Calcium in Permanent Fruit Crops

(Sponsored) Calcium is an important nutrient in fruit crops, but the majority of Ca applied by growers goes to waste. Let’s explore why.

There are three golden rules to remember in calcium nutrition, once learned they can form the best practices on a crop.

1. Crops cannot store excess Ca.
2. Calcium can only move up.
3. Calcium can only be absorbed if there is auxin.

Let’s look at each point and apply it to permanent crops.

Plants can’t store excess Calcium

Unlike potassium and many other nutrients, plants have no capacity to store reserves of Calcium. Ca is stored in calmodulin proteins between the cell wall and cell membrane, once these Ca storage sites are all occupied the plant ejects any extra calcium as it is not beneficial to plants to have free calcium in cytosol. This means that plants precipitate out large amounts of calcium oxalate from leaves, even when there are calcium deficiency symptoms on fruit.

It is also the reason that tissue tests are a poor way of assessing need for Ca in fruit crops:  A. Leaf analysis tells us little about fruit tissue content which is usually a local problem and, B. the difference between sufficient Ca and a problem like bitter pit (in apples) is only 2ppm which is outside of analytical test method tolerances.

Calcium can only move up Calcium is not phloem mobile, meaning that plants cannot easily mobilize it and move it from one place to another.  Instead Calcium moves through the Xylem with water transpiration. This means Calcium follows water through plants from the roots to the places of highest water loss (usually the foliage at the top of the plant). This is why there is usually a difference observed between the shady half of a fruit and the sunny half). It is also why any conditions effecting water transport such as drought, waterlogging and wind can lead to worsening calcium related quality problems.

Calcium can only be absorbed if auxin is present Calcium transport into cells is directly related to auxin content in plant tissue, as calcium transport is governed by polar auxin transport. This means that there are places in crops that can not absorb calcium properly no matter how much is applied.

To understand how this effects fruit crops we need to understand when and where fruit produces auxin. Auxin is a growth hormone involved in cell division, so only new tissue has a good content. When fruits are small they are producing lots of new cells, and have good auxin content and good ability to absorb applied Ca. However when the fruit gets over 4mm in size it has all its cells and shifts to cell expansion, whereby the ability to absorb Ca decreases rapidly. This means that young fruit can absorb Ca well, but mature fruit struggle.

So what can we do to help with fruit quality?  We can work with the crops physiology to support better calcium nutrition.

OMEX^® Cell Power® SizeN^® Ca combines Levity’s LimiN chemistry with calcium. The product emphasizes root growth and a good compact growth habit which is vital to fruit trees ability to supply Calcium to fruit. Remember Ca moves up from active root tips to vegetative growth at the top (through transpiration stream), and is absorbed mostly in the actively growing parts. When trees receive standard N sources we see reduced root growth and too much focus on apical shoot growth. This means that a huge Ca sink is created at the top of the tree which effectively diverts Ca away from developing flowers and fruit.

When we use OMEX^® Cell Power® SizeN^® we encourage good root activity, and do not create a source sink imbalance. Good growth habit is the first key to good fruit quality.

LoCal is another Levity technology.  Cell Power^® Calcium Gold and Cell Power^® Calcium Platinum, containing LoCal technology, allows parts of plants low in auxin to properly absorb Ca where they would normally have a low ability to do so. Calcium fertilizers Cell Power^® Calcium Gold and Cell Power^® Calcium Platinum) that use LoCal technology can supply calcium to fruit very effectively, preventing disorders like bitter pit in apples. Best timing in any fruit crop for Ca applications is a foliar spray between flowering and fruit setting.

OMEX^® USA Cell Power^® Calcium Gold and Cell Power^® Calcium Platinum formulated products we can use as little as 2 x 1pint/acre and see better results than any amount of standard foliar calcium products regards correcting physiological disorders. For fruit firmness late season applications are very effective, where conventional products will see little or no benefit as fruit can’t absorb Ca from conventional sources when mature.

Recommendations Almonds – Cell Power® SizeN^® Ca applied as a dormant spray (1% solution to soak bark) 1-4 weeks before bud break.

Then Cell Power® SizeN^® K 4 applications at 2 Quarts/acre. Applications through drip to keep roots alive, a good shape, and high fruit load.

3 applications at 1Pint/Acre application. Cell Power^® Calcium Gold and Cell Power^® Calcium Platinum formulation at flowering, top up after 2 weeks, then 1 more ahead of harvest.  This will reduce shell seal breakdown and increase yield.

Apples, Pears Cell Power ® SizeN^® K applied through drip regularly through season, 4 applications at 2 Quarts per application. This will allow a reduction in total N applied from other sources, and will increase fruit load and size. Can also be applied foliar at 2 quarts/acre.

5 applications at 2 pints/acre.   Cell Power^® Calcium Gold and Cell Power^® Calcium Platinum formulation at flowering, top up after two weeks. Then 2-3 further applications through the season. This will dramatically reduce bitter pit and russetting.

Stone fruit/Cherries Cell Power® SizeN^® 4 applications at 2 quarts/acre application. Applications through drip to keep roots alive, a good shape, and high fruit load.

3 applications at 1pint/acre per application. Cell Power^® Calcium Gold and Cell Power^® Calcium Platinum formulation at flowering, top up after 2 weeks, then 1 more ahead of harvest. Will reduce cracking and increase yield. 

Table Grapes Cell Power® SizeN^® Ca applied as a dormant spray (1% solution to soak bark) 1-4 weeks before bud break.

Cell Power® SizeN^® K 4 applications at 2 quarts/acre per application.  Applications through drip to keep roots alive, a good shape, and high fruit load. Shift toCell Power® SizeN^® K after first application.

3 applications at 1 pint/acre per application. Cell Power^® Calcium Gold and Cell Power^® Calcium Platinum formulation at flowering, top up after 2 weeks, then 1 more ahead of harvest. This will improve berry size, reduce ‘Hen and chickens’ giving better bunch shape, and improve shelf life.

For more information on products please contact OMEX^® Agrifluids at OmexUSA@Omex.com or call 559-661-6138.

— By Dr. David Marks, Levity Crop Science