Micronutrient Disorders

By Dr. Claudio Pasian, Department of Horticulture and Crop Science

The Ohio State University

Micronutrient disorders are the fertility problems that I see most often while visiting growers as an Extension Specialist (Figure 1 and 2).  Micronutrients (from the Greek Micro=small and nutrient=nutritive) are mineral elements needed by plants in small quantities.  Small variations from the optimum level required for plant growth can be damaging.  By the same token, levels slightly above those required for good growth can be toxic.  It is very important for growers to have a clear understanding about micronutrient management.  This article is a brief overview of the principles that control the availability of micronutrients in soilless mixes and how to correct imbalances.

Figure 1. Typical iron deficiency symptoms on Streptocarpella. Please, note that the symptoms manifest on young leaves.

Figure 1. Typical iron deficiency symptoms on Streptocarpella. Please, note that the symptoms manifest on young leaves. Photo by Claudio Pasian.

Figure 2. Typical iron-manganese toxicity symptoms on Geranium. Photo by Claudio Pasian.

Figure 2. Typical iron-manganese toxicity symptoms on Geranium. Photo by Claudio Pasian.

Deficiency or Toxicity?  A micronutrient disorder may be a deficiency (when the micronutrient is in deficit) or a toxicity (when the micronutrient is in excess).  Deficiencies can occur either because the nutrients are not present in the growing mix or because the nutrient is present but unavailable to the plant.  (Occasionally, plants with roots damaged by Pythium or other pathogens may show micronutrient deficiency symptoms.)  Some commercially prepared mixes have a fertilizer charge that may include micronutrients.  Growers preparing their own mixes should use one of the many commercially available micronutrient complexes to ensure that the micronutrients are present in the growing mix.

Nutrient Availability.  Sometimes, the micronutrient present in a growing mix is not available to the plant (the plant cannot take it up).  Micronutrient availability is influenced by media pH: except for molybdenum, the availability of micronutrients decreases with increasing media pH and vice versa.  Water alkalinity is an important factor modifying media pH and hence micronutrient availability.  It is important to maintain the pH for soilless media between 5.5 and 6.3.  Some crops are more sensitive to media pH than others:  petunias and gerberas must be maintained at pH levels of 5.5 in order to avoid micronutrient deficiency symptoms.  Other crops are more tolerant of pH changes.  Table 1 shows the minimum and maximum critical foliar levels for floral crops.

Table 1.  General critical foliar ranges for floral crops.  (After J. Biernbaum, Water, growing media, fertilizer, and root zone management.  OFA Short Course, July 1994.)

Nutrient Minimum ppm Maximum ppm
Iron (Fe) 50 ?
Manganese (Mn) 30 500
Zinc (Zn) 20 100-200
Copper (Cu) 5 20-100
Boron (Bo) 25 100-300
Molybdenum (Mo) 0.5 15

Substrate pH.  If the deficiency is due to pH imbalance, the approach is to modify the pH of the mix.  In this case, adding micronutrients can make matters worse because the level of individual micronutrients may affect the level of other micronutrients in the plant through a process called antagonism.  For example, too much iron may produce manganese and zinc deficiencies, while high levels of manganese may result in iron and zinc deficiencies.  Copper and zinc are also antagonistic: too much of one may produce a deficiency of the other (Table 2).

Nutrient Toxicity.  Toxicity on the other hand, can occur when micronutrients are applied in excess (usually more than one application).  Common sources of micronutrients are: the charger in the mix and fertilizers applied during the crop cycle.  Growers MUST have an idea of how much micronutrient they are adding through each of these sources in order to avoid toxicities.  Toxicity symptoms are difficult to recognize visually (only someone with a lot of experience can do it) and are usually mistaken by deficiency symptoms by growers.

Correct Diagnosis.  How do we resolve these problems?  First of all, only a correct diagnosis of the problem will lead to the proper solution.  Do you have a micronutrient deficiency or is it an excess?  Identify the micronutrient causing the problem.  Identify the cause of the deficiency/toxicity: is the nutrient not present or is it present but unavailable? Answering these questions will help you (and your extension agent or consultant) tackle the problem.

