Changing soil pH is an easy process and most people do it without realising it. Have you ever thrown the dregs of your coffee cup onto the garden? If so, you changed the pH in the direction of acidity.

Changing the soil pH needs to be done slowly and mindfully. If we make the changes too suddenly we risk killing off all or most of the inhabitants in the soil. It would be like someone taking us from our normal oxygenated living situation and putting us in a 10,000 feet above sea level with its attendant thin air.

We could breath that air but only if we slowly acclimatise. The same is true for the microbes. Slow changes allows the soil biome to adapt to the changes over time.

Raising soil pH

To raise the pH of soil we generally use an alkalising agent such as agricultural lime (aglime). It’s a powder that will alkalise soil. We can also use crushed eggshells however unless we powder the shells, crushed shells take more time to alkalise than powder.

For the best results I put a little bit (a pinch) of aglime into a watering can and fill the watering can with water and then water it into the soil. That ensures a more even distribution and reduces the risk of microbe shock. A little bit of aglime will have an alkalising effect. Add a little bit and then wait for at least a few weeks before retesting the pH.

Reducing soil pH

To reduce the alkalinity and increase soil acidity we can use a host of things. In horticulture it’s customary to use sulphur however anything acidic will generally work. Urine is acidic as is coffee, lemon juice and a whole host of things we consume daily.

However all of these other things… urine, coffee, lemon etc add other nutrients other than one that will alter the hydrogen ions. If you have a salty diet, you might not want your salty urine on your soil. Therefore, powdered sulphur is the best for altering the least other chemical elements.

To acidify a soil, we use a tiny bit of acidifying agent and dilute it or water it in as soon as possible. We want an even steady mix and we want to reduce the risk of harm to our earth worms and microbes. So we add a little bit gradually and over time.

If we use the process I’ve covered here and the mix we choose is diluted into water then we can test the soil in about 2 to 3 weeks to see the change in pH.

For the best and most lasting results, once we alter the base soil’s pH we should use composts and mulches to help build up a habitat for more microbes to flourish. The more diverse microbes we have the healthier the soil and more neutral the soil’s pH will become.  

As a side note, next time you’re in a landscaping or gardening store, have a look at the ingredients in a bottle of chemical fertiliser. Notice how much sulphur is in the mixture. Imagine what all that sulphur is doing to the soil…

Click here to read more about soil pH.

Categories: soil enhancement


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