Ag 101 Week 51

Agronomic Testing Options

My titles have not become any more creative, but I get my point across.

This is the second to last post of the 52 Weeks of Agronomy Series. I would be lying if I didn’t say I’m slightly relieved. At the same time, I’m looking forward to having more time for other projects that do not require typing, or at least me doing it.  Maybe one will require me wearing out a red pen ripping apart someone else’s grammar. Who knows!?

What I do know is that we have come to the time of year farmers have questions. They have them year-round, now they have more time to ask them.

One of the most recent questions I’ve gotten is regarding the different types of agronomic testing available to farmers and growers.

The following is part of an email conversation with a grower I work within Maryland-

The farmer asked,

“I was thinking about doing a sap sample of the grass and clover in the field and also a Brix's reading at the same time. What are your thoughts?”

My response was,

“As far as the sap and Brix's testing, from an agronomic standpoint they won't change any soil fertility recommendations I would have. Everything I look at and take into consideration is based on soil tests in conjunction with tissue testing depending on the type of crop, farming system, and whether the grower will see an economic return for the costs of the tests. I'm looking at the actual nutrient levels of nitrogen, phosphorus, potassium, calcium, etc. There are so many variables like time of day the sample was taken, what part of the plant was sampled, and what calibration standards were used, it would make it difficult for an agronomist to base a soil fertility assessment on sap and Brix's levels. 

Tissue testing utilizes dry matter - it’s a picture at the moment at that part of the plant sampled as to what is there

Sap testing utilizes the fluid portion of the plant; it's similar to a blood test - keep in mind that fluids are constantly moving and every nutrient moves at different rates 

There are always variables in any kind of testing; you can't mitigate for everyone. However, soil and tissue testing are the best tools currently an agronomist has to look at what is going on at that moment in time.

That being said, and due to the fact, you are testing sugar and protein levels in the plant with the Brix's test, from a forage quality standpoint, the results may be of value to an animal nutritionist when determining rations and taking animal health into consideration.”

Here are some common agronomic tests, followed with a brief description and some of my thoughts on them.

Standard soil test- I talk in detail about what a soil test should include in week 24

Soil health assessments conducted by universities include soil typing and physical analysis of samples similar to what Cornell offers at the following link

In general, I recommend a standard soil test and use the link at the Web Soil Survey

Using both of those is comparable to Cornell’s package costing considerably less

 Soil paste test-

In general, this test shows what nutrients are immediately available to a plant because they are not bound to a colloid.

It is also one of the most accurate tests for measuring soil salinity which can be a common problem in soils in the central and western part of the country.

Some agronomist’s feel a standard soil test plus the paste test is the most accurate way to determine soil fertility needs. In my experience, it is farm, soil type, and management dependent as to whether you will see a return on investment for the extra cost.

 Plant tissue test-

As stated before in my email response; tissue testing utilizes dry matter - it’s a picture at the moment at that part of the plant sampled as to what is there.

It is a good measure of the nutrient status of a particular plant at that moment in time giving you a picture of what may typically be happening. It is a good indication of the efficacy of your fertility program as well. Tissue tests are dependent on timing, plant temperature, and growth stage the sample was taken.

Typically, guides are offered for the plant stage at which a tissue sample should be taken based on crop type. The sample is taken when the plant is actively growing, so timing is critical.

Spectrum Analysis offers a detailed guide to plant tissue testing

Plant sap analysis-

This is the best analogy I have come up with for sap testing-

Sap testing utilizes the fluid portion of the plant; it's similar to a blood test - keep in mind that fluids are constantly moving and every nutrient moves at different rates 

The following is an interesting article regarding sap analysis

I believe it can be a useful in-field test. However, there are variables such as operator error that would make me uncomfortable using it as the sole means of making fertility recommendations.

There are a few labs in the states that conduct sap analysis. One of them being

Brix test-

A brix test is the measure of the sugar content found in a plant tissue sample that has been pulverized, and the aqueous solution from that is then put in a refractometer and read.

Once again as with the sap testing, I believe it has in field use especially in a grazing operation. However, the variables associated with it make it suitable for field use and not what I would base a sound soil fertility program on.

I work with growers that use it in the field to help with harvest decisions with a tremendous amount of success. Using well-calibrated equipment with consistent protocols for testing has saved them time and money ensuring they harvest at that crop’s peak quality and nutrition levels.

