A lesson learned anew: Test soil before planting

“No occupation is so delightful to me as the culture of the earth, and no culture comparable to that of the garden. Such a variety of subjects, some one always coming to perfection, the failure of one thing repaired by the success of another. … Under a total want of demand except for the family table, I am still devoted to the garden. But although an old man, I am but a young gardener.”

Thomas Jefferson, Aug. 20, 1811

We created a new raised bed in Marjorie’s garden this spring, a berm formed from purchased loam. The entire garden is sited on ledge covered with only a few inches of native soil, so all of the existing beds were started this way, their soil depth maintained over the years with generous top dressings of compost. In the oldest beds you can sink a spade up to the hilt before hitting rock. High-bush blueberries, raspberries, strawberries, onions, tomatoes and other vegetable crops all thrive in these beds.

Marjorie began construction of the new bed last summer, piling the loam on top of a fabric weed barrier. Weeds grew in the new soil, creeping in from the edges or sprouting from windblown seeds, and these were removed with the first turning of the soil this spring. Several wheelbarrow loads of composted goat manure were then forked into the soil.

I wasted no time in planting the entire bed with cucumbers and sunflowers. At the end of the day, Marjorie found me leaning on the garden rake, content with my accomplishment, and announced that the results of a soil test on the loam should arrive any day. There was more than a hint of chagrin in her message.

When the soil test report arrived two days later, we learned that levels of phosphorus and calcium were above optimum while levels of potassium, magnesium and sulfur were below optimum. The pH of the loam, 7.1, was well above the optimum 6.5.

At present, the sunflower seedlings look good, but the cucumbers are failing, perhaps a result of the high pH, but also because temperatures may be still too cold for cucurbits. In the harsh light of the soil test results, however, I will start over, throw out the declining cucumbers and transplant the sunflowers to a holding area while I rework the soil chemistry.

Instructions for correcting the nutrient deficiencies and high pH came with the soil test report and were geared to our desire to have an organic garden. To correct the deficiencies in potassium, magnesium and sulfur, we will apply Sul-Po-Mag, the commercial name of a naturally occurring mineral containing significant quantities of sulfur, potash and magnesium. Water-soluble, it can be broadcast at the recommended rate and tilled into the soil.

To lower the pH, we were advised to apply elemental sulfur, tilling it in well. Again, the report told us exactly how much to apply.

Taking into consideration a relatively high organic matter content, the report also advised that we bolster the new bed’s nitrogen levels by working in either blood meal or soybean meal. The addition of the goat manure should serve the same need, I think.

It seems that there are some lessons that this young gardener must keep learning. Have the soil tested, and then plant. I blame my failure to follow this rule on unbridled enthusiasm to be planting something.

All the information you need on how to have your garden soil tested can be found in the University of Maine Cooperative Extension Bulletin 2286, www.umext.maine.edu/onlinepubs/htmpubs/2286.htm. Or contact your county Extension office at http://extension.

umaine.edu/counties.htm or the Maine Soil Testing Lab at 581-3591. At $12 a sample, a soil test is the best money a gardener can spend.

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to rmanley@ptc-me.net. Include name, address and telephone number.