Pruning

Old fruiting canes (floricanes). These should be cut out at the soil level. Do not leave stumps—this helps to control crown borer. Usually fruiting cane removal is best done after September or October. However, if Botrytis cane wilt or spur blight is a problem in wet years, old canes can be cut immediately after harvest to increase air circulation.

New canes (primocanes). The undersize or unwanted new canes are best removed after most of the leaves have dropped – usually about December. Pruning out these canes earlier is sometimes necessary but the risk of winter injury is increased as plants become more exposed. Select up to 12 vigorous new canes per plant. Remove all weak canes. Tie canes to the wires in small bunches of 3 or 4 canes. On average, one 50 lb bale of binder twine is needed to tie 1.2 ha (3 acres) of raspberries. At this time, arch or loop over new canes in plantings trained to this system. If topping new canes, wait until late February when the plants are fully dormant and top to a height of 1.5 m (5 ft).

Cold Areas

In areas of cold winters or deep snow, delay all pruning until late winter. The old canes help to protect the fruiting canes. However, an initial topping 30 cm (12 in) higher than the final topping can be made when the canes are nearly dormant to minimize wind and snow damage.

Fall Fruiting (Primocane) Varieties

Cut all canes off to the ground in the winter. In the spring, keep only about 12 new canes per plant for fruiting. Prune or hoe out all excess canes as they appear during the growing season.

Pollination

Insect pollination is essential for raspberry production. Most pollination is done by honeybees and wild insects (bumble bees, syrphid flies) so it is critical that they are not killed with insecticide sprays during flowering. Wild pollinators, such as bumble bees, are especially important in cloudy or rainy weather, when honeybees do not fly. Placing commercial honeybee colonies in fields during bloom can increase raspberry yields by increasing the amount of pollen transferred. This results in larger fruit. This is particularly important in areas of concentrated cropping and few wild pollinators. For information on renting honeybee colonies and their placement in the field, refer to Pollination in this guide.

Cover Crops

Annual or permanent cover crops can be planted between the raspberry rows. Cover crops suppress weeds, take up excess nitrogen left in the soil in the fall, improve soil structure and drainage, and improve trafficability.

Annual Cover Crops

These are planted every year after harvest and before September 15. Barley and oats are preferred as they grow rapidly in early fall but are usually killed by colder winter temperatures. In the spring, cover crop residue can be flail mowed along with prunings or rotovated into the soil surface. Nitrogen from the decaying cover crop is then released into the soil for use by the raspberry crop. Fall or cereal rye, or annual grasses, can also be used. They are less effective at trapping leachable nitrogen in the fall or winter as their main growth period is in the spring. These cover crops may require additional management in the spring – such as mowing, discing, or herbicide application –to prevent them from competing for nutrients and water.

Perennial Cover Crops

Fescue can be used as a permanent cover crop in raspberries but must be managed to prevent it from growing into the raspberry row. Permanent cover crops prevent weed growth, compaction and soil erosion, however, they are difficult to repair if ruts form from driving on them when the soil is too wet.

Nutrition

Leaf Analysis

Leaf analysis can be used to determine nutrient needs in raspberries but it has not been well-tested in BC. Leaf analysis can also be used if a nutrient deficiency is suspected. Take leaf samples from mid-July to early-August to determine the fertilizer requirements for the following year. For the best interpretation, take leaf samples at the same stage of plant development (e.g. mid-harvest or late-harvest) each year and monitor year-to-year trends in nutrient status. Collect the most recently fully expanded leaves from the new primocanes, about 30 cm from the tip of the cane. Leaves must be free of soil, pesticide and irrigation water residue. Select about 10 leaves from each of 5 plants distributed at random throughout the field. When checking for suspected nutrient deficiencies, take separate samples from good and poor growth areas and compare the results. These samples can be taken at any time during the growing season. Air dry all samples in an open paper bag or take them directly to a laboratory.

Source: OSU EM 8903-E Nutrient Management Guide - Caneberries (2006)

Soil Analysis

Soil analysis is the most accurate guide to fertilizer requirements for raspberries.

Sampling method. Take soil samples from each sampling location in the field: Site (1): at base of the bed between the plants in the row, and Site (2): at the centre of the bed between plants in the row (see figure below). Take samples from 10 to 20 different locations for each 8 hectare (20 acre) field area. Mix all the samples together. Avoid areas in the field that are not typical such as low spots or gravel outcrops. Where fields have more than one soil type, the areas should be sampled separately. Take soil samples for nitrogen analysis from the 0 to 30 cm (0 to 1 ft) of soil. Take soil samples for all other nutrients from 0 to15 cm (0 to 6 in).

