiple samples with a single kit.
Chemical /dye testing kit
These work in a similar way to the strips we just talked about, and you’ll have to get a soil sample from your garden and then pop it into the supplied vials. Next, you add one of the capsules that come with the kit and shake it. Just like with the strip tests, you will then match the colour of the solution in the vial with ones on a chart that shows the pH level.
Chemical kits aren’t the most accurate ways of testing your soil’s condition, but they will give the casual gardener enough info to go with, and they aren’t too expensive. The number of tests you can do is limited though, and once the reagent runs out, it’ll be time to buy another kit.
Lab testing kits
These testing kits are not completely DIY, and you will have to wait a while for the results, but they are the most accurate way of measuring the pH and nutrient levels in your soil.
How they work is that you take samples of your soil and prep it in the vials that come with the kit. Then you send the vials via mail to the laboratory address that comes with the kit. The lab then tests the samples and gets back to you with a detailed report within a couple of weeks. You can also visit your local nursery and ask them to do the same thing for you if you prefer.
These tests are great for gardeners who really want to fine tune their soil for perfect growing conditions, but you have to be patient and wait for the results to come back, and for most people starting out, this might seem like a lot of hassle.
Analog soil tester
Analog testers can be good for measuring pH levels and moisture if you’re in a hurry. What’s more, they don’t require batteries and instead measure the natural electrical energy in your soil through 1-3 rods.
Although they are easy to use and fast, the results aren’t as precise as some digital soil testers, and you won’t really know about the NPK levels or other useful information. They do have their uses though, and some can tell you how much sunlight is being received by your soil, but only at the exact time you are doing the test. They can also make very good moisture meters as is the case with both the XLUX and Gouevrn soil moisture meter.
Homemade pH test
You can actually do a very basic pH test using water, white vinegar, and a little baking soda. The results will obviously not be anywhere near accurate, but it can tell you if your soil is generally too acidic or alkaline.
All you have to do is grab two containers, make sure they’re nice and clean, and then pop a small soil sample in each of them. Mix around half a cup of water with one of the soil samples and then another half a cup of baking soda onto the same sample. If you see bubbles or hear a fizzing noise, it indicates that the soil is too acidic.
With the other sample, simply add half a cup of white vinegar and look for the same reactions as mentioned above- i.e., fizzing and bubbling. If this is the case, the soil is too alkaline. If nothing happens then your soil is probably quite well balanced, pH-wise.
The following clip shows what I’m talking about:
Best soil testers reviewed
Now its time to take a closer look at the best soil tester kits you can currently buy. We’ve had some hands-on time with a load of different kits and selected these few as the top options in their respective categories. However, there’s no such thing as a perfect product, and where any tester has fallen a little short, we have pointed that out in their reviews.
1. XLUX Soil Moisture Meter, Plant Water Monitor, Hygrometer Sensor for Gardening
Sometimes its easy to be enticed by products claiming to do everything but take the dog for a walk, but what I’ve found to be true is that more often than not, these multi-function products are ‘Jack of all trades, master of none’ situations. Before we get into the nitty gritty let’s take a look at a sensible review from a nice chappy:
So, when I was about to try out XLUX’s dedicated soil moisture meter, I had high hopes. Was I pleased with the results? I have to say that I was, especially when compared to many of its rivals like the Gouevrn or Kensizer that we also put through their paces. I definitely preferred this more when I compared the two analog soil testers together. I feel this gave a far more accurate reading for moisture hence being my top pick for soil testers.
This analog device is so straightforward and simple to use – you literally push it in your soil and watch the magic. There are no batteries needed, and only a single rod protruding out of the main meter. All you have to do is stick the rod down into the soil until it reaches about the same depth as your plant roots (roughly 2-5 inches) and then wait for the needle on the dial to stop moving to get your measurement.
The dial is very clear and easy to read, and is marked with ten levels of moisture from dry to wet. Now, that might not seem like the most scientific reading in the world, but for the majority of home gardeners and hobbyists it will do just fine.
I’d say this Hygrometer is sturdy enough, but the instructions that come with the product tell you to avoid hard soil as it could damage the measuring rod. I’d also say this to be true of rocks under the soil and hard roots too, so you can’t be too careless when using it.
When used properly though, it gives accurate readings and is perfect for those of us who are guilty of over or under watering on a regular basis. Please keep in mind though that this won’t let you know the pH or nutrient levels in your soil and is only for making sure your plants are getting the H2O they need.
Pros
- No batteries required
- Clear and easy to read dial
- Gives accurate moisture level readings
- Quick and easy to use
Cons
- Can only measure moisture and nothing else
2. Luster Leaf 1605 Rapitest Digital Soil Testing Kit
I’d heard mixed feedback from customers about the Luster Leaf Rapitest soil testing kit, but thankfully some very good, and detailed, advice about how to get the most out of it from a good friend of mine.
