How to Fertilize Raspberries

Wikifarmer

Editorial team

4 min read
19/12/2024
How to Fertilize Raspberries

Raspberry Fertilization: Key Practices for Optimal Growth

It is essential to highlight that no two fields are the same, nor can anyone advise a farmer on fertilization methods without considering the soil and tissue analysis results and crop history of a specific field. However, some common schemes and fertilization strategies used by many farmers are presented below. 

The amount and type of fertilizers needed per raspberry crop highly depend on the following: 

  • soil characteristics and fertility,
  • cultivation system (open field or high tunnels)
  • type of raspberries (summer- or fall-bearing) 
  • the age of the plantation

For these reasons, it is recommended to do a soil analysis occasionally to test your pH and make necessary arrangements to keep the soil pH between 5.8-6.2. If the pH is below or above the acceptable limits for raspberry growth, the farmer can incorporate lime or sulfur into the soil before planting the plants. Furthermore, if the organic matter is below 3%, it is best to add some compost to enrich the soil. You can avoid applying fertilizers when planting because they can damage the young and sensitive root system of raspberries. You can conduct a leaf analysis from the second year after planting and every other year after. 

If farmer want to cultivate their raspberries organically or want to decrease the use of synthetic chemical fertilizers, they can use manure, cottonseed meal, or other nutrient-rich mixes. Good results have been obtained by adding 10-15 lbs (4.5-6.8 kg) of well-rotted (composted) manure (7.5 lbs or 3.4 kg if it is from poultry) per 10 feet (3 m) of row in early spring. A complementary application can be performed in early-mid-summer (early July for the northern hemisphere). Keep in mind that the composition of manure for the 3 main nutrients (N-P-K) from different sources:

  • Cattle manure: 0.6–0.4–0.5
  • Horse manure: 0.7– 0.25–0.6
  • Manure, yard-debris compost: 1–0.2–0.6
  • Cottonseed meal: 6–7–2

The synthetic or organic fertilizers that need to be added can be delivered by granular broadcast or with fertigation. Despite the good results obtained by fertigation in other crops, leading to higher yields, experimental results in raspberry fields have not confirmed this. In this case, the advantages of this method are limited to saving time and more precise control in nutrient application. Good results can be obtained by combining granular fertilizers (spring application) and fertigation (during summer). 

What nutrients do raspberries need, and when to apply them

Raspberries are usually planted as canes. The plant's fertilizing needs are very basic and not challenging to keep up with. 

As a rule of thumb, we use phosphorus to promote root growth, but in the case of raspberry, we add nitrogen-based fertilizer. We do this to encourage leaf and cane growth rather than root growth so the plant can start photosynthesizing and growing. That is why Nitrogen should be added annually. The quantity of Nitrogen you can apply depends on the variety and plant age. Always consult your local agronomist before using any fertilizers. 

The most common practice is to apply 500-800 pounds of balanced, complex fertilizers (10-10-10, 16-16-16 ορ 20-20-20 of N-P-K) per acre (or 446-713 kg/hectare) during the season. This amount is best divided into two applications: one in early spring (most of the amount) and the other at the end of spring. For young raspberry plants, it is recommended to split the total amount into three applications: two weeks after planting, one month later, and one month after (2). 

Quick-release fertilizers such as Ammonium nitrate, ammonium sulfate, and urea can also be used for nitrogen (N) fertilization. Generally, ammonium sulfate makes the soil more acidic, so it is preferred for alkaline soils. More specifically, growers are advised to add 1.6–3 oz N (0.05-0.09 kg) per 10 feet (3 m) of row yearly at flowering for summer-bearing red and yellow raspberries. While for everbearing, black or purple raspberries use 3 oz N. A general recommendation is to apply 120-275 pounds per acre (134-308 kg per hectare) of urea (45-0-0) or ammonium sulfate (21-0-0) per year (4). For plants 1 and 2 years old, half of the amounts mentioned earlier should be used.

If fertigation is applied, the farmer can divide these amounts into equal weekly or bi-weekly irrigations:

  • For 1st year plantation: 2 weeks after planting until mid-summer.
  • For well-established raspberries: 

floricanes raspberries→ from mid-spring until mid-summer 

primocanes raspberries→ from mid-spring until early autumn. 

Depending on the soil and leaf analysis, the farmer may need to apply 18-26.7 lb per acre (20-30 kg per hectare) of phosphorus (P2O5) and 89-107 per acre (100-120 kg/ha) of potassium (K2O). Specifically, K can be applied through fertigation in 5 doses, with the highest amount to be added during the fruit set and fruit growth of raspberries. 

Raspberries suffer a lot from Iron deficiency. This is quite common when they are grown on alkaline soils. The symptoms are yellow leaves with dark green veins. The best practice is prevention. Avoid alkaline and poor-drained soils, such as deserts. Ammonium sulfate can be applied regularly to lower the pH. You can control and, if needed, decrease nitrogen fertilization and excessive irrigation during early spring. If iron chlorosis starts developing, you can apply iron directly to the plants (foliar spraying with chelates) for rapid but short-term results. Always follow the label instructions on any fertilizer because these products can damage the leaves. For long-term solutions, you can prefer applications of chelated iron from the soil twice a year (late spring and early autumn). 

References

  1. https://organicgrowersschool.org/ask-ruth-raspberries/
  2. https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec1306.pdf
  3. http://whatcom.wsu.edu/ag/edu/sfc/documents/sfc2014/Bryla_RaspberryIrrigation_SFC14.pdf
  4. https://extension.usu.edu/yardandgarden/research/raspberry-management-for-utah
  5. https://extension.umd.edu/resource/watering-fertilizing-harvesting-raspberries-and-blackberries
  6. https://extension.umn.edu/raspberry-farming/irrigation-and-nutrient-management-raspberries

Further reading

10 Health Benefits of Raspberries

Interesting facts about Raspberries

Types of berries-Superfoods

Raspberry Plant Information and Variety Selection

How to Cultivate Raspberries Commercially

Raspberry Soil Requirements, Site Preparation and Planting

How to Grow Raspberries from Seed

How to Grow Raspberries in Containers

Raspberries Propagation and Pollination

Raspberry Irrigation: Best Practices for Healthy Growth and High Yields

How to Fertilize Raspberries

How to Train and Prune Raspberries

Raspberry Yield, Harvest, and Storage

Raspberry Pests & Diseases and Best Management Practices