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Thread: The Myth of Foliar Feeding

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    Default The Myth of Foliar Feeding

    I have seen posts recently where growers have disputed that spraying the leaves of a plant is the best method of feeding there grows. All though it can be beneficial it doesn't have the effect most growers think it has.

    Does anyone here spray there plants through the veg cycle until reaching the 1st week of flowering...? I spray for a max of 2 weeks when there babies but not after that period of time.

    What nutes do you spray if you are a spray grower...?


    The Myth of Foliar Feeding

    Fertilizers sprayed on the leaves of trees and shrubs are more effective than soil applications

    The Myth

    Recently, I received an email from a professional colleague whose clients often ask about foliar feeding
    as a method of fertilizing plants. As he says, “All the water soluble fertilizer companies advertise the
    practice all the time.” What, he wondered, was my opinion of the practice?
    Foliar feeding involves spraying the foliage of target plants with water-based fertilizers. The logic for the
    practice is based on scientific research from the 1950’s, which demonstrated that leaves can take up
    minerals through their stomata, and in some cases through their cuticles. This research is consistently
    cited in the argument that foliar feeding is 8, 10, or even 20 times more effective than traditional soil
    application.
    In assessing the advertised claims for foliar feeding of shrubs and trees, I had particular questions that are
    answered in bulleted lists below (all bullets are directly from marketing media):

    (1) What are the advantages of foliar feeding over soil application?

    • Immediate results
    • Prolong bloom
    • Increase crop yields
    • Increase storage life of food crops
    • Boost growth during dry spells
    • Increase cold and heat tolerance
    • Increase pest and disease resistance
    • Maximize plant health and quality
    • Help the internal circulation of the plant

    (2) When should one use foliar nutrients sprays?

    • When the soil is too cold for conversion of nutrient elements into usable forms
    • When it is at least 72°F
    • Any time except when it is too hot or too cold
    • Transplant time
    • Bloom time
    • When a quick growth response is desired
    • After fruit set
    • Every 2-3 weeks
    • Any time of stress
    • As long as the plant has leaves that aren’t dormant
    • When the soil is deficient in nutrients

    (3) What time of the day, and in what quantity, should you apply foliar fertilizers?

    • Early morning
    • Until it drips from the leaves
    • There is no improper way

    (4) How long will material last on the leaves?

    • 24 hours
    • 1-2 days
    • Four weeks

    (5) What nutrients are critical components of foliar feed fertilizers?

    • Nitrogen
    • Phosphorus
    • Micronutrients

    (6) Apart from commercial formulas, what should homemade mixtures contain?

    • Seaweed
    • Compost tea
    • Natural apple cider vinegar
    • Blackstrap molasses
    • Fish emulsion
    • Baking soda

