AMES, Iowa — Strawberries, raspberries and grapes can be quite productive when planted in a favorable location and given good care. One important cultural practice is fertilization, note horticulture specialists with Iowa State University Extension and Outreach. Proper fertilization promotes plant vigor and maximum crop yields. Contact the Hortline at firstname.lastname@example.org, or 515-294-3108, with any additional questions.
When should I fertilize strawberries?
Established plantings of June-bearing strawberries should not be fertilized in spring. Spring fertilization stimulates foliar growth, produces softer berries and increases disease problems. Lush, vegetative growth may make picking difficult. Also, soft berries are more likely to be attacked by fruit rots. As a result, a spring fertilizer application may actually reduce the fruit yield.
Fertilizer should be applied to June-bearing strawberries during the renovation process immediately after the last harvest of the season. Apply approximately 5 pounds of 10-10-10 or a similar analysis fertilizer per 100 feet of row.
Everbearing and day-neutral strawberries can be fertilized in early spring and again in early August. Apply 5 pounds of 10-10-10 or a similar analysis fertilizer per 100 feet of row.
When should I fertilize raspberries?
Fertilize established raspberries in early spring before new growth begins. Apply 4-5 pounds of 10-10-10 or a similar analysis fertilizer per 100-foot row. Uniformly broadcast the fertilizer in a 2-foot band. If the raspberries are mulched with sawdust or wood chips apply a slightly heavier rate (5-6 pounds of 10-10-10 per 100-foot row) of fertilizer. Conduct a soil test every four or five years to determine if nutrient levels are adequate.
Do not fertilize raspberries in late spring or summer. Late spring or summer fertilization encourages succulent, late-season growth. Late season growth is susceptible to winter damage.
Should I fertilize grapes?
Fertilization is generally not necessary for grapes in Iowa. Our fertile soils contain adequate supplies of essential plant nutrients. Excessive fertilization is harmful. Too much nitrogen may promote rampant vegetative growth and delay vine and fruit maturity. Fertilize grapevines only when plants exhibit weak growth or poor leaf color.
When poor growth dictates fertilization, apply a complete, low analysis fertilizer, such as 10-10-10, in early spring. Do not fertilize grapevines in late spring or summer. Late spring or summer fertilization encourages succulent, late season growth which is more susceptible to winter damage.
— Richard Jauron, Iowa State University Extension and Outreach
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