Certificado de Origen

Soil management systems used in raspberry production can be defi ned as clean culture, herbicide strips with grass (sod) culture, herbicide strip with cover crop system, and a combination of grass culture and woven weed barrier. The clean culture system refers to hand weeding or a combination of cultivation using mechanical hoes, disks or harrows, and hand weeding.

In Maryland between 1890 and 1930, black raspberry growers used hand weeding and cultivation using horse-drawn cultivators (Ross and Auchter, 1930). The fi elds were weeded three to four times per year. To minimize damage to the raspberry roots, cultivation was shallow and/or kept some distance from the crown. Animal manures were used, increasing the quantity of weeds, as seeds in the straw or hay bedding used for the animals got into the fi eld. Cultivation, during and soon after harvest, loosened the soil which was packed down by the people (pickers) who harvested the fruit. Further, cultivation during harvest could result in dropped fruit.

Economically, this system over time destroys soil structure and requires many hours of labor.

During the 1970s, growers in the eastern USA converted to using herbicides in the row and using grass (sod) as a permanent ground cover in the row middle or drive row. This reduced hand weeding labor by 80% and reduced the destruction of soil structure, improved organic matter, and reduced erosion. Certain herbicides are used immediately after planting so as to not harm young roots. Diff erent herbicides are recommended for year three and older plantings.

Raspberries require open, porous and slightly acidic soil (pH of 6.0–6.5) for good growth, movement of water and good nutrition availability. A balance of calcium, potassium and magnesium is necessary for optimal plant growth, optimal yields and the best fruit quality. Water from rainfall and supplemental irrigation is necessary to allow the transfer of nutrients from the soil to the plant roots. The ideal soil is well drained (good percolation below the root zone); a sandy or silt loam soil with good moisture retention and an organic matter content of 2–4%. Poor drainage can result in problems with root rots, the cause of much winter injury. The wet soil stimulates late autumn growth and the plant fails to harden off properly. Raspberry roots are generally in the top 60 cm (2 ft) of the soil. Thus, the water level should not come within 1 m (3 ft) of the soil surface for more than a few days. Where soil water percolation may be marginal, soils can be modifi ed slightly to correct some problems. Raised beds that are 20–25 cm high (8–10 in) can reduce root rot problems (Funt and Bierman, 2000). Raised beds are drier than fl at surfaces and will require more frequent irrigation (Fig. 9.1).

Soils can be modifi ed with organic matter (humus), such as green manure, animal manure and plant or animal based composts. This will improve the moisture-holding capacity, the fertility and the cation exchange

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capacity (CEC) of the soil. A silty clay loam soil or a sandy clay soil, well supplied with organic matter, is desired and hardens less than those with a lower level of organic matter. Adding organic matter, such as leaf compost, to a raised bed and incorporating it into the top 10 cm (4 in) creates an improved rooting environment for plant growth.

Soils should be tested before planting. Any major or minor nutrients/

minerals that are defi cient should be incorporated into the upper 30 cm (12 in) of soil before planting. Soil fertility, gas exchange (oxygen), pH and CEC may be improved with organic matter. Organic matter can be incorporated into the soil prior to planting (refer to Chapter 8).

The CEC is generally related to the soil texture; clay soils have a higher CEC than sandy soils because they have a higher total particle surface area than sandy soils. One to 2 years prior to planting, raspberry growers should take a soil sample to determine the amount of sand, silt and clay (soil texture), organic matter and CEC. Materials should be applied to improve the soil if required (refer to Chapter 8).

After the soil has been prepared and the plants have been planted, the amount of fertilizer for optimal production and winter hardiness is a major concern. In general, phosphorus, potassium, calcium and magnesium should not be required for the fi rst several years. However, a soil test 1–2 years after planting may be necessary to maintain suffi cient levels. Raspberries can be heavy feeders of nutrients, such as nitrogen (N), potassium (K), and possibly magnesium (Mg) and phosphorus (P), depending on soil type and climate.

Maintaining a pH of 6.0–6.5 can aid in uptake of nutrients and reduce the Organic mulch

Soil mixed with organic matter Ponded water

after heavy rain

Natural level of soil surface

Seasonal high water table in spring Fig. 9.1. Raised bed for water management of raspberries.

106 R.C. Funt and D.S. Ross

likelihood of defi ciencies. Therefore, the importance of applying the necessary nutrients before planting and incorporating them into the soil cannot be overemphasized. After planting, only N may be needed for the fi rst several years. Additional amounts of K may be necessary in years 3 or 4. Foliar sprays of minor elements, such as boron (B), can be helpful under wet (slow percolation) soil conditions in the spring after bud break when the leaves are beginning to show.

Soil applied N, P, Mg and calcium (Ca) are cheaper than, and just as eff ective as, foliar applications. However, some research indicates that new and more eff ective foliar nutrients may be benefi cial when applied in early autumn just before leaf fall and before a frost. Fertilizers injected into drip irrigation systems (fertigation) do show promise in being effi cient, plus the amount used is much less than with materials applied to the soil (Fig. 9.2).

Caution is advised in that certain fertilizers can clog fi lters and emitters in drip systems. In certain areas in the USA growers are required by the government to create a nutrient management plan and to report what nutrients were applied and in what amounts.

Certain grasses planted in the sod drive row can reduce soil compaction when farm equipment is used under wet soil conditions. In areas of slow soil

Rowcrop tape

Fig. 9.2. Components of a typical drip irrigation system for raspberries. (Source:

Ross, 2004.)