Table 2.  Availability of micronutrients as affected by other micronutrients (antagonism) and macronutrients in soilless mixes.

Element Availability reduced by:
Boron Organic nitrogenous fertilizers and high levels of phosphorus.
Manganese High levels of potassium, phosphorus, iron, copper, zinc.
Copper High levels of zinc, nitrogen, and phosphorus
Iron High levels of copper, manganese, zinc, and phosphorus.
Molybdenum High levels of manganese and nitrate-nitrogen fertilizer.
Zinc High levels of copper and phosphorus.

How to Correct the Problem.  If deficiency or toxicity are suspected, soil and foliar analysis are recommended for several reasons.  First, visual identification of the problem is difficult in the absence of information (made available through analysis).  Second, damage may be occurring that is not yet visible and by the time it becomes visible, the damage may be irreversible.

Deficiencies can be corrected by adding the micronutrient that is in deficit or by correcting the factor that makes it unavailable (e.g. high pH).  This second course of action is very common among growers who have high alkalinity irrigation water.  If only one micronutrient is deficient, DO NOT apply a micronutrient complex fertilizer because, as we mentioned above, imbalances can cause antagonism.  Apply a salt that contains only the deficient micronutrient.

Micronutrients can be I) added over time in small amounts with the irrigation water (Table 3); II) applied once with a concentrated solution during a normal watering (Table 4); III) applied as a single foliar spray (Table 5).

Table 3.  Sources, rates, and micronutrient concentration for continuous soil application of one or more micronutrients with every liquid fertilization.    (After D.A. Bailey and P.V. Nelson, Managing micronutrients in the greenhouse.  NCSU Extension, Leaflet No 553, 1991.)

Micronutrient source

Weight of source per 100 gal (oz)

Concentration (ppm)
Iron sulfate–20% iron 0.13 2.00 Iron
Iron chelate (EDTA) — 12% iron 0.22 2.00 Iron
Manganese sulfate — 28% manganese 0.012 0.25 Manganese
Zinc sulfate — 36% zinc 0.0018 0.05 Zinc
Copper sulfate — 25% copper 0.0027 0.05 Copper
Borax — 11% boron 0.030 0.25 Boron
Sodium molybdate — 38% molybdemum 0.00035 0.01 Molybdemum
Ammonium molybdate — 54% molybdenum 0.00025 0.01 Molybdemum

Toxicities are not easily corrected.  The first step is stop adding the micronutrient that is in excess (switching to a fertilizer without the nutrient causing the problem).  Slightly changing (raising, for most Micronutrients) the media pH will decrease the availability of all micronutrients (including the one in excess).  Growers trying to correct a micronutrient excess should raise the pH at the maximum level that the species/cultivar can tolerate for normal growth.  Lastly, use antagonism as a tool: increase slightly the level of a micronutrient that will reduce the availability of another (e.g. if zinc is at high levels, slightly increase the level of copper).

Table 4.  Sources, rates and micronutrient concentrations for a single corrective application of one or more micronutrients applied to the soil*.  (After D.A. Bailey and P.V. Nelson, Managing micronutrients in the greenhouse.  NCSU Extension, Leaflet No 553, 1991.)

Micronutrient source

Weight of source per 100 gal (oz)

Concentration (ppm)
Iron sulfate–20% iron 4.0 62.0 Iron
Iron chelate (EDTA) — 12% iron 4.0 36.4 Iron
Manganese sulfate — 28% manganese 0.5 10.0 Manganese
Zinc sulfate — 36% zinc 0.5 13.9 Zinc
Copper sulfate — 25% copper 0.5 9.3 Copper
Borax — 11% boron 0.75 6.25 Boron
For soil-based media (>20% soil in media)
Sodium molybdate –38% molybdemum 0.027 0.77 Molybdemum
Ammonium molybdate — 54% molybdenum 0.019 0.77 Molybdemum
For soilless media
Sodium molybdate –38% molybdemum 2.7 77 Molybdemum
Ammonium molybdate — 54% molybdenum 1.9 77 Molybdemum

* Do not apply combinations without first testing on a small number of plants.  Wash solution off foliage after application.