I think without this advice, I might not have chosen this testing kit to be featured on this list and I’ll explain why. You see, I’m not always the most careful and accurate measure of things, and I don’t always follow instructions to the letter (although experience is slowly teaching me to do otherwise), and with this kit that isn’t a good thing at all.
If you are the kind of person who got excited every time the Bunsen burners were brought out in science class, and it wasn’t to burn your friend’s workbook but to actually enjoy the experiment, then you will love the Luster Leaf kit. If not, maybe a different product would be better.
This kit does need you to get your measurements as accurate as possible, and to follow the instructions precisely and with patience. However, if you do take the time to get things right, it is a decent kit that will give you a lot of info on the nutrient levels in your soil, as well as pH.
What I liked about this kit is that you can select each of the NPK nutrients individually by pressing a button and then the device shows you whether it is depleted, deficient, adequate, sufficient, or surplus through LED lights. The pH level is shown through more LED lights running up the side of the device. It’s all very easy to read and understand.
The Luster Leaf isn’t the cheapest kit out there, but you do get a fair bit of stuff in the box. There are 25 capsules for running your tests, 4 colour coded test tubes and a tube holder, a pipette, and pH references for hundreds of plants as well as tips on fertilisation and adjusting pH levels.
Altogether, you can perform 25 soil tests- 10 for pH and 5 each for the macronutrients NPK. Unfortunately, this brings up the biggest flaw with this kit, and that is how difficult it will be to find replacements for the capsules here in the UK as this is a US product, and this obviously hurts the value for money rating.
Pros
- Great to be able to select individual macronutrients
- Easy to read LED display
- Can measure pH and NPK levels in your soil
- Kit contains a good deal of equipment
Cons
- Difficult to find replacement capsules from this brand
3. Sonkir Soil pH Meter, 4-in-1
It’s no secret that the world is suffering supply chain problems at the moment, and as most electrical goods are made far from our shores it means that we aren’t as spoilt for choice as we used to be when it comes to digital products.
This was clearly the case when we were looking for digital soil testers for this article, and many of the available products were basically clones of each other. Despite all this, I’m happy to say we managed to find a diamond in the rough with the Sonkir 4-in-1 soil meter.
Now, I’m not usually a big fan of multi-function electrical devices, as I’ve had some bad experiences, but I have to say that I was pleased with how Sonkir’s soil meter performed in all tasks and it’s basically a direct rival for the other multi use soil tester: the Kensizer. Is it the most accurate thing in the world? No, but that could be said for 99% of digital and analog soil readers out there. You want 100% accuracy? Then send a sample or two to a lab and wait. If you’re looking for a decent guideline, this is probably the way forward – but remember multi testers aren’t as good.
At only 12.2 inches long you can definitely say this is a compact device, and lightweight too, but I wouldn’t say that it feels flimsy at all. Don’t get me wrong, I wouldn’t advise playing rough with it, and just like with any similar device you have to be careful when inserting it into the soil, but overall, it feels sturdy enough.
This device can be used to measure moisture levels, give pH readings, tell you the current temperature, and also the amount of sunlight getting through to your soil. I liked that you can switch from Celsius to Fahrenheit, and also change modes with simple button pushes or switches. It’s very user friendly.
There is something that annoyed me about Sonkir’s soil meter though, and that is the auto battery save feature. Yes, I know it sounds like I’m moaning about a power saving feature, but it’s just that it automatically switches off the screen after a little while of no interaction. This ‘little while’ just seemed too short for me, and I felt like I was switching it back on again more often than I’d have liked.
Other than that little annoyance, I was pleased with how this product performed- giving quick results that are accurate enough for the average gardener to take advantage of. Is it perfect? No. But it’s one of the best options available at the moment.
Pros
- Digital display gives you a lot of information
- Selectable temperature readings from Celsius to Fahrenheit
- Lightweight and compact
- 4-in-1 tool and can be used to measure light, moisture, pH, and temperature
Cons
- Power save function kicks in a little too quickly for me
4. Kensizer Soil Tester, 3-in-1 Soil Moisture/Light/pH Meter
What I like about analog soil testers is that they are just ‘plug and play’. There’s no need to keep batteries hanging around, you don’t have to worry about a digital screen having problems, and they are usually quite affordable.
All these aforementioned things apply to the Kensizer soil tester, a lightweight 3-in-1 analog device that can give you readings on moisture, light, and pH by simply inserting the two rods into your garden soil.