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water percolation with clay-type soils and during periods of heavy rainfall, grasses such as tall fescue can aid equipment travel between the rows for applying pesticides and/or the use of mechanical harvesters. Also, sod is mowed and creates a solid pathway for pickers. Overall, this reduces soil compaction, allows water infi ltration under rapid rainfall, reduces erosion on hillsides and reduces weeds (biological weed control) between rows.

New cultivars of tall fescues include dwarf types, which are drought tolerant, require fewer mowings (less trash for mice and voles) and are usually

‘endophytic’, unless the label specifi es they are endophyte-free. Endophytes are also found in certain perennial rye grasses, tall chewing or hard fescues, and improve sod survival. Non-endophytic types do not do well under diffi cult conditions when the seeds become infected with a fungus (Neotyphodium coenophialum), which creates a toxin for insects and nematodes. Also, the endophyte infection causes early closing of the stomata to conserve moisture during droughts. Early closing of the stomata also conserves nutrients. These chemicals can reduce chinch bugs, thrips, bill bugs, sod webworms and aphids that feed on grass stems. The endophyte also aids the fescues in storing more organic carbon (global warming) and nitrogen in the soil. Because endophytes also produce substances toxic to livestock, cattle or other animals should not be allowed to eat these types of fescues or grasses.

Another system in use is an inter-row cover crop that is killed by winter conditions, by cultivation or mowing, or by the use of herbicides. A seasonal cover crop, such as oats, is planted between the rows, usually in the summer, and is incorporated into the soil the following spring. This improves organic matter, improves soil structure and increases soil organic matter; it can also be used to reduce levels of nematodes and other pests. A herbicide is used within the row of raspberries. Seasonal cover crops can also reduce excess nitrogen.

In very fertile soils in the north-eastern and Midwestern USA, raspberries grow too vigorously and too late in the fall, which can result in early freeze injury. Further, when the cover crop is incorporated into the soil in the spring, the nitrogen will be released back into the soil, reducing the need for nitrogen fertilizer.

Raspberries grown in a high tunnel can be grown in any of the systems mentioned above, although in four-season tunnels, sod cannot be grown between the rows without irrigation. In greenhouses (glasshouses), soil or potting media can include other non-soil derived materials, such as sand, peat moss or vermiculite mixtures plus nutrients for optimal plant growth, either for in-ground or pot culture.

Raspberry growers may want to consider specialty buildings or shelters, such as a greenhouse or high tunnels. Greenhouses are considered to be permanent structures and use heat and electricity. They may be used for berry production. In many operations, these structures are used for annual bedding plant production or vegetable starter plants. Raspberry producers should consider a design for the placement of structures near water supplies,

108 R.C. Funt and D.S. Ross

electrical sources and waste management. New systems can recycle water or water-containing fertilizers, reducing water and fertilizer usage.

In Ohio, where 60% of the soil requires improvements in internal drainage, raised beds have been recommended for raspberries. Generally, the top layer of soil (10–15 cm/4–6 in) is a silt loam but going deeper it can be a clay loam, which is slow in water percolation. By placing an additional layer (10–15 cm/4–6 in) of topsoil in the planting row, with a one- or two-bottom plow, the grower can create an environment of 12–25 cm (5–10 in) of well-drained soil. Loosening the soil, with deep rototilling prior to making the beds in dry soil, can provide greater success in heavy soils. Generally, beds are made in autumn and prepared for planting in spring, although in milder climates autumn planting with dormant plants may be favored for facilitating herbicide control of weeds. A soil test should be completed and, based on the soil test results, nutrients such as Ca, K, zinc (Zn) and P should then be incorporated into the top 10–13 cm (4–5 in) with a rototiller.

However, deep rototilling is not advised because it will destroy or fl atten the raised bed.

Many raspberry plantings are grown in soils where peach and cherry trees can be grown. These soils tend to be fertile, well drained and have porous structures with ample oxygen for roots in the upper 20–30 cm (8–12 in). Further, the Puyallup Valley in Washington State probably represents an intensive small fruit district in the USA and provides good soil tilth. In Washington County, Maryland, black raspberries are grown on gravelly loams; the rocks in these soils include sand, slaty and shaly types. The heavier soils in this area and in Oregon are well drained and seem well adapted to berry growing.

Root health is increased with improved soil structure from the application of organic matter; and therefore, increased pore space, thus increasing oxygen and gas exchange and internal water drainage. In Ohio, on Crosby silt loam, composted yard waste decreased soil bulk density, decreased water-fi lled pore space, and therefore increased porosity of the soil by 10–40%.

When compost was incorporated into the soil and applied to the surface of the soil, soil water holding capacity and the rate of infi ltration was increased by 36–40% and was 7 to 21 times faster, respectively, in the fi rst 2.5 cm (1 in) depth as compared to the non-treated soils (Funt and Bierman, 2000).

Raised beds allow better soil water drainage under heavy prolonged rainfall.

However, raised beds also dry out much faster and to a greater depth than fl at (non-raised) beds (Fig. 9.1). Thus, irrigation becomes a part of the raised bed system of culture. Further, when the highly susceptible root rot cultivars, such as ‘Titan’, were planted on a silt loam soil containing Phytophthora fragariae, raised beds (35 cm/14 in high) dramatically reduced the incidence and severity relative to fl at beds (Maloney et al., 1993). Accordingly, the reduction in disease severity provided by the raised bed was due to the provision of a rooting zone in which the soil water tension generally exceeded that which

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supported zoospore activity. With all these factors, plants are healthier and can resist more insect and disease pressure than plants grown with lower amounts of nutrients, organic matter or porosity soil.