Q. Is there a mulch will not lower the pH of my garden beds as it decomposes? I have Goji berry plants which do best at a pH of 6.8 to 8.1. I want to use something to protect the soil from the summer sun and to prevent the winds from blowing the soil away.
A. Surface mulch always lowers pH as it decomposes. In normal desert soils, you can expect it to drop to about 7.6.
Hopefully you used a good compost when you amended the soil at planting. This will also help a lot. If you want to drop it more than that you have some options such as sulfur that has been ground to a dust rather than large granules.
|Soil sulfur is granular sulfur and slowly breaks down in soils. Its effect at lowering soil pH is minimal at best in desert soils.|
|Water dispersible or degradable sulfur is like a powder or dust. Because of its small size and large surface area, it breaks down very rapidly in warm soils and is a bunch better choice to lower soil pH than granular sulfur.|
An example is Dispersul which is water dispersable sulfur. Should sell for about $1 per pound or so. Sulfur granules just sit there and don’t dissolve in our soils and about the same price. Sulfur needs moisture and warm soil temperatures to work.
|I was surprised when this product dropped the pH of water down to 3.5 in about 15 seconds. It doesn't need warmth or microorganisms to work.|
The other is a product I have worked with called Garden Magic which drops the soil pH without warm soils. It will drop pH in water to about 3.5. Works very very well and also sells for around $1 per pound and it is in a $30 bag. I think the Dispersul is a 50 lb bag. Both you can get at Viragrow in North Las Vegas. I don’t think any other retailer carries it. They all carry sulfur granules instead. The other option is aluminum sulfate.