Best Way to Acidify Soil for Blueberries, Rhododendrons and Azaleas.

how do you lower the pH of your soil that's what we're going to investigate today I'm going to discuss several methods that are properly recommended online some work and some don't work we'll sort through that mess and then I'll give you some advice about buying the products that actually work and how to use them now in this video I'm not going to worry about why you're lowering pH I'm not going to discuss the kind of plants that need lower acidity that's a topic for another video I'm going to assume you've done your homework you know you want to lower the ph and now you're looking for a solution but before we go on I have to give you one piece of advice changing soil pH is difficult and it's not long lasting once you lower the ph you're going to have to keep doing something to that soil to keep the pH low it's not a one-time fix so if at all possible grow plants that grow in the soil you have and don't try to change pH but okay you you want a lower pH let's figure out a high here's a list of the options I'm going to have a look at compost coffee grounds pine needles oak leaves peat moss several chemicals and also fertilizer all of these suggestions are reported to add acid to your soil it's the acid that will acidify the soil and that's true but I want you to consider something when rain comes through the sky it picks up CO2 water and CO2 form carbonic acid when that rain hits the ground it has a pH of around 5.5 that's fairly acidic it has been raining for millions of years and your soil is still alkaline or perhaps the pH is a little under seven but you want it lower for the plants you're trying to grow so this acid rain that has been falling forever is not getting the pH loan what that means is that we have to add had a fair amount of acid more than rain to accomplish the job now let's look at some of the claims for doing this the first one is compost and this is recommended by a lot of people now if we look at finished compost the pH of that is around neutral pH of seven or slightly higher a lot of compost is around the 7.4 Mark so it's not acidic I don't understand why people think that we can add compost to soil and drop the pH it's not an acidic material when you add composted soil it's adding organic matter organic matter buffers pH what that means is it prevents the pH from changing very much so if we add compost to soil and it's alkaline the soil is going to tend to stay alkaline even if we treat it with acids that buffering capability keeps the pH where it is it doesn't make the soil very acidic compost is not going to work how about coffee ground for some reason a lot of people think coffee grounds are very acidic but they're really not now depending on what kind of beans you're using and how the coffees Brew there is a variation but most coffee grounds have a pH that's very slightly acidic 6.5 to 6.8 is a very common range so they're very slightly acidic which means they're going to have virtually no fact on the pH of soil happy grounds just aren't going to work for you pine needles I see this one all the time pine needles are acidic collect them from the Pine Forest bring them home put them in your soil or use them as mulch and the pH drop for some reason people think that pine trees make the soil where they're growing acidic and that's not what happens pine trees like to grow in acidic soil so you find more of the them if the soil is acidic but they grow just fine in alkaline soil too I mean my pH is 7.4 and we have Pines growing here they self-seed all the time the soil underneath them stays at 7.4 and in fact scientific Studies have shown that even 50 years later that pH hasn't changed pine needles are slightly acidic when they're green and on the tree by the time they get brown and fall off they're no longer acidic they do not acidify soil oak leaves again same claim as pine needles same story oak leaves are slightly acidic when they're on the tree but by the time you collect them they're not acidic so you're not adding any kind of acid to your soil they have no effect on the pH of soil they don't work how about peat moss well pmos is at least acidic it has a pH of about 5.5 so it makes sense and if I add this to soil it will lower the pH of that soil and that's actually true it does that the question we have to ask is how long does that lower pH last a number of years ago I went looking for an answer to that question and I couldn't find it anywhere so I did my own study now this isn't very scientific but I did do several samples and a control and the results are pretty clear here are the results I mixed pmos with my soil at the time the pH of my soil measured at 7.7 and I mixed peat moss and soil in various amounts so I had a pot with just peat moss and no soil and I had a pot with soil and no peat moss and then I had three pots in between these with 25 50 and 75 percent peat moss then I measured the pH of that soil over a period of time so you can see at the start of the experiment the PhD did drop and the more pmos that was added the lower the ph which is exactly what we'd expect the problem is that even after one day the pH of all the pots that had soil in them was up over seven so the acidifying effect of peat moss lasted less than a day lots of people swear by peat moss and if you add huge amounts to soil you will get a slight drop in pH for a certain period of time but as you've seen after nine days the pH is back up to where it was that's not much good for growing plants that need a low PH so peat moss is a very poor choice for trying to lower the pH of your soil now let's look at some chemicals that are commonly recommended the first one I'd like to look at is sulfur when sulfur is put into soil the microbes come along and they change the sulfur into a compound called salt fade sulfate is the main ingredient in sulfuric acid it's an acid when that's added to soil it does lower the pH of soil an important Point here is that this reaction is not a chemical reaction it's a biological reaction it requires