Quite often I hear people say to me that there plants aren’t  doing so well.  They tell me, “I keep adding fertilizer but it just does’nt seem to be getting any better, in fact sometimes worse!” My reply usually comes with, “Have you checked your soil pH?” To which I often also hear, ”What’s pH?”

pH (or percentage of hydrogen) is a typographical scale that tells how acidic or alkaline your soil is. The pH scale range is 0 (which is acidic) to 14 (which is alkaline) with 7 being neutral.

If soil is too acidic it will be infertile and lock certain nutrients away from the plants thus making it become sick and stunted, if the soil is too alkaline, it becomes toxic and will poison plants too. Most vegetables grow best between 6 and 7, which is slightly acidic.

The importance of correct pH is so vital to the plants health, just as water, sun, love and fertilizers are. In fact without correct pH in the soil, the plants will surely suffer distress in some form or another.

Think of correct soil pH as a key for instance. If the wrong key is in the wrong lock it can’t open the door. But if the right key is in the right lock, the door opens. This is the same as incorrect pH.

To make things even more confusing, there are certain plants and vegetables, that require different pH levels, some like acidic and some like alkaline, while the most prefer neutral to slightly acidic (6-7).

There are many ways of adjusting the soil pH to suit the plants requirements. There are choices between artificial, Bio-organics ( half and half) and organic/natural. I prefer the latter as its the best and least harmful to the most important little dudes in the soil, the Microbes and beneficial organisms. Manures and mulches are the best way to get correct pH, as they break down slowly making the levels settle and rise accordingly to the soils needs.

When using artificial supplements, the soil changes rapidly and thus the plant and microbes have a harsh time adjusting to the new levels. This also doesn’t last as long as you may think, compared to manures there is about a ¼ life span. So basically, organic manure will last about 2-3 months whereas artificial will only last around 1 month respectivly.

So what is organic? Basically anything that has a carbon atom and once lived. When inorganic meets organic there is an uptake issue due to the lack of carbon atoms and sometimes the plants react both positively and negatively.

Things such as yellowing and chlorosis around the leaves, stunted growth habits and general poor health are signs that there may be a pH issue and to check it out is wise.

Let’s have a squizzy at how we can do this.

There are two main ways to check the soil pH. Theses being either a probe type instrument or a powder/dye chemical set. The latter is by far the best as it demonstrates a larger, more accurate reading as opposed to the probes. But then again, it depends on the amount you spend on both tools. I myself use a combination of both. The probe is simple to use, stick it in the ground around the root zone and depth, wait a few minutes and read the dial. The other, is a lot more involved with adding soil, powders and dyes together can seem overwhelming to some so the probes would suit better in that case. For the initiated, doing both allows a better, average reading.

So what do we do if we find that our soil is, too acidic or too alkaline?

If you have acidic soil – A quick way to get the soil to adjust and go towards neutral/alkaline is to use garden or better dolomite Lime. It is used to increase the pH. There are two basic types of lime – agricultural lime which only contains calcium and the preferred choice dolomite lime which contains both calcium and magnesium.

How much do you add in? These are approximate amounts to raise the pH by 1 point.

  • Sandy soil add 5 pounds per 100 square feet
  • Loam soil add 6 pounds per 100 square feet
  • Silt or Clay soil add 8 pounds per 100 square feet

If you have alkaline soil pH:

To correct soil that is too alkaline you will need to add powdered sulfur.

How much do you add in? These are approximate amounts to lower the pH by 1 point.

  • Sandy soil add 1 pound per 100 square feet
  • Loam soil add 1.5 pounds per 100 square feet
  • Silt or clay soil add 2 pounds per 100 square feet

Both lime and sulfur are considered soil conditioners. It is important to add either separately from soil fertilizers; a few weeks to a month before is best but always make sure you follow the manufacturers instructions ok guys!

When adding lime and sulfur to your garden beds make sure you rake it evenly into the soil. If your soil is extremely acidic or alkaline make an application in the SPRING TIME and another one in AUTUMN so as not to give the soil too much all at once. It can take a few seasons to get to the optimum number you want.

But in my opinion, organic manures are the best way to raise and lower the pH. Manures such as Sheep poo and Cow poo are the best. Slowest brakedown points and allows the soil to react accordingly to the breakdown of the manure and the most important, the Microbes movements.

I add a 30-40L bag of manure to 1m2 and rake it in just before winter and just after summer myself. No need for any other additions if you keep your soil health checks up and maintenance.

I hope this help explain a little bit about pH and its ever important role within gardening and successful gardening!


By Mark Petruzio


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