Just as with plant sap analysis I believe it can be a useful in-field test. However, there are variables such as operator error and calibration protocols that would make me uncomfortable using it as the sole means of making fertility recommendations.

Soil Biological testing-

   Co2 Burst test-

This test is a soil health indicator, measuring the amount of microbial respiration.

The following pdf is the best explanation I have found

I would recommend growers use this in conjunction with soil nitrate tests to make a comparison and better calibrate any side-dress nitrogen applications that might need to be applied during the growing season.

The following is a well-written extension guide from Penn State explaining pre-side dress soil nitrate testing

  Microbial Identification-

Microbial identification is done with a microscope.

There are several consultants that provide soil microbiological identification services at the following link

 Water testing-

Water can be the carney in the coal mine especially when it comes to greenhouse management. pH is the most critical aspect of water testing in term of a soil fertility program and soil health. However, with water and its natural pH due to its source, comes with its dissolved elements that could be beneficial or not depending on the situation. The best measure to determine the impact irrigation water will have is through testing.

The following are links to labs I regularly use for soil and water testing

Entomological/ Pathological testing for field crops-

Before I started the 52 Weeks Series, I wrote a post titled “What’s an Agronomist, Anyway?”

Here’s an excerpt-

“On any given day as challenges and questions are posed to me, I have to think like a biologist, a chemist, a botanist, sometimes a pathologist, and if I’m really confident an entomologist. Usually, I defer to experts on the pathology and entomology. I know enough to be dangerous and kill stuff. “

As an agronomist, I kill stuff or keep it alive depending on what the farmer wants me to do.

What I can also say is I have been doing this long enough to make a definite diagnosis like thrips, aphids, blights, rusts, etc. However, when it goes beyond the obvious, I send a sample to the local land-grant university for identification. That’s what they are for, as well as other services.

Some good references to have on hand to make common identifications easier are-

Introduction to Plant Diseases: Identification and Management by George B. Lucas & Lee Campbell

Garden Insects of North America by Whitney Cranshaw

The Ortho Problem Solver by Michael D. Smith

 Forage test-

Ask an animal nutritionist or forage specialist. I can’t be an expert at all things.

In week 44 I discuss potassium and admit what my dad refers to me as

With that in mind here are basic ratios I look at when interpreting a soil test for forages-

Calcium to phosphorus 1.7:1

Calcium to magnesium 2.7:1

Calcium to sulfur 2.1-1

Potassium to calcium 1.5:1

Potassium to magnesium 4:1

Protein to sulfur 50:1

Nitrogen to sulfur 8.8:1

Potassium should be between 3.0-3.5% Calcium between 70-75% of the base saturation

One of the best agronomists who has an extensive forage background and one I’ve had the pleasure to be around and learn from is Dave Wilson from Penn State Extension.

Here’s a link to two articles he has written

In summary-

This is in no way an exhausted list. There are several tests that are similar but have different names based on the lab offering them.

I am not suggesting that every farm needs to be doing all the mentioned tests. Each one mentioned is another layer of management in the overall plan of how you are running your farm. They are not meant to be used in every case all of the time. Every farmer needs to weigh if the results from the analysis will yield an adequate return on investment for their operation.

Just as the title states, they are agronomic testing options.

Ag 101 Week 50

Leaves Never Lie


Neither does my tongue. Here’s the story.

I’ve been going to acupuncture every week now for the past month. Every week Brian the acupuncturists asks to see my tongue. He reads it like I read leaves when I’m on a farm or in a greenhouse.

For the past two weeks, I have been getting a gallon of what is hands down the best ice cream I have ever had since the time I was in doing farm visits around the O’Brien, Florida area. The ice cream I had at one farm would blow your mind. I could be considered somewhat of an ice cream snob.

Every time I’m standing in the kitchen eating some while thinking everyone else is preoccupied, my daughter inevitably comes around the corner and says,” Brian’s going to ask to see your tongue.” I respond with, “I know and I’ll tell him the truth.”

This week I go to acupuncture, he asks to see my tongue, it has a greasy film, he gives me a look, and I confess to the fact I’ve been eating the best ice cream found in the state of Pennsylvania every day for the past several weeks. We have a conversation much as I would have with a grower. I leave realizing the error of my ways and how my ice cream eating is only holding back my progress.

