Even though I added an entire truckload of horse manure, several lawn-tractor cart loads of seaweed, and so many wheelbarrow loads of compost that my body ached from moving it, the peppers, tomatoes, and other fruiting plants in my garden had less than ideal yields this year. The lower-than-normal harvest of tomatoes especially suggested that soil issues might be to blame. So to find out, I ordered a soil test from the Soil Nutrient Analysis Lab at the University of Connecticut. Fall is an ideal season for getting such a test done because you then have time to correct any soil problems before your next spring planting.
When I saw my test results, I was greatly surprised at how acidic my soil was. New England soil is known to be generally acidic partly because much of it is glacially derived from granite rock, but also because emissions from industrial factories to our west cause acid rain in this part of the country. In addition, for my soil in particular, the highly acidic peatmoss in the planting medium I’ve been using to start my seedlings for the past 20 years has undoubtedly also been contributing to soil acidity in both my garden and my greenhouse. But the effects of all these factors together was far greater than I had expected. This information alone made my soil testing worthwhile.
Fortunately, high soil acidity (meaning a low value on the pH scale) has a well-known antidote, which is to add the calcium carbonate contained in lime. As the lime slowly dissolves in moist soil, a chemical reaction is triggered that raises the pH, bringing it closer to a neutral level. The lab at the University of Connecticut suggested 100 pounds of lime for every 1,000 square feet of soil, which for me meant that about 70 pounds of lime needed to be spread. Doing this in the fall worked well because it takes about six months for the desired chemical process to occur. So by spring, if I’ve added enough lime, I should have made the soil measurably less acidic, although by how much can only be known with another soil test. Note that lime isn’t a fertilizer. But by lessening soil acidity, it does make it easier for plants to absorb the essential nutrients that fertilizers provide.
To further combat acidic soil in both my garden and my greenhouse, I’m taking some additional steps. One is switching to a coir-based potting medium for starting my plants, coir having quite close to an optimal pH level. I also plan to add plenty of compost to my soil come spring. Because my compost is made from yard, garden, and kitchen waste, it has a near-neutral pH, so adding it helps to neutralize the soil in addition to providing nutrients.
The soil test that I received contained lots more valuable advice. Since all this information is too much to include in a single post, I’ll say more about the other elements in the garden next month. The takeaway message now is that, if you want your plants to thrive both in your greenhouse and outdoors, knowing the composition of your soil helps enormously when you are growing your own harvest.