the microbes to carry it out if I take a pot of sterile soil and I put sulfur in it the pH won't drop sterile soil has no microbes so the sulfur stays as sulfur and it has no effect on ph now that won't happen in your garden or in potted plants because all that soil has microbes in it but as you will see later the fact that microbes are doing the action is important in this discussion there's another compound that's recommended a lot and that is aluminum sulfate notice that part of the name is sulfate that's the same sulfate that's created with sulfur sulfate is an acid and it does lower PA aluminum sulfate will lower the pH of your soil because the sulfur does not have to be converted to sulfate aluminum sulfate is actually much faster than using sulfur your pH will drop almost instantly within a day or two but there's some downsides to using aluminum sulfate first of all it's much more expensive than sulfur the second problem is that aluminum is a metallic ion we don't want those kind of heavy metals in our soil they're toxic too much aluminum is toxic to us and there have been reports that aluminum might be causing diseases in humans we do know that too much aluminum is toxic to plants so you can use a little bit of aluminum sulfate and drop the pH a little bit but if you need a whole bunch of it to drop the pH farther you can add so much aluminum that you're making the soil toxic to plant another reason you shouldn't use aluminum sulfate is that it's less of effective than straight sulfur because it's got the aluminum component in there you have to add about five times as much aluminum sulfate as sulfur doesn't make it very effective stay away from aluminum sulfate if for no other reason because of its toxicity in soil now because of that toxicity some people have come along and said well why don't we use iron sulfate again you'll recognize a sulfate part that is the acid part iron sulfate will lower the pH of your soil it is also fast acting it's already in the sulfate format so as soon as you put it on your soil PH starts dropping much faster than using sulfur but again we have the same kind of downfall iron is not as toxic to plants or humans so that's not as big of an issue but it's less effective and you're going to have to add five times as much as sulfur and it's more expensive for those reasons iron sulfate is not really a good choice but it does work how about fertilizing how do fertilizers affect the pH of soil and can they be used to lower the PA well the answer is maybe it depends on the fertilizer now some fertilizers have ingredients like ammonium sulfate calcium sulfate potassium sulfate is very common in fertilizer and let's not forget magnesium sulfate which is Epsom salt and if a fertilizer is adding magnesium then it probably is in the form of magnesium sulfate again you'll recognize all of these as nutrients plants need but they're in a sulfate format the sulfate will acidify the soil so if you buy fertilizer with a lot of sulfate compounds in it it will lower pH the other main ingredient in fertilizer is nitrogen and this is kind of an interesting nutrient fertilizers have nitrogen in three common and formats nitrate ammonium and urea and you can tell which one they have by looking at the label personally all fertilizers should have this clearly marked right on the front of the bottle but most products tend to hide it because they think oh gardeners don't really care but you should care look at the label on the back and it will tell you which of these it has nitrate ammonium or urea and it's important if you're working with ph when we add nitrate it actually increases the pH or has no effect at all if we add ammonium ammonium actually lowers the pH of soil so if you're trying to get a lower pH you want your soil more acidic than pick a fertilizer that has ammonium in it and not nitrate in fact a really good ingredient is ammonium sulfate the ammonium lowers pH and the sulfate lowers pH and together they're more effective than the two separate what about urea it's an inexpensive form of nitrogen and so you do find it in a lot of fertilizers well urea doesn't stay as urea and soil microbes come along and converted to ammonium since ammonium lowers the pH so will urea so urea is also a good choice in your fertilizer if you're trying to lower PA if you don't care about the pH urea is still a good choice because it's a pretty inexpensive form of nitrogen now the advantage of picking a fertilizer with ammonium and sulfate in it is that these are released very quickly in the soil they lower the pH of soil almost instantly a very fast reaction it's a chemical reaction they don't have to wait for microbes to come along and make those changes so pick the right fertilizer and it will lower your PA the problem you have with fertilizer is that you can only add so much you might need to drop your pH this much but if you add this much fertilizer it's toxic to plants you know that if you had too much nitrogen to your soil you'll burn your plants you'll kill your plants so with fertilizer you can only add a certain amount and that only lowers the pH a certain amount it's not a good way to lower it a long way so what is the solution the solution is to use the right kind of fertilizer and at the same time use sulfur use the two together sulfur is the main ingredient you're going to use the lower pH but whenever you fertilize you're going to use the right kind of fertilizer to keep it lower or lower it a little bit more that's the real solution now let's have a look at Saul for a little closer when do you apply it what form of sulfur should you use how much should you use those are all important questions it's no good just buying some stuff and spreading around and hoping the pH will be where want not that simple let's go back to something I discussed a couple minutes ago sulfur has to be converted to sulfate and that's a biological reaction microbes have to carry out that reaction for you now the first important point is that that's a slow process if you put sulfur on today and you've got lots