Preparing the Soil for Berry Production: The Basics

Table of Contents

1. Introduction
2. Soil Considerations
3. Organic Matter
   • Sorghum sudan
   • Winter rye
   • Oilseed radish
4. Soil Fertility and pH
   • Soil drainage
   • Soil compaction
5. Soil Pests
   • Weeds
   • Insects
   • Diseases and nematodes
6. Related Links

Introduction

Successful berry production depends on careful attention to every aspect of production. Most important is proper land preparation, long before strawberries, raspberries or other berry crops are planted. If mistakes are made during the preplant process, the effects can be felt for the life of the planting, and the economic potential of the crop becomes limited. The best management and cultural practices cannot compensate for soil problems that should have been corrected before planting.

Soil Considerations

In general, strawberries and raspberries should be planted on sandy loam to loam soil that is 60 - 120 cm deep. Other soil types may be acceptable with good management. However, heavy soils tend to be too cold and wet, while sandy to gravely soils have a poor water holding capacity. A good site for berry production will have good air drainage and wind protection, minimal land slope, an available water supply and physical separation from wild berry plants. Assuming the site is suitable for berry production, the main soil management considerations include the organic matter, fertility, pH, drainage, soil compaction and soil pests.

Organic Matter

Soils for berry crops should have an organic matter (OM) content of 3% or more. The OM can fluctuate considerably up or down according to good or bad management practices. The importance of maintaining a good level of OM should not be underestimated. OM serves as a source of energy for helpful micro-organisms, and acts like a sponge, holding nutrients so they don't leach but remain available to the plant. OM is helpful for breaking heavy soils and for binding light soils. OM also facilitates air movement and the entrance and percolation of water into and through the soils. OM improves the water-holding capacity of the soil. In a dry year, plants growing in soil with low OM will not do as well as those in soils with adequate OM.

There are several ways to increase the OM content of soils. The most traditional has been with the use of manure. However, for most horticultural producers a ready supply of manure is not available. Weed-free cattle or swine manure applied at 25 - 40 tonnes/hectare is beneficial especially if it contains bedding material. Manure that is decomposed can be applied in the spring, otherwise it should be applied in the previous fall and worked in. Poultry manure could be used but it does not contribute that much to the soil OM. Where poultry manure is used, no more than 7 tonnes/hectare should be applied the fall before since fresh poultry manure can burn the tender strawberry and raspberry roots.

As manure becomes less and less available to horticultural producers, a good substitute is hay or straw applied at 7 tonnes/hectare in the spring a year before planting. Unless the residue contains at least 1.5% nitrogen, the soil organisms will actually remove nitrogen (about 30 kg/ha) from the soil to break the residue down. Legume materials have enough nitrogen but for non-legume materials 4 kg N/tonne (20 lbs./ton) of hay or straw should be added at the time of application. As the residues break down, most of the nitrogen will be slowly released and made available to the plants.

A third strategy for improving the soil OM content is to plant a cover crop either in place of, or in addition to the other OM amendments described above.

Cover crops are most beneficial where the soils are too light or too heavy and the OM is low; where no manure is available and where a legume cover crop can be used.

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Sorghum sudan is an excellent choice for growing as a cover crop for soil improvement. The root growth is extensive and the top growth lush. A pre-plant herbicide treatment is recommended for crop establishment. Plant after all threat of frost is past; mid June. The crop will benefit from the warm temperatures of early to mid summer. Approximately 50 kg/ha of N will help the crop achieve maximum top growth.

Caution: Sorghum sudan should be mowed before it reaches the height of 1metre, in order to encourage tillering and to ensure that stalks are not woody and will break down readily.

Winter rye is seeded from late August into mid-October, often following field or vegetable crops. It grows until freeze-up, and then commences growth again in March - early April (slightly earlier than winter wheat). Growth rate is very rapid during May. The stand is generally killed in late April or early May by tillage or herbicide use. Rye can produce significant root and top mass for return to the soil. A rye cover crop suppresses winter annual weeds effectively. Winter rye can be seeded later than any other crop and still survive over winter. For good ground cover and erosion protection, it should be seeded at least a month before freeze-up.

