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Managing Salinity

Winter – An opportunity to leach away some salts

During the growing season, various salts accumulate in the soil around the tree roots. We introduce salts with the irrigation water and there is not always enough displacement and water movement in the soil to remove them from the profile.

During winter dormancy there is often significant rainfall and its movement down through the soil can be very useful in taking salts along for the ride and away from the tree roots. Some soils (especially heavier soils with clay) have a stronger bond with the salts and many of the salts remain attached to the soil particles in the root zone. This can mean that the sodium “hangs on” to the soil throughout the winter and becomes a problem for the tree in the spring.

Sodium is one of the less desirable forms of salt to have in the roots (especially in the spring) as it prevents other important nutrients such as calcium and potassium getting to the tree. If sodium is allowed to dominate in the root zone, this can cause stress to the tree and lead to burning and dropping of leaves in the extreme circumstances.

One of the best things that you can do for tree health is to flush salts away in the post-harvest and winter periods. Stoller has a specialty liquid called Aqua-Cal which contains positively charged ions such as calcium and amine nitrogen. These ions are effective in displacing sodium from the root zone and allowing it to be pushed away from the trees.

The process of using these cations (positively charged ions) to displace sodium is called “mass action”, our technique is to overwhelm the undesirable ions with “good ions” such as calcium. Aqua-Cal contains abundant “good ions” in a very soluble form so that mass action displacement can be achieved.

Note: It is important to ensure that the soil has somewhere to drain so that the flushing solution can wash the salts away from the roots. We need to avoid areas where the soil is not penetrable or where there is a perched water table.

Calcium in the root zone makes for healthy root growth in the spring and ensures that there is competition for the uptake of sodium in the form of soluble calcium.

Aqua-Cal is a liquid and is applied through the micro irrigation system or can be banded along the tree drip line and watered in.

Different orchards have different ideal strategies based on the level of salts, the drainage and the soil type, so it is always good to check with your Stoller reseller or agronomist.

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