When I do farm or greenhouse visits, I’m often looking at leaves more than I’m listening to the farmer. Well, I’m doing both sometimes simultaneously. All because much like my tongue, leaves will always tell me exactly what I need to know. They are the first indicator of everything from management decisions to fertilizer and amendment applications or the lack thereof. It all goes back to week 7, Thinking Like an Agronomist. Being observant and asking questions to put the pieces of the puzzle together

Leaf appearance is also a determining factor for deciding the necessity of further analysis such as sap, tissue, pathology or entomology testing.

You can google resources for all types of leaf issues. The following are the best I found and I still use them.

Image courtesy of Google Images

Image courtesy of Google Images

Image courtesy of Google Images

Image courtesy of Google Images

An app I’ve used is called Plantix.

Plantix for Android

Plantix for Android

You can pick up to four crops at a time, submit a post for others to comment on and use pictures from your phone. The library is fairly extensive for some common and uncommon issues.

The next time your walking around your fields or greenhouses look at the leaves, they never lie.

Ag 101 Week 42




Last week I said I was going to start and break down what goes into a bag of fertilizer. If you recall, I likened each component to a piston in an engine. Put the right pistons together, and you get a locomotive engine, put others together, and you get a Yugo.

You buy a bag of blended fertilizer, and you are getting a mix of nutrients that supply a plant with nitrogen, phosphorus, and potassium - NPK. In some cases, you can get some magnesium, calcium, sulfur, and trace minerals. I’m sure most of you know that already.

So, I want to go over a few questions I get; then we’ll take a look of some more commonly used components within the organic or softer chemistry area of fertilizers.

Why are the numbers, otherwise known as NPK values, so much lower in organic fertilizers than conventional?

The numbers representing NPK are a ratio of the percentage of available nutrients. The amount of the nutrient that is soluble and readily available for the plant to use. The more solvent, the higher the number and the more significant amount that the plant can uptake sooner. In the case of organic fertilizers, you have to also consider variabilities due to the fact components are naturally sourced materials, i.e., mined from clay deposits or animal by-products. Nature is not always consistent. One of the best benefits of organic fertilizers is a more extended nutrient supply over the growing season given the fact they are comprised of soluble and insoluble forms of nutrients. Given adequate moisture, biological actively, and crop type a natural fertilizer can take you through from planting to harvest. Once again, I stress it is crop specific and dependent on other management decisions. I will often suggest a split application if at all possible or fertilizing with a liquid to get through a season depending on all the variables.

Keep in mind from week 5 when fertilizing you are feeding the plant and the soil. Some are hungrier than others and at a different rate.

What is the difference between soluble and insoluble nutrients?

A soluble form of a nutrient is readily available to the plant for immediate uptake. Insoluble nutrients are held in the soil longer and need to be converted to plant available forms by the bacteria and fungi present in the soil. Other factors determining the rate at which they become soluble are soil moisture, temperature, and pH.

 What does it take to ensure a fertility program is effective?

1.      pH management -You want to manage pH to accomplish two things

First be in a range for optimal nutrient uptake based on soil type and crop variety while staying slightly acidic to help make nutrients available through mineralization and biological activity.

2.      Irrigation management

A fertility program is only as effective as your irrigation.

3.      Good amendment & fertilizer practices

Fertilizing is strategic and should be applied at the right rate, time, location using the right source. I discussed that in weeks 6 & 10

You could say I’m finally getting around to talking about the fourth – the source.

Let’s talk about nitrogen-

Nitrogen is used for several functions in the plant including the production of proteins that lead to tissue development

It also plays a role in chlorophyll production.

It is critical in leading to the vegetative growth in a plant but can become problematic when over applied for several reasons.

Such as-

Environmental issues

Increased insect pressure

A plants’ inability to retain blooms, such as in tomatoes

Balancing a plant’s need for nitrogen at the time it is required by the plant is a matter of timing it’s application. Even though it is abundant in the air we breathe, unlike phosphorus and potassium, it is not found in sufficient levels in the soil because it is not present in the parent material giving soil its properties.

By themselves, plants cannot use atmospheric nitrogen. It has to be converted by nitrogen-fixing bacteria in the form of NO3¯ or applied in a plant available form at the right time.

Due to the fact, the form most available to plants has a negative charge, it is not held in the soil and is more sustainable to leaching. If you recall, the cation exchange capacity is a soil’s ability to hold onto positively charged ions.

