When it comes to fertiliser nutrients, everyone talks about the big three: NPK (Nitrogen, Phosphorus, and Potassium).
It’s true that these elements are needed in the biggest quantities for crop growth. We can calculate the requirements by looking at crop removal, soil/tissue tests, and growth stages; and there is no doubt that they are important.
Little things mean a lot
The worldwide Stoller group look at integrated crop systems, and pay particular attention to secondary and micro nutrients.
Any element in short supply will become the limiting factor—reducing potential yield and fruit quality as it relates to specific deficiencies (e.g. bitter pit from a lack of calcium).
Also, adequate nutrient levels in the soil don’t guarantee sufficiency in the plant, as the elements need to be available to the roots. Elements such as calcium can be collected by the roots but are delivered mainly to the leaves (follow the transpiration of water), bypassing the fruit.
Importance of micronutrients
My favourite micronutrient is zinc because it affects the plant like a hormone.
If there is not enough zinc, vegetative growth is stunted. A small addition of zinc turns things around and makes the leaves big and allows the growth of the roots and top to proceed.
When a plant is young it must have adequate zinc. Zinc is the precursor for a hormone called auxin. Auxin allows the plant to grow, without zinc growth may be restricted.
Early growth is most important to the plant because it sets the scene for the rest of the season. Remember the roots get their food from the leaves, so bigger healthier leaves become the factory for food production that feed all plant growth.
Delivery and uptake
Let’s talk about uptake, continuing with the zinc example.
Zinc is not very mobile in the soil and only moves in xylem the of plants (it can’t move down in the phloem) so zinc doesn’t transfer to a new leaf from an old leaf.
Early in the season it is important to have a highly available zinc form for delivery to the plant. A chelated form of zinc will move into the plant more quickly and be absorbed and utilised by the plant more efficiently.
A chelated zinc will get into the plant quickly and be available for cell initiation and expansion and can aid with proper pollination and early fruit development.
Stoller’s Zinc Chelate is highly available and (with its low pH) can move directly into woody tissue when applied as a foliar.
The finer points to zinc application
Use caution when applying zinc to trees during the growing season. Some varieties of stone fruit can defoliate if zinc is applied during stress or critical growth stages.
For sensitive varieties, zinc can be applied through the soil, post-harvest, or during dormancy when leaf fall is not an issue.
Chelated elements applied to the soil are less likely to be tied up than basic metal elements.
Stoller has a range of phenolic acid chelates incorporating a formula that performs well with individual or combined nutrients and doesn’t give preferential chelation to particular elements.
Besides the range of phenolic chelates, Stoller has specialised products for fertigation (supplying NPK and other elements), foliar sprays for fruit quality and development, and plant physiology products that can help with pollination, sizing, and maturity.
The Stoller team have the tools and the know-how to manage the crop through all stages of growth, prevent deficiency and optimise marketable yield.
For more information contact Stoller Australia
phone 1800 FERTILISER
www.stoller.com.au
See this article in Tree Fruit July 2018
