Welcome to the Ultra Gro Agronomy Letter!
Welcome to the April ’23 Agronomy Letter from Ultra Gro. We asked Ultra Gro Agronomist Robert Smith to write a few timely articles addressing the current agronomic situation faced by our growers. Please check it out… Robert touches on citrus bloom, saturated soils and cold soils. We have also provided a write-up regarding a new foliar product we put together for this year – we call it Boost-23. And finally, Ultra Gro Crop Advisor, Sean Hixson (father of new baby boy, Shep!!!), has added his ideas about post-bloom in citrus. Thank you, Robert and Sean.
Citrus Bloom
By Robert Smith, Agronomist
As of Wednesday, April 19, the Tulare County Agricultural Commissioner’s office has announced we have officially started the citrus bloom period, things are warming and spring flush has arrived!

Foliar nutrient applications are not a new concept to the citrus industry. For more than five decades, foliar nutrient applications on citrus have been recommended to correct zinc, manganese, boron, copper, and magnesium deficiencies. Foliar nutrient applications are more efficient than traditional soil applications because of better, faster nutrient uptake and reduced losses. Field research has shown that supplemental foliar nutrient applications can increase yield by 10 to 25 percent compared with conventional soil fertilization alone. Zinc, manganese, calcium, and boron are four especially important micronutrients for citrus. 

Zinc (Zn) is critical during the early growth stages as it is essential for numerous metabolic reactions. Having adequate zinc levels throughout the growing season is critical to prevent premature leaf fall and improve bud development, flowering, and fruit set. Deficiencies in zinc cause small leaves and chlorosis which significantly reduces shoot growth and yield potential. Low zinc levels reduce fruit number per tree.

Manganese (Mn) plays a strong role in photosynthesis, chlorophyll formation, and nitrate reduction. It helps plants use N more efficiently. Manganese is a common deficiency in Central Valley citrus. Symptoms start on young, fully developed, and medium-sized leaves. Yellow/green discoloration and yellow blotches appear (leaf mottling) in between veins that eventually extend over the interveinal areas. Necrotic spots develop with severe deficiency. Manganese deficiency is often associated with zinc and iron deficiencies. These are also common on Central Valley citrus. In practice, a combined foliar application of Zn and Mn is often more effective in alleviating the respective deficiency symptoms, in lieu of single sprays on their own.

Calcium (Ca) is a key component of cell walls and has a direct influence on the regulation of enzyme systems, phytohormone activities and nutrient uptake. Calcium also influences pollen tube elongation. For years, we have seen that persistent applications of calcium helps to produce high yields. In fact, trial data shows that after seven years of regular use, calcium boosted orange yields in USA trials by up to 56%. Regular use of soluble forms of calcium is beneficial on high calcareous soils. In addition, Calcium has a significant effect on reducing many fruit disorders. Foliar calcium nutrient applications, reduce splitting, creasing and pitting diseases of oranges and mandarins.

Boron (B) is involved in various enzyme systems and carbohydrate metabolism/translocation. Boron will minimize fruit drop, prevent fruit deformities or storage problems from peel breakdown. Boron, like calcium also has an important role in cell structure and cell wall integrity. Citrus is extremely sensitive to low boron levels and has shown significant yield responses in the field. Yield increases result from a higher fruit number per tree, minimizing fruit drop, boosting fruit weight, preventing fruit deformities and/or storage problems from peel breakdown.
Ultra Gro BOOST-23
by Robert Smith, Agronomist
This is a new product for Ultra Gro. We designed it specifically for the challenges that our growers are facing this year with wet soils, late Nitrogen applications and concerns about Phytophthora and other water-borne pathogens (it contains phosphite). A simple one-gallon rate in a foliar spray will make an impact on these concerns. It is priced at $20 per gallon.

Ultra Gro BOOST-23 is a concentrated source of three major nutrients to provide readily available nitrogen, phosphorous and potassium that contains a full micronutrient package to all types of crops. This combination of essential, high-quality nutrients at specific ratios provides optimum uptake, enhancing fruit and nut size and production. It also contains Phosphite to help fight Phytophthora.