Nitrogen management is centered around optimizing nitrogen fixation by the soil biology and minimizing loss by using good management practices such as timing and location of fertilizers and manures.

With some conventional forms of nitrogen such as ones that are ammonium based, except ammonium sulfate, they have an acidifying effect on soil. Meaning they lower the pH. This can be an issue with over applying it and repeated long-term use. It is often not seen immediately but as somewhat of a cumulative effect based on cropping history, moisture, temperate, etc.

Over the past several years I have not seen that to be as much of an issue with organic sources. However, I have not found much research or data on the subject either. It should be noted that everything you put into the soil at some point in time effects it, whether immediate or long term.

Let’s talk about some common organic nitrogen components used in fertilizers.

First, I’m going to start with a three that are conventional component equivalents. Meaning they are still a naturally derived source, that can be used in an organic system but is more soluble and available to the plant quicker rather than later making them somewhat similar to that of conventional chemistries.

Blood Meal

It typically has an analysis of 10-13%N

It has been shown to have deer and rabbit repellant properties when used as a top dress. However, it may attract other animals such as raccoons and dogs.

Blood meal is primarily hemoglobin, which is a protein, and iron. In my experience, I have found the concentration of iron not to be an issue, just something to be mindful of

It can be cost prohibited to use it as a single source of nitrogen. However, when added to a blend It is a rapid release source making it a significant component when used with other mid and slower release forms

Chicken Manure

Of all the manures it is, in general, the one highest in nitrogen typically ranging from 2-8%

Keep in mind the analysis of manures of any type can be extremely variable based on source and solid to liquid ratios

It is available in several forms from liquid to pellets and relatively inexpensive depending on what part of the country you are in

It is also a good addition if lime and phosphorus are needed

Sodium Nitrate (Chilean Nitrate)

It is water soluble at a guaranteed 15% total N availability, with 2% potash, and 1% sulfur. The new formulation has allowed for ease of shipping because it is no longer considered a hazardous material.

The fact it is readily solubilized in water makes this the best choice for a starter fertilizer, especially for corn. It gives corn the boost it needs to get out of the ground even if planted into soils that might be cooler than what is generally required to get the best germination rate.

It can be an expensive insurance policy if not used accordingly and applied with good seed to fertilizer placement at the right rate. This is when cleaning, calibrating, and using the right equipment are essential as well.

I highly recommend using it in a blend as opposed to a straight source of nitrogen for several reasons. First, it can be expensive. Second, it is available almost immediately to the plant, making it the first to be used during the growing season, leaving the plant with nothing in reserve for the next several weeks that nitrogen is vital to develop enough vegetation for the plant to efficiently and adequately be able to perform photosynthesis. Remember it is a balance between vegetative growth and reproductive growth.

Next, the following have medium to slow release rates of nitrogen. They are relatively insoluble.

Fish/crab/shrimp meal

Typical analysis ranges from 5-30%N

Typically, fish ranges from 5-9%N depending on whether it is a meal, powder or liquid

Crap and Shrimp range from 10-30%N with 11-18%Ca depending on the shell to meat ratio

Crab makes an excellent addition to a fertilizer blend for the extra calcium, and the addition on an enzyme called chitin that has been shown to help control nematodes in the soil

Peanut meal

A typical analysis is 8-9%N

Can be cost prohibitive and not allowed due to allergen restrictions

Bone meal

A typical analysis is 3-4%N

It is also a good source of phosphorus and calcium

Feather meal

Typical analysis 11-15%N

Apply early in the season to take advantage of slower release rate providing nitrogen over the course of the growing season

 Soybean meal

A typical analysis is 6-7%N

A good source for full season nitrogen supply

Soybean meal has been shown to burn new seedlings and reduce germination rates potentially. Care should be exercised when timing the application


For years now, agricultural manures have gotten a lot of press. After taking the PA Nutrient Management courses, I concluded – shit’s complicated. Gone are the days you cleaned the barn and piled it out of the way so you could spread it when you had more time. Raw manure is the most nutrient dense. The longer it composts it losses its nutrient value. Over applying it, can lead to not only environmental issues also pest and disease challenges.

However, there is one manure that is gaining popularity with tobacco and cannabis growers, and its bat guano. It is cost prohibitive to use on a large scale, but I feel it is important enough to mention as a potential source of not only nitrogen but phosphorus as well, while being low in salts.

