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Fertilizer Application Rate Calculator

I occasionally get emails from people who need some help figuring out how much of each organic fertilizer and microbial inoculant to use.

So - I've made you this fertilizer application rate calculator!

Choose your products, area and application frequency below and click 'Submit'. Cool right?

Feel free to ask questions down below...




Choose All Of Your Products












Choose Your Area

100 square feet (10 square meters)
250 square feet (25 square meters)
500 square feet (50 square meters)
1000 square feet (100 square meters)
2500 square feet (250 square meters)
5000 square feet (500 square meters)
1 acre
Plants in pots

Choose Your Application Frequency

Twice A Week
Once A Week
Every Other Week
Once A Month
4 Times A Year



I'm sure there are some things this calculator won't answer, so feel free to ask any questions down below.

83 Comments

  1. sam brown on June 7, 2014 at 2:28 pm

    when I click “Submit” is simply refreshes the page?

    • Phil on June 7, 2014 at 3:36 pm

      It’s working for me Sam – did you checkmark some products first?

  2. Stephanie on June 7, 2014 at 3:44 pm

    do you need to use the mix immediately, or can it be kept in the sprayer for a while, how long?

    • Phil on June 7, 2014 at 3:56 pm

      Good question – it depends on the products used, but usually it’s best to apply it within a few hours of mixing.

  3. Bear on June 7, 2014 at 11:58 pm

    Really like your new application rate calculator, but “Dextrose (or Sugar)” is confusing to me. I have molasses on hand; do I need to order dextrose and/or sugar as well? Or is it all “sugar”? Thanks.

    • Phil on June 8, 2014 at 2:12 pm

      Your molasses is perfectly fine.

  4. yasmine on June 9, 2014 at 8:00 pm

    This is so useful! Thanks a mil

  5. Ann on June 13, 2014 at 11:41 pm

    Is this with sprayer at 1 Tbsp rate? Thanks.

    • Phil on June 14, 2014 at 12:50 pm

      After you check the boxes and click submit, the text above will tell you the rate. It’s usually the 1 Tbsp rate if ProBio Balance/Bio Ag is involved. Otherwise it’s often 5 Tbsp when using just liquid fertilizers. More details above though.

  6. Russ Verkest on June 30, 2014 at 8:13 pm

    When spraying a mixture of Horticultural or Neem oil and water onto your plants, is it OK to spray the flowers or buds that will turn into vegetables when pollinated? Same question for spraying liquid fertilizers?

    • Phil on July 1, 2014 at 2:52 pm

      I recommend staying away from the flowers and the buds with neem oil when they’re open. I’m not so careful with liquid fertilizers, and have never had a problem spraying them on flowers.

      • Russ Verkest on July 1, 2014 at 3:08 pm

        Thanks!

    • John Herrick on May 5, 2019 at 2:11 pm

      Great material. My question is this – when growing tomatoes don’t you have to vary the spray recipe for the stage the plant is in? By stages I mean vegetation, flowering and then fruit set.

      • Phil on May 12, 2019 at 11:51 am

        Good question. For most of the fertilizers I sell, such as kelp and sea minerals, they’re more “broad spectrum”, used for overall plant health, not for specifically promoting growth or fruiting. There are certain nutrients that are especially effective at helping a plant (tomato or any other) move from growth to fruiting such as ammonia, boron, and phosphorus, but this is more of an advanced technique that I rarely see gardeners using.

  7. Kim on August 10, 2014 at 12:11 am

    Is it OK to spray liquid fish, liquid seaweed and Bio Ag on edibles like tomatoes, zucchini and basil? If so, do I need to make sure to wash them before eating?

    • Phil on August 10, 2014 at 11:55 am

      Yes, it’s good to spray on these plants. As for washing, it depends. If it has rained or you’ve had a sprinkler on since the application, or if awhile has gone by since the application (I can’t really say how long, but let’s say a week), washing won’t be as important because the residues will be mostly gone.

