Crop Guide – Strawberries

Climatic and Soil Requirement

Berries prefer to grow in areas where the winters are very cold followed by mild summers. They need full sun for the highest yields at least 6 (six) hours a day. The soil requirement differs according to variety. Avoid soils with a high clay content. Strawberries grow well in soils that are well drained and high in organic matter.

Cultural Practices

Planting

It is important to plant strawberries at the correct time of the year as the crop is sensitive to changes in daylight length. Strawberry plants should be planted at the correct depth (not too deep or too shallow). The crown of the plant must be above the soil surface. Strawberries are normally planted in staggered double rows with an in-row and diagonal spacing of 20 cm x 20 cm. However, this spacing can differ. Plants should be spaced wider (30 x 30 cm) when planted early but closer (10 cm x 10 cm) when planted late. Plants should not be spaced too densely as this will create favourable conditions for pests and diseases.

Fertilization

Soil sampling levels are important and differ according to variety. No lime or phosphorus should be applied after planting as it has already been applied during soil preparation. However, regular applications of nitrogen (N) and potassium (K) throughout the season are essential. Potassium is vital for the formation of flowers and to ensure quality fruit. Enough potassium will also ensure a good yield and quality fruit. Potassium should be applied monthly, starting from the date on which the first flowers appear. Strawberries also need a constant supply of nitrogen, especially after planting. Any source of nitrogen can be used.

Actual N Application (kg/ha/day)

Plants use mainly stored organic nitrogen

Fertilization Methods

Commercial cultivation of strawberries normally takes one of the following fertilization schemes:

• Base dressing + a few side dressings throughout the growth cycle of the crop. This method is common among growers who are not equipped with a nutrigation (fertigation) setup.
• Base dressing + many side-dressing sessions throughout the growth cycle of the crop. "Many" can take the form of once weekly, once daily, or even many daily applications, carried out by nutrigation (fertigation).
• Usage of controlled release fertilizers.
• A combination of the above-mentioned methods, according to the grower's capability and preferences.
• Hydroponics
• Foliar feeding. This method serves normally as a complementary treatment to assist the application when encountering problems of soil uptake, and when fast correction results are needed.

Irrigation

Irrigation is necessary to produce quality fruit. Certain factors should be considered in deciding on the time and frequency of irrigation. Such factors include soil type, water quality, weather conditions, season, type of fruit, the type of irrigation system used as well as mulching. Strawberries require 15 mm to 25 mm of irrigation per week and this will depend on the time of year and the stage of production. Sandy soils have low water-holding capacities. It is therefore essential to apply small volumes of water at relatively short intervals, i.e. 2 to 3 days between irrigations. Loamy and clayey soils, on the other hand, have higher water-holding capacities. Larger volumes of water should therefore be applied with longer intervals between irrigations such as once every 4 to 5 days between irrigations.

Weed Control

Grass and weeds absorb considerable quantities of nitrogen and water to the detriment of trees. Weeds can be controlled either mechanically or chemically. However, hand hoeing is labour intensive and time consuming. Hoeing can also damage the roots or fruit of the strawberry plants. Caution should be taken when herbicides are used for weed control. The herbicide must not come into contact with the strawberry plants. User instructions, as supplied by the manufacturer of the herbicide, should be adhered to.

Authority (Sulfentrazone)

Authority is a selective, soil applied herbicide for the control of wild buckwheat, lambs' quarters, pigweed, groundsel and other broadleaf weeds. Authority may be applied as a broadcast spray or as a banded treatment. Applications should be made to dormant strawberry plants and only once per production season. The recommended timing is to apply to dormant plants before spreading mulch in the late fall. Spring applications may be made during dormancy to established plantings only, very soon after straw removal and before new growth resumes. Applications to strawberry plants with emerged growth are not recommended due to leaf burning and possible stand loss.

Use 0.22 to 0.29 L/ha of Authority per application, depending on soil organic matter and texture.

Dual Magnum (S-Metolachlor)

Dual Magnum is registered for control of American nightshade, Eastern black nightshade, crab grass, barnyard grass, fall panicum, foxtails, witch grass, yellow nut sedge (pre-plant incorporated only), and for suppression of redroot pigweed. Dual II Magnum's strength is generally on control of annual grasses. Pre-emergent applications sometimes provide better control of nightshades than pre-plant incorporated applications. Dual II Magnum is registered for use at 1.25 to 1.75 L/ha. The higher rate is recommended when the weed pressure is high. Apply in a minimum of 150 L water per hectare. Do not apply Dual II Magnum to the cultivar Joliette.

Planting year: Apply as a pre-plant incorporated or pre-emergent treatment after planting. Only one application per year is permitted. Some initial injury may result, but it is temporary and does not reduce yields the following year. If Dual II Magnum is used, do not harvest berries from any variety in the planting year.

Glyphosate (any formulations)

Although glyphosate is common to many products, the salt formulation and surfactants present may vary. Differences in weed control between these products are generally considered minimal. Make sure to use the application rate on the product label for the formulation of product that you are applying. Glyphosate kills susceptible plants by inhibiting growth. Treated plants become pale green and slowly turn brown. Glyphosate will damage or kill most green plants and must therefore be used in a manner to avoid spray contact or drift onto strawberry plants or other crops.

Site Preparation: Glyphosate is used mainly for site preparation in the year(s) prior to planting. It must be applied to actively growing weeds at the appropriate growth stage as specified on the labels. Glyphosate is absorbed by the foliage and translocated to above and below ground growing points. Fields treated with glyphosate can be tilled as early as 3 days (72 hours) after application, with little loss in weed control. Glyphosate should be applied in 50 to 200 L water per hectare. Lower water volumes (50 to 100 L/ha) will usually provide the best results. If glyphosate is mixed and applied in hard water, reduced weed control may occur. The addition of ammonium sulphate to hard water can counteract the negative action and improve weed control.

Fusilade Forte (fluazifop-p-butyl)

It is registered for the control of emerged annual grasses, volunteer cereals and quack grass in either the planting or fruiting years. For barnyard grass and volunteer cereals, apply at 0.8 L/ha between the 2 and 5 leaf stage. Suppression of top growth will be obtained with the 1 L/ha rate. Fusilade will not control broadleaf weeds or sedges. Venture L must not be applied to strawberries within 30 days of harvest. Fusilade applications should not be made when strawberries are in bloom. Fusilade is absorbed through the leaves, and translocated to the areas of active growth where it inhibits further growth. It is a slow acting herbicide. Injury symptoms on susceptible grasses may take up to two weeks to become apparent. Growth, however, stops soon after application. Fusilade is less effective if grasses are under stress or are too large.

Pest & Disease Control

Regular monitoring of pests is of the utmost importance. This will ensure timely intervention to control the pests before the infestations reach critical levels. There are several insecticides which are registered for strawberries to control specific pests. It is important to adhere to the user instructions as supplied by the manufacturers. Red spider mite, leaf spot and botrytis could be problems on strawberries. The key to good control of leaf spot is good sanitation. Botrytis is a grey mould which is most probably the biggest enemy of strawberries and can be controlled by fungicides.

Nematodes

Immediately After Planting

Starting One Month After Transplanting