Care for Your Soil
Plants need certain minerals in soil in order to live. The presence and
availability of these minerals-in other words, the fertility-in your soil
can be supplemented with either organic or inorganic sources. In turn,
healthy plants maintain healthy soils by contributing organic matter and
reducing soil erosion.
Fertilizers
Plants need three primary nutrients, nitrogen (N), phosphorus (P), and
potassium (K). They also need smaller amounts of secondary nutrients,
sulfur (S), calcium (Ca), and magnesium (Mg). In addition, plants have
varying needs for micronutrients.
Plants can absorb nutrients
only when they are in solution. However, most nutrients don't come dissolved
in water; they are found in soil minerals and in organic material. They
are released slowly into soluble form by soil organism activity and temperature
changes.
In some instances, acidic soils (soils with a low pH) can also inhibit plants from taking up nutrients. A soil test can determine your soil's pH level as well as its levels of nutrients. Several local laboratories can perform soil tests; check the phone book for listings.
Soils won't always have the nutrients that plants need. Western Washington soils lack nitrogen and sulfur and calcium, magnesium and boron are sometimes low as well. To supplement the nutrients found in soil, many people use fertilizers. They can be made from either organic or synthetic sources.
Over applying or misapplying fertilizers, regardless of whether they're made from organic or inorganic sources, can be bad for both your plants and the county's streams and lakes. Plants can only absorb a certain amount of nutrients; any extra will simply wash away into a stream, lake, or aquifer. More is not better-over-fertilized plants are much more susceptible to pests, such as aphids and spider mites. So apply only what your plants need, and apply it to your soil, not your driveway or sidewalk. Otherwise you'll waste your money, possibly damage your plants, encourage weeds, and pollute water.
For Lake Whatcom, the major nutrient concern is phosphorus, which can cause algal blooms in lakes and streams. When the blooms die and decay, they decrease the amount of dissolved oxygen in the water, which aquatic life depends on. In particular, lawn fertilizers can have an impact on water quality because they are used in much larger amounts than other fertilizers. For established lawns in the Lake Whatcom watershed, where soils generally have adequate amounts of phosphorus, Whatcom County Cooperative Extension recommends a phosphorus-free fertilizer. Look for one with a 2-0-1 ratio (for example, 16-0-8), and with 50-60% slow release nitrogen.
Compost
Adding organic matter helps to build and improve soil structure, as well
as providing a slow release of nutrients over several years. Be careful
about the kind you use, however. Organic matter with high nitrogen levels,
such as raw manure and blood meal can lead to over-fertilization, but
organic matter that is low in nitrogen, such as straw and bark, have so
little nitrogen that they actually reduce your soil's nitrogen content
when mixed in.
Compost is a good source of organic matter. It can be used throughout your lawn and garden to enrich your soil. When worked into your soil or used as mulch, compost can:
- Loosen up clay soils so air and water can penetrate
- Help sandy soils retain water and nutrients
- Add essential nutrients and soil microorganisms
- Hold moisture and reduce erosion
- Hold and break down pollutants
- Close the recycling loop by turning waste into a useful soil amendment
For more information on composting your own kitchen and yard waste, or for sources of local compost, please contact the Master Recycler/ Composter Program at Whatcom County Cooperative Extension or visit: http://whatcom.wsu.edu/ag/compost.