of microbes there the pH is not going to drop quickly it takes months anywhere from six months to a year for that pH to drop it's a slow process I see a lot of advice online that goes something like this apply the sulfur in the fall let it sit there all winter and then in spring when you're ready to plant the pH will be lower you've given those microbes a chance to convert the sulfur to sulfate sounds reasonable except for one thing these microbes aren't active in the winter time they're only active once the soil temperature is above 55 degrees Fahrenheit now if you're in a a warm climate that may work fine all winter long the microbes are active it's above 55 fahrenheit everything works but if you're in a cold climate I am a zone five when I put salt from the soil in the fall it just sits there till spring nothing happens until the following summer so we need about six months for this to happen during the warm weather so you might as well spread it in Spring there's no point of putting it on in the fall now how do you put it in the soil do you layer it on like a mulch or sprinkle it around or dig it in well remember the microbes have to be there they have to act on the sulfur so we have to get it in the soil now in a vegetable garden the best thing to do is to dig it right in if it's a permanent planting you're trying to reduce the soil PH spread it on the top and then scratch it into the top inch or two we have to get it in the soil the other reason is that sulfur is a very fine powder and if you just sprinkle it around it's likely if the wind will blow it away so put it on the soil get it into the soil now the microbes can act on it what form of sulfur should you buy and there are a variety of choices here so the two common ones is powdered sulfur and pelletized sulfur now I recommend you use powdered sulfur mostly because of cost it's a yellow powder you can spread it around I mean you don't want to breathe a whole pile of it in but it's not really going to harm you it's a very safe chemical very inert it doesn't do anything it does have a bit of odor but not too bad so that's what I would recommend for a commercial farming operations they now make pelletized sulfur they squeeze it down into a little pellet so it's not so dusty and it's a little easier to apply the problem is that it takes time for that pellet to now break apart and so it slows down the process and it's more expensive to buy the pellets but either of those products will work just fine now if you're going to buy some of this try to get it from a feed store or a place that sells it in larger bags It's relatively inexpensive now I looked up powdered sulfur now this comes in 50 pound bags and it's pure sulfur it's a hundred percent sulfur and that bag costs about thirty dollars so it's a dollar a pound now the other alternative is you could go down to your Nursery or your home hardware store and buy one of these little bags and I looked up one of these products too I found this online the espoma organic acidifier now it's available in 30 pound bags too but it's only 30 percent sulfur the other 70 percent is just some sort of inner material that's of no value to you and the price is a lot more expensive when you actually calculate the cost per pound of sulfur it worked out to 18 a pound compared to one dollar a pound so don't buy the fancy Brands go and find some pure agricultural sulfur and it's very inexpensive now how long does it take to react in soil well it depends on a lot of things how many microbes you have in the soil the soil temperature how well it's mixing the soil and so on but it is a slow reaction you'll start seeing a drop in PH after about three months but it can take a full 12 months to see the full drop the full conversion of that sulfur to sulfate it's a slow process so plan for that how much do you have to add well there's three questions you have to ask yourself what is your starting pH the higher your pH the more you're going to have to add to make it aesthetic what is your target p8 are you trying to go from 7.5 to 6.5 or are you trying to go from 7.5 all the way down to 4.5 which is what a Alias and blueberries like so what is your target pH and the third thing that's important is the type of soil you have it turns out that organic matter in clay act as buffers we talked about this a little bit already what that means is they stabilize pH they make this soil stubborn they turn it into soil that doesn't want to change pH even when you put some sulfur on it that's what buffering it they slow down the reaction and soar with a lot of organic matter and or clay requires more sulfur to drop the pH of your soil so the soil type is important now here's a chart with some value and you can see different starting points different ending points and different types of soil and the chart tells you how many pounds of sulfur you need for every 1 000 square feet and when I say one pound of sulfur I mean pure self if you end up buying a product that is only partially sulfur you'll have to add more of it to compensate if you have to add a lot of sulfur to get to the pH you want it's a good idea to add a little bit at a time add some every four months or so spread it out over the next year so I've given you a lot of information so let's summarize if you want to drop the pH in your soil make sure you really need to do that I strongly recommend you grow things that grow in your soil and don't bother dropping PA if you need to drop the pH use sulfur as the main ingredient to do that if you just want small drops in PH and you're fertilizing you can use ammonium sulfate fertilizer and that will give you a bit of drop in PH but the thing that works best is sulfur if you want to learn more about soils have a look at my books soil signs for garden and if you want to learn more about soil myths have a look this video right here happy gardening

Channel: Garden Fundamentals

Views: 257,725

Keywords: Blueberries, Rhododendrons, Azaleas, vinegar, sulfur, sulphur

Id: 00nNA-RsFds

Length: 21min 5sec (1265 seconds)

Published: Sat Aug 05 2023