    As one company states, “In our opinion, foliar feeding is by far the best approach to use to insure
    maximum growth, yields, and quality by overcoming limitations of the soil and its ability to transfer
    nutrients into the plant.”
    The Reality
    If these laundry lists look more like a multiple choice test rather than solid information, it’s not surprising.
    Foliar feeding is yet another agricultural practice best suited to intensive crop production under specific
    soil limitations rather than as a landscape management tool. Thus, advertisers take great liberties with the
    facts, often resulting in contradictory messages (note especially the recommended temperature
    conditions!). Rather than individually refute the numerous errors in the claims, I’ll explain when foliar
    feeding might actually be beneficial.
    The original 1950’s research came from Michigan State University and was particularly useful in
    understanding how nutrients move within plant tissues. As explained by Dr. Tukey in his testimony to
    the Joint Committee on Atomic Energy, use of radiolabelled nutrients allowed his team to discover
    “…that a leaf is a very efficient organ of absorption. The amounts may at first seem relatively small, but
    to offset this handicap, the efficiency is high.” From this advertisers claim that foliar feeding is 8, 10 or
    20 times more effective than soil application. This is not accurate for several reasons.
    Obviously, materials applied directly to a leaf are more likely to enter the leaf in large quantity than the
    same materials applied to the soil. Leaching, chemical reactions, microbial activity, etc. can decrease
    what actually reaches the roots and is taken up into the plant. But materials applied to the leaf do not
    necessarily travel throughout the entire plant as effectively as they do through root uptake. They often
    remain in the same or adjoining tissues but travel no further. This is especially true of those elements
    recognized as “immobile” within plant tissues (apart from root uptake and xylem transport).
    Research over many decades has explored the mineral uptake and transport of many species of fruit trees,
    conifers including pine and spruce species, and some hardwoods of ornamental or commercial value.
    Results have been mixed in many cases, with some species responding well to treatment and others
    remaining unaffected. Generally, the results suggest that foliar application of particular nutrients can be
    useful in crop production situations where soil conditions limit nutrient availability. For instance,
    alkaline soils do not readily release many metallic nutrients, especially iron and manganese. Zinc,
    copper, magnesium, molybdenum, boron, and calcium are other micronutrients required in small
    quantities that have been applied to foliage in an effort to relieve deficiencies and combat fruit disorders.
    Fruit, as adjacent tissue, can benefit from foliar spray. But this is a localized application that does not
    affect the trunk or roots – and therefore is not a solution to soil imbalances. In fact, researchers
    consistently state that foliar treatments are a specialized, temporary solution to leaf and fruit deficiencies
    in tree fruit production but will not solve larger soil management issues.
    On the other hand, macronutrients, such as nitrogen, phosphorus and potassium, are needed in larger
    quantities. While many of these are mobile in the plant, it is pointless to apply them to foliage as leaves
    cannot take up enough material to supply the entire plant’s demands. Furthermore, foliar application of
    high concentrations of such nutrients often results in leaf burn as water evaporates and the fertilizer salts
    remain behind. Substituting numerous, lower concentration applications would not be cost effective.
    Species differ widely in their ability to take up nutrients through their leaves. Differences in cuticle
    thickness, stomatal resistance, and other genetic factors will influence uptake, as will environmental
    conditions. Plants in a protected situation (like a greenhouse) have thinner and more porous cuticles than
    plants in the field and take up foliar sprays much more readily. Likewise, plants adapted to arid
    environments naturally have thicker, less penetrable cuticles than those from more moderate locations.
    A better management solution to the problem of nutrient availability is to choose plants that can adapt to
    the existing soil conditions. If you have alkaline or calcareous soils, for heaven’s sake don’t install acid
    loving plants! Poor plant selection in terms of mineral nutrition will be a management problem for the
    lifetime of the plant – which may be pretty short. Choose cultivars of species that are more resistant to
    alkaline soils – they are able to acidify the root environment so that micronutrients are remobilized from
    the soil and available for uptake.
    The existing research does not justify foliar fertilization of landscape plants as a general method of
    mineral nutrition. It can be useful for diagnosing deficiencies; for instance, spraying leaves with iron
    chelate can help determine if interveinal chlorosis is from iron deficiency. It would obviously have
    benefit for those landowners with landscape fruit trees that perpetually have flower or fruit disorders
    associated with micronutrient deficiencies. Applying fertilizers to leaves (or the soil) without regard to
    actual mineral needs wastes time and money, can injure plant roots and soil organisms, and contributes to
    the increasing problem of environmental pollution.

    The Bottom Line

    • Tree and shrub species differ dramatically in their ability to absorb foliar fertilizers.
    • Proper plant selection relative to soil type is crucial to appropriate mineral nutrition.
    • Foliar spraying is best accomplished on overcast, cool days to reduce leaf burn.
    • In landscape plants, foliar spraying can test for nutrient deficiencies, but not solve them.
    • Micronutrients are the only minerals that are effectively applied through foliar application.
    • Foliar application will not alleviate mineral deficiencies in roots or subsequent crown growth.
    • Foliar spraying is only a temporary solution to the larger problem of soil nutrient availability.
    • Minerals (especially micronutrients) applied in amounts that exceed a plant’s needs can injure or
    kill the plant and contribute to environmental pollution.
    • Any benefit from foliar spraying of landscape trees and shrubs is minor considering the cost and
    labor required.

