It only takes a few days of sunny weather to inspire most gardeners to get outside and begin working in the soil. In most cases however, soils throughout our coastal area are simply too wet to work — especially when they have a high clay content. Our persistent rainfall this time of year tends to keep soils on the wet side. It’s really best for your garden’s long-term health to resist the urge to work the soil when it’s still wet. Whether you are using a tiller or a garden spade, working wet soil can badly compact it, and the negative effects can last for years.

    You can easily turn a well-drained soil into a poorly draining soil by cultivating or tilling the soil when it is wet. Working in wet soil causes compaction, which occurs when the large air spaces or pores between soil particles are collapsed. Without large pore space, water penetration becomes very slow. In addition, soil tilled too wet usually dries into hard clods, making preparation of a good seedbed difficult.

    Sandy soils tend to dry fairly rapidly, allowing you to begin preparing your garden early in the season. Even so, you should not work sandy soils when they are wet.  If your soil contains even moderate amounts of clay, it is even more critical to wait for the right moisture content before tilling. Clay soils, because they are composed of smaller-sized particles, have a greater tendency to compact than sandy soils.

    To determine if your garden’s soil is dry enough to work, dig a trowel full of soil and squeeze it in your hand. Soil that crumbles through your fingers when squeezed is ready to garden. However, if the soil forms a muddy ball, give it a few days to dry and then sample again later.

    Once you’ve determined that the soil is dry enough to work, be sure to not over till. Rototilling until the soil is pulverized into a fine dust damages the soil structure. Till the soil just enough to break any surface compaction and incorporate compost.  Adding a good soil amendment, such as compost will help improve soil structure. If the compost has been sitting on the soil surface as a mulch it has actually been insulating the soil from warming up. Mixing the compost into the soil will speed up the warming process, allowing you to plant earlier.

    We were told we could get an early start on planting our garden this year by using a plastic mulch to warm up the soil. Does it really work?

    You can quickly warm your soil’s temperature by using a clear plastic mulch. Unlike black plastic, clear plastic mulch absorbs little solar radiation, but transmits between 85 to 95 percent into the soil beneath it. In addition, the condensed water droplets that appear beneath the surface of clear plastic trap heat are normally lost to the atmosphere from a bare soil. Daytime temperatures under clear plastic mulch are generally 8 to 14°F. higher at a 2 inch depth and 6 to 9°F. higher at a 4 inch depth compared to those of bare soil. The negative side of using clear plastic mulches however, is the fact that they produce a nearly ideal environment for weed growth.

    Most gardeners are familiar with the weed control attributes of using black plastic mulches in the garden. When used correctly, they will also increase soil temperatures and conserve soil moisture.

    For black plastic mulches to increase soil temperature, however, it is critical that the soil surface be smooth and the plastic adhere to the soil surface. It is not unusual for soil temperatures under black plastic mulch during the daytime to be 5 °F higher at a 2 inch depth and 3 °F. higher at a 4 inch depth compared to those of bare soil.




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