NC State Extension Publications

General

As stated in chapter 3, Site Selection, the ideal soil pH for caneberries is 6.0 to 6.5. Preplant soil testing, discussed in chapter 4, should be done a minimum of six months to a year in advance of planting to allow adequate time to make all the necessary amendments to the soil. The only economically feasible time to amend a low soil pH, a low phosphorus level, and to a lesser extent, potassium, in the subsoil is before plantings are established. At that time, soil amendments can be applied, worked into the upper few inches of soil by disking or rototilling, and followed by deep plowing to move the amended soil to a lower depth. Failure to adequately prepare the site from a nutritional site could compromise performance of the planting throughout its life.

Nitrogen is the element most likely to need to be applied every year. Use good records from previous years and observations on leaf color, cane growth, and crop load in the current year to refine the rates of nitrogen suggested below. In an established planting, use leaf analysis to decide which, if any, other plant nutrients need to be applied.

General pre-plant soil optimum nutrient contents are given in Table 6.

Table 6. Soil nutrient content in lb/acre at pre-plant (based on University of Arkansas recommendations).
Nutrient Soil Nutrient Content
(lb/acre)

Phosphorous

40-60

Potassium

200–400*

Calcium

1000–2000**

Magnesium

100–250

Sulfur

21–40

Iron

101–200

Manganese

51–200

Zinc

1.1–3

Copper

1.1–3

Boron

1.0–2.0

* Recommendations from Oregon State for potassium are higher (300–600 lb/acre). Because this mineral is not mobile in the soil, growers might want to use the higher rates, but take care not to cause “salt” injury to new plantings.
**Optimum calcium levels depend on soil type. Liming the soil usually supplies enough calcium.

Blackberry Fertilization

Year of planting. Apply a total of 25 to 50 pounds of actual N per acre over the entire season. Make applications beginning about 30 to 60 days following planting and continuing every four to six weeks until late July/early August, at which time applications should be discontinued. The higher rates are suggested for sandy soils. When fertilizing individual plants, apply fertilizer in a circle around the plant, or make applications in a narrow strip about 12 inches wide in the weed-free zone on each side of the row, taking care to keep the fertilizer at least 12 inches away from the base of the plants.

Second year. Use a total of 50 to 80 pounds of actual nitrogen per acre using a split application. Apply ½ to ⅔ of the total amount being applied in spring when primocane emergence begins and make the second application immediately following harvest for floricane-fruiting cultivars. Make applications in the weed-free area on each side of the row.

Third and subsequent years. Use a total of 60 to 80 pounds of actual N per acre in a split application as outlined above for second year plants.

NOTE: It is assumed that the planting is under irrigation.

Raspberry Fertilization

Year of planting (first year). Use a total of 25 to 55 pounds of actual nitrogen (N) per acre in a split application. Apply about ½ to ⅔ of the total amount at least 30 days after planting and the remainder about 60 to 90 days later.

Second year (summer-bearing cultivars). Use a total of 40 to 80 pounds of actual N per acre in a split application. Broadcast ½ to ⅔ of the total amount at the onset of bloom, with the remainder being applied immediately after harvest. Applications should be made to the weed-free strip and on each side of the row.

Second year (primocane-fruiting cultivars). Use a total of 50 to 60 pounds of actual N per acre in a split application. Apply ½ to ⅔ of the total amount when new primocanes begin to emerge and make the second application 60 days later.

Third and subsequent years (summer bearing cultivars). Use a total of 40 to 80 pounds of actual N in a split application. Apply ½ to ⅔ of the total amount at the onset of bloom and the remainder immediately after harvest.

Third and subsequent harvest (primocane-fruiting cultivars). Use a total of 40 to 80 pounds of actual N per acre in a split application. Apply ½ to ⅔ of the total amount when the first new primocanes begin to emerge and the remainder about 60 days later.

For established plantings, spread fertilizer uniformly across the row in the weed-free zone or side-dress on each side of the row in a 3-foot wide band. If using fertigation, utilize weekly applications beginning at the onset of bloom and going through harvest for summer-bearing cultivars and until late August for primocane-bearing cultivars.

Leaf Analysis

In an established planting, the correlation between soil test results and the actual nutrient status of the plant tends to be poor. However, soil testing at regular intervals is needed to monitor soil pH, as this can impact nutrient availability. Leaf analysis provides an accurate measure of the nutrient status of the plant. A combination of routine soil testing, annual leaf analysis, good records from previous years, and observations of plant growth and fruiting are all needed to develop and maintain a good fertilization program.

With leaf analysis, as in soil testing, the validity of the test results depend strongly on collecting good samples for analysis. Consider the following when collecting leaf samples:

  1. Collect leaves from only one cultivar per sample, preferably from plants of about the same age.
  2. Take the most recently matured leaf on primocanes shortly following harvest for summer-bearing cultivars.
  3. Collect leaves from healthy plants. Those leaves showing signs of disease or arthropod damage, or different growth characteristics should be sampled separately.
  4. Collect a total of about 50 to 100 leaves (one leaf per cane) located on the sixth to tenth nodes of primocanes in mid- to late-July. The area represented by a single sample should not exceed 5 to 10 acres. Variations in plant growth and terrain within a field may reduce the area that should be represented by a single sample.
  5. In primocane-fruiting cultivars, sample the most recent fully expanded leaf on primocane branches at the green to red fruit stage (usually late July to August).
  6. Collect leaf samples before a spray application as opposed to shortly after one.
  7. If leaves are dusty or have spray residue, rinse them briefly in distilled water, blot dry, and place them in a clean paper bag. Let the leaves air dry in a dust-free area prior to sending them to the lab for analysis. Use the procedures outlined by the lab you will be using to obtain samples for analysis. Because different labs use different methods, use the same lab to interpret the values received from the analyses. General foliar sufficiency recommendations are given in Table 7.

Table 7. Macro- and micro-nutrient sufficiency ranges for fruit crops.
Nutrient Range
--- % ---

N

2.00–3.00

P

0.25–0.40

K

1.50–2.50

Ca

0.60–2.50

Mg

0.60–0.90

S

NA

--- ppm ---

Fe

50–200

Mn

50–200

Zn

20–50

Cu

7–50

B

20–50

Authors:

Extension Specialist (Small Fruits)
Horticultural Science
Professor
University of Arkansas
Professor
University of Tennessee

Publication date: Nov. 2, 2015
Last updated: May 12, 2017
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