A typical analysis is 5-12% depending on the source

It is fast acting and soluble in water making it a great addition to a liquid program for cannabis especially vegetative and flowering stages

I have several growers using it in sub-irrigation systems for starting organic tobacco. They like the fact its water soluble and doesn’t seem to burn the way other fertilizers have a tendency to do if not managed correctly.

 There are several other sources I could mention that are used for nitrogen such as corn gluten, alfalfa meal, legumes, and cottonseed meal.

We’ll cover those and more during the time remaining in the 52 Weeks of Agronomy Series.

Ag 101 Week 22

I Got Nothing...

I'm not going to lie, coming up with a topic for this week has been challenging. I usually get inspiration from things I've been doing or things I've been questioned about in the previous week. But these past couple weeks have been doozies. 

I have dealt with everything from gray mold on strawberries, hail damage on lettuce, making fertilizer recommendations, nailing down seeding rates, explaining my opinion on sap and Brix testing, etc. I've been to pasture walks and spoke for the Williamsport Herb Guild. I've touched base with clients and needless to say I came up with lots of topics and still no real inspiration as to exactly what to write about.  

To cap off the week, I spent 4 hours updating the terms, conditions, and privacy policy for the website to be in compliance with the GDPR.  Don't ask me what that stands for, I'm not good with acronyms or military time. All I know is feel free to stop reading at any point, feel free to unsubscribe at any point, feel free to not deal with me at any point. I will not be offended, TRUST ME! If you do stay, you will hear some ranting and you will wear down your red pen fixing typos. But hopefully, you will also get at least one piece of something that will help you to be the best farmer, grower, or producer you want to be.

So, when it came to writing a post, I was just not feeling it...

Then while I was taking pictures of my peonies after I had told my husband I was writing, I thought "Give them something useful. Something practical. Something to help them through the season." Then they can unsubscribe to go look for a highly trained world-renowned agronomist. Just kidding. 

Well-fed plants are usually less susceptible to soil-borne organisms than are poorly nourished plants. Good fertility may so enhance the resistance of the (host)plant that the parasite can not successfully attack the roots.
— U.S Dept. of Agriculture 1957 Yearbook

It can be said that having a well-nurished plant will deter insect and other disease issues as well.

Earlier this week I shared a liquid fertilizer program for strawberries. You can go to this link and sign up for the newsletter to get a printable copy.

This year growers I work with have had success in high tunnels, while those growing outside have been challenged. The weather is a dominant factor for the challenges. Sometimes all we can do is mitigate the best we can, looking ahead to the next crop.

So that leads me to give you some suggestions of things you can have on hand to help grow through any up and coming challenges that might be on the horizon. I've also tried to make them things that could be readily available at any home and garden or farm store. 

Kelp Meal/Kelp Liquid

Anyone that has been around me for five minutes knows I like kelp. It is effective and multi-purposeful. 

Kelp is not curative, however, it can be used to help boost a plant's immune system helping it to get through periods of stress. It has growth simulant hormones called cytokinins, gibberellins, and auxins that encourage cell health, strength, and growth. 

It has insect repellant properties due to the fact it has iodine which has been shown to deter sucking and piercing insects. I do caution that it is only effective if we use it judiciously. I have growers that use it in the insecticide box when planting corn. The first year the rate would be 6-8#/ac. If planting corn after corn, which is never recommended, however, sometimes practiced, the rate would need to increase to 10-15#/ac. 

Just as other chemistries, its overuse can diminish its efficacy. 

That being said, I add 1-2oz of liquid kelp per gallon to any irrigation water I'm using in my containers and vegetable garden. I generally water with it every 7-10 depending on rain amounts, which equals out to be roughly every other time I water.  

The meal can be steeped in water/vinegar to make the liquid, leaving you with the meal to use as an amendment and the liquid to water with.

For example:

1/2 cup water

1/2 cup vinegar

1 cup kelp meal

Let steep for several days, drain off the liquid and add 1-2oz. per gallon of water and apply every 7-10 days or as needed.

The meal can be used at the time of planting or as a side dress throughout the growing season. 

