Welcome to the Ultra Gro Agronomy Letter!
Fall of 2022

In this year of tumult and angst, business has been anything but normal. So, what are the key factors facing our growers as we enter the post-harvest phase for fertility? How do we navigate through water scarcity, low almond prices, poor well-water quality, tight budgets and stressed trees and vines? These are the questions we try to answer every day, and here’s a brief attempt to examine these issues for this Fall.

In this issue of our Agronomy Letter, we asked Ultra Gro Agronomist, Robert Smith, to give us a current “state-of-the-farm” article about soils and trees. Robert’s article helps us understand the science/agronomy of deficit irrigation, sodium issues and deferred care that is prevalent this year. Chase Thomas provides a very timely article that serves as a simple primer (that all of us can understand) about interpreting your tissue reports. And finally, we provide a basic Ultra Gro Post-Harvest Program that can save money for many growers in this challenging year.

Thank you for your business!
Soil Issues We Face in 2022
by Robert Smith, Agronomist
As we push forward onto harvest the effects of deficit-irrigation, poor irrigation water quality, and heat are taking a toll on almond orchards throughout the valley. Subtle changes have occurred increasing the adverse effect of salt buildup. Droughts and reduced water deliveries only exacerbate the situation. The problem is a gradual buildup of salt levels in orchards. Whether this problem originated from poor water quality, a reduced water supply, poor irrigation management, or consecutive droughts, the ramifications of this salt buildup, if left unchecked, will negatively impact almond production.

Salinity reduces water availability for plant use. High salt levels hinder water absorption, inducing physiological drought in the plant. The soil may contain adequate water, but plant roots are unable to absorb the water due to unfavorable osmotic pressure. This is referred to as the osmotic or water-deficit effect of salinity. Plants are generally most sensitive to salinity during germination and early growth.

The second effect of salinity is shown when excessive amounts of salt enter the plant in the transpiration stream and injure leaf cells, which further reduces growth. This is called the salt-specific or ion-excess effect of salinity (Greenway and Munns, 1980). Damaging effects of salinity involve disturbances of ion balance, induced by reduced plant uptake of nutritional elements such as K, Ca and P, and excess accumulation to toxic levels of Na or Cl Symptoms include restricted root growth, marginal or leaf tip burning/ browning, inhibited flowering, reduced vigor, and reduced crop yields.

Irrigation water high in soluble salts and sodium adversely does affect almond productivity by increasing the electrical conductivity (ECe) and the exchangeable sodium percentage (ESP) of the soil. Salinity becomes a problem when enough salts accumulate in the root zone to negatively affect plant growth. Excess salts in the root zone hinder plant roots from withdrawing water from surrounding soil. This lowers the amount of water available to the plant, regardless of the amount of water in the root zone.

There are several more reasons we are recently seeing these changes. Obviously, if the source of irrigation water servicing the orchard has had a decline in quality (i.e. higher salt levels), problems will surface. However, even if water quality is marginally good, problems will arise if irrigations are not properly managed. 

Damaging effects of salinity involve disturbances of ion balance, induced by reduced plant uptake of nutritional elements such as K, Ca and P, and excess accumulation to toxic levels of Na or Cl (Munns & Tester, 2008;Bernstein, 2013;Parihar et al., 2015). Salinity alters mineral composition of plants via integrative effects on the ratio between ions in the rhizosphere, uptake processes into the root, and transport or partitioning within the plant body. ... the four most salt-tolerant rootstocks (Empyrean 1, Cornerstone, BB 106 and Bright’s Hybrid 5).

These changes tend to gradually increase the levels of chlorides or sodium each successive year. Because the changes occur slowly over the course of several years, the actual levels may seem un-alarming, even though they may be well above the thresholds that are normally considered toxic to the trees. In addition, this slow change rarely produces the “acute toxicity” symptoms normally associated with salt burn. What does occur is a reduction of shoot growth and smaller kernel sizes. Trees may take on the appearance of being dry stressed, even shortly after an irrigation when soil moisture is ample.

