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COMPOST & FERTILIZER

June 12, 2020 1:30 PM | Ryan Ewing

As a substitute for in-person programming, we’re offering a series of posts on starting a vegetable garden. This science-based information comes from the Seed to Supper program, developed by the Oregon Food Bank. During these difficult times, the Oregon Food Bank welcomes your donations.  OSU is also offering its vegetable gardening class online.

Soil naturally contains a small amount of organic matter. Adding compost every year increases the organic matter in your soil. When you add compost, your soil can absorb moisture better and hold onto it longer, so you don’t need to water as often.

Compost also provides habitat for beneficial soil microorganisms and earthworms, which help provide nutrients to your plants. And since soil with compost in it acts like a sponge, nutrients stay in your garden instead of creating harmful runoff in nearby streams and lakes.

You can buy compost pre-made in bags, but if you make it yourself, you’ll save money while recycling nutrients into your garden. To make your own compost, alternate layers of “green” and “brown” materials in a bin or other container that’s at least 3 feet high, 3 feet deep, and 3 feet wide. Make holes in your container, top and bottom, to allow it to breathe; if you plan to add kitchen scraps, make sure rodents can’t get in.

Green materials include garden waste (no weeds or diseased plants), kitchen scraps (no animal products), coffee grounds, grass clippings, and pet hair. Brown layers include dry leaves, straw, sawdust, torn paper bags, dry corn husks, and shredded newspapers. The smaller the pieces, the faster they’ll decompose.

Keep your compost pile damp (like a wrung-out sponge) and use a pitchfork to mix the materials after a week or two, then once a month thereafter. When you can no longer identify the green materials, the compost is finished. For more on making compost, see this free resource from OSUExtension.

Add 2 to 6 inches of finished compost (either purchased or made yourself) to your garden beds each year. Spread it loosely over the soil. If your soil is heavy with clay, you may need to mix in your compost. For looser soils, you can use a digging fork or “hula hoe” to wiggle in new compost without mixing. For perennial crops like asparagus, artichokes, and berries, you can top dress 2 inches of compost onto the soil surface each year without mixing it in.

Because some vegetables, like tomatoes, are “heavy feeders,” you may need to use fertilizer to supplement the nutrients in your compost. Fertilizing the garden is important to keep the plants healthy.

Plants need 16 nutrients to thrive.  Nitrogen (N), phosphorus (P), and potassium (K) are important nutrients that are found in most fertilizer mixes. Plants need much smaller amounts of the other 13 nutrients, called “micronutrients.”

The three numbers on a fertilizer label tell you the percentages of available nitrogen (N), phosphorus (P), and potassium (K) contained in the product. For example, a fertilizer labeled 15-5-10 contains 15% nitrogen, 5% phosphorus, and 10% potassium.

For the first 2 or 3 years of a new garden bed, a balanced fertilizer is fine.  Balanced fertilizers contain N, P and K in the same amounts, like 10-10-10. Organic fertilizers are healthy for your garden but can take longer to work than chemical fertilizers, which are like a fast food meal.

In the first year of a new garden, work organic fertilizer into the soil in the spring, about a month before you sow seeds or transplant. This gives the soil microorganisms time to break down the fertilizer into a form that the plants can use. After a season or two, you can fertilize at planting time without waiting. If transplanting starts instead of growing from seeds, you can fertilize “in the hole” according to package directions. Following package directions is also important when you use a chemical fertilizer.

Check seed catalogs and seed packets to learn more about the fertilizer needs of each variety. Throughout the growing season, you can “side-dress” with fertilizer by working it into the soil next to your vegetables.

If you notice a pale green or yellow color and slow growth about 4 – 5 weeks after planting, your crops may need more nitrogen. But don’t apply too much nitrogen to peas, tomatoes, or squash— it can make those plants produce only leaves and no fruit.

Vegetables grown in containers need fertilizer every two weeks.

Next up: Garden beds

With the vision of enhancing our environment for generations, CCMGA endeavors to be the best source for quality gardening knowledge on the north coast.

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Astoria, OR 97103

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