New Hampshire gardeners are eager to get their hands in the dirt, but after a long winter and April showers, you may need to let the soil dry out more before you pick up a shovel.
Homegrown New Hampshire host Emma Erler, lead horticulturist with Kirkwood Gardens, uses a quick test to check if the soil is too wet to work. “If you can make a ball with a handful of soil and it doesn’t fall apart when gently poked, the soil is too wet to work,” she says.
Erler says healthy soil contains pores which are responsible for holding and conducting the water, nutrients, and air necessary for healthy plant root activity.
About half of healthy soil is made up of mineral particles: sand, silt, and clay, plus organic matter. The remaining half consists of pore space which creates room for air and water to move around the mineral particles. It is essential for plant roots and beneficial microorganisms.
How to tell if soil is compacted? Plants growing poorly, difficult to dig, water tends to collect or puddle after heavy rain and is slow to drain.
Soil compaction occurs when soil particles are pressed together, reducing pore space between them. Compacted soils contain few large pores, less total pore volume, and have a greater density.
You can see for yourself that compacted soil has a reduced rate of both water infiltration and drainage. This happens because large pores more effectively move water downward through the soil than smaller pores.
Gas exchange also slows down, causing an increase in the likelihood of aeration-related problems. It becomes harder for plant roots to push through the soil. Compaction can stunt plants by preventing normal root development.
Wet soils are particularly susceptible to compaction. So stay off of soil while it’s wet. This means in the spring after snowmelt or even after rain. Erler says she tries to avoid gardening or at least heavy foot traffic when the soil is soggy.
Other strategies to improve soil structure include adding organic matter to the soil. Erler suggests adding mulch or compost to the top of a flower bed, or hand-spading it into the soil.
It may seem like tilling the soil will fix compaction, but the air that’s introduced into the soil doesn’t have any load-bearing capacity and the soil is easily compacted again.
You can also grow a cover crop, like annual ryegrass, winter wheat, or tillage radish.
If you have a gardening question for us, email us or send a voice memo to HomegrownNH@NHPR.org.
See you in the garden!
Homegrown New Hampshire is a collaboration between Squam Lakes Natural Science Center and NHPR.