Conclusion.  Micronutrient management is complex and difficult.  A more complete treatment of this subject would require more space than we have available here.  I hope, nevertheless, that my description of the problem piqued your curiosity.  At the very least, I hope that you follow this advice: Don’t guess. Test!

Following, is the contact information of some laboratories where you can send your samples for tissue analysis.  Additional labs for media, water, tissue and disease diagnosis can be found here: 2015 Analytical Laboratories for Greenhouse Nursery Fruit and Vegetable Producers. Consult with your local Extension Agent for a local plant testing laboratory.

Brookside Labs
308 S. Main Street
New Knoxville, OH 45871

Calmar Lab
130 S. State Street
Westerville, OH 43081

CLC Labs
325 Venture Dr.
Westerville, OH 43081

421 Leather St.
Marion, OH 44654

Soil and Plant Nutrient Lab
Department of Crop and Soil Sciences
81 Plant & Soil Sciences Building
East Lansing, MI 48824-1325

Soil Testing Laboratory
University of Kentucky
103 Regulatory Service Building
Alumni & Shawneetown Roads
Lexington, KY 40546-0275

Spectrum Analytical Inc.
PO Box 639
Washington Court House, OH 43160

Agricultural Analytical Services Laboratory
Penn State University
University park, PA 16802

A & L Great Lakes lab
3505 Conestoga drive
Ft. Wayne, IN 46808

Brookside Labs
308 S. Main Street
New Knoxville, OH 45871

Calmar Lab
130 S. State Street
Westerville, OH 43081

CLC Labs
325 Venture Dr.
Westerville, OH 43081
This article lists lab references, but such reference should not be considered an endorsement or recommendation by the Ohio State University Extension, nor any agency, officer, or employee at the Ohio State University Extension. No judgement is made either for labs not listed in this article.



Floriculture Trends from IPM Essen

The National Floriculture Forum recently returned from a tour of the Netherlands greenhouse industry followed by a visit to the international trade fair for plants (IPM ESSEN) in Essen, Germany.  The trade fair exhibition featured nearly 1600 vendors from more than 48 countries covering 1.1 million square feet of space with a focus on technology, plant material, nursery stock, floristry, garden center goods, and much, much more.  Some of the noted floriculture trends include miniature plants and containers, succulents, and living walls. Here are just a few examples of the magnificent plant material, displays and ideas encountered in Essen!

2016 NW Ohio Greenhouse Winter Conference

Please join OSU Extension, Maumee Valley Growers Association, and USDA-ARS for the 2016 Greenhouse Winter Conference in NW Ohio!  Located in Delta, OH, the program includes a tour of Schmidlin Greenhouse and their new tomato growing operation and solar array, 1 hour of private CORE re-certification, 1 hour private Category 5 re-certification, lessons from a Kentucky food hub, and catered lunch. Please see the attached flyer for registration details and the RSVP deadline.


  • 8:15       Registration and coffee
  • 8:30       Tour of Schmidlin Greenhouse – Don Schmidlin
  • 9:00       Schmidlin Solar Project and USDA-REAP Funding – Mike Litman, Sunlit Solar
  • 9:30       Pesticide Applicator and WPS Updates – Beth Scheckelhoff, OSUE (1 h private CORE)
  • 10:30     Research updates for greenhouse application – Jennifer Boldt , USDA-ARS (1 h private Category 5)
  • 11:30      Lessons Learned from a Food Hub – Lilian Brislen of Food Connection
  • 12:30      Lunch and depart


For additional information, please click here: 2016 Winter Conference Flyer

Managing your Latino Workforce, Part II: Learning Spanish

By Dr. Claudio Pasian, Department of Horticulture and Crop Science

The Ohio State University

A greenhouse grower from the South once told me: “If I couldn’t hire Spanish speaking workers, I’d be out of business very fast. In my area that’s the only help I can get”. It seems that only immigrant workers are willing to do many jobs that we Americans will do not do. Most of the comments I have heard regarding Spanish-speaking workers have been very good. However, poor communication skills have frustrated growers with limited Spanish speaking capabilities.

