Asparagus should be fertilized prior to planting, in the spring of each season, and following the final harvest.
Asparagus Soil pH Requirements
To understand exactly what additional nutrients asparagus will require, you should always perform a soil test and base the fertilizing decisions on the results. Asparagus performs best in a soil with a pH of 6.5 to 7.5. It will not perform well if the soil pH is lower than 6.0 so you will need to raise or lower the Ph of the soil accordingly.
Initially Fertilizing Asparagus
In the absence of a test, you can fertilize the soil prior to planting your asparagus. Work in two to three inches of compost then add a 10-20-10 fertilizer at a rate of two pounds per one-hundred square feet to the soil that is worked to a depth of six inches.
After the final harvest at the end of the season, the soil will benefit from additional nitrogen. Work into the soil a small amount of nitrogen fertilizer, such as 34-0-0, at a rate of a few ounces per one-hundred square feet.
Unlike most garden vegetables, asparagus is a perennial that will reemerge year after year. You can fertilize your asparagus bed in early spring prior to the emergence of the new spears. Apply one to two pounds of an all-purpose fertilizer such as 10-10-10 per one-hundred square feet.
“Answers to Frequently Asked Asparagus Questions .” Iowa State University Horticulture and Home Pest News. N.p., n.d. Web. 27 Feb. 2014. <http://www.ipm.iastate.edu/ipm/hortnews/2004/3-26-2004/asparagusfaq.html>.
“Asparagus – An Early Spring Treat.” West Virginia University Extension Service. N.p., n.d. Web. 27 Feb. 2014. <http://www.wvu.edu/~agexten/hortcult/homegard/spgasparg.htm>.
“Growing Asparagus In The Home Garden, HYG-1603-94.” Ohio State University Extension. N.p., n.d. Web. 26 Feb. 2014. <http://ohioline.osu.edu/hyg-fact/1000/1603.html>.