Aragonite/Oyster Shell

Aragonite can be harder to find, but well worth the effort. Oyster shell would be a good substitute. Both are an excellent source of calcium and can be used dry or steeped in vinegar.  This could be good for tomatoes when they are lacking calcium showing signs of Blossom End Root(BER). BER is really not a calcium issue but an irrigation one. However, a quick readily available calcium application can help the plant get through it and keep producing. I think I sense another idea to write about...

For example:

1 cup aragonite/oyster shell

1 cup vinegar

Let steep for several days, drain off the liquid and add 1-2oz. per gallon of water and apply every 7-10 days or as needed.

5% - 10%Vinegar

This has a multitude of uses. You can use it in liquid fertilizer blends to stabilize a mix and help balance the pH. It can be a good liquid to use an as extractant, like with kelp meal and aragonite. If used appropriately it will have a nominal effect on water pH but not to a level that would be detrimental. However, always use caution and test pH of any irrigation system and soil regularly.

Liquid Fish

There are several formulations on the market. I look for one that has sulfate of potash (SOP) and kelp in it.  If you can find one with sodium nitrate, then that is an added bonus. It is a great stand-alone fertilizer however, I have growers using it in the following mix and see great results.

Liquid Fish Blend:

1-2 gallon liquid fish

1-2 quart liquid kelp

1 pint 5-10% Vinegar

5 pounds sugar or 1-3 oz. molasses per gallon(optional, but recommended)

Add 1-2oz. per gallon of water and apply 1-2 times during the growing season dependant on the crop and soil tests. 

Another blend that is easy to mix yet effective is 

Fish/Kelp Blend:

1/2 Fish Fertilizer

1/2 Liquid Kelp

Add 1-2 oz. per gallon of water and apply every 7-10 days, or as needed. 

This is great for transplanting or times of stress, fertilizing and stimulating growth at the same time. 

As always soil and tissue testing are recommended before implementing any type of program. These are merely suggestions and not an exhausted list of things you could potentially have on hand. If you are experiencing challenges, a call to your local extension office or an agronomist might be necessary before making any fertilizer/amendment applications as well.

*Please take cation as to the time of day you apply liquids when using as a fertilizer, early morning is optimal, or in the evening. 

Once I have recovered from the whole GDPR thing, I'll put together a PDF with the information in this post. At that time you will be asked to subscribe to my newsletter to get it. Then, once you have done that and gotten your free printable fertilizer recipe PDF you can unsubscribe, no hard feelings. 

As always, if you have questions, don't hesitate to ask. Better yet send pictures and we can talk through some issues you might be having. 

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Ag 101 Week 21

What’s Your Threshold?

This spring has been extremely challenging for growers in the northeast and other parts of the country.

I find myself saying the same thing throughout the spring season, “The weather has not been on our side.” Growers are facing extreme weather events that are leading to increased crop damage, insect, and disease pressure resulting in decreased yields or total crop loss.

I also hear myself saying,

“Summer doesn’t matter if you don’t have a good spring.”

I realize that statement is dependent on the crop your growing and how you manage your farm. I’m usually referring to management decisions made before their growing season gets started, then during the summer months they have to live with them. But lately, spring weather conditions have lead to more challenges effecting the rest of the growing season.

This year I have growers that will no longer be growing crops like strawberries due to weather conditions being so unfavorable they can’t afford the risk. For economic reasons they need to focus on crops they can manage in the weather conditions we are now experiencing. Management has now taken on a whole new level of importance.

At the opening day for a local market this week, vendor numbers where low due to spring weather impeding their ability to bring sellable products. One farmer and I were discussing the amount of hail damage on his lettuce and if he could even sell it for an amount that would at least cover his travel expenses for that day.

As I’m writing, it’s raining for the 6th day this week, I know the sun will eventually come out, and things will start to perk up and grow again. Before we know it, we will be in the dog days of summer, and everyone will be hoping for some rain, so they don’t have to run their irrigation. It is a never-ending cycle.

All of this and experiencing my own crop loss this week due to a hungry family of bunnies has me thinking about what threshold a grower can tolerate before they have to make management decisions about harvesting, spraying, or even writing a crop off as a total loss. Do most farmers even know what factors to consider or how to establish a value? And, do they have a plan in place if that threshold is reached.

The dictionary definition of threshold is

ˈTHreSHˌ(h)ōld/ noun

noun: threshold; plural noun: thresholds

2.     the magnitude or intensity that must be exceeded for a certain reaction, phenomenon, result, or condition to occur or be manifested.