  8. DBL J on November 19, 2014 at 6:17 pm

    I live in S.Calif – when is best time to apply – liquid seaweed & Sea Minerals to my new beds? should I apply in November or December?

    • Phil on November 20, 2014 at 8:29 am

      How about both? I like to apply a small amount monthly. Sometimes I’ll do a spray right when I create the beds and then the next spray when I’ve planted them.

  9. larry on February 15, 2015 at 8:51 pm

    Hi Phil, do you ever foliage spray with magnesium sulfate? if so, whats your ratio per gal?

    • Phil on February 15, 2015 at 10:50 pm

      Yes, I do at 1 Tbsp per gallon of water in my hose end sprayer.

  10. Bob V on February 18, 2015 at 1:21 pm

    I have a question about mixing BIO-AG along with seaweed, fish, and dextrose in a hose end sprayer . The calculator says to add at least 1 quart water, but then it says the water will come from the hose when using a hose end sprayer, but it says under hose end sprayer to add at least as much water as noted above ? Do I add a quart of water to the hose end sprayer or not ?

    • Phil on February 18, 2015 at 8:11 pm

      Hi Bob, what I mean is to just make sure at least that much water gets used overall, so you don’t need to add it to the hose end sprayer because the hose will take care of it.

      • Bob V on February 19, 2015 at 12:19 pm

        Thanks Phil, I noticed though that you usually do add some water to the hose end sprayer. In my calculation I am only spraying 100 SQ feet once a week so the amount of EM, Fish, and seaweed is very small. In this case do I add like a cup of water to ensure the hose end sprayer sucks it up? Else there will be only about 2 teaspoons of liquid in the hose end sprayer. is this enough liquid?

        • Phil on February 19, 2015 at 2:04 pm

          Good question. Yes, I would add some water in there. That will make the spray more diluted, which is fine, or alternatively, it will allow you to choose a higher setting on the sprayer.If you add a cup of water to 2 teaspoons of fertilizer, that’s about a 1:24 ratio already, so instead of using a 1Tbsp per gallon setting on the sprayer, you can increase it to whatever you want – even the full 10Tbsp per gallon would be fine.

  11. Robert Wilson on April 7, 2015 at 4:15 pm

    When the calculator recommends 2 T of the Pro Bio is that Mother Culture or Activated solution?

    • Phil on April 7, 2015 at 10:22 pm

      It’s the same application rate for each, as they should have somewhat similar biology counts.

  12. GP on April 10, 2015 at 5:29 pm

    When I click Submit it only refreshes the page. Yes, I checkmarked products prior to clicking submit. Thank you!

    • Phil on April 10, 2015 at 9:12 pm

      Hmmm, it’s working for me. Can you try again?

  13. Ellen Erickson on April 20, 2015 at 1:24 am

    Would like to see humic acid added to the feeds.

    • Phil on April 20, 2015 at 12:37 pm

      Will try to do this some time.

  14. Annamarie on April 24, 2015 at 11:43 am

    Thanks for this calculator! Really helpful. Since there are a lot of different products.. and I have a not so big garden (something like 400 sq. feet) I’m thinking to combine some of them in a sprayer. Any problem with that?

  15. Annamarie on April 24, 2015 at 11:44 am

    Oh oops. I see you did answer this.

  16. Bill Steppuhn on April 30, 2015 at 1:25 pm

    I have small back yard I put my tomato plants pepper and cucumber plants in big flower pot with the bottoms cut out so the roots can grow into the ground how would I apply your products that way

    • Phil on May 2, 2015 at 2:40 pm

      Hi Bill, you would still use the same ratios and spray the foliage just like you would in a regular garden. Most important is to get the ratios correct of fertilizer to water.

  17. Amy Boelk on May 15, 2015 at 1:46 pm

    Do these fertilizers keep for over a year? I live in Iowa (so can’t garden year round) and my garden is only about 200 square feet. It seems a quart is the smallest portion to buy for the beginner recommendation. Wondering if they will keep for the next year? Thanks.

