Increasing Fruit Quality and Uniformity in Blueberries
Increasing Fruit Quality and Uniformity in Blueberries
Good nutrition management starts early in the season, and it can pay off big at harvest. In blueberries, the right nutrients at the right times build large, firm fruit and can significantly increase uniformity.
Rick de Jong, International Business Manager at Agro-K, says fruit firmness is becoming more important as labor shortages continue and more growers are relying on mechanical pickers.
“Historically, fresh-market blueberries were hand picked, and machine-picked berries went for processing,” de Jong says. “With labor shortages, even fresh-market growers are turning to mechanical harvesting. There has been a lot of improvement in the machines, so they handle the berries more gently. Blueberry varieties are being bred for increased fruit firmness. Nutrition can also play a huge role in creating a firmer berry that can stand up to machine picking and have the quality needed for the fresh market.”
Calcium is Key to Strong Fruit Structure
Getting calcium into the fruit early is key, de Jong says. Calcium is required for cell division and cell wall strength. During the critical four-week period between fruit set and the end of fruit cell division, the number of cells within the berry is determined. Once that time has passed, the cells will expand and grow, but will not increase in number. The more cells that are created during this critical window, the larger the potential size of the fruit.
Fruit firmness is directly related to cell wall strength, and calcium has a major impact here, as well. Without enough calcium as the fruit is forming, cell walls will be weaker and less able to handle excess water and fruit will be more likely to split. The fruit will also be more vulnerable to damage from mechanical picking.
Agro-K’s Vigor Cal-Bor-Moly™ applied at pink bud and full bloom gets calcium into the plant early, de Jong says. Two more applications of calcium in the form of Vigor SeaCal™ at petal fall and at the early green BB stage continue to support cell wall strength along with leaf development and function. Agrobest® 9-24-3 can be tank mixed and applied each time along with the calcium for macronutrient support.
“The ‘Sea’ in SeaCal refers to Agro-K’s Symspray seaweed, one of the active ingredients,” de Jong says. “Sympray, with its’ unique blend of Ascophyllum nodosum fortified with minerals, really supports fruit set and bulking. Once fruit begins to color, we recommend our Potassium Finishing Solution to really push the sugars into the fruit. Our program really does a good job of getting the sugars into the fruit and getting them to ripen at the same time. We’ve had research trials in New York that showed a 200% increase in uniform maturity at the first pick. It was great news for the grower, because that’s when you get your best crop and best price. And, you’re optimizing your labor.”
Understanding Nutrient Interactions Leads to Better Outcomes
It’s important to understand how nutrients interact with each other so you are not wasting your efforts. One example de Jong sees too often is applying potassium early. Potassium is antagonistic to calcium and can interfere with the calcium you are applying to the crop during the critical fruit cell division window. Blueberries don’t need much potassium early in the season, so hold off until later in the year, he says. Many growers apply potassium early, but this can lead to problems later.
“One study we did compared our program plus potassium phosphite with our program alone, and there was a 53% increase in fruit splitting in the crop that had potassium phosphite applied early,” de Jong says. “The cell walls were weaker, and after the major heat event last summer, the grower started applying a lot of water to make up for it. The water went into the fruit, but the cellular structure wasn’t there to support the bulking, and the berries just split.”
There was also a significant drop in fruit firmness in the potassium phosphite treated fruit after 21 days in storage when compared to the fruit without it.
“These studies just continue to show the importance of calcium in fruit quality, de Jong says. “It’s important to apply it at the right time, in the right formulation, and make sure you don’t do anything to antagonize it. The end results will be worth it.”