Postharvest Foliar Fertilization Gets Next Year’s Crop Off to a Good Start

Postharvest Foliar Fertilization Gets Next Year’s Crop Off to a Good Start

At the end of the season, fruiting crops such as apples, cherries, pears, peaches, and nuts contain reduced levels of nutrients. Macro and micronutrients applied during the season have gone into plant development and fruit production. Yet, this is the time in the crop cycle when next year’s leaf and flower buds are developing. Providing a boost of essential nutrients in the fall, post-harvest, can improve bud formation and bud winter hardiness, setting the stage for a successful crop next season.

After harvest there is only a sliver of time to apply fall nutrients and have them absorbed by the plant. Once leaves are starting to senesce, it’s too late for foliar applications. The window of opportunity for fall foliar nutrient applications is just after harvest, while the foliage is still green and actively conducting photosynthesis.

“The postharvest application should really be looked at as the first nutritional application for next year’s crop,” says Rick de Jong, international business development manager for Agro-K. “How you put the crop to bed for the dormancy period impacts how well it’s going to do in the spring and throughout the next growing season. Before dormancy that tree or vine is already developing the flower and leaf buds that will drive next year’s crop. The maximum yield potential is set and if it is to be realized these buds needs to be supported.”

De Jong says a fall, foliar fertilizer application can help buds over winter better and ensure that the right nutrients are in the right places to support in-season fruit set, size, and quality. Certain plants such as cherries and highbush blueberries begin bloom before leaves emerge. Even later-flowering crops, like apples, often bloom when soils are still cold and wet, which can inhibit nutrient uptake. During this early season time period the plant uses stored nutrients to support crop development.  Fall foliar fertilization is key to supporting these early season needs.

The Right Nutrients, in the Right Amounts, at the Right Times Get the Crop Off to an Optimal Start

Research supports the need to apply boron in the fall so it can be incorporated into the flower bud during bud development pre-dormancy. This ensures that boron will be available in the spring during bud break in support of flower health and pollen viability. Waiting to apply boron until the early spring, when the plant is in bloom or shortly before, could potentially leave the plant boron deficient when it is needed most. JP Jacobson, technical sales representative at Agro-K, says fall boron is especially necessary on apple crops in seasons where excessive flowering is expected. This can be the result of fruit production cycles being altered due to temperature extremes or biennial bearing cycles. The year 2022 is expected to be such a season for both these reasons in various regions in North America. Postharvest, foliar applications using Agro-K’s TopSet (9% boron, 0.5% molybdenum) ensures there is early season boron in sufficient quantities to support flowering and fruit set.

“Zinc is another key nutrient to get into buds in the fall,” de Jong says. It has been shown to help buds over-winter better. Nutritional copper and molybdenum can boost plant health benefits the following year. Agro-K’s Zinc +5 (4% zinc, 0.5% magnesium, 2% manganese, 1 % iron, 0.5% copper, 0.2% molybdenum) is a key product for foliar postharvest applications.

“Potassium plays a role in winter hardiness – it helps the plants harden off and slow down,” de Jong says. Phosphorus will be needed early season to support cell division as the spur leaves develop. Agro-K has several products ideal for supplying phosphorus and potassium during this fall period, including Agrobest® 0-20-26, Agrobest® 3-18-18 and Agrobest® 9-24-3. “These products are designed for foliar applications and can be used as needed, depending upon the crop,” de Jong says.

Foliar Formulation Allows Quick Uptake

Using the Right formulation for foliar, fertilizer applications is important for nutrient penetration at any time during the year, but it is essential postharvest. “If a product isn’t designed for foliar uptake, even though it coats the leaf, it doesn’t penetrate very well,” de Jong explains. “Then, two or three weeks later, the leaf drops off taking the nutrients with it. It’s always important to use the right formulation for the application, but it’s critical for this fall application because the window is so small and the benefits so great. Many of our products use simple sugar complexes that will penetrate the leaf almost 100% within 48 to 72 hours.  This simple sugar complex technology requires little plant energy for the plant to metabolize the mineral nutrition. Using an Agro-K simple sugar micronutrient complex that takes less energy from the plant to absorb is pretty important – especially at this time of year.”




Tree crops? [JJ1]


Biennial bearing cycles [JJ2]

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