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Foliar Feeding Vegetable Crops- Is there a Time and Place for it?

Chuck Bornt, Team Leader, Extension Vegetable Specialist
Eastern New York Commercial Horticulture

May 30, 2018

 Chuck Bornt, ENYCHP & Steve Reiners, Cornell University                                                                                                          

Those of you that have worked with me long enough know that I have some pretty strong opinions when it comes to certain things and foliar feeding vegetable crops is one of those topics on which I have some opinions. The bottom line is, I can't really find good research information on what to use or what rates etc., but over the years I have learned a couple of things that I would like to share with you.                                                                                                                      

 Let's define the nutrients I'm talking about. Micronutrients are needed by plants in low amounts, from just a few ounces per acre for molybdenum to a few pounds per acre for zinc, manganese, boron, copper and iron.  Compare that to macronutrients like nitrogen, phosphorus and potassium that are needed in amounts ranging from 40 to 150 pounds per acre. Also considered macronutrients are sulfur, calcium and magnesium which may be needed in the 20 to 40 pound range. First, I believe foliar feeding micros is only part of the solution and is meant as a temporary corrective measure! Foliar forms of these micros may be more readily available to plants compared to soil applied forms. However, foliar feeding should be considered only part of the nutrient management plan.  Continue to soil sample and address micronutrient deficiencies through liming/pH corrections when possible. In many cases, these materials can be added to many of the dry or liquid starter fertilizers we use.                                                                  

Determining if you have a micronutrient deficiency is sometimes very difficult as often the symptoms look the same as some environmental issues. The best way to tell if you have a micronutrient issue is to collect a foliar sample and send it to a lab that can run an analysis for you.  I have had good luck with Waters Agricultural Labs in Kentucky: www.watersag.com (also a location in Georgia). Their turnaround time is usually quick and they supply you with recommendations including foliar feeding recommendations. You can also submit a soil sample from the same field to determine if your soil levels are also low.  When looking to take a foliar sample, the recommendation for most crops is the youngest fully expanded leaf.  Collect at least 15—20 leaves from across the planting (composite sample like you do with soil sampling) and put them in a paper bag (do not use plastic bags) and get them in the mail as soon as possible.  I would recommend that you not pull samples on a Thursday or Friday since they could sit in the post office for a day or two before being delivered.  You can find more information at their website on nutrients they analyze for, con       tact information and fees.

I also thought this information from the Michigan State Bulletin was important when treating a micronutrient deficiency:  "For a preventive spray program, spray the crop about four weeks after emergence or transplanting. Because many micronutrients are not readily translocated within the plant, a second spray will be needed two weeks later to cover the new foliage. When a known nutrient deficiency develops, spray the crop with the appropriate nutrient at the recommended rate every 10 days until the deficiency is corrected. Complete coverage of the foliage is important, especially for iron. Adding a wetting agent to the spray solution will improve the coverage and may increase absorption, especially in crops with waxy surfaces, such as cauliflower and onions.

Micronutrients may be mixed with most fungicides and insecticides. However, some combinations are incompatible and may injure crops. When in doubt, spray only a limited acreage until compatibility is established. Any injury will usually appear within 48 hours." I should also add that a minimum of 30 gallons of water per acre should be used.

I am not a believer in delivering the necessary macronutrients such as nitrogen, phosphorous and potassium by foliar means—but with that said, I do think that there are times when plants may respond to these nutrients being applied as a foliar.  Most vegetables require these three nutrients in large quantities (40—150 lbs per acre). Soil biological processes make these nutrients available, and plants have been evolved to take these nutrients up most efficiently through their roots, not their leaves and stems. Here comes the "however" - over the last couple of years I have seen where adding a couple of pounds of these nutrients, especially nitrogen during stressful times does seem to help the plant "weather" the stress and help it recover quicker when the environment turns more favorable. In particular, I have seen where a foliar feeding nitrogen on sweet corn damaged by hail did help the plant recover quicker.  However, the key is making sure you have some foliage left there for the nutrients to be taken in.  Calcium and magnesium sprays can also help feed plants when soil application is not practical.