Ultra Gro BOOST-23 nitrogen derives from Triazone-CRN, which enhances nitrogen absorption, translocation and remobilization, thus providing an immediate plant response. Triazone-CRN liquid fertilizer functions as an efficient source of nitrogen at critical growth stages in all crops.

Ultra Gro BOOST-23 provides a direct plant response supported by a phosphate/phosphite blend for the release of stored energy not only through the Krebs Cycle but also to drive secondary metabolic responses and as a precursor to amino acids, leading to greater crop reaction. It enhances nutrient uptake to improve plant health and vigor, resulting in better plant nutrition, higher fruit quality, leading to increased yield potential.

Ultra Gro BOOST-23 supplies beneficial, carbon, carbon-based organic material, promoting microbial activity and nutrient availability to the plant. 

Ultra Gro BOOST-23 is extremely clean, containing no unwanted sodium and chlorides that negatively affect growth and productivity. It is a highly soluble, liquid formula, held in solution for effortless applications and fantastic results. 

Key Advantages/Benefits:
■ Applied directly to the leaf surface for rapid absorption
■ Delivering enhanced foliar uptake over an extended period. 
■ Low salt index and low levels of ammonia and biuret, it is a safe fertilizer solution 
■ Compatible with a wide range of micronutrients and plant protection chemicals
■ Improves photosynthesis
■ Aids overall plant establishment 
■ Drives secondary metabolic responses

Its use is suggested as a supplement to a regular, balanced fertilizer program to enhance yields and improve overall quality. We designed this product to ride easily with your fungicides and other sprays. It is relatively inexpensive ($20 per gallon) and one gallon per acre gets a lot done. Do not mix with strong acid products or oil.

Reach out to your Crop Advisor if you have any questions about this product.
Dealing with Saturated Soils
by Robert Smith, Agronomist
The power of prayer is incredible! As a result of a series of “atmospheric rivers”, California’s San Joaquin Valley has experienced record-breaking rainfall and snowpack events in January, February and March. These have resulted in very high river flows, breeched levees, and saturated soils. With the record-breaking snow pack, there is great concern as to how long the rivers will have high flows and to the extent, we will have to contend with additional flooding this spring and summer. 

By the summer months, we will have a better idea of orchard tree losses due to flood-induced root system damage. Tree damage from flooded soil is usually minimal if: a) the flood occurs when the trees are dormant, b) respiration rates are lower in the roots, c) soil temperatures are lower, or, d) spots where the water continues to flow rather than remain standing in the orchard as there is more dissolved oxygen in running water. When water stands for extended periods in an orchard, two potential problems are of concern: a) waterlogging of the root system, and b) diseases caused by Phytophthora.

Waterlogging can be viewed as an “oxygen starvation” effect of flooding. When an orchard soil is flooded or otherwise saturated with water, the air in its pore spaces is displaced, removing the supply of oxygen to the roots. Tree roots require oxygen for respiration. Respiration fuels growth and energy reactions leading to water and nutrient uptake. During cool winter conditions, trees can withstand longer periods of saturation since respiration rates are lower when trees are dormant. Again, flowing water is less damaging than standing water, most likely due to greater amounts of dissolved oxygen. Reduced root activity and nutrient uptake can produce pale leaf color or interveinal chlorosis.

When tree roots are surrounded by saturated soil, they can die from lack of oxygen even without any major pathogens present. The terminal portions of new roots can be killed within one to four days in a saturated soil. As saturation is prolonged, damage to roots becomes greater and can lead to chlorosis, leaf wilting, and in extreme cases, entire root systems can be killed.

This may be a transient problem in some cases, affecting only small feeder roots followed by tree recovery as new feeder roots grow out of the problem. In more severe cases, larger roots die, and trees begin a gradual decline producing small, off-color leaves, little new growth with a thinning canopy, display leaf burning, wilting and defoliation, followed by tree death.

Waterlogging also provides ideal conditions for the development of Phytophthora water molds. These pathogens are stimulated under saturated conditions to produce swimming spores (zoospores) which orient towards root exudates.

