Asparagus fertilize when and what
Portland Oregon. We have a nice bed of asparagus 3 years old. About 3' by 2' that had lots of of large spears last year. The plants were big 6 feet tall in summer . When should I fertilize and what fertilizer is best? We have clay soil that was amended when planted. (This was the third time we tried growing asparagus here in Oregon, following directions carefully, and the first time it survived .) Any other tips for growing asparagus are welcome.
Multnomah County Oregon
Here is information for general growing tips and more specific information about fertilization from OSU. Best of Luck with your garden.
Asparagus beds usually remain productive for about 10-15 years, so to get 20 productive years is remarkable. Growing asparagus west of the Cascades can be a challenge, as asparagus does not like water-saturated soil, but you've done well. Most asparagus is grown east of the mountains in sandy soil.
It's best to choose a new site for your bed to get a fresh start with no holdover problems. Asparagus beds are usually planted in the spring, so starting now will give you time to optimize your soil. The key to soil for asparagus is drainage. The beds should be deeply dug with lots of organic material added and with a pH 6.0-7.5. They need full sun
You can plant asparagus from seed or from crowns. Most asparagus plants now in cultivation are males, from hybrids, which are higher yielding. This is because seed production takes alot out of female plants, and doesn't help with crop production.
These articles give additional information on growing asparagus, Growing Asparagus in the Garden http://vric.ucdavis.edu/pdf/asparagus_growingasparagus.pdf, Asparagus Production Guide https://www.extension.umn.edu/garden/fruit-vegetable/asparagus-production-guide/index.html
If the bed is in the first three years, you would be using more nitrogen than you would once the bed is established. If you are using high nitrogen organic matter in the beds, you would use somewhat lower amounts.
New plantings: Oregon State University recommendations are for 3.7 ounces of nitrogen per 100 square feet of asparagus bed. This translates to just under 2 pounds of a 12% nitrogen product, such as blood meal. For a 5% nitrogen product, you would need around 4.5 pounds.
For new plantings, half of the nitrogen is applied in spring and half when the spears are up about 6 inches.
Established plantings (three- to four-year old beds): Use 2.9 ounces of nitrogen per 100 square feet of bed. That’s about 1.5 pounds of a 12% nitrogen product, such a blood meal, or about 3.5 pounds of a 5% nitrogen product.
To ensure that other nutrients are available to the plants, maintain the pH of the bed between 6.0 and 7.5.