Blueberries

NaanDanJain has been providing products and agronomical advice to blueberry farmers all over the world for more than 80 years.

We have acquired experience in many agronomical conditions, from different soil types to a wide range of climate zones.

Even though blueberries are native to North America, they were domesticated in the early 20th century by the USDA. Today, blueberries are known as one of the ‘super foods’, meaning they have numerous health benefits, thanks to the high content of antioxidants. Many scientific studies have proven that blueberries can reduce cholesterol, and lower the risk of heart attacks, cancer and Alzheimer’s disease. Blueberries are one of the most nutrient-dense berries.

A single cup of blueberries contains:

Fiber: 4 grams

Vitamin C: 24% of the RDA (recommended dietary allowance)

Vitamin K: 36% of the RDA

Manganese: 25% of the RDA

Small amounts of various other nutrients

All this goodness for just 84 calories.

All blueberries belong to the genus Vaccinium. This genus also includes cranberries, lingonberries, and bilberries.

Most commercialized blueberries belong to the high bush species, and many varieties are cross-breeds between the northern and southern species. Blueberries are also highly sensitive to lack of oxygen in the soil. Effective ways to prevent water logging is to plant on raised beds and to schedule irrigation effectively.

SOIL

The management of soil pH is important throughout the life of a blueberry plant. Blueberry plants are more vigorous, take up more nutrients and are more productive when grown in acidic soil conditions with a pH below 5.0. If the pH is higher, micro-nutrients will be deficient. One method of acidifying soil is adding elemental Sulphur to the soil. This practice was very common prior to widespread use of drip irrigation. Another extremely effective way to lower soil pH is by fertigating with N-NH4 fertilizers.

Blueberries are also highly sensitive to lack of oxygen in the soil. Effective ways to prevent water logging is to plant on raised beds and to schedule irrigation effectively.

PLANTING

Blueberries are planted with a spacing of 3-4 m between rows. For varieties with low vigor, 0.8 m is recommended between plants, while 1.2-1.5 m is suitable for vigorous varieties. Mulch is commonly applied to the plant row after planting to help keep the roots cool and moist, and to suppress weeds. Today the use of a permeable fabric for weed control is more common.

Mulching 5-10 cm high increases plant growth and yield by insulating roots from high temperatures, increasing organic matter and retaining moisture. Mulching also helps control weeds. Peat moss, shredded leaves, straw, wood chips, or sawdust can be used. When using

sawdust or any other material with a high C/N ratio, increase the nitrogen application or add 1 kg of ammonium sulfate per 20 kg of mulch. The pH of Douglas fir sawdust is about 4.2. Other low pH mulch options include bark mulch and pine needles.

Re-mulching is recommended every 1-2 years.

FRUIT AND HARVEST

POLLINATION AND HARVEST TIMING

For some varieties, cross-pollination is mandatory (Brigitta, Spartan, Chippewa, Polaris and Toro). Other varieties benefit from crosspollination, improving fruit set and fruit size (Blue crop, Legacy, Jersey, Liberty, Elliott and Aurora).

Still other varieties do not require crosspollination at all (Duke, Draper, Blue jay, Nelson, and Ruble). Use two different varieties with similar bloom timings to promote crosspollination.

Plant in a 1:9 ratio of the pollinator variety. Use 2-5 hives of honeybees per acre (depending on the type and age of the field). Blueberries are generally less attractive to honey bees than other flowers due to relatively low amount of nectar. It’s recommended to introduce the bees once the crop has started to bloom so that the bees feed more on the blueberries than on neighboring fields. It’s best to move bees into a field when it’s at 5%-20% bloom. Note that the viability of blueberry flowers reduces greatly after 3 days. Still, some cultivars (notably Jersey)

have low attractiveness, and bees may still fly over this cultivar to reach another.

Bumble bees are very efficient at pollinating blueberry with activity at lower temperatures than honey bees. They visit flowers faster and provide higher rates of pollen transfer per flower visit.

AGRO-TECHNIC

PRUNING

Plants should be cut to a comfortable size for fruit picking. Pruning will improve flower induction and pest control, so crossing branches must be removed. Fruit is formed on two-year-old branches, so it is important to cut away old branches and always create alternative new ones. This can be achieved by cutting away 25%-30% of the whole bush and by cutting the oldest branches every year.

CROP PROTECTION

The following are some of the more common pests and diseases that affect blueberries:

• Symphyla This is a ‘worm’ the size of a few millimeters that eats roots. Pre-plant sampling in heavy soil is important to diagnose symphylan presence.

• Root Weevil The larvae eat the roots, while the adults eat the leaves. Tillage might help reduce weevil larvae populations.

• Stubby-root and root-lesion nematodes Both these eat the roots. Cover crops can help get rid of nematodes. Grow grass or Brassica (e.g. rapeseed, mustard) crops for 1 year.

• Aphids These may be present from the period after vegetative bud break to post-harvest. Honeydew secreted by the aphid can cause the fruit to be contaminated and reduce photosynthesis. It becomes a vector for viruses.

• Leafrollers Oblique-banded leafrollers and red-banded leafrollers can be found on blueberries. The larvae may be present from bud break through to harvest. Larvae of both species feed on developing buds, leaves and fruits and can subsequently reduce yields. First generation larvae

are active before and during bloom. The summer generation larvae are active during fruit ripening, feeding on fruit and foliage.