    • Phil on May 15, 2015 at 9:58 pm

      Yes, most of them have an expiry date of 1-2 years away, and they keep beyond the expiry as long as they’re stored at room temperature, not in direct sunlight. I use them for 2-3 years.

  18. Jason Brindell on May 22, 2015 at 3:11 am

    I have recently purchased several products including the Hudson hose end sprayer. Our garden is only 100 square feet. So after adding the appropriate measurements into the sprayer bottle, I must have to fill it with water. If not there is not enough in there to siphon out. Also, according to the directions on the bottle for teaspoon usage, the brass screw is inserted into the top of the siphon tube. So does the dial on top of the Hudson get set to the #1 for this size of garden?

    • Phil on May 22, 2015 at 12:33 pm

      No, you don’t have to use the brass screw. You still want to spray at a minimum dilution of 1 Tbsp per gallon of water (when using the EM/ProBio Balance), so that’s just setting 1 without the brass screw. In your case, you can absolutely just add some water into the container in order to allow the fertilizers to be siphoned out properly, and that means you could actually set the dial up higher because you’ve already diluted the mixture some. So if you add 10 times as much water into the bottle as you added fertilizer, you could set the dial up to setting 10, although it doesn’t hurt to have a greater dilution with water either, so you could just leave it at setting 1 or somewhere in between.

  19. Mick on July 11, 2015 at 1:05 pm

    Phil,In much of the microbial growing and mixing literature and discussion we’re told to avoid using chlorinated city water; I do. However, we’re then told to use garden sprayers using the hose and “City water”. Does it matter?

    • Phil on July 17, 2015 at 1:26 pm

      I’ve never found any specific data on it. We know that chlorine isn’t ideal, and certainly too much chlorine is a problem, but a small amount of chlorine isn’t the end of the world. Indeed, a small amount is actually a plant nutrient. I love your idea you mentioned to me before of using rainwater for the application. And certainly it makes sense to improve soil water-holding capacity with compost and mulch in order to be able to decrease he need to water with chlorinated water, but most people have to at some point. When I’m hand watering, I mix a little bit of liquid seaweed and other organic fertilizers into the water first, hoping they might help ‘tie up’ some of the chlorine. Even better is to throw in a tiny amount of humic acids or vitamin C or a small handful of compost, which should definitely tie up the chlorine.

  20. Karen Dwyer on August 20, 2015 at 7:40 pm

    Regarding calcium carbonate. 1 lb. of Calcium Carbonate = how many cups? I usually measure by the cup. Thank you.

    • Phil on August 26, 2015 at 3:15 am

      Sorry Karen, I haven’t been able to find an answer for this. I found wildly varying answers online, one of which was 10X higher than the other.

  21. Philip Barlow on August 27, 2015 at 8:02 am

    The question ” 1 lb. of Calcium Carbonate = how many cups? ” Cups. This unit of measurement has a big danger of variation, not just because different sized cups can be used but also because lime can have variable bulk density according to the fineness of the powder. Getting the correct spread rate is critical. Use Lbs Acre, ounces per square yard. Better still metric; Kilos per hectare which divided by 10 equals grams per square metre

    • Phil on September 4, 2015 at 12:37 pm

      Thanks for sharing Philip. Excellent info.

  22. Golf1 on September 14, 2015 at 12:54 am

    Hello Phil best fertilizer I need for North Carolina centipede lawn thanks!

  23. Barbara Mate on March 4, 2016 at 4:22 pm

    Hi, I have an orchard with apple, peach, plum, pear, and failing cherry trees. Only cherry is diseased, Two of each tree, just to give you an idea, all avg 10 ft. Before pulling the cherries, I want to make one last effort in saving them, what do you recommend and how do I apply and can I apply now in late Winter? Thank you so much.

    • Phil on March 7, 2016 at 9:31 pm

      Neem oil can be very helpful and you can start applying it now Barbara. I mix it with liquid fish. Then spraying with effective microorganisms and molasses and sea minerals fertilizer (on a different day than the neem oil) will bring in the beneficial biology that the trees need along with more broad-spectrum nutrition.