Sampling time. For mature crops, take soil samples for nitrogen after crop harvest, or between August 15 and September 15. A spring soil test cannot be used to assess nitrogen fertility levels of a raspberry field. For all other nutrients, fall or spring soil sampling can be used.

Nitrogen Management

Most of BC’s raspberry crop is grown on irrigated sandy soils over the Abbotsford-Sumas Aquifer. This situation increases the risk of nitrogen leaching into the aquifer. Follow the nitrogen recommendations below to minimize the risk of groundwater contamination. Excess nitrogen application can result in leaching and may be harmful to the crop. Irrigation should be managed to prevent nitrogen leaching in the summer.

Nitrogen is supplied to the crop in various forms including cover crop residue, compost or manure, irrigation water, and fertilizer. To determine the amount of nitrogen fertilizer to apply, follow the Calculation of Nitrogen Fertilizer Requirement for Raspberries, Tables 3 to 7 below.

Cover crops. See Table 4. When determining the nitrogen credits for cover crops, the following assumptions are made:

• barley or oats are used,
• seeding rate of 100 kg/ha (40 kg/acre),
• planted on all bare ground between rows and on headlands

• about one third of all the nitrogen taken up by the cover crop is available in the following season.

Manures and Compost. Poultry manure is an effective source of nitrogen for raspberries but must be stored and spread in an environmentally responsible manner. As manure can be a food safety risk, only composted manure or manure aged at least 3 months should be used. Different food safety programs have varying waiting periods between application and harvest. Check with your program or packer. Manure releases nutrients slowly, and it will continue to release nitrogen after raspberry harvest when the plant uptake is reduced. For this reason, it is highly recommended that a cover crop be planted on fields where manure was applied. Nutrients are captured by the cover crop and prevented from leaching into the groundwater. These nutrients will be available to the raspberry crop the following spring when the cover crop is incorporated.

It is difficult to distribute manure evenly over the field at a low enough rate to provide the optimum level of nitrogen needed by the crop. This can be addressed by applying manure to alternate rows. Each row will get a portion of the nutrients applied without over fertilizing the crop. A manure spreader designed for side delivery or band application can also be used to apply poultry manure directly to the root zone. Spread manure only once each season – broadcast and incorporate into the soil in the early spring (after February 15 and no later than dictated by your food safety program). Most poultry manure contains up to 12 kg/yd³ of total nitrogen. Poultry manure is generally very high in calcium and contains high levels of ammonia nitrogen that is readily available to plants. Some ammonia nitrogen is lost during application. Losses are greater when manure is left on the soil surface for more than 12 hours.

Established plantings. Apply poultry manure at no more than 17 yd³/ha (7 yd³/acre) and immediately incorporate. This provides most of the nitrogen requirement of established raspberries. See Table 5 for manure N credits.

A soil nitrate test about 3 weeks after application of manure can be done to determine if more nitrogen is required.

Fertilizer Nitrogen. The timing of the fertilizer application is dependent on the soil texture. Coarser soils (gravel and sands) have less ability to retain nutrients and require several applications. On sandy soils, experience has shown that nitrogen fertilizers should normally be applied twice per year (50% in early April and 50% in early May). Raspberries grown on stony or gravelly soils will benefit from three equal applications of nitrogen fertilizer. Start in early April and apply at monthly intervals. Excess nitrogen after harvest, regardless of the source, is especially harmful as it may delay cane dormancy and increase the risk of winter injury. It also is prone to leaching.

Slow-release fertilizers have been used with some success on very coarse or heavily irrigated soils. A single application, usually in early April, will provide nitrogen over an extended period of time. Follow the manufacturers’ directions to avoid late season nitrogen release.

Commercial fertilizer can be applied in a band 30 to 40 cm away from both sides of the raspberry rows and about 10 cm below the soil surface. Alternatively, it can also be broadcast over the surface of the bed. Rain or irrigation is then required to carry nutrients into the root zone.

Nitrogen and other nutrients may be injected and applied by drip irrigation. For more information refer to B.C. Ministry of Agriculture publication, “Chemigation Guidelines for BC” at http://www.agf.gov.bc.ca/resmgmt/publist/500Series/578100-1.pdf.