Table 1. Nutrient sufficiency ranges for vegetables, potatoes and corn*

 

ELEMENT

VEGETABLES

Most recently mature leaf

POTATOES

Petioles most recently mature leaf sampled

at midseason

CORN

Ear leaf sample at initial silk

Percent (%)

NITROGEN

2.5 - 4

2.5-4

2.76-3.5

PHOSPHORUS

0.25 - 0.8

0.18-0.22

0.25-0.5

POTASSIUM

2 - 9

6-9

1.7-2.5

CALCIUM

0.35 -2

.36-.5

0.2-1

MAGNESIUM

0.25 - 1

0.17-0.22

0.15-0.6

SULFUR

0.16 - 0.5

0.21-0.5

0.15-0.5

Parts per million (ppm)

MANGANESE

30 - 200

30-200

20-150

IRON

50 - 250

30-300

20-250

BORON

30 - 60

15+40

4-25

COPPER

8 - 20

7-30

6-20

ZINC

30 - 100

30-100

20-70

MOLYDENUM

0.5 - 5

0.5-4

0.1-2

*Vitosh, M.L., D.D. Warncke, and R.E Lucas. 1994. Secondary and Micronutrients for Vegetables and Field Crops. https ://ww w. ms u. ed u/ ~war ncke// E 0486. pd f


See Table 3 for rate recommendations. This foliar application followed by either a sidedress application or injection via a drip system for crops on plastic would be a way to promote nutrient uptake and keep that plant moving along. I think and hope that most crop advisors and salesman would think along these same lines and tell you that you need to make sure you're doing your best to provide the crop with the nutrient needs through amending your soils and not through relying on foliar applications. With that said, if you have questions about foliar nutrients, sampling or other fertilizer questions

Table 2. Relative response of selected crops to micronutrient fertilizers*

Crop

Mn

B

Cu

Zn

Mo

Fe

Asparagus

L

L

L

L

L

M

Broccoli

M

H

M

--

H

H

Cabbage

M

M

M

L

M

M

Carrot

M

M

M

L

L

--

Cauliflower

M

H

M

--

H

H

Celery

M

H

M

--

L

--

Cucumber

H

L

M

--

--

--

Lettuce

H

M

H

M

H

--

Onion

H

L

H

H

H

--

Parsnip

M

M

M

--

L

--

Pea

H

L

L

L

M

--

Pepper

M

L

L

--

M

--

Potato

H

L

L

M

L

--

Radish

H

M

M

M

M

--

Snap beans

H

L

L

H

M

H

Spinach

H

M

H

H

H

H

Sweet corn

H

M

M

H

L

M

Table beet

H

H

H

M

H

H

Tomato

M

M

H

M

M

H

Turnip

M

H

M

--

M

--

 

Highly (H) responsive crops will often respond to micronutrient fertilizer additions if the micronutrient concentration in the soil is low. Medium (M) responsive crops are less likely to respond and the low (L) responsive crops do not usually respond.

 

Table 3. Suggested rates and sources of secondary and micro- nutrients for foliar application*

 

Element

Pounds of element/ acre

 

Suggested Source

Calcium (Ca)

1-2

Calcium chloride or calcium nitrate

Magnesium (Mg)

1-2

Magnesium sulfate (Epsom salts)

Manganese (Mn)

1-2

Manganese sulfate or finely ground manganese oxide

Copper (Cu)

0.5-1

Copper sulfate or copper oxide

Zinc (Zn)

0.3-0.7

Zinc sulfate

Boron (B)

0.1-0.3

Soluble borate

Molybdenum (Mo)

0.06

Sodium molybdate

Iron (Fe)1

1-2

Ferrous sulfate

1Iron is not usually deficient in New York vegetable soils

*Vitosh, M.L., D.D. Warncke, and R.E Lucas. 1994. Secondary and Micronutrients for Vegeta- bles and Field Crops. https://www.msu.edu/~warncke//E0486.pdf

 



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Upcoming Events

Produce Safety Alliance Grower Training Course

Event Offers DEC Credits

February 25, 2020
Albany, NY

A grower training course developed by the Produce Safety Alliance (PSA) that meets the regulatory requirements of the Food Safety Modernization Act (FSMA) Produce Safety Rule.  At least one person per farm producing more than $25,000 worth of fruits and vegetables must attend this course once.  Participants will receive a certificate of course completion by the Association of Food and Drug Officials.