      • Barbara Mate on March 9, 2016 at 11:07 pm

        Phil, How often should I spray the neem oil? There are no leaves on the trees yet, so just hit branches and trunk? How would I introduce composted matter to the trees roots? (as they are very established)

        • Phil on March 14, 2016 at 2:41 am

          Hi Barbara, here’s what orchardist Michael Phillips says about when to use neem oil: “I apply pure neem oil along with liquid fish at the week of quarter-inch green, pink, petal fall, and 7 to 10 days after that. This early season program addresses many orchard health fronts including the primary infection period of fungal diseases like scab and rust. I continue to use neem through the summer on a 10 to 14 day schedule, again coinciding with any other specific spray needs. A late August spray on the later varieties finishes up the use of neem oil for the season here in northern New Hampshire.” The only thing I would add is that I believe it can be helpful to spray once in late winter/early spring before the buds have even begun to open. And yes, it will just hit the branches and trunk. As for compost, you can dig some hole around the tree and fill them with compost, if you feel there’s a good reason, or you can just top dress with compost.

  24. Belinda on May 10, 2016 at 1:29 pm

    Can unused solution be kept for the next application, say 2 weeks?

    • Phil on May 11, 2016 at 2:57 pm

      No, not if it’s been mixed with water. Best to use it within a day. I’d spray it onto the soil or compost pile now.

  25. Bruce Turner on May 30, 2016 at 5:12 pm

    I would like to include my asparagus bed in with the weekly schedule of spraying with the EM, Sea Minerals, Molasses and Liquid Fish. Should this be done in the Spring, Summer and Fall ?

    • Phil on May 31, 2016 at 4:00 pm

      Yes, all growing season is ideal.

  26. edgar cliett on May 24, 2017 at 4:37 pm

    i am using a drip irrigation system with an injection system. I want to use the sea, fish and molasses ingredients with 1 acre of watermelons. Whats the formula please?

    • Phil on May 30, 2017 at 9:22 am

      It doesn’t seem to work as well mixing the Sea-Crop and Fish together, so I apply them separately. The general rule of thumb is 2-4 gallons of Sea-Crop PER ACRE per year, 6-12 gallons of Fish, and 2 gallons of molasses. I’d also add in 6-12 gallons of Bio Ag ( https://www.smilinggardener.com/sale/effective-microorganisms-and-scd-probiotics/ ) to make this whole recipe even more impactful.

      I’d apply Sea-Crop 3 times a year at 1 gallon per acre, mixed with 1/4 gallon of molasses (and 1 gallon of Bio Ag) and diluted with at least 50 gallons of water. I’d also apply the Fish 3 times a year at 3 gallons per acre, also mixed with 1/4 gallon of molasses (and 1 gallon of Bio Ag) and diluted with at least 10 gallons of water (although I generally go with more like 50 gallons of water for the fish, too).

      Of course, with your drip irrigation system, if you’re able to fertilize more frequently, you can divide the above up into smaller, more frequent applications.

  27. Darrell on July 3, 2017 at 7:21 pm

    Hi Phil,

    If I am using actual ocean water instead of the sea minerals (I live in Bermuda), what would the recommended calculations be for the below recipe?

    Here’s your main recipe, for 250sqft, sprayed once a week:

    1.5 tsp ProBio Balance or Bio Ag (or EM)
    1.5 tsp Liquid Seaweed
    **1/2 tsp Sea Minerals**
    1.5 tsp Blackstrap Molasses
    1/2 gallon Water (or more)

    Thanks!

    • Phil on July 25, 2017 at 12:14 pm

      I would use 1 quart of ocean water per 250 square feet, mixed in 10 times as much water, 4 times a year. I’d probably apply it separately from the others because I’m not sure how it would impact the ProBio/Bio Ag. The applications could be applied one right after the other – I just wouldn’t want to mix a bunch of ocean water directly with the ProBio/Bio Ag. Hope that helps 🙂

  28. Fernando Morales on October 18, 2017 at 5:37 pm

    I would like to know for hydroponic what is the concentration, I was told 2 onces,of sea water per gallon of fresh water.