Lack of good communication between workers and their supervisors not only creates inefficiencies but also can be dangerous. Please, keep in mind that language is only part of good communication. Symbols, signs, expectations or behavior — which are all influenced by culture — are an integral part of the communication process.

In this article, I will discuss aspects that deal with the learning of Spanish as well as communication in general of which language is only one aspect.

Should I learn Spanish? Not necessarily. However, if you have to deal with a Spanish speaking workforce, knowing even some rudimentary Spanish can save you many headaches and earn good will.

Is it difficult to learn another language? That depends. Urgency, cultural interest and talent all play a role. For some people, learning languages is relatively easy. If you are like me, you will have to work a little harder than average. Regardless, if you want to, you will learn enough to communicate with your workers. To avoid frustrations, set realistic goals: start by learning a certain number of words and after that try a few verbs, etc. As much as you can, try to make it a fun project.

Is Spanish difficult? Yes and no. If you are a person who likes structured things with clear rules, you will like Spanish. A one letter-one sound system makes reading much easier. Verbs are more difficult than in English. Pronunciation will be a killer at the beginning. For most English speaking people, it’s just as difficult to pronounce the open vowels of Spanish as it is for us nonnatives of English speaking countries to pronounce the English language vowels. Do not despair! Time and effort will take care of the bumps at the beginning of the road.

What is the best way to learn another language? Different people learn in different ways. Find what works for you. Two effortless first steps: if your office is connected to the internet, you can pick a Spanish language radio station and play talk shows (no music) as background throughout the day; you can do the same with CD’s and records of Latin music.  This will allow you develop the ability to distinguish words. Whatever method you choose, be sure to make it fun. Here are some suggestions: take a conversational class; travel to a Spanish speaking country; tapes (bookstore or library); find a tutor (Can it be one of your employees?); TV; make your own tape; get to know your Spanish-speaking employees.

Are there different types of Spanish? Yes, just like New York English and Mississippi English are different from Australian English. These national and regional differences should not be a problem if you learn basic, standard Spanish. Standard Spanish is identical from country to country so everyone can communicate using this form of the language. It is estimated that less than 10% of Spanish may be different from country to country. The only problems encountered may be if slang is used or when people have a heavy accent. Do you have problems understanding someone from New Zealand or England? In my opinion, most of the differences between the Spanish from different regions are at the same level as those from different English speaking countries.

Resources. In addition to the traditional Spanish teaching tools available in bookstores or libraries I suggest you get some of the following:

  • Spanish in the Field. Practical Spanish for Ranchers, Farmers, or Vintners. By C. P. Clough, J.C. Comegys, and J.K.M. Saddler. agAccess Davis, CA. 1990.
  • Ball Floriculture Dictionary. y V. Hoyosde Martens and M.L. NydiaPalma de Villareal Ball Publishing, Batavia Illinois, 1995
  • Thomson’s English/Spanish Illustrated Agricultural Dictionary. By Robert P. Rice, Jr. 1993.
  • WPS video in Spanish. EPA approved and prepared by MSU.
  • Spanish for Greenhouse Supervisors. Claudio Pasian. Ohio State University Extension Publication and CD.

This last one is a collection of word and phrases both in English and Spanish strictly dealing with floriculture terminology. It is sold out at present, but if you need it, please get in touch with me (pasian.1@osu.edu).