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2020 ENYCHP Fruit & Vegetable Conference

February 25 - February 26, 2020
Albany, NY

Join us for two days filled with informative sessions on Tree Fruit, Vegetables, Small Fruit, Grapes, Hemp, and more!

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Hands-on Pruning Demonstration with Dr. Terence Robinson - Capital Region

February 27, 2020
Altamont, NY

Join us for a morning of hands-on pruning discussion and demonstration with Dr. Terence Robinson.  Terence will walk us through the key steps of pruning the tall spindle orchard, and will also review pruning techniques for other orchard systems commonly grown across the Capital Region. Please note this meeting will be held the morning following our annual winter conference in Albany.  

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Announcements

2020 ENY Fruit & Vegetable Conference


Join us for two full days of informative sessions on Tree Fruit, Berries, Vegetables, Grapes, Hemp, and more...many of which will offer DEC credits.

When registering, please be sure to choose the correct cost option depending on your enrollment status with Eastern NY Commercial Horticulture and whether you will be attending one day or two.

Lodging: Individual guests may call The Desmond directly at 518-869-8100 (or 800-448-3500) to book rooms at the discounted rate of $115.00 per night. Reservations must be received no later than February 9, 2020 to get the discounted rate. When requesting a room, guests may refer to the "Eastern NY Fruit & Vegetable Conference Room Block" or by referencing Block Code: FVG.

2020 Fruit & Veg Conference credits are as follows:
  • Tree Fruit - Day 1 morning - 2.0 credits in categories 1a, 10, 22
  • Tree Fruit - Day 1 afternoon - 2.25 credits in categories 1a, 10, 22
  • FSMA - Day 1 all day - 2.0 credits for 10, 1a, 23
  • Grapes - 2.25 credits in categories 1a, 10, 22
  • Berries - 2.75 credits in categories 1a, 10, 22
  • Veg - Day 2 morning - 1.50 credits in categories 1a, 10, 23
  • Veg - Day 2 afternoon - 2.00 credits in categories 1a, 10, 23
  • Hemp - 1.75 credits in categories 10 and 1a; 1.25 credits in categories 21, 24


Resources from CCE ENYCHP!

We are developing new ways to connect with the CCE ENYCHP team this year! We have a Youtube page located at this link. Check out videos on Table Grape Production, Pest Updates and the 20 Minute Ag Manager - in 4 Minutes series

We have a Facebook Page here as well as an Instagram page. We keep these places updated with current projects, events, and other interesting articles and deadlines.

There are also text alerts available. Fruit and vegetable farmers in 17 Eastern NY counties can now receive real time alerts on high risk disease and pest outbreaks texted directly to their cell phone. The Eastern NY Commercial Horticulture program, which is supported by local Cornell Cooperative Extension associations, will now offer text alerts to those that enroll in our program in 2019. 

The text alerts will be reserved for important crop alerts that could impact management decisions immediately. For instance, if there were an outbreak of Late Blight in the area, this would be transmitted to vegetable growers.

Farmers can choose the crop for which they wish to receive updates. Additionally they can request that Ag Business Alerts be sent to them. These alerts might include due dates for crop insurance deadlines, market opportunities etc.

If you have questions, please contact enychp@cornell.edu


Podcasts

Tomato Disease Resistance

February 17, 2020
Teresa Rusinek discusses new tomato varieties being developed by Dr. Martha Mutchler-Chu at Cornell University with improved resistance to early blight, late blight, septoria leaf spot, and other foliar diseases. Rusinek also covers the basic biology and current management options for the primary tomato foliar diseases, including bacterial spot and speck, found in Eastern New York.

Dr. Meg McGrath: What’s New in Managing Tomato Diseases in 2019 (fungicide efficacy trials for several tomato foliar diseases, including OMRI options)
http://vegetablemdonline.ppath.cornell.edu/NewsArticles/Tomato%20Diseases-McGrath-NJ%20ACTS-2019-NY.pdf

Tomato Disease Resistance Breeding http://vegetablemdonline.ppath.cornell.edu/NewsArticles/Cornell%20Disease%20Resistant%20Tomatoes-2019.pdf

Hot Water Treatment
http://vegetablemdonline.ppath.cornell.edu/NewsArticles/HotWaterSeedTreatment.html

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