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  3. #2

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    Good post wrams mate
    ive been saying for a while that as long you keep your ladys happy in terms of feed and humidity then you should NEVER need to spray plants. it can lead to all kinds of problems you really dont want like mould/stem rott/damping off to name a few

    cock

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    just to add a wetting agent, i use yukka extract[shidigara sp ]is good to use when foliar spraying to stop the fluid going into droplets and running off.
    Last edited by wert; 26-03-10 at 03:01 PM.
    if you're retired or you ain't got a job and you ain't growing and smoking weed ,i don't know what the fuck you are doing!

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    Quote Originally Posted by CockRoach View Post
    Good post wrams mate
    ive been saying for a while that as long you keep your ladys happy in terms of feed and humidity then you should NEVER need to spray plants. it can lead to all kinds of problems you really dont want like mould/stem rott/damping off to name a few

    cock
    Your welcome buddy.

    To be honest I only ever spray when I plant cuttings and that is always Carbonated Water, I sometimes spray babies to for a week to 10 days there abouts, this does help them because carbonated water gives plants the much needed 'Carbon Dioxide' which plants thrive on so does them wonders in my humble opinion. Once plants become more than 10 days old they never get sprayed by me again during the entire cycle.

    Anyway glad this post was something you found useful.
    Last edited by Wrams; 26-03-10 at 04:27 PM.

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    Taken from Wikipedia:

    Atmospheric concentrations of carbon dioxide fluctuate slightly with the change of the seasons, driven primarily by seasonal plant growth in the Northern Hemisphere. Concentrations of carbon dioxide fall during the northern spring and summer as plants consume the gas, and rise during the northern autumn and winter as plants go dormant, die and decay. Carbon dioxide is a greenhouse gas as it transmits visible light but absorbs strongly in the infrared and near-infrared.

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    quote---"The Reality
    If these laundry lists look more like a multiple choice test rather than solid information, it’s not surprising.
    Foliar feeding is yet another agricultural practice best suited to intensive crop production under specific
    soil limitations
    rather than as a landscape management tool."

    isn't that what us indoor growers do??

    imo foliar feeding during veg, and the 1st 2 weeks of flower is more than beneficial to our sacred herb.

    my experience tells me that the growth/foliage from the inside nodes is more dense when i foliar feed compared to when i dont.

    i think this guide is for outdoor farming not canna growing.

    e2a alongside normal feeding i use a seaweed foliar occasionaly on a new strain. i think this article dispenses with soil/hydro feeding altogether.
    Last edited by Rizla; 26-03-10 at 04:44 PM.
    understanding why you REALLY need a KINGSIZE since 1796

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    i also spray my plants all through veg with a diluted compost tea.

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    I know people who use this and say there yields drop drastically when they don't use it, its called 'Liquid Light Spray' and if you Google it you can see the results in some websites.

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    As with a couple of the other guys above, i too spray my plants regularly all through the veg cycle. I use a seaweed 'tea' which the plants love, and IMO the growth and health is increased.

    In the wild all plants get a regular spray, it helps to wash dust, salts/toxins and microscopic organisms off the leaves, in turn opening the 'pores' to more light. = More light that goes in, more bud that comes out!
    **********************************************************


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    To be honest I didn't look at it from that point of view before. Rain does what we are talking about and it also contains lots uf useful nutrients for plant life so yea I suppose a spray everyday or even now and then wouldn't do any harm. I may try this on my next grow and see what the results are like compared to not spraying. I would be interested in purchasing some Liquid Light Spray which has some amazing reviews by the way of maximum growth and yield

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