"nothing happens until the signal passes the threshold"

synonyms: lower limit, minimum "the human threshold of pain" a limit below which a stimulus causes no reaction.

"everyone has a different pain threshold"

But what does threshold mean in agronomic terms?

Every farmer needs to establish their “pain” or economic threshold they can withstand to keep themselves profitable and in business for years to come.

First, let’s look at specific thresholds-

Economic injury level(EIL) - The smallest number of insects (amount of injury) that will cause yield losses equal to the insect management costs. EIL is also referred to as the break even point.

When pest density is above the EIL - damage exceeds the cost to control

When pest density is below the EIL - damage is lower than the cost to control

Economic threshold - The pest density at which management action should be taken to prevent an increasing pest population from reaching the economic injury level.

The economic threshold is also referred to as the action threshold. That is the point at which insect numbers (population) have gotten to the point you need to mitigate them through cultural practices or inputs such as spraying in order not to reach the economic injury level.

You as a grower have to determine what is the pest density that will justify the cost of applying control measures.

Deciding levels and thresholds at which you have to reach before action is taken can include using formulas and having an understanding of the pest and crop it is affecting.

I work with a specialty grower that produces a niche crop. He sells to high-end wholesale buyers only. He knows the value of his crop and grows a certain number of plants to accommodate a 25% loss. All his management decisions are based on that, and it works for him.

I grow in my backyard. I grow whatever I feel like that year. I give most of it away and eat what is leftover. I know the value and can assume a 100% loss. It works for me.

It’s a good thing it's easy for me to write my season off as a complete wash. The rabbits have decimated everything I planted, and they keep coming back night after night to clean up what they left behind. I realize I’m not growing for profit this year so let them eat, and I’ll figure something else out when I have more time. 

Both of us have established the level of pain or our threshold we can tolerate and how to plan for it. He grows more plants to accommodate; I live with it.

But what if you are growing for market and need to establish that number.

Here are several factors to take into consideration-

1. How much aesthetic or economic damage can be tolerated?

2. What is the value and production costs of the crop at various levels of damage?

3. What is the history of the field?

4. Do you understand the difference between injury and damage and what level is tolerable?

Injury - the effect of pest activities

Damage – monetary value lost due to the pest activities causing injury

5. How much do the control measures cost?

6. Is the insect or disease distributed in the field so effective control can be reached without further crop disturbance?

7. Do you have the ability to control the pest quickly and effectively?

8. Do you have a market or use for a less than perfect product?

9. Do you have the ability grow enough to make up for a certain percentage of loss?

Lastly, here is a simple equation that can be used in conjunction with the factors above to help establish a comfortable threshold for your farming situation

EIL (Economic Injury level) = C*N / V*I

C = cost of controlling the pest per acre

N = number of pests injuring the commodity per acre

V = value of the commodity per acre

I = percentage of commodity injured (% loss expressed as a decimal)

EIL is expressed as the number of pests per acre or pest density that justifies the cost of applying control methods i.e. spraying

Why is all of this important?

Bottom line you need to stay profitable to stay in business. Having established thresholds will help make management decisions to do so, even if it is as simple as growing more to accommodate a percentage of loss or knowing at what pest density you can justify the cost of applying control measures.

Extremely unprofitable broccoli, thanks to the family of rabbits living in our hedge

Extremely unprofitable broccoli, thanks to the family of rabbits living in our hedge

Ag 101 Week 17

The Power of Biology

When I first started college, I went with the intent of becoming a dog trainer. Not just any kind of dog trainer, but a Seeing Eye Instructor. I was also determined not to get into agriculture. I had milked enough, bailed enough, and seen enough corn, alfalfa, and chickens to last me a lifetime.

Fast forward to my second year at Delaware Valley University. I’m majoring in biology and love it. I’m gearing up to start psychology classes so I can get my minor. When all of a sudden I’m asked by my advisor to pick a track in the biology program to specialize. I went with environmental biology, because why not.

I started taking agronomy classes to satisfy the requirements for my specialization and wanted to change my major to agronomy. Unfortunately, my advisor passed away, and no one knew what to with me. The biology department did understand why and the agronomy department did seem to want a biology major lurking around.

That was until the head of the agronomy department meant with me and changed the course of my future. He laid out a plan for the rest of my senior year that landed me a job with an environmental remediation company that was looking to hire someone with my background. Win-Win I was in!