Electronic Dictionaries and Technology. This “artificial intelligence” translation, whether by electronic device or internet, cannot convey subtleties of language and only occasionally work by translating word for word (literal). Beware! It is commonly said, “The translator is a traitor”…

Emergency Translations. Some companies offer on-the-phone translation services through bilingual English-Spanish speaking telephone operators. This service is frequently used by hospitals and other public agencies that provide emergency response. The cost varies according to the company.

Communication. Finally, keep in mind that “Communication is a process by which information is exchanged between individuals through a common system of symbols, signs, or behavior”. In other words, how we say something may be as important as the words we use to say it, and this is influenced by culture.






Managing your Latino Workforce, Part I: Cultural Traits and Management Styles

By Dr. Claudio Pasian, Department of Horticulture and Crop Science

The Ohio State University

Who are the Latinos?  Latino is someone of Latin American heritage. Hispanic, on the other hand, means “of Spanish or Latin American background.” For the most part, both terms are used interchangeably. There are no definitive and accurate statistics about the origin of the Latinos working in US horticulture.  These Latino workers come from all over Latin America, but anecdotal information and some surveys indicate that most of them (at least 60%) are from Mexico.

Typically, Latino workers in US horticulture were raised in rural communities in Mexico and are young, and most likely in their 20s most likely.  Most often, they have a basic level of education with no knowledge of the English language or very basic English language skills, and are following a dream.  Some move to the US permanently, others plan to stay here only for a few years to work and to send money back home.

According to A. Saunders, a cross-cultural trainer, “A very big barrier for a new project team where members are from different parts of the world is not language. It is the baggage each team member carries in his/her own cultural suitcase”. We all carry a cultural suitcase containing a set of values. These values originate from the family and country in which we were raised and can be influenced by the organizations we belong to or even the work place. Therefore, to facilitate good communication it is important to have an idea of the cultural baggage or customs of other individuals.

In all my writings and presentations about this topic, I emphasize the importance of going beyond learning Spanish to communicate: learn about the culture of your Latino workers. In that vein, I want to share with you information about cultural traits and management styles I found in a book that should be a “must read” for everyone who supervises Latino workers.  The book is called “Management in Two Cultures. Bridging the Gap Between US and Mexican Managers” by Eva S. Kras.  Intercultural Press, Inc.

This book of only 104 pages is meant to be read by business managers doing business in Mexico.  However, most of the information in it can be applied to any situation in the horticulture industry where Latino workers are involved.  Ms. Kras’ book is based on a series of in-depth interviews she conducted with 72 Mexican and US executives.

In her work, Ms. Kras describes US and Mexican cultural and social traits and then describes, compares and contrasts the different management styles prevalent in the two cultures – without judging them.  This will be my approach while presenting some of her work.  You may agree or disagree with her findings and her interpretation.  What is important is that you consider these terms when trying to improve your communication with your Latino workforce.  Communication is much more than language.  It requires understanding the culture!

What are cultural traits?  Ms. Kras defines them as broad, strong, pervasive, and dominant generalizations about a culture.  Obviously, such traits are not universal because each person is unique.  The reality is that the perfect “typical” American or Mexican does not exist, and because of that, it is important to avoid stereotyping!  We all want to be respected and appreciated as unique beings. The cultural and management traits described in the book are shown below.

Cultural Traits Management Traits
  • Family
  • Religion
  • Education
  • Nationalism
  • Personal Sensitivity
  • Etiquette
  • Personal Appearance
  • Status
  • Aesthetics
  • Ethics
  • Work/Leisure
  • Direction/Supervision
  • Theory vs. Practice
  • Control
  • Staffing
  • Loyalty
  • Competition
  • Training & Development
  • Time Planning

Just as examples, let us choose two Cultural Traits, Etiquette and Personal Sensitivity plus two Management Styles, Supervision and Competition for a brief description.

Etiquette in Mexico. Ms. Kras’ research found that courtesy in Mexico is extremely important.  Mexicans consider courtesy as an indicator of education (“bien educado”) since they assume that good manners are taught in school.  First impressions are very important.  Poor manners (informality that we Americans like so much can be interpreted as such) when people meet can mark the relationship in a negative way for a long time.

