continued from last month: Where do we want the food to go?
Food movement is all about the points of demand—and the signals that determine food movement are sent by hormones.
Where do we want the food to go?
Well, we don’t want it to move to the vegetative growth because that will be falling on the ground soon.
We want it to move to the roots and storage tissue. The storage tissue includes the buds that will be important next season—so it helps if they are furnished with food.
Movement to the roots keeps the roots alive for longer and keeps their ability to supply water and nutrients to the trees as they approach dormancy.
What does this mean in practice?
There is valuable food stored in the leaves.
After harvest we want it to move back into the tree and not into new vegetation. If possible, we want the vegetative growth to slow down leading up to harvest, so all the energy is not put into feeding the new vegetation.
Post harvest fertiliser
Once the tree has settled after harvest, there is a good opportunity to provide food, especially if the tree is in storage mode.
The tree stores reserves in the roots and woody tissue and these reserves are critical to healthy growth in the spring.
Many species of tree rely on stored arginine nitrogen for a large part of their spring growth. This can be applied to the tree in post harvest treatments.
Many secondary and micronutrients can also be applied at this time.
Root growth flush
Most trees experience a root growth flush after harvest, so this is a good time for soil applied fertiliser.
Potassium is important in moving sugars out of the leaf cells and into the phloem.
Magnesium drives the ATPase pump that is integral in this function, and boron helps the discharge of sugars—especially when the tree is slightly vegetative.
Calcium applied post harvest will add to the reserves in the tree.
Other elements such as zinc, manganese, copper and iron can all be valuable in post harvest conditions and this is a good time to apply these elements to crops that are sensitive to certain trace elements in the growing season.
Suggestions for post harvest
- Avoid practices that will promote vegetative growth close to harvest time such as heavy irrigations or high nitrogen applications.
- Make sure nutrient elements are at optimum levels especially potassium, magnesium and boron.
- Immediately after harvest make an irrigation without fertiliser to reduce stress.
- Follow up with a post harvest nutrient treatment for the tree—this provides the reserves that are needed for the next growing cycle.
- Post harvest nutrients can be applied both through the soil and the foliage.
Contact Stoller Australia Freecall 1800 Fertiliser
email
For more information, see Tree Fruit May 2014