These rods react with the natural electrical energy in the ground, and then use that to tell you what you need to know. From the time I spent with this gardening tool, I can honestly say that it surprised me how well it worked, especially for moisture and light.
The pH readings weren’t that accurate though, and I wasn’t expecting them to be, but they are good enough to give you an indication about what to do with your soil as long as the measurement is taken in wet soil.
On the plus side, the readings come back very quickly, so you can always do more than one test to see if you’re getting consistent results. Just remember to wipe the rods clean first. Also, don’t test this in liquids to see if it is calibrated properly, as it is not designed for that and you will get false readings.
Weighing under 100 grams, you can definitely say that this is a lightweight device. However, the meter feels sturdy enough, though you should still be careful not to damage the rods when you insert them in the soil like with all of these types of soil testers.
At first glance, the dial that shows the results looks a little cramped and confusing, but it only takes a minute or two to get used to the layout and then it is relatively easy to read. The controls to select the thing you are testing (moisture, light, etc.) are also really simple and can be used by complete beginners.
Pros
- Analog device and doesn’t need a power source
- Very lightweight at under 100 grams
- Can measure moisture, pH, and light
- Quick results
Cons
- Dial can seem a little over complicated at first glance
5. Garden Tutor Soil pH Test Kit (3.5-9 Range) | 100 Soil pH Test Strips
If you’re just looking for an inexpensive way to be able to test your soil’s general pH level, then you could do a lot worse than spending a few quid on this pH strip test kit from Garden Tutor. Before we get into the review – take a look at how easy pH test strips are to use – in my personal experience they are one of the easiest ways to accurately test:
Not only are pH test strip kits one of the cheapest ways to check those levels, they could also never be called sluggish, usually giving you results within a single minute, and with minimal messing around.
All you need to do is mix a 120ml soil sample in the same amount of water and then dip one of the strips into it for a few seconds. After you take it off, you shake off the soil and excess water and then compare the colours of the three tabs on the strip to the chart featured on the bottle. It’s quick and easy, but I have to say that sometimes it can be a bit hard to find a perfect match for all three colours, so it isn’t as accurate as a good digital meter.
Included in the bottle are 100 strips, so you’re definitely getting value for money. On the other hand, though, and as I just mentioned, the accuracy of the results of the tests are not the best with any kind of strip test, and this is no exception, although I noticed that the readings at either end of the scale were more accurate than in the neutral zone.
If you just want a quick way to know which end of the pH scale your soil is on, in a general way, then these strips can be useful. If accuracy down to decimal points is important, then this type of kit is not for you.
Pros
- Good for up to 100 soil tests
- Good value for money
- You can get results in under 1 minute
- Very simple way of testing pH
Cons
- Not the most accurate in the neutral zone of the pH scale
6. Gouevn Soil Moisture Meter, Plant Moisture Meter Indoor & Outdoor
I’ve said it before, and I’ll say it again- the simpler the tool, the better it usually is, and after testing out Gouevn’s soil moisture meter over a few days, my opinion has only been cemented.
There’s nothing fancy about the Gouevrn, well apart from that almost unpronounceable name that is, but it is a solid and dependable tool that gives you very accurate readings of the moisture levels in your soil.
The dial to show these readings is large, clear, and marked with numbers, colours, and the words dry, moist, and wet, so there’s no way anyone could get confused about what the meter is trying to tell them.
Using this moisture meter is child’s play, just like with most analog soil testers. You simply insert the single rod carefully into your soil and wait for the needle on the dial to settle. It really couldn’t be simpler.
As I’ve said numerous times in this article, you need to be careful when impaling the soil with the rod as they aren’t the strongest of things, and if your soil is visually dried out on the surface, don’t try to stick this tool down there. The soil needs to be at least soft to the touch in order for you to be able to use this moisture meter. The casing of the meter is a bit sturdier though, and it should see you through a few seasons as long as you don’t abuse or neglect it too much.
I found that the readings we got from the Gouevrn moisture meter were quite accurate, but one thing I noticed was that it wasn’t possible, at least with our item, to leave it in the soil while we watered it and see a change in reading. Instead, we had to take it out of the soil, wipe it down, and then reinsert it to see a change on the dial. Obviously, this isn’t exactly a hard thing to do, but it would have been nice to just to leave it in there.
My final thoughts on this product are that it is a good moisture meter for the money, and as long as you follow the instructions properly, especially the part about not testing it in water, you will get a useful product. Ignore this advice, and you won’t be happy with the results.
Pros
- Very accurate moisture readings
- Solid plastic casing for the dial
- Very easy to use, just ‘insert into soft soil
- Clear and easy to read dial
Cons
- You have to pull the rod out and reinsert it to see changes in the soil’s moisture levels