Calculation of nitrogen fertilizer requirement for Raspberries

To determine the amount of fertilizer nitrogen to apply to the crop (Table 7), obtain the total N crop requirement from Table 3. Then determine nitrogen credits for cover crops (Table 4), manure use (Table 5), and irrigation water (Table 6). Finally, calculate the rate of nitrogen fertilizer required.

Table 3. Crop Nitrogen Requirement Based on Yield Potential

Young, vigorous crops with a yield potential of greater than 12 tonnes/ha may utilize up to 80 to 100 kg/ha of nitrogen. If the crop is near the end of its life or in decline due to nematodes or other root problems, it will use less nitrogen, in the range of 40 to 60 kg/ha.

Enter the nitrogen requirement into Table 7 – Line A.

Table 4. Cover crop nitrogen credits

Enter the cover crop credit into Table 7 –Line B.

Table 5. Nitrogen credits for spring applied poultry manure*

Enter the manure credit into Table 7 –Line C and D.

*Notes:
• The kg N/yd³ takes moisture content and density variations into account. This is an expected average value of layer, broiler, and turkey manures provided by the Sustainable Poultry Farming Group 1994 Fact Sheet “Standard Characteristics of Poultry Manures (Nutrient Contents).”
• Assumes that manure is kept covered after leaving the poultry barn and is in a solid or semi-solid form.
• N credits assume 50% N availability for incorporated manure and 33% for unincorporated manure.

Table 6. Irrigation water nitrogen credit

Find your closest location.
Multiply the nitrate concentration from your analytical report (ppm or mg/L) by the conversion factor.
Irrigation Water Nitrogen Credit = Nitrate concentration (ppm or mg/L) X conversion Factor

Enter the resulting Irrigation Water Nitrogen Credit into Table 7 – Line E.

Notes:
The conversion factor assumes a drip irrigation system with 95% efficiency, a crop adjustment factor of 0.7 for raspberries, and imperial to metric factors (Water Conservation Factsheet, B.C. Ministry of Agriculture).
An alternative to this calculation may be used if you know the expected volume of water use. Volume of water (acre-inches applied) X Nitrate concentration (ppm or mg/L) X 0.254 = Kg N/ha

Table 7. Calculation of nitrogen fertilizer requirement for Raspberries.

Example explanation:

Post-harvest soil nitrate test. (PHNT) The PHNT is a “report card” test which measures how successful the crop was in utilizing available nitrogen. It is desirable for the soil nitrate-N level (0 to 30 cm depth) to be less than 25 ppm nitrate-N for a sample taken between August 15 and September 15. This level shows that the crop was able to use most of the soil and applied nitrogen. Greater levels indicate that nitrogen was applied above crop requirements and there will be an increased risk of nitrate leaching. In this case, adjustments need to be made to the management program including a reduction in applied fertilizer nitrogen.

Laboratory results of the PHNT are generally interpreted as follows:

Low test results ( <15 ppm): The nitrogen applied in the previous season was efficiently utilized by the crop. Follow similar nitrogen management for the upcoming season.

Medium test results (16 - 25 ppm): Slightly higher than desirable concentrations of nitrate-nitrogen remain in the soil. Consider reducing the amount and/or improve the placement, form, and timing of nitrogen fertilizer for the upcoming growing season.

High test results (26 - 50 ppm): An excess concentration of nitrate-nitrogen remained in the soil suggesting that excess nitrogen was applied to the crop and/or poor soil/crop health limited proper uptake. Management practices must be evaluated including a significant reduction in manure and nitrogen fertilizer applications for the upcoming growing season. Consider options to improve the placement, form and timing of nitrogen fertilizer

Very high test results (> 50 ppm): Results indicate an extreme concentration of nitrogen in the soil. A complete nutrient management plan should be done including substantial reductions in manure and nitrogen fertilizer application and improvement in the placement, form and timing of fertilization.

Other Nutrients

New plantings. Based on soil test results, split potassium (K2O) applications—broadcast and incorporate one-half the necessary amount before planting and band the remainder with the nitrogen and phosphorus.

Magnesium, boron and calcium deficiencies. Magnesium, boron and calcium levels are frequently low in coarse, sandy soils. Soil test to find out the amount available to the crop.

Foliar fertilizer sprays. Apply in slow-drying conditions for the best uptake. Do not apply during very hot weather as leaf-burning may occur. The plants generally respond better to foliar feeding during the earlier portion of the growing season when the leaves are younger and less waxy.