The pre-harvest to post-harvest water deficit period also coincides with the flower bud initiation period. The usual practice of ‘holding off’ the water in preparation for, and during harvest and drying, must be managed carefully because pre-harvest water stress affects current season nuts, and post-harvest water stress directly affects bud initiation and development, and therefore the subsequent season’s yield. The benefits – minimized trunk damage from shakers, hull rot, and ground moisture and humidity for drying of pre-harvest deprivation must be balanced alongside the less desirable effects – increased soil salinity, reduced kernel weight, increase in ‘partial splits and/or ‘hull-tight’ nuts, reduction in late season leaf function, and stress presenting as wilt and/or premature leaf drop and biomass reduction.

Stress results in reduced carbohydrate development. With less sugars available to the tree, there is less energy to devote to flower formation. Consequently, “bloom” the following year will be lower in quantity (fewer flowers) and possibly quality. Water stress also affects the tree beyond flower formation. Premature leaf drop will prevent movement of macronutrients (nitrogen, potassium, phosphorous) from the leaves to the spurs for use in the next growing season.

Remember that all the soil amendments in the world will be of little value if the salt they free up is not leached out the bottom of the rootzone. If reduced water allocations prevent irrigating with leaching considerations, or in many cases even to full ET, problems with salts can be expected.

The perfect cure is a steady rain over several days during the dormant period, since that is when soils temperatures are lowest (reduces Phytophthora risk), root activity, shoot activity, and ET are at a minimum, and crop and cultural activities are not compromised. Recently we have not been blessed with such winters. If supplemental water (either surface or well) is available to winter leach, preferably in early January or sooner, it should definitely be implemented.
Pictured Above: UG Crop Advisor Dennis Laux with 43 August tissue samples.
How to Read Tissue Samples
by Chase Thomas, Crop Advisor
If you are like me, it is easier to look at a pretty graph and see red or green to know if we are at normal or adequate levels on our leaf analysis. Lab analyses give us ranges for our tissues from Very Low to Very High. When we look at our tissue samples we usually are satisfied if we are in the Good to High range. But what do those numbers and percentages really mean? When we are in certain ranges, how can we get our levels to a more desirable level, and, what is that desirable level?

There are six macro nutrients we pay attention to on our tissue samples. These nutrients are Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Sulfur (S), and Magnesium (Mg). They are considered macro nutrients because they are what the plant uses the most of to grow. 
It is important to have a balance ratio of these six macro nutrients to increase yields each year. Here is the formula we use when looking at tissue samples to make sure we are balanced and getting the most for our crops:

  • It all starts with Nitrogen. For these formulas Nitrogen will always equal 100%. No matter what your nitrogen levels read, the rest of the macro nutrients levels will be based on a percentage of the nitrogen levels. 
  • Phosphorus should be 10% of the nitrogen level percentage
  • Potassium should be 80% of the nitrogen level percentage
  • Calcium should be 80-120% of the nitrogen level percentage. This is a big range because Calcium level will go up when Nitrogen levels will go down. So, levels vary.
  • Sulfur should be 25% of the nitrogen level percentage
  • Magnesium should be 10% of the nitrogen level percentage

Let’s do an example. Here is a tissue sample I pulled in preparation for Post-Harvest on almonds.

UG Suggestion:

Based on this formula we are deficient on P, K and S. Look at what you are most deficient in and correct that nutrient first. For this example, we would recommend our 2-17-17. If we can apply foliar, we can have a higher absorption than if going in the ground. It can be cost efficient if we can catch a ride with a pesticide spray. But for post-harvest purposes, most farmers do not want to go back and do a spray after harvest, so we may need to make our corrections in the ground.

If you have questions about how to read your tissue results, reach out to your Ultra Gro representative and we will be happy to help.
Please call your Ultra Gro Crop Advisor for more information .