Caution: Rye should be killed in the fall or early spring to avoid loss of soil moisture, and difficulties in incorporation. Full season rye is an excellent host for root-lesion nematode, while cover crop or short term rye is no different than wheat.

Oilseed radish is commonly seeded in August or early September. It is unaffected by early frosts, can grow to a height of 50 to 90 cm and blooms in October. The plant has a thick but short taproot, varying between carrot and turnip shaped. It is killed by severe frosts in late November or December. Oilseed radish provides a reasonably rapid soil cover and excellent erosion protection over winter and returns moderate amounts of organic matter to the soil. For good growth, this crop must have a large amount of available nitrogen, either applied as fertilizer or manure left from a previous crop. Some oilseed radish varieties release compounds which are toxic to nematodes, but only when large amounts are tilled green into the soil.

Caution: Growth will be poor if soil nitrogen levels are low or if soil compaction is severe. Scattered volunteer plants usually appear in the following crops.

For more information on growing cover crops, see also Cover Crops, consult OMAF publications #360, Fruit Production Recommendations, and #811, Agronomy Guide for Field Crops.

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Soil Fertility and pH

The most reliable way to determine fertility and lime requirements for strawberries and raspberries is to take a soil test preferably a year before but no later than the fall before planting.

If a cover crop is grown, the soil test can be used to determine the recommended fertility requirements for that planting. In general, the amount of phosphate and potash for forage type crops is around 20 ppm and 120 ppm respectively. For strawberries and raspberries the recommended levels are 40 ppm and 180 ppm. Therefore, after the cover crop another soil test could be taken and the appropriate amounts of phosphate and potash added prior to planting, if needed.

Where manure has been added, it is advisable to take a soil test also, since manures are generally high in phosphorous. Publication #360, Fruit Production Recommendations, provides tables to indicate the reduction in fertilizer where manure has been applied.

Most fertilizer requirements can be added just prior to planting. The recommended rate for nitrogen at that time is 50 kg of actual nitrogen per hectare. Nitrogen fertilizer should not be applied in the fall since it could be lost through leaching. Where phosphorous is required, it should be incorporated at least 20 cm. into the soil. Phosphorous does not move very readily through the soil and if it is not incorporated properly the plants will not be able to use it.

Magnesium (Mg) levels should be between 40 - 100 ppm on the soil test. If the levels get below this, yields may be affected because Mg is essential for chlorophyll which produces the food for the plants. If Mg levels get below 40 and if the pH is below 6.5 then dolomitic limestone (which contains 11 - 22% Mg) should be added. If the levels are below 30 ppm and the pH is higher than 6.5 then 30 kg/ha of soluble Mg should be applied to the soil as one would apply potash. Many fields have potash levels that are too high. In the presence of excess potash, plants will not take up enough Mg even though there should be enough in the soils. Therefore if the Mg levels are between 31 - 39 ppm and the potash levels are greater than 250 ppm, then additional Mg should be applied.

With the current soil tests manganese and zinc analysis can be requested. If either of these two micro-nutrients drop below 8 ppm then deficiencies may occur. These nutrients are not soil applied but can be applied as foliar sprays if deficiency symptoms show up in the leaves.

The optimum pH for raspberries and strawberries is slightly acidic (around 6.0 - 6.5). In Ontario, if the level gets below 6.1 then lime is recommended for coarse and medium textured soils. On fine soils lime is recommended if the pH dips down to 5.6. At a low PH calcium, magnesium and possibly phosphorous may not be readily available to the plant. If Mg levels are low then dolomitic lime can be used to correct acid soils otherwise calcitic lime is suitable. The lime should be applied in the fall and preferably one year before planting to allow time for the soil chemistry to change.

If the soil pH is high it usually is not economical to bring it down with sulfur. In most cases the crops will grow well enough at a higher pH. Several micronutrients such as iron may become limiting if the pH gets too high. These deficiencies are best corrected through foliar sprays.

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Soil Drainage

Strawberries and raspberries cannot tolerate poorly drained soils. Optimum production will never be achieved if the crop has wet feet, even for a short time. Near perfect drainage is required. Actively growing roots will begin to suffocate and die within 24 hours of being submerged. In addition, wet conditions favour the occurrence of soil borne diseases. Strawberries can be severely damaged by black root rot or red stele. Raspberries are susceptible to Phytophthora root rot. Advice on drainage requirements can be obtained from a drainage contractor.

