A Healthy Soil Diet -- Drought Resilience in Your Garden

Drought may be the “new normal” even here in New England.  This year, most of the state has been in severe drought, and 2010 and 2012 were two of the hottest growing seasons on record, with precipitation below 50% for some of that time.

Source: National Drought Mitigation Center

In our first blog post we highlighted the importance of deep watering, especially of new transplants.  While watering is critically important, there is a more profound leverage point in our landscapes: the soil itself.  

The health of your garden soil can make the difference between plants that wilt and turn yellow in summer, and a garden that stays vibrant with minimal watering.  The biggest factor in terms of how much watering you have to do is how much organic matter (basically, compost) is in your soil.  

For every 1% organic matter, each cubic foot of soil can hold 1.5 quarts more of water. Imagine a 1 cubic foot sized milk crate is a cubic foot of soil; these quart-sized water bottles illustrate just how much water that soil can hold:

Organic matter and water holding capacity

When it rains, or when you water your plants, you want the soil to hold onto as much of that moisture as possible.  

One of the gardeners we work with in Florence has been composting regularly for years.  Besides new transplants, she did not water once this season -- and her garden flourished.  When you dig into her soil, it’s like cutting into chocolate cake: soft, dark, and moist.  All that organic matter acts like a sponge, and also serves as a home for desirable microbes, insects, and worms which further contribute to a healthy soil structure.

Is there such a thing as too much compost?  It turns out there is, although opinions vary as to the upper limit on organic matter.  UMASS Soil & Nutrient Testing Lab says 8% in a vegetable or ornamental garden is the limit -- after that, things get out of wack due to too much organic matter. The extra compost acts as a greedy actor in the soil, holding on tight to nutrients and keeping them from your plants. During storms, these unused nutrients can leach into nearby waterways, causing algae blooms (that green color you see in lakes and ponds) that can be toxic to the watershed’s delicate ecology.  All that water-holding organic matter can also waterlog your plants.

Tracy Allen of the UMASS soil lab tells us that too much organic matter is like eating a diet of all fruit -- it can throw your whole system out of balance.

One of the best things you can do to be proactive about soil health for drought resiliency is get a soil test.  This is a great time of year to do it! The lab is less busy and hence the results come back quickly. And it also happens to be a great time to spread compost (and other nutrients and amendments), following their recommendations.  This way, your beds will be ready for spring planting.  You can get a test done for cheap ($21) by simply dropping off a bag of your soil at UMASS’ soil laboratory.  Here’s an example of what your results will look like:     

Soil Test Image 1 bar graph.jpg

Make sure you opt into the Soil Organic Matter percentage test.

Handy bar graphs tell you what range your nutrient levels fall into, and each soil test comes with further written interpretation and recommendations below. We can help you make sense of any questions you have reading the report.

Need more help learning how to make your soil as healthy as possible, so you can take off for vacation next summer and not worry about your garden during another season of the “new normal”?  Disturbed by the prospect of another season of drought and its effect on your landscape? Click on the title above to tell us what's on your mind. Give us a call if you want help getting it done.