The Dirt of Buying Dirt

By Dr. Francis Gouin

To get the topsoil you want, you’ll have to be precise in your order.
Ask a sand and gravel company to bring a load of topsoil without any more specific instruction, and you may get more, or less, than you bargained for.

In the Garden this Week

Pick Your Bagworms While They’re Small

    Bagworms have hatched, and the young are already feeding. Until early July, the bagworms will grow slowly. But by the time they’re three-quarters of an inch long, they’re big enough to do damage.
   Look for young bagworms on the needles on pine and spruce trees. If there are only a few, at this stage they can be controlled by simply plucking them from the plants and throwing them on the ground.
   If there are many it is best to spray them with BT such as Dipel or Thurcide, which are equally effective trade names for the same bacteria. These are the same sprays that are used to control cabbage loopers on cabbage, broccoli, cauliflower, eastern tent caterpillar and gypsy moth on trees and shrubs. They are approved for use by organic gardeners.
   If you delay controlling bagworms until the bags are an inch or longer, you will have to either pick by hand or use a hard pesticide such as Sevin.
   If you pick by hand, simply discard the bags on the ground to encourage the establishment of your own BT population to help control future bagworms in your yard.

    A landscaping project I was involved with was located on sandy loam soils. The load of topsoil that was delivered appeared to be a clay loam. The landowner spread it, thinking that he was doing the proper thing. Next he sowed grass seed in the lawn area and planted a variety of shrubs in the garden area. When none of the grass seeds germinated after three weeks, he made a second seeding. Summer came and went with still no grass. Meanwhile, the new shrubs appeared discolored and some were dying. Finally concluding that he had problems, he called a landscape contractor, who immediately called me, requesting a house call.
   This poor guy had several problems. Using a soil auger, I discovered that he had spread a substantial layer of clay loam soil over a very sandy loam soil without blending the two together. Based on the visible chlorotic symptoms on the foliage of the plants and the poor growth of weeds in the identified lawn area, I also knew the soil was contaminated with an herbicide.
   To determine herbicide toxicity, I took soil samples. Seeds of tomatoes, lettuce, radish and snap beans were planted in the sampled soil as well as in known garden soil. None of the seeds in the suspected contaminated soil germinated, while most of the seeds in the known garden soil germinated, and the seedlings grew normally.
   My recommendation was to remove and replace the topsoil.
   When importing topsoil there are certain criteria that should be specified. Accept only topsoil that has been removed from agricultural lands that have not been in production for a minimum of four years. Request soil test results, and accept only soils with a pH above 5.0, low to medium levels of phosphate (P) and potash (K) and low levels of manganese (Mn) and sodium (Na) plus at least 2 percent organic matter.   Soils should be free of stones and sticks larger than three inches in diameter, and the soil should not be transported when it is soggy or frozen.
   If you are placing the soil over existing topsoil, you also need to specify soil structure such as sandy loam, silt loam, loam, clay loam, etc. This means you’ll first need a mechanical analysis of your soil. Never dump a clay loam over a sandy loam, or a sandy loam over a clay loam without blending the two together, thus making a new soil.
   The word topsoil is a nebula term, so you have to know what you want and ask for it.