    • Phil on October 20, 2017 at 7:45 pm

      I’m not sure, but for the concentrated ocean water product I sell ( https://www.smilinggardener.com/sale/sea-minerals-fertilizer/ ), the amount is 2-3 Tablespoons per gallon of water, which makes me think you would probably use more than 2 ounces of regular ocean water per gallon of water.

  29. Shana Redmon on May 27, 2018 at 10:51 pm

    what ratio of the BioAg do i use to germinate my seeds??

    • Phil on May 31, 2018 at 10:52 pm

      It needs to be quite diluted for germinating seeds. I do 1:1000, so max 1/4 teaspoon per liter of water.

  30. V J Deutsch on June 20, 2018 at 5:42 pm

    Firstly, I thought I purchased the bio Ag on your website Sunday evening. However I’m not sure if it went through because I never got a final page giving me a receipt
    I paid $22 for the bottle and shipping.
    Can you tell me if it’s on its way, please.
    I sent you an email 2 days ago but I haven’t heard anything?
    Now,
    Phi,l I just bought a Hudson 1 gallon sprayer with a brass hose gun end.
    My community garden is 400 ft.²
    Just bought 8 oz bottle NimBioSys neem oil from my local organic garden center.

    Active ingredients: 100% cold pressed neem oil that contains azadirachtin at 3750 ppm ( concerned me a bit because you said something like 2240 ppm was the high end)
    It says for 0.5% concentration use one and a 3rd tablespoons per gallon of water and 1/3 to 2/3 teaspoons of soap suds (I bought Dr. Bronner’s as you recommended).
    Meanwhile, I want to apply the neem and suds today. The first day in 4 we haven’t had thunderstorms and hail which really beat up my poor plants.
    Didn’t you recommend 1.5 teaspoons of neem? And about a half a teaspoon of suds?
    Only about 3/4 of the garden is planted with veggies and edible flowers at this point. And the flowers, the calendula doesn’t seem to need anything at all, whereas my veggies look emaciated and pale. And most have flea beetle holes because they’re not very healthy as you say.
    I think maybe I should spray every week to begin with. Your chart doesn’t say anything about the soap % to add to the neem.

  31. Paula Lerner on June 25, 2018 at 7:06 am

    Please write about how to use all your info for container gardening. People are gardening on roof tops!
    I have to go vertices, using 55 gallon rain barrels with ola watering system. Advice please,
    Thanks,
    Paula

  32. Karen lewicki on March 28, 2019 at 3:27 pm

    Hi Phil,
    I’m trying to use the calculator, but when selecting the products, I am immediately linked to the page to order my selection.
    Other than that, what I have read, I love the detail and amount of dedication and passion you put into your work.

    • Phil on March 28, 2019 at 6:38 pm

      Hi Karen, you need to check the checkboxes, not click the blue links.

  33. Debra Litt on April 27, 2019 at 6:22 am

    What is the application rate for humid acid for 5000 sf? Is it ok to mix with everything else?

    • Phil on April 30, 2019 at 7:03 pm

      Yes, you can mix with the other products. The only no-no is mixing humic acid with liquid calcium, as it causes a reaction that gums up the sprayer. As for the application rate of my humic acid, here are my instructions from my humic acid page:

      Before application, first dissolve the powder in warm water at 5 Tbsp (1/3 cup) per quart of water. That quart will cover 2000 square feet, but doesn’t have to be used right away – you can store it. When you’re ready to use it, mix that liquid with at least 50 times as much water, which is again 5 Tbsp (1/3 cup) per gallon of water, or 3 gallons of water for each 1 cup of the liquid.

  34. Larry on May 22, 2019 at 7:59 pm

    This calculator is a great feature! It make it very easy to determine how much Bio Ag, Fish Fertilizer, and Molasses to mix & spray on the raised beds depending on the frequency. Thanks, Phil!