To make a long story short, I ended up graduating with a degree in biology minoring in agronomy and working on Superfund sites.  I got to use both biology and agronomy and save the earth at the same time.  Well, sort of save the earth. As long as the client was happy and I could bill my hours to them, so my employer was happy. So not my plan, but I enjoyed it and was making a decent living. I even had a secretary. Everyone needs a secretary, trust me.

Jump ahead even further in time, and I find myself working for an organic fertilizer company. Totally out of my wheelhouse, I grew up in conventional agricultural, and it was all I knew. I had never heard of anything remotely associated with the industry I was working in now. I remember calling my dad and asking him if he had ever heard of the company I had just gotten a job with, he said no. We concluded that they must not have been that big of a company if he or the rest of the family had never heard of them. Little did I know what I was about to get myself into.

All this to say, I am a total outsider to the world of organic agriculture. I understand farming, but this was unlike anything I had ever had experienced. I found myself in the same situation I was in college. No one knew what to do with me. Only this time I was coming from conventional agriculture and now working with organic farming. As I started working with more and more natural growers, I began to see similarities between the two types of mindsets and I could also see the differences.

This post is not an editorial to pursued one to see the light and change to one side or the other. I don’t get why there has to be such a dichotomy between the two. Both have positives and negatives associated with them. I have always said that it is up to the grower to be willing to assume the level of management that is required for the way in which they want to grow a crop. But there is one hang up I’ve had with conventional growers, especially traditional no-till.

Why do they underestimate the power of biology?

As I started going to conferences and meetings held by the organic counterparts to conventional, I became more aware that organic growers harness the power of soil biology and employ management strategies to use it in their favor. While some conventional growers know its there, however they often use inputs or management practices that are counterproductive to encouraging the microbial populations in soil.  

Why don’t some farmers see all that biology can do for them? It seems as if it has been taken out the equation. Remember the triangles?


Lately, I’ve taken the time to go to more conventional conferences and meetings. I sat in on a meeting with a highly respected traditional agronomist and after listening to him talk it cleared all my confusion as to why in my opinion there is such an under-appreciation for biology in conventional farming.

Biology can’t be quantified; chemistry can


Inputs whether organic or conventional are chemistries. However, the affect a chemistry has on a crop can be measured. For every action, there is a reaction, A+B=C, and so on. You can calculate how much you will need to achieve a specific yield. You can forecast an outcome based on inputs and have actual numbers to back everything up. As long as you get your timing within a particular window and your placement relatively precise, you can rest assured barring any catastrophic weather event or unforeseen circumstance the input you use will do its job. It will do its job because it was chosen based on criteria already established and proven to work.

Soil microbe’s -aka biology- don’t work like that. Biology is a variable dependent on weather, pH, temperature, moisture, soil type, organic matter, compost type, amendment type, crop selection, previous crop, the sun, the moon, the stars -I think you get the point. Harnessing its power is being entirely dependent on things we cannot always physically control. We can not talk to the microbes and ask them to break the phosphorus in our soil down and make it plant available at the specific growth stage we need it. We can not go out to the field and ask the microbes to show up at the right time the right location and do everything we know it is capable of doing when it is most critical for the plant. We can use biologically enhanced inputs. However, there is still the question as to how viable they are due to all the for mentioned variables.  You can count them under a microscope but, do we still have a scientifically proven measurable way to explain, or quantify, all that microbes do, and how that translates into a profit? In most cases, all we can do is hope the microbes are there and show up at the right time and place.

Farming is part hope and expectation. You hope the weather will be in your favor; you expect the seed will germinate, you expect your yields will make a profit. And if a farmer can stack the deck in one’s favor they should, right?

Conventional growers rely on inputs, organic rely on biology.  That’s the great divide. That’s it. Right or wrong it is just using a different corner of the triangle to achieve the same results. However, both use management. 

So how does a farmer stack the deck in their favor harnessing the power of such a variable like biology?

You create conditions and an environment the natural biology of your soil wants to live. You create one that it wants to thrive and flourish in by using chemistries and management practices that encourage biological activity. You use management strategies such as cover cropping and minimal tillage to promote plush living conditions for the very microbes you want to do the work while hopefully starting to minimize inputs.

Harnessing the power of biology-

Simple on paper, not always simple in practice. If it were, everyone would be doing it.