Several species of Phytophthora are found in the soils throughout California. These fungal-like organisms can be carried along by the water and swim in it. Flooding can bring active Phytophthora inoculum in contact with the aerial portions of trees, resulting in infections of the tree trunk, scaffolds, and shoots. Flooding also increases the risk of root and crown infections by Phytophthora. Some Phytophthora species preferentially infect roots, but many preferentially infect the root, crown, or aerial tree parts.

In general, cool to moderate temperatures and water-saturated conditions in or on soil favor tree infection by Phytophthora species. Some Phytophthora species are more active than others, and risk of disease also depends on genetic resistance of the rootstock or scion.

Follow these tips to help alleviate problems you might be experiencing with a flooded orchard:

  • Drain or pump standing water out of orchards.
  • Reduce vehicle/farm equipment traffic. Wet soils are easily compacted. Delay all operations that can wait until soil is dry enough.
  • Apply a phosphite spray where Phytophthora is found or suspected. A summer and early fall application may also be needed.
  • Remove deposited silt and debris around the root crowns, when possible, to decrease the chances of root/crown decay.
  • Encourage the growth of cover crops or even weeds that will help dry the soil after flooding; the plants are effective in drying waterlogged soils.
  • Fill in eroded areas in orchards if soil is available.
  • Check for salts (chloride and sodium); a continued high water table saturating surface soil may result in these salts accumulating. Neither leaching nor gypsum treatments will be effective until the water table is lowered, and good drainage can be achieved.
Dealing with Nutrient Deficiencies in Cold Temperature Soils
by Robert Smith, Agronomist
Potassium, zinc, iron, and manganese nutrient deficiency symptoms are more prevalent where soils are wet, cold, and saturated. Reduced root activity and nutrient uptake can produce pale leaf color or interveinal chlorosis (pale or yellowing between the veins in the leaf). Micronutrient deficiencies often show symptoms in only a small part of an orchard, or, if due to saturated soil or flooding, may only appear during part of the season. Foliar nutrient application can provide quick correction of symptoms and improve tree color and vigor if indeed, that is the reason trees were performing poorly in the first place.

When thinking about fertility in your orchard, the first step is to review tree nutrient status by re-examining your leaf tissue analysis from last July to determine if any nutrients are borderline or deficient. Root activity increases when soils warm and dry out, hence, deficiency symptoms may correct themselves as spring progresses. 

Originally, it was thought that using foliar nutrient applications was only appropriate when a nutritional deficiency was present. This is not the case. Ongoing scientific research has consistently shown that periodic applications of certain nutrients in various crops can have a positive effect on both quantity and quality of fruits and nuts. Although most supplemental nutrients are absorbed through the root system, it is also important to note that leaves, flowering plant tissues and even fruit surfaces can absorb nutrients. It is crucial to understand which nutrients can be supplied effectively by foliar applications, especially if the soil-supplied nutrients are inadequate or impaired in some way.

Potassium (K)
When first leafing out, trees displaying K deficiency symptoms appear pale in color and have small leaves with little new growth. Later, trees show rolled leaves with marginal leaf burning. This symptom is classic when it occurs in the tree top on leaves in the middle of new shoot growth. In almonds, the Butte variety is a good indicator of this deficiency because it is likely to exhibit leaf scorching before other varieties show symptoms. K is deficient if July leaf analysis is below 1.0%.

A true K deficiency can be corrected now by foliar sprays of potassium nitrate when sufficient material is applied. The standard approach that corrected K deficiency for the season in the past applied 40 pounds of potassium nitrate per acre with each of the three 400 gallon dilute applications for a total of 120 pounds of potassium nitrate per acre. In a typical concentrate, spray applied at 100 gal/ac, rates of 20-30 pounds of potassium nitrate per acre can be safely applied to almonds to provide the boost needed in a wet spring.

