Follow these steps to replenish nutrients in raised beds: Ask an expert

March has been balmy and springy, which means it’s time to garden. If you have any questions, turn to Ask an Expert, an online question-and-answer tool from the Oregon State University Extension Service. The OSU extension faculty and master gardeners respond to requests within two working days, usually less. To ask a question, simply go to the OSU extension website and type one and include the county you live in. Here are some questions asked by other gardeners. What is your?

Q: We have two raised beds in our garden and I was looking for some advice on how best to prepare the ground for this year’s garden. Both garden boxes are approximately 8 feet by 2 feet long by 2 feet wide by 2.5 feet deep. One was built two summers ago and the other was built last summer. Both beds were filled with compost when they were built.

Last year we added some compost to the original garden box and mixed it with the soil that was already there. Other than that, we didn’t add anything else to the ground. Is there anything we should add to these garden boxes to replace the nutrients the plants have used for the past two years before we planted them this year?

In a garden box, we grew potatoes, peppers, basil, carrots and garlic. The more recent of the two had tomato plants, green onions and carrots, although the tomato plants took over so the other vegetables did not survive. – Marion County

A: Vegetables generally do well for about a year in a new bed, but because they are annuals, they quickly deplete nutrients, which need to be replenished regularly.

Compost is a great amendment to condition your soil and improve it over time. However, decomposition is a slow process, so compost is not considered a fertilizer. Many of the plant nutrients needed are minerals such as those found in rock. Nitrogen is quickly used by plants and leached from the soil by rain; this is why most fertilizers contain a combination of nitrogen (N), phosphorus (P) and potassium (K).

It does not mean that vegetables need After nitrogen (in fact, too much can result in lush foliage and little fruit); but the nitrogen must be renewed more often. Typically, you will see numbers on the fertilizer packaging for all three primary ingredients in the order mentioned above, but many fertilizers also include secondary and microphone nutrients that plants need in small amounts as well.

In a raised bed, it is difficult to customize nutrients and soil pH for various vegetables. Your best approach is to look for a slightly acidic soil (pH 6.0 – 6.5). Rotate your vegetables every year so that those from the same family aren’t grown in exactly the same place, which will also help reduce the build-up of pathogens that can cause disease. Families include nightshade (tomatoes, peppers, potatoes, and eggplants), the allium group (onion, leeks, garlic), and leafy greens.

Ideally, you should do a soil test to determine what your soil is now, and then amend or fertilize it accordingly. A lot of people don’t want to test a small garden, but understand that it’s a bit like working in the dark without testing.

Good soil is made up of about 3% to 5% organic matter in various states of decomposition. This will ensure good soil health, tilth and maintenance of healthy soil microorganisms. Additionally, you will also need fertilizers which can be organic or non-organic (i.e. conventional or synthetic). Look for a quality balanced fertilizer that contains proportionately more phosphorus and potassium than nitrogen, such as 10-20-20.

For more information, please see this OSU publication.

In addition, this publication is an excellent guide to market gardening in general.

A final point I would like to stress is that tomatoes are often best planted in a very large pot where they don’t fill other vegetables. You can also prune and prune them so that they grow out, not out. Learn more in this post. – Lynn Marie Sullivan, OSU Extension Master Gardener

Q: I want to implement no-till gardening and combine it with green manure / cover crops to improve my soil structure. However, I don’t know how to start. My garden has issues with massive amounts of weed seeds, clay soil, compaction where I walked, and a section where we are dealing with invasive blackberries and thistles. How can I implement no-till gardening with all these problem areas? – Marion County

A: You may want to deal with the obvious issues to start the garden first and then implement the no-till / green manure techniques once you get started. The wet, unprotected clay soil is very prone to compaction, so I would draw the garden space and decide which areas would be dedicated lanes and what will be the growing space.

Compaction that exists in grow spaces is a short-term problem, so you may want to consider digging into organic matter when the soil is dry enough to break it up using a minimally invasive tool like a garden fork. You can maintain the soil structure after this with the use of mulch or green manure.

I wouldn’t let the weed seeds put you off. Remove perennial weeds and annuals as they germinate and you will gradually reduce the seed bank and the number of weeds to treat. Blackberries are an invasive weed, so of course you want them to go away as well, but they may have had the benefit of protecting, or even improving, the soil structure under the canopy and removing some ‘other weeds.

Their removal, including root systems, may reveal soil already ready for no-till gardening, with the caveat that there are undoubtedly blackberry seeds that will germinate, which will require continued weeding of these. . You do not mention the thistle involved, I hope it is an annual species and not Canada thistle, which is perennial and very difficult to eradicate. Do not hesitate to answer us and give more details on this subject.

This short article provides some additional suggestions:

This Extension post provides a lot of additional tips, but not specifically on no-till gardening. As I mentioned, feel free to write with questions. – Neil Bell, OSU Extension horticulturalist

Q: We grew red clover as a cover crop this winter. We handed it over last Saturday. My master gardener material says to wait three weeks before planting. How critical is this period? What are the disadvantages of planting earlier? Does it matter that we put in seeds or starters? – Multnomah County

A: In this Washington State University extension publication, here under the section on stopping a cover crop, is “Residues from freshly completed cover crops may inhibit seed germination. , including germination of desirable vegetable seeds. Waiting to plant vegetables for three to four weeks after cover crops have ended often improves their establishment. “

The OSU Extension “Grow Your Own” publication provides timelines for planting. The soil is too cold and wet for most plantings this early, so maybe the wait won’t hurt your garden plans. – Jacki Dougan, OSU extension master gardener