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Soil Compaction

Soil that is compacted can have dramatic affects on the productivity of berry plantings. A hardpan will restrict the movement of water down through the soil resulting in poor drainage. Root development will also be restricted. To break up hardpans sub-soiling should be done before planting. The depth of subsoiling should be no more than a few centimeters below the zone of compaction because any deeper uses more energy and risks the potential of deeper compaction. The best time to subsoil is when the soil is dry, (e.g. August) so that the hardpan shatters. If subsoiling is done when the soil is too moist the hardpan will not be properly disrupted.

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Soil Pests

The final consideration for preparing the soil is to control pests such as weeds, insects and diseases.

Weeds

The primary weed concerns are perennial weeds such as quackgrass, Canada thistle, bindweed, etc. If these weeds are not controlled before planting then they can become a real problem, and will limit the life of the planting.

In the season before planting it is possible to reduce the perennial weeds through intensive cultivation of fallow land. However, this approach is expensive and severely reduces the soil OM . Herbicides are the most common approach to eradicating these weeds.

The weed that seems to cause the most problems is quackgrass. An approach to controlling quackgrass is to apply Roundup in the spring before planting when the grass is a minimum of eight inches high with 3-4 leaves. If the field was not fall plowed, an application around May 15 - 20 is probably the earliest application date or else there will not be enough leaf growth to ensure net movement down into the roots for adequate kill.
If the field was fall plowed, an early spring application will not be successful because the quackgrass will emerge sporadically. For fallow fields, make two applications, one in May and another in September. For heavy infestations use the high rate on the label.

For broadleaf perennials a suitable herbicide applied over the cover crop as described earlier could be selected. If a cover crop is not grown, a broad spectrum herbicide such as Roundup can be used. Timing is crucial for proper control as outlined in OMAF Publication #75, Guide to Weed Control under the heading "Special Methods of Weed Control - Site Preparation."

In some cases it may be advisable to rotate into a row crop where a vigorous herbicide program can be implemented. In all cases care should be taken to avoid herbicide residues that can hurt berry plants.

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Insects

White grubs and wireworms are two serious soil-borne pests that are common in sod and pasture crops. Berry crops should not be planted within two years of any type of sod. A row crop such as corn or pumpkins could be grown for at least one year prior to planting to help reduce the incidence of grubs, wireworms and other soil insects.

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Diseases and Nematodes

To prevent the build-up of certain diseases a crop rotation scheme should be adopted. Strawberries or raspberries should be never be planted back to back. Pythium and Rhizoctonia are known to build up in strawberry plantings. The main soil borne disease encountered in both strawberries and raspberries is Verticillium wilt. In addition to infecting strawberries and raspberries, this fungus is also the cause of wilt in solanaceous crops such as tomatoes, potatoes, peppers and eggplants. Therefore strawberries and raspberries should not be planted (preferably within 4 years) after one of these crops. Similarly, lamb's quarters, pigweed and nightshade are known to harbour Verticillium so weeds should be controlled.

Nematodes are soil borne pests common in both raspberries and strawberries. These are small eel-like worms invisible to the naked eye but easily seen under a microscope. They can be a problem on sandy soils but usually not on heavier soils. Nematode numbers can be determined through analysis of a soil sample. If the numbers are high, fumigation is a proven and effective means of control. Crops such as sudan grass, red fescue , and marigolds, will suppress nematodes. In contrast, legume crops encourage nematode populations. For information on nematodes, sampling and control see Nematode Management.

In summary, optimum production throughout the life of a strawberry or raspberry planting can only be achieved if the soil is properly prepared before planting. Proper preparation includes building up the organic matter content, fertility, appropriate pH, ensuring good drainage and control of pests such as weeds, insects, and diseases.

Related Links

• Cover Crops
• Publications 360: Fruit Production Recommendations
• Publication 811: Agronomy Guide for Field Crops
• Publication 75: Guide to Weed Control
• Sampling Soil and Roots for Plant Parasitic Nematodes