Blueberries are one of the fastest growing agricultural commodities in South Africa, with farmers taking advantage of high market demand and favorable prices.

However, with the expansion of water and soil resources remaining at a standstill, the key to sustaining the growth of the blueberry industry is to farm smarter, using less water and other resources, for a larger harvest.

With this in mind, Wikus Strauss, co-owner of Seven Growers in Franschhoek, Western Cape, set out to establish the farm's blueberry production. The farm is partly planted with stone fruit, and the land where strawberries used to grow was converted to blueberries in 2017.

Strauss aims to increase the area planted with blueberries each year, and it is currently 21ha. He notes that although the market has been volatile, it is starting to stabilize.

“Last year was not good for blueberry prices and sales. There is a lot of volume in the global market, but the quality is not always good,” she says.

“Every industry has its ups and downs; I think there is room for further growth in the [blueberry] industry, and South Africa has a good reputation globally as a quality producer.

Focusing on quality and flavor will be key to increasing and maintaining market share."

The Seven Growers farm is planted with five Berryworld cultivars, and these are being tested to find the 'holy grail' of blueberries: those that are large, sweet, high quality and that can withstand the long period of shipping to markets. export.

Farm by farm.

Strauss explains that since each farm has a unique microclimate, what works on one won't necessarily work on another.

“So each farmer has to test cultivars to find the one that works best for them. We just removed a cultivar after four years as it was not performing as it should.

“The general consensus is that the bushes should be able to produce crops for 12 years before they need to be replaced. But genetics are developing very quickly, and new varieties are always appearing on the market that have different (sometimes better) qualities,” he says.

“But the cost of orchard development is high, so switching between varieties is not always economically feasible. There is a lot of trial and error when it comes to finding the right varieties. We have neighbors struggling with the same varieties that are flourishing here.”

The Strauss harvest season runs from August to December and reaches a yield of 40 t/ha in mature orchards. The minimum standard is 20 t/ha, depending on the planting density; Seven Growers averages 450 plants/ha.

Strauss is also looking at the differences between shrubs planted in an open field and those planted in pots under shade nets.

Data from the last five years shows that yields do not differ between the two, although shrubs planted in pots do yield much faster. However, the cost of erecting networks is cause for pause.

“Networks are a massive investment. It costs around R250/ha and can go up to R000/ha, depending on the material you use. Plastic gives you an advantage as you can harvest while it rains, but the risk is too high for plastic in this area due to strong winds,” he explains.

“There is a slight benefit to shade netting as it reduces damage to the fruit if there is a freezing rain around August.

But we have found that if we harvest the first round of fruit before then, the harvest is not affected."

The farm has an acid sandy loam soil, which is ideal for growing blueberries. Shrubs planted in open ground have been placed on ridges to prevent roots from submerging in water during the rainy season.

The farm receives an average of 800 mm of rain per year, which occurs predominantly in winter. This means that there is less chance of rain during the harvest season and therefore less chance of damaging the fruit. However, more water is needed for irrigation in the hot summer months.

Since blueberries require around 7 m³ of water per year, compared to 000 m³ for stone fruit, Strauss has had to carefully consider his irrigation system to make the most of every drop of water.

advanced irrigation
Since there are a lot of river rocks on the Seven Growers farm, Strauss decided to plant a portion of his blueberry plants in pots with a growing medium made up of coco coir and perlite.

He notes that the benefit of potting is that the bushes can be moved around the farm if they are not comfortable in a specific microclimate.

“Soil pH and plant water and nutrient uptake can be much better controlled in pots since runoff can be measured.”

Gutters are placed under the pots to catch excess water and direct it away from the roots. They also ensure that any runoff is clearly visible, so irrigation can be managed accordingly.

Strauss explains that irrigation cycles are determined by calculating the field capacity of the pots.

“We measure how long it takes for the pots to fill up to their maximum water capacity before the water starts to come out of the bottom. So we know that this watering time should never be exceeded. There should be a slight runoff, but never more than 5%.”

The Seven Growers pump house allows for individual irrigation lines for each block, so they can be managed individually. Seven Growers uses anti-leak valves on Netafim's drip lines, which were installed at the end of each line to ensure that if the tap in the pump room is turned on, there is a rapid flow of water from one end of the orchard to the other.

Once the taps have been closed, the rate of water extraction is also faster, so the plants at the entry point of the irrigation pipe do not receive more water than the rest, as they would if the water were flowing slowly through the system.

The main irrigation pipes coming out of the pump house are divided between the rows. They are then further divided into smaller tubes or spikes, with each pot receiving two on each side.

This ensures that if the smaller tips on one side fail, the pot will still receive water from the two on the other side, thus mitigating the risk.

While Strauss says he hasn't had any problems with the system, he runs peroxide through the pipes once a year as a precaution to remove any blockages and keep the system clean.

Each spout provides 3ℓ of water per hour. They are moved in the pots twice a year so that the roots do not have a chance to accumulate around them.

This also prevents the formation of pockets of salt in the pots. Strauss does not follow a set watering schedule and instead relies on information from weather stations on the farm, as well as actual water consumption rates of the plants.

On average, irrigation cycles of 10 minutes each are carried out five times a day. A longer pulse of about 30 minutes is done in the morning, followed by pulses of 10 minutes throughout the day, ending with a lower dose of water in the last pulse, since the plants should not be too wet during the night.

“Because the pots are first filled to field capacity and then backfilled, it means that all the roots receive the same volume of water. This ensures that the roots grow evenly and optimally to absorb all the nutrients,” explains Strauss.

“We can't confirm this with scientific studies, but it seems that berry plants grow best with a free-flowing water supply. When plants need water, it must be there. If the plants wilt, we stop watering, because it means it's too hot and the plants have died."

Quality management
Given the high summer temperatures in the area, the farm's irrigation pipes run the risk of heating up to the point that the water burns the roots of the plants; The water that remains inactive in the pipes has been measured at a temperature of 50°C.

To combat this, Strauss had white irrigation pipes installed, which lowered the temperature of the water. This is especially prudent for newly established gardens, where the bushes are not large enough to shade the pipes.

White 'skirts' have also been placed around the black pots. In summer they protect the pots from excessive heat, and in winter they can be raised to allow the pots to absorb additional heat from the sun.

According to Strauss, little data is available to determine whether the quality and flavor of blueberries can be manipulated through fertigation. “However, extensive studies of strawberries have found that nutrients play a very important role in raising the Brix level of the fruit.

“Potassium, for example, can improve fruit quality. However, potassium uptake is largely determined by the calcium content of the plant, and this is very difficult to manage. "Blueberries do not easily absorb calcium, so it is difficult to try to increase the sweetness of the fruit through nutrients."

Strauss believes that ultimately the greatest gain in sweetness is determined by genetics.

“You can't grow good quality fruit if the genetics aren't there. However, good farm management will decide if those genetics will give you a return on your investment.”