This year is our first year in our house, and the first year we’ve used this garden space. The raised beds in our garden were a big selling point of the house. Last winter we bought our seed for the year, the garden tools we were lacking, and some soil test kits. Busy with life, we got much of the garden planted late (not terribly late, just later than we wanted) and skipped the soil tests. Bad idea.
About half way through the growing season, the lackluster performance of some of our veggies prompted us to pull out the test kits and check our soil out. The most important discovery is that throughout our garden the soil PH is far higher than it should be, over 8 in some places. Most plants perform best in a range of 6 to 7, with some acid loving plants performing well as low as 5. An elevated soil PH can keep plants from absorbing available nutrients, which inhibits growth, invites pest problems, decreases yield, and makes the food produced less rich in micronutrients.
The most common method of lowering soil PH is with a commercial soil acidifier, the most common organic acidifier being sulfur. Elemental sulfur is natural and organic, but can be harmful to plants if applied too directly, or to liberally. It is available in quick acting powered form that can be worked into the soil between crops (and allowed to rest for a week or two before replanting anything), or slow acting forms that can be worked into the soil, or used as a top-dressing while the garden is planted.
Applying pure powdered sulfur is the quickest fix. Some simple math can tell you how much to use per square foot to lower the soil ph by a given amount. See the directions on the packaging for more information. While this is the quickest way to fix a high PH, it can be damaging to soil organisms, and is easy to over or under apply.
Slow acting sulfur dissolves more slowly, which is better for soil organisms and plants. It is also less concentrated, which makes it easier apply the correct amount and distribute evenly.
Another, more sustainable solution, and one that can be utilized without locating or buying sulfur is compost. When compost decomposes, it is generally acidic, especially if it contains many leaves or wood products (bark, wood shavings or chips, sawdust, etc.). Applying compost to your garden regularly will usually lower the soil PH over time. As you grow things and compost the garden waste, recycling that organic matter back into the garden will slowly bring the PH to a more desirable level. The time it takes to fully correct a PH imbalance can vary greatly with the amount of compost used and the type of material being composted.
If your PH is already too high, do not use wood ash or lime in your garden, as both of these will raise the PH.
We intend to fix our problem with a combination of the long-term solution of composting and the quicker fix of slow-release sulphur. The one we have begun using is Espoma Organic Traditions Soil Acidifier. The hope is to get the PH down to acceptable ranges quickly using the sulfur, then further work to bring it to optimal levels through repeated applications of compost. Luckily our compost should be fairly acidic, as it contains the wood shavings from our chicken coop bedding.
If you aren’t sure what your soil PH is, an inexpensive PH meter is a great option. Another good option is a soil test kit. Kits like this give a dependable reading of PH, while also providing readings of the three major nutrients plants need. Make sure to get multiple kits, or a kit that has more than one use, so you can test initially then again after you’ve made amendments to see that you’ve actually fixed your problem. A meter is reusable again and again, and will be more economical if you plan to check your PH frequently.