Plant Doctor Archive

Macrocarpa mulch for sandy soil

Question I’VE been given a couple of trailer-loads of mulch made from macrocarpa and was told that if I put it on my garden, it will make the soil acidic. As I live at the beach and most of my garden is basically sand, I need mulch for the summer. I don’t know what the pH of my soil is and don’t know what pH is normal for sandy soil. Any help would be much appreciated.

Answer  SANDY soil needs lots of organic matter like compost and mulch. Adding a layer of mulch helps conserve moisture as well as building up the soil when it breaks down. As far as I’m aware, macrocarpa is not overly acidic, unlike pine needle mulch.

You can test your soil pH easily by getting a pH Tester Kit from your local garden centre. These cost only a few dollars and will provide a rough indication. It’s best to test the soil in at least three different places on the property, as soil pH can vary within a few metres.

Sandy soils are usually more acidic due to nutrients being leached out of the loose structure. You may need to adjust the pH of your soil now or at a later date by adding limestone or garden lime. To get a pH of 5.5–6.5 for a sandy soil, you will need to add 100–150gm per sq.metre of soil.

Weekend Gardener, Issue 107, 2002, Page 22