• Spotted Wing Drosophila A female SWD lays 1 to 3 eggs in each fruit, and a single female can lay several hundred eggs in her lifetime (3 to 4 weeks). The small white larvae feed inside the fruit for about 5 to 7 days until they are ready to pupate.

• Anthracnose Ripe Rot This fungal disease appears on the fruit before harvest and as post-harvest rot. It can also cause shoot tips to become blighted and flowers to turn brown or black.

• Phytophthora Root Rot Infected roots transport water and nutrients poorly, causing small, reddened leaves and overall plant stunting. Avoid planting in poorly drained fields or improve drainage by planting on raised beds and adding organic matter to the soil. Some

blueberry varieties are more sensitive to this disease. Plant only healthy, disease-free stock.

• Botrytis Blossom Blight and Fruit Rot These fungi is dormant during the winter, surviving on twigs that were pruned and dead organic matter. In spring, the fungi spores are released and spread by wind or splashing water.

In the case of systematic pesticides, the chemicals can be delivered via the irrigation system.

They are taken up by the root and reach every part of the plant. This makes irrigation a valuable tool in pest management.

For chemical treatment, always follow label instructions and consult your agronomist. Always consider your local and exporting destination regulation. Always consider bee toxicity.

Blueberries are very sensitive to over- or under- irrigation. For this reason, a well-aerated soil with pulse irrigation through drippers is ideal.

This method also provides constant pH management of the root zone.

An effective way to manage irrigation is to use the crop coefficient (Kc) method. Daily evapotranspiration (ET) is measured by local weather stations, using the Penman-Monteith equation. By multiplying the Penman- Monteith value with the crop coefficient, you can estimate the daily consumption of your blueberries.

It has been shown that irrigating blueberries on one side only can result in significant differential growth and disrupted fruit production (Source: D. Byrla. USDA, Abbott & Gough 1986). It is therefore recommended to use two drip lines, thus improving even distribution of water and nutrients across the root zone.

A good irrigation schedule can be determined by using tensiometers.

Determine the available water volume of your soil between field capacity and the minimal tension. It should not drop lower than 30-40 cbar (kPa=cbar) at any time. Water-holding capacity greatly differs between soil types. For more details, you are welcome to consult with our NaanDanJain agronomists.

Remember that a poorly designed irrigation system can mean that too much water is delivered too quickly for plants to take up, which can result in the loss of water and nutrients, and suffering plants.

FERTILIZATION

Blueberries favor N-NH4. This form of nitrogen reduces the soil pH at the root zone

Keep in mind that blueberries have a shallow root system with most of their active roots at a depth of 30 cm. This means that irrigation should be carefully designed and operated to prevent nutrient leaching, which wastes money and pollutes the environment.

The smart use of water-soluble fertilizers (fertigation) can provide higher yields than granulated fertilizers that are applied dry (*accumulative yield of 5 years)

AmnonDrip PC

Thick-walled, pressure-compensating PC for maximum accuracy at variable topography, pressure fluctuation and long laterals.

High clog resistance due to Cascade labyrinth and strong self-cleaning mechanism

TopDrip HD

Cost-effective PC dripper Accurate performances at variable topography and

pressure fluctuations. High clog resistance due to Cascade labyrinth.

ClickTif HD

Heavy-duty range of on-line button drippers and accessories in various configuration.

Flushing mechanism of regulating diaphragm.

CNL model:

Pressure-compensating, non-leakage design reduces lateral filling time.

• Ideal for pulse irrigation.

• Ideal for soilless, pot production.

• Easy to achieve uniform distribution of water in each pot.

SDI

Sub-surface drip irrigation can provide solutions to a few problems:

• Free surface with no obstacles allows for machinery movement and other activity in the modern orchard.

• Positioning the water source at the root active area keeps soil surface dry and reduces soil compaction.

• Reduces water loss caused by evaporation.

• Reduces weed germination.

The Amnon Drip AS is specially designed for these conditions

IRRIGATION FOR FROST PROTECTION

Global warming is causing extreme weather events. One of these events is spring frost.

According to an article published by the University of California, more economic losses occur due to freeze damage in the United States than any other weather related hazard.

Some growth stages of the blueberries are very resistant to low temperatures. At leaf bud break, for example, plants can tolerate temperatures as low as -12 ˚C. But after fruit set, frost damage can occur from <0 ˚C.

Frost can reduce yields dramatically and damage plants so severely that the following year’s yield will also be reduced.

In most cases, the use of sprinklers is the most efficient way of providing frost protection.

In most cases, the use of sprinklers is the most efficient way of providing frost protection.

Water Application Rate

Minimum of 3.0 mm/h is required in order to protect plants at temperatures as low as -3 ˚C.

A further 0.5 mm/h is required for every additional degree of temperature drop.

Overhead sprinkler irrigation is a very common practice in frost protection. Overhead irrigation provides excellent frost protection in temperatures of -7 °C and lower if the application rates are sufficient and the application is uniform.

Overhead Full Cover Solutions

233 B – Impact Sprinkler

Super 10 – Ball-driven Sprinkler

Flipper

The latest, most adaptive frost protection solution is strip application. Flipper sprays the water directly onto the plants with smaller amounts of water falling between rows.

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