Planting Site Preparation
The first step in developing a comprehensive fertilization program for strawberries begins the year before a spring planting. Soil samples should be taken in the summer, allowing for time to apply lime during the fall. This soil test is a key way to evaluate not only nutritional levels in the soil, but also pH and Cation Exchange Capacity (CEC). Strawberries prefer a soil pH 6.5 – 6.8 with 6.0 – 7.06.8 being acceptable. CEC is important as it will measure the ability of a soil to absorb calcium (Ca), potassium (K), and magnesium (Mg) ions (among others) and its resistance to change pH in response to liming and sulfur additions. Clays and soils high in organic matter have a high CEC, whereas sands have a low CEC.
Organic matter is a small but important component of soils. As organic matter continuously breaks down, the process of mineralization can provide some nutrients for plant growth. Organic matter also improves soil structure, allowing for good drainage while improving its moisture holding capacity. A range of 4 – 6% organic matter is ideal. If the organic matter level of the soil is historically low, cover crops (plowed in) and compost should be considered.
Overall fertilizer practices should be based on the results of yearly soil tests and leaf analysis if warranted. The following is guidance for our suggested practices.
Whether you are on a matted row or plasticulture system, fertilizing prior to planting is a key first step in your strawberry nutrition program. Rates should be determined through soil tests taken the previous summer. Depending on soil type (light, medium or heavy) we recommend 50 – 60 units actual nitrogen per acre with corresponding amounts of phosphorous and potassium, in a slow-release form. On matted row, this is about half of the total 90 - 120 units per acre seasonal requirement. For growers on plastic, fertilizer should be worked into the soil, prior to bed shaping. Matted row growers, when fertilize is incorporated well in the root zone, can begin that process 1-2 weeks prior to planting.
Establishment Year – Matted Row System
The goal with fertilization practices in matted row systems, in the establishment year, is two-fold – encouraging runner development and aiding in flower bud initiation. For runner development, we recommend 20 - 30 units actual nitrogen, side dress when first runners start. This should be followed up with an additional 20-30 units top dress in August prior to fruit bud initiation.
Establishment Year – Plasticulture System
In the Plasticulture system, whether you are planting bare root in late June/July or plugs in late August, the goal is to get branch crowns (2-3) along with excellent crown size in the mother plant. Since you are pushing plants in a short period of time, in addition to your pre-plant fertilizer, recommend 1-3 lbs. of actual nitrogen per week through the drip system. We alternate 9% calcium nitrate with a balanced fertilizer that includes micronutrients – one calcium application for every three balanced fertilizer applications.
Fruiting Year(s) Spring Fertilization
When a complete fertilizer program is followed the previous season, there is little fertilizer needed in the spring with two exceptions. One exception - light applications of 8-15 lbs. actual N total in cases of moderate to severe winter injury. The second exception is the addition of micronutrients to fungicide sprays during blossom. On certain varieties (Sonata, Cabot, Darselect), the addition of Solubor (boron) or Epsom salts (Magnesium) can improve fruit quality.
Fruiting Year(s) Fertilization at Renovation
Having used much of its nutrient’s resources through plant establishment and fruiting, renovation is a key time for fertilization. We recommend 70 units of actual nitrogen as part of a complete fertilizer applied after mowing and narrowing of the row. This includes phosphorous, potassium and any micronutrients found low on a soil test prior to renovation. Irrigate after application.
Fruiting Year Late Summer/Early Fall Fertilization
Similar to the establishment year, an additional late summer application of 20 – 30 units prior to fruit bud initiation is recommended. Knowing your soil nutrient status through routine soil tests, combined with timely application of complete fertilizer, including appropriate levels of nitrogen for your soil type should yield an excellent crop of berries! Please let us know if you have questions or need additional information.