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.


  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


  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.

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