Zinc (Zn)
Zinc is part of the enzyme system that regulates terminal growth and plant cell expansion. Trees with severe deficiency may experience dormant flower bud drop and decreased fruit set, will have shortened internodes and small ‘little leaf’ symptoms, and have chlorotic leaves with wavy margins. With mild deficiency, leaves may be slightly smaller than normal with areas of interveinal chlorosis. Young trees can be deficient without showing any visual symptoms so it is important to get a July tissue analysis even in young orchards. Zinc is deficient if a July leaf analysis is below 15 ppm.

Foliar sprays to correct Zn deficiency are effective and inexpensive. A spring foliar treatment can be timed once leaves have attained nearly full size. On spring foliage, basic zinc sulfate or zinc oxide sprays are normally safe and effective. Either form can be applied at 5 pounds per 100 gallons of water or at 15 pounds per acre when sprayed at 100 gallons water per acre. Word of caution: rain within 48 hours of zinc foliar applications can reactivate the zinc and produce phytotoxic “shot-hole” symptoms on leaves.

Iron (Fe) and Manganese (Mn)
Both iron and manganese are important in chlorophyll formation, thus, a deficiency of either shows up as interveinal chlorosis in young leaves. Deficiencies in iron and manganese, although rare in the Sacramento Valley, are occasionally seen in orchards with soil pH above 7.5, on calcareous soils, or on heavy or poorly drained soils.

Iron deficiency causes interveinal yellowing with the small leaf veins remaining green. When severe, leaves will be uniformly yellow throughout the leaf. Iron deficiency may show early in the season and continue until leaves yellow and drop, or it may show in the spring and then gradually disappear as soils warm up and dry out. Leaf analysis is not a reliable indicator of iron deficiency so learn to recognize leaf symptoms.

Manganese chlorosis appears as a herring bone pattern with major veins green between yellow interveinal areas. Manganese is adequate when July leaf analysis is over 20 ppm. Manganese deficiency can be corrected with foliar sprays of manganese sulfate at 2 pounds per 100 gallons water sprayed at 100 gallons per acre. If you have a small problem area, banded soil applications of manganese sulfate at 10 pounds per tree have been effective for longer term correction.

Foliars- We must understand that at times only a small amount of a specific nutrient is required, and due to low soil mobility of the nutrient, it is actually more efficient to supply the small amount of needed nutrient as a foliar application. This can be the case for both macronutrients and micronutrients. Foliar-applied nutrients have the benefit of being 4 to 30 times more efficient than soil applications.

Remember, foliar nutrition cannot and should not replace soil fertilizer applications (especially for nitrogen, phosphorus, and potassium). However, the benefits of foliar nutrition cannot be ignored during certain situations, including:

  • Supplying nutrients during periods of peak plant demand.
  • Supplying nutrients when soil or root conditions are not conducive to uptake.
  • Precision timing is desired.

Post-Bloom in Citrus
by Sean Hixson, Crop Advisor
With the 19th of April here and passed, we are now officially in citrus bloom. It's not only the best smelling time of the year, but also the most important for citrus. In an effort to get ahead of things, many of us are starting to think about post-bloom in citrus. It's where a lot of the so-called "magic" happens, especially considering cell development and fruit set.

Cell Division/Development
We have 28 days after pollination when cell development happens, and we don't get to build more cells later. Having said that, the idea is to focus on building cells and setting fruit, and as the season progresses, we can fill up those cells as we manage the nutrient demand.

Ultra Gro Recommendation - Petal-Fall Foliar
We have had success with cell development applying a petal-fall foliar. We recommend a blend of our Cal-K (7-0-7-7Ca) and "Excite Seaweed" (0-0-17). These well-known products will build calcium levels, provide for shoot growth and act as a plant growth regulator to help reduce stress in hot temperatures.

"Excite" is our newest addition to the Ultra Gro line-up, and it is the only Concentrated Powdered Acadian Seaweed on the market. It's a very consistent and highly soluble seaweed product that is tried and true over and over again.

Material can be tank mixed with most pesticides, fungicides and plant growth regulators, but you should always consult with your Crop Advisor before mixing.

2 gallons/acre Cal-K
1 lb/acre Excite Acadian Seaweed Powder
Please call your Ultra Gro Crop Advisor if you have any questions.
Thank you!