The key fundamentals used for building soil applied fertiliser programs, the 4 R’s: (right place, right product, right rate and right time) are just as relevant when building foliar fertiliser programs for permanently planted tree and vine crops.  

Starting with the right place and right time, the mobility of the applied nutrient varies widely and is associated with the nutrient applied, says David Coombes, Yara sales agronomist for Sunraysia and Victoria.

Mr Coombes said the timing and spray droplet target are important factors that influence the adequacy of foliar programs.

“The application target changes with crop development cycles. During bud burst/pre flowering, buds and newly emerged leaves are the primary target as they provide essential nutrients and energy for developing flowers and fruit.

“Maximising nutrient availability in these plant parts will help get the season off to the best start.”

Results of recent trials conducted by Yara North America on almonds in California demonstrated that an application of 3 L/ha of YaraVita Frutrel at full bloom was effective at increasing nut set.

“Generally, a higher nut set has been shown to produce higher yields in almonds crops. That’s the reason Yara’s foliar program targets bud burst and bud development applications,” Mr Coombes said.

“Calcium is a nutrient that is widely regarded as immobile in plants. Calcium generally only moves with water from the roots, through the xylem and mostly to the leaves, which is driven by transpiration or water loss.

“Fruit which has a low surface area relative to fruit volume, for example apples, can have issues with low calcium concentration in the fruit, such as bitter pit (as seen by the apple on the left in the image below).

“Foliar applied calcium can be effectively taken up by the skin and fresh tissue, just below the skin in apples.

“However, for the spray application to be effective, thorough coverage of the developing apple is necessary,” Mr Coombes said. “Calcium spray droplets that land on leaves will not improve fruit calcium levels as it cannot be translocated from the leaves to the fruit.

“Growers who apply multiple applications of foliar calcium such as YaraVita Stopit and are focused on the coverage of their developing fruit, generally have less issues with bitter pit.

“Combining foliar applications of YaraVita Stopit with soil applications of YaraTera Calcinit in their fertiliser program is essential for apple producers,” Mr Coombes said.

To cover the last 2 R’s, right product and right rate, Mr Coombes said YaraVita products have been specially formulated for foliar applications.

“YaraVita formulation chemists select high quality raw materials and combine them with adjuvants, wetters, stickers and compatibility agents to manufacture products that are easy to use, safe on crops and supply plant available nutrients.

“Yara’s approved application rates by crop ensure agronomists and growers select the correct rate for their situation.”