Jump-Start June!

Here comes the heat. With that comes heat stress, fruit development, water penetration issues and higher sodium levels. So many stressors, so little time. Let’s see if we can keep the heat on ourselves with a little chemistry.

Gypsum’s Traditional Role
Historically, we have used gypsum to help with water penetration. Why is that? Gypsum, or calcium sulfate, is a large molecule that wedges the ground open. If it is incorporated, that is, or there are enough soil cracks to allow for penetration. Gypsum is hydrophobic, which is why it is used in wallboard. This means it does not like to absorb water. It is used to keep our home interiors dry and acts as a moisture barrier to insulation, framing wood and outside humidity.

Its primary function in soil was always as a soil conditioner for water penetration and soil tilth. To that end, it has worked well for decades, especially if it is incorporated. Typically, in orchards, we just spread it on top of the berms. It does not get incorporated. When it washes down to the floor, eventually it breaks down and becomes part of the soil but has not really addressed the issues on the berms where most of the feeder roots are. Calcium is a macronutrient, as is sulfur. But together, they repel water and take up space.

Understanding Sulfates and Nutrient Availability
Let’s talk about sodium reduction. Calcium can only attach to the soil ionically if it is in ionic form and looking for a negative charge in the soil. Calcium carries a double positive charge and is a strong magnet. Gypsum is only 0.26% soluble. If calcium is already bound to another anion, it is not attaching to soil, it is just wedging the ground open. And it certainly is not feeding the plants.

Take a look at your soil reports. How much sulfate do you have in the percentages? Sulfate is a large molecule itself. My buddy and fellow CCA Derek Sissom likens sulfate to all the cars in the parking lot at the mall at Christmas. There’s no place to park, so you just drive around looking for one. Except it is a little different. With high soil sulfates, those anions are also looking for cations to attach to. Like what, you ask? Calcium, potassium, magnesium… get the picture?

It can bind up other nutrients the plants need and make them unavailable for absorption. It may cause more harm than good. We have really never seen a sulfate toxicity for the most part, but we certainly have seen cation deficiencies because they are not solubilized in the soil solution. Plants drink their food. Again, get the picture? Plenty in the soil, not in the trees.

‘Calcium moves with water, making irrigation management just as important as the fertilizer source itself.’

Why Soluble Calcium Matters
What if we could put soluble calcium in the water we are already running, save time, labor, diesel and actually affect the root zone in the wetting pattern? Well, I’m glad you asked.

CAN-17 can. Calcium nitrate can. Calcium thiosulfate can. Fermented calcium products, chelated and complexed, can as well.

Why not deliver your calcium to the roots in a form the plant can drink and in ionic form where it can kick sodium off the colloid and leach it out? I say yes. Do that. Often. Not just in the fall before it rains. Feed soluble calcium all year.

Feeding Calcium Throughout the Season
Calcium is also immobile in plant tissue. Once it’s there, it stays there. So our trees need a constant supply. Give that to them.

We typically end up in the 4% to 5% range at the end of the season. Our soils typically have 1,000 to 6,000 ppm in soil tests. That should be plenty, but not if it is not solubilized. Feed it.

One more note: If the soil pH is above 7, which most of our orchard soils are, less is solubilized. Do you see a trend?

Often, our efforts to help end up causing other issues. In my articles, I like to say actions have reactions. Never more so than in our soils. Keep things balanced. Fertility is often delivered as a salt. It is the salinity index that can burn or feed the roots. Keep an eye on those values and use more soluble products when applicable.

Taking a Whole-System Approach
As farmers, our seasons get really busy. We tend to treat fertility like the express lane at the coffee stand drive-through. Quick fixes for specific problems without taking into account the entire picture.

Slow down.

Ask your crop advisers and reps for big-picture solutions, with emphasis on the solutions part. Feed your plants in season, in the wetting pattern, with solutions they can actually drink.

These fertigation events do not have to be long irrigation sets. Keep those valuable nutrients in the root zone longer with shorter water shots when feeding. Use formulations that will not cause other issues down the road.

It will save time and money while hopefully improving yields. We only have so long every season to get it right. In the heat of it, mistakes can be costly.

Reduce the stress on you and your trees by applying what is actually going to be effective when it is needed.

Publisher’s Take

The Big Picture: What to do Next

1. Check your sulfate levels before applying more gypsum.
High sulfate soils can tie up calcium, potassium and magnesium, limiting nutrient availability.

2. Prioritize soluble calcium sources during the growing season.
Fertigated calcium products can reach active feeder roots more effectively than surface-applied gypsum.

3. Target the root zone, not just the soil surface.
Evaluate whether your calcium program is actually reaching the wetted area where roots are feeding.

4. Monitor sodium and calcium together.
Don’t assume adding gypsum automatically solves sodium issues. Review soil and water tests to confirm sodium is being displaced and leached.

5. Feed calcium throughout the season.
Because calcium is immobile in plant tissue, consistent in-season applications are often more effective than a single fall treatment.