Fertilizing Strawberries

Table of Contents

1. General Soil Fertility
2. pH Requirements
3. Fertilizer For New Plantings
4. Fertilizer For Established Plantings
5. Leaf Analysis For Strawberries

General Soil Fertility

Strawberries are shallow-rooted, perennial plants. Heavy demands are placed on the root system, especially in the short period when berries are developing. Strawberries require well-drained soils with 2% or higher organic matter and high fertility. Providing an optimum environment for strawberry root growth is an important step in obtaining a profitable, perennial planting.

For more information on the production of strawberries, please see OMAFRA Publication 360, Fruit Production Recommendations

pH Requirements

The optimum soil pH for strawberry production is 6.0- 6.5. Strawberries will grow at a wider range of soil pH, however some micronutrients become less available as pH increases. This may be a problem when soil pH is above 7.0. A soil pH below 5.6 on clay loam and below 6.1 on sandy loam should be adjusted upwards by applying lime the year before planting.

Fertilizer for New Plantings (the planting year)

Phosphorus (P)

Use soil test results to determine the best rate of phosphorus to apply. Work phosphorus into the soil before planting. Soils differ in the amount of phosphorus available to plants. Generally, fields that have been cultivated for a length of time require less phosphorus than recently developed fields.

Starter Solutions: If the transplanter allows, you could use a starter solution at planting. This helps the plant establish, particularly if the soil is cold, because phosphorus availability is significantly reduced when soil temperatures are low. Use a starter solution high in phosphorus such as 10-52-10, 6-24-6, or 10-24-0. Follow the manufacturer's suggested rate of application.

Potassium (K)

Use soil test results to determine the best rate of potassium to apply.

Incorporate potassium into soil before planting. Side dressing of potassium is not generally recommended.

Nitrogen (N)

Nitrogen can be applied with the P and K, or as a side dressing 2-3 wks after planting. Apply 50 kg of N/ha.

Apply an additional 25-35 kg N/ha in mid-Aug. to further invigorate plants as they initiate fruit buds for the following year's crop. Use whatever form of nitrogen is economical. Brush pelleted forms, such as ammonium nitrate, off the leaves to prevent burning. Do not apply nitrogen when leaves are wet. Urea forms of nitrogen may volatilize under certain conditions. Volatilized ammonia can cause strawberry leaves to blacken. Incorporation of the urea will prevent this problem.

Strawberries require annual applications of nitrogen. The timing of nitrogen application is as important as the rate of nitrogen. Improper timing and/or rates of nitrogen may lead to an increase in winter injury, softer fruit, and higher incidence of disease. Adjust nitrogen rates proportionately if manure has been applied.

Fertilizer for Established Plantings

Nitrogen (N)

Do not apply nitrogen in the spring, particularly on vigorous varieties. Spring applications cause extra vegetative growth and vigour resulting in softer fruit and dense foliage canopies. This increases the potential for botrytis fruit rot. Although spring-applied nitrogen may increase berry size, it also delays maturity by a day or two.

Some growers with coarse-textured soils have reported benefits from applying low rates of nitrogen (10-20 kg N/ha) in the spring after mulch removal. Established fields on sandy soils or fields suspected of having winter injury might benefit from light spring applications of nitrogen. Experiment with spring-applied nitrogen on a small scale.

The best time to apply nitrogen in established fields is at renovation. After mowing the foliage, apply 50 kg N/ha using whatever form of nitrogen is economical. Brush pelleted forms such as ammonium nitrate off the leaves to prevent burning. Do not apply nitrogen when leaves are wet. Urea forms of nitrogen can volatilize under certain conditions. Volatilized ammonia can cause strawberry leaves to blacken. Incorporation of the urea will prevent this problem.

An additional 25-35 kg N/ha is recommended in mid-Aug. to assist the plant in forming next year's fruit buds. It is important that soils are well irrigated after renovation, throughout the summer and early fall. Adequate soil moisture is needed to optimize nitrogen uptake.

Phosphorus (P)

If a need for phosphorus is determined by a soil test, apply phosphorus at renovation with the nitrogen and potassium. Excessive phosphorus levels may cause zinc deficiency, especially on sandy soils.

Potassium (K)

Apply potassium, as determined by a soil test, at renovation with the nitrogen and phosphorus. Application at this timing allows incorporation. Use soil testing and/or leaf analysis to determine what rate to apply. Excessive levels of potassium induce magnesium deficiency, particularly on sandy soils.

Leaf Analysis for Strawberries

Leaf analysis can be used to assess the nutrient status of strawberry plants and to more accurately determine fertilizer requirements. Take leaf samples by July 1 for fruiting or Aug. 20 for non-fruiting plantings. Collect at least 50 fully expanded, recently matured leaves, with petioles removed. Sample different varieties and plantings separately. For more information refer to OMAFRA Factsheet.

Learn more:

• OMAFRA Horticulture Crops Newsletters
• Publication 360, Fruit Production Recommendations
• Pub.811 Agronomy Guide for Field Crops: Chapter 8- Soil Management
• Pub.811 Agronomy Guide for Field Crops: Chapter 9- Soil Fertility and Nutrient Use
• The Phosphorus (P) and Potassium (K) Soil Testing and Fertilizer Recommendation System in Ontario
• Soil Fertility and Nutrient Use: Fertilizer Recommendations: Soil Acidity & Liming
• Sources of Agricultural Limestone
• Publication 611, Soil Fertility Handbook
• Soil Fertility and Nutrient Use: Soil Testing
• Soil Management
• Soil and Water Management
• Best Management Practices Order Form
• Micronutrients for Berry Crops
• Lead and Petiole Tissue Analysis