    Question: I have read that it is best to spray the EM and/or Compost Tea after a rain for it to be most effective – is this true? If so, how much difference does it make. I am planning on doing the first monthly application of the Bio Ag/Fish Fertilizer/Molasses this weekend, using the Chapin 1949 tank sprayer. I am not sure if I can schedule that around a rain.

    • Phil on May 23, 2019 at 9:27 am

      I’ve never seen any studies. If I can help it, I do try to spray after a rain, but I don’t sweat it too much. As long as it doesn’t rain right after spraying, which would wash the spray right off the leaves, I’m happy.

  35. Beth Robertson on June 30, 2019 at 10:54 pm

    Hi, Phil,
    I have been using your EM, mychorrhizal fungi, and liquid seaweed for the last year on my lawn and gardens. I recently discovered that I have cucumber beetles (the striped variety) on my cucumber plants and cantaloupe plants. I ordered some beneficial nematodes to help. Can I put the beneficial nematodes in with the above in my hose end sprayer, or do I have to apply them separately?

    Thanks,
    Beth

    • Phil on July 2, 2019 at 8:18 am

      It may be fine to combine them but I would apply them separately just to be safe.

      • Beth Robertson on July 2, 2019 at 9:21 am

        Thanks! I will let you know how it goes.

        • Debra Litt on August 21, 2019 at 3:51 pm

          Just wanted to let you know that I tried for over 30 years to grow cucumbers, but every time I did, the cucumber beetles would eat all of the flowers and, thus I didn’t get any cucumbers. So, last year I discovered beneficial nematodes and at the garden walk that I had in my yard, people walking through the yard pointed out 9 cucumbers amongst the vast number of leaves on the plant (all of which I gave away that day at the garden walk). The next morning I found 20 more, and that continued the rest of the summer. I haven’t seen one cucumber beetle this year! As long as you get the beneficial nematodes that eat the cucumber beetles every year, I’m sure you’ll be happy ( and probably lots of your friends and family will be too.)

  36. Kathleen on August 10, 2019 at 10:11 am

    What would the ratio be for spraying rose bushes? I have a gallon hand sprayer and I would like to use the Neem and Seaweed together. May I mix enough in the gallon sprayer and then keep it to spay weekly or do I need to mix fresh each time?

    Thank you for your help

    • Phil on August 13, 2019 at 4:43 pm

      Hi Kathleen, to mix, mix 1/2 teaspoon of non-toxic liquid soap and then add 1.5 Tbsp of neem oil into your gallon of water. Shake like crazy before and during application to keep it emulsified. Don’t use dish detergent – use a true liquid soap. And then add 2 Tbsp of seaweed. This amount will do about 500 square feet of garden. I would spray this every 2 weeks. You’ll need to mix it fresh each time.

      • Larry on August 13, 2019 at 4:58 pm

        I have found that when using Neem Oil it is much better to emulsify it before adding it to the sprayer. I take a pint, fill it about 1/2 full with hot water, add the non-anti-bacterial soap (Castile?) and pure Neem Oil, and shake heavily until the oil is fully emulsified in the water (The hot water will allow the oil to become fully emulsified, which is hard to accomplish in cold water). Then add this emulsified water to the water in the sprayer, shake to mix, and begin spraying the plants.

        • Kathleen on August 14, 2019 at 5:53 am

          Thank you very much I appreciate your expertise and your time have a beautiful day Kathleen

        • Daniel Hoisington on August 21, 2019 at 4:58 pm

          Hello, I just received my order, very excited. Have a question about the endomycoffhizal Inoculant.

          At this point in the season, would it be better to save it for next springs planting, or if I do the soil drench now, will it establish itself and still be in soil next spring?

          Thank you
          Daniel

          • Phil on August 23, 2019 at 2:59 pm

            If you don’t do too much tilling, it should still be there next spring. Or you could always do half now and half in the spring – doesn’t hurt to spread it out like that.



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