Abe Isaak Shares Expert Advice on Managing Heat Stress, Sodium, and Crop Nutrition
As California enters the hottest months of the growing season, orchard and specialty crop growers face one of their biggest annual challenges: protecting crops from extreme heat while maintaining yield and fruit quality. During a recent interview with “The Ag Meter” Nick Papagni, longtime Reedley grower and Certified Crop Advisor Abe Isaak of AgroLiquid shared practical, science-based strategies that can help growers prepare their orchards before temperatures soar.
Drawing on decades of farming experience and crop nutrition expertise, Isaak explained why proactive nutrient management—not reactive treatment—is the key to helping California’s permanent crops withstand summer stress while setting up next year’s production.
An Early Season Creates Marketing Opportunities
Following an unusually warm March and a cooler, wetter spring, California’s growing season has remained ahead of schedule.
According to Isaak, many growers are preparing for harvest one to two weeks earlier than normal. While harvest timing may gradually move closer to average as the season progresses, the earlier start has already created important marketing advantages for stone fruit growers.
For producers of peaches, plums, and nectarines, even gaining three to five additional marketing days can significantly improve profitability. Rather than having fruit from multiple production areas flood the marketplace simultaneously, growers have more flexibility to manage shipments, avoid oversupply, and capitalize on stronger pricing opportunities.
Instead of experiencing the market gluts that often occur during late harvest years, growers have a better chance to control product flow and improve their bottom line.
Modern Varieties Have Extended California’s Tree Fruit Season
Isaak reflected on how much California’s tree fruit industry has evolved over the years.
When he first entered the business, harvest generally began near the end of May and wrapped up by mid-August.
Today, thanks to improved genetics and newly developed varieties, fresh California peaches, plums, and nectarines can begin shipping in April and continue well into September, sometimes even reaching early October.
However, because the season began earlier this year, consumers shouldn’t expect fresh tree fruit to remain available as late into the summer as they may have in previous years.
Isaak also noted that forecasts for a strong El Niño weather pattern could bring late-summer storms that may affect both fruit availability and marketability. His advice is simple: enjoy California tree fruit while it’s in season.
Heat Stress Begins Before Most Growers Notice It
One of Isaak’s biggest concerns heading into July and August is heat stress.
He explained that once temperatures climb above approximately 85 degrees, trees begin responding negatively if they aren’t properly prepared nutritionally.
Heat stress reduces photosynthesis, slows plant growth, limits sugar production, and ultimately decreases both fruit size and yield.
Rather than waiting for visible symptoms to appear, Isaak encourages growers to prepare before the first major heat event.
That preparation includes:
- Regular soil testing
- Tissue sampling throughout the season
- Water quality analysis
- Balanced fertility programs
- Adequate potassium, phosphorus, calcium, and micronutrient levels
“Being proactive instead of reactive” was one of the central messages throughout the interview.
Water Quality Is Just as Important as Water Quantity
Many growers focus primarily on irrigation scheduling, but Isaak says understanding irrigation water chemistry is equally important.
Testing irrigation water for naturally occurring nitrogen, calcium, bicarbonates, and other dissolved minerals helps growers fine-tune fertility programs while maximizing nutrient uptake.
Knowing what’s already entering the root zone prevents over-application of certain nutrients while ensuring deficiencies don’t develop later in the season.
Sodium: The Silent Killer in California Orchards
One of the strongest warnings Isaak delivered involved sodium accumulation.
He described sodium as one of the most overlooked factors limiting production throughout the Central San Joaquin Valley, particularly following years of drought and challenging irrigation conditions.
Many growers mistakenly believe scorched almond leaves indicate insufficient irrigation.
In many cases, however, adequate soil moisture exists.
Instead, excessive sodium interferes with the plant’s ability to regulate water movement and withstand heat.
Symptoms include:
- Leaf edge burn
- Premature defoliation
- Reduced vigor
- Lower yields
- Poor fruit quality
Once leaves begin dying and dropping, Isaak says growers cannot reverse that season’s damage—they can only minimize additional losses and prepare to prevent future problems.
Potassium Gives Trees More Time to Produce
Potassium plays a critical role in helping plants tolerate extreme temperatures.
Isaak explained that well-nourished trees continue photosynthesizing longer during hot afternoons and resume normal activity sooner as evening temperatures cool.
Although these improvements may only amount to a couple of extra productive hours each day, those hours accumulate throughout the season.
Over an entire month, growers may gain the equivalent of several additional productive growing days.
The benefits include:
- Larger fruit size
- Better fruit firmness
- Improved cold storage performance
- Better customer satisfaction
- Fuller almond kernels
- Increased overall yield
Specialty Crops Face Similar Challenges
Annual crops like tomatoes generally don’t experience the same dramatic calendar shifts as permanent crops because transplant timing remains relatively consistent.
However, excessive heat still accelerates development, shortens the growing season, increases sunburn risk, and reduces fruit quality.
Proper nutrition helps these crops continue normal respiration and remain productive during periods of high temperatures.
Grow Two Crops at Once
One of Isaak’s most valuable lessons focused on looking beyond the current harvest.
During June and July, stone fruit trees begin determining which buds will become next year’s crop.
If trees become deficient in potassium or other essential nutrients during this critical period, they redirect resources away from reproductive bud development simply to survive current stress.
Isaak pointed to pistachios as a classic example.
A tree producing a record crop one year may carry very little production the following season because it sacrificed next year’s buds to mature the current crop.
He encourages growers to take advantage of pesticide applications by adding foliar nutrition whenever possible.
Although additional foliar applications represent added cost, they help ensure consistent annual production and protect long-term profitability.
Don’t Let Sodium Replace Potassium
As the interview concluded, Isaak returned to what he considers one of the most important agronomic lessons growers should remember.
Sodium naturally exists in many California soils.
If potassium levels are low when extreme heat arrives, trees will often absorb sodium because it is easier for the plant to take up.
Unfortunately, sodium cannot perform potassium’s role in protecting plants from heat stress.
Isaak recommends:
- Applying calcium to help leach sodium below the root zone.
- Using sulfur where appropriate to reclaim sodium-affected soils.
- Maintaining sufficient potassium levels before summer temperatures arrive.
- Regularly monitoring soils and irrigation water.
By managing sodium before problems develop, growers can improve both crop quality and overall productivity.
Contact Abe Isaak
Growers interested in learning more about crop nutrition, soil fertility, water quality, or AgroLiquid products can contact Abe Isaak directly:
Abe Isaak
Certified Crop Advisor – AgroLiquid
Cell: 559-240-1987
Email: ABE.Isaac@agroliquid.com
Website: AgroLiquid.com
Isaak also encourages growers to explore the extensive research and educational resources available through AgroLiquid, which demonstrate the science behind the company’s fertility recommendations.
Listen to the Full Interview
This conversation only highlights a portion of the valuable insights shared during “The Ag Meter” Nick Papagni’s interview with Abe Isaak.
To hear the complete discussion—including practical recommendations for managing summer heat stress, maximizing crop nutrition, improving soil health, reducing sodium damage, and preparing orchards for long-term success—be sure to listen to the full interview. Whether you grow almonds, stone fruit, citrus, pistachios, tomatoes, or other specialty crops, Isaak offers timely advice that can help improve yields, protect crop quality, and position your operation for continued success.