In Spanish, the way titles and pronouns are used indicate the level of formality.  It is still common in Mexico to refer to a person of authority using a title such as “Señor” (Sir) or “Don.”  Both “TU” and “USTED” are translated in English as “YOU.”  However, TU indicates that the two people talking know each other well, and are possibly the same age and rank.  USTED is used when there is no familiarity or when rank is involved.  Most likely, a Mexican worker will refer to the boss as USTED.  American supervisors of Latino workers who are learning Spanish are advised to use the USTED, a sign of respect, more than the TU.  It is better to err on the side of formality…

In Mexico, it is common at work to shake hands when workers begin the day.  This is followed by greetings and chitchat about the weather, health, family, etc.  Mexican bosses earn the respect and loyalty of their employees through courtesy and diplomacy. A “good boss” never “toots his own horn” as it would be perceived as bad taste in Mexican culture.

Etiquette in the US. Efficiency is king in the US.  “Let’s get to the point” is the key attitude: “Don’t slow me down with stuff that is not job related.”  When addressing issues, Americans appreciate the “unvarnished truth” and sometimes without much regard to sensitivities on the other side.  Does this mean that Americans are insensitive?  No. It means that unlike Mexicans, Americans are expected to separate their emotions from their work.  Yet, this very emphasis on objectivity can be interpreted as “bad manners” by other cultures.  Outside of work, Americans are as sensitive and warm as anybody else is.  One way some Americans try to show friendliness is though informality.  It is more common in the US workplace to refer to a person of authority by first name instead of Mr., or to tell a joke to break the ice in an effort to establish rapport.  However, for the Mexican employee, this behavior may achieve exactly the opposite effect.

Personal Sensitivity in Mexico. Ms. Kras says it all in one sentence: “Mexicans are extremely sensitive to the world around them and have a marked capacity to empathize with the people with whom they interact”.  They are masters in avoiding confrontation and saving face.  Because of this, they are very sensitive to criticism.  Even at work, constructive criticism may be taken personally.  Never criticize your employees in front of other workers, much less if the employee is also a supervisor!  While face-saving is a human characteristic (found in all cultures), Mexicans have made an art of it to the point that they practice it even when not needed.

Personal Sensitivity in the US. As said earlier, Americans are expected to suppress emotions at work.  Therefore, constructive criticism is not only tolerated but also expected in order to improve efficiency. In the US, to be tough at work is, more often that not, considered a “virtue.”

Supervision in Mexico. Mexicans have great respect for authority.  Orders given by a superior are seldom commented on and much less questioned.  Delegation of authority is not common.  Employees will do as told, no more, no less.  It is the boss’ responsibility to communicate well all that needs to be done and how.  If a mistake is made, with this system it is the boss’ responsibility.  Typically, Mexicans value being part of a group;  work – often carried out along side other members of the extended family – is an extension of the group.

Supervision in the US. Americans place a high value on individualism and in the workplace, the “ideal” employee works independently.  American bosses appreciate being able to delegate authority and supervising workers who like to “take ownership” of the job.  Problems that arise on the job are seen as challenges and it is acceptable to make minor mistakes without loosing the boss’ support.  In fact, meeting these challenges may represent a valued learning experience.

A detailed contrast and comparison of all cultural traits and management styles can be found in Ms. Kras’ book. I strongly recommend that you buy and read it. While reading, consider that these are broad generalizations. If you do not identify with some of the traits and management styles described, that is okay. Most likely, you will be able to recognize these characteristics in some of your fellow Americans. Also, keep in mind that societies in general and people in particular change over time. Doing business with the US and Canada through NAFTA is bringing change to many Mexicans and their business practices. However, this change may be less noticeable in people coming from small towns in rural areas (the source of most Mexican horticulture workers). Also, remember that the poisonous effect of what we call “Hollywood” (the movies) is being felt all over the world and it is changing many traditional cultures – in my opinion, usually for the worst.