You seem to be confusing watering with fertilizing. You can put fertilizer in your irrigation water, but irrigation water in general doesn't have fertilizer in it. If I applied my irrigation water at the suggested dilution for liquid fertilizer I'd be spending HUGE amounts of money on fertilizer, and I'd probably kill my plants anyway. Lots of people use liquid fertilizer, and just use it occasionally. Certainly not every time they water. I apply liquid fertilizer every few weeks. I water every few days.

If you regularly irrigated with water that had the recommended dilution for fertilization, it would be the same as dumping truckloads of solid fertilizer on your plants .

I’m talking about using something like this:

https://www.dripworks.com/ez-flo-hose-thread-unit-3-4-gallon

I realize you dilute it more, but over the course of the season isn’t the goal still to add the same amount of nitrogen or whatever nutrient you’re going for?

Which still means it would get ridiculously expensive.

I'm saying that if you want to fertilize every time you water, it has to be vastly more dilute than if you were fertilizing occasionally. In my example, if I fertilize with liquid fertilizer every three weeks, and I wanted instead to apply that fertilizer in my irrigation water every three days, I'd need that irrigation water to have a 1:21 dilution of the regular liquid fertilizer strength. That way, after three weeks, I end up with the same amount of fertilizer in my soil.

That's like saying that, instead of having one cup of coffee in the morning to get my caffeine for the day, I instead choose to have only caffeinated coffee for anything I drink during the day. I'd really get buzzed! Of course, I could get the same amount of caffeine if I diluted one cup of coffee in the all the water I drank for the day. That way, I could drink caffeine all day and not overdose.

OK, I’ll put it another way. On the drip depot website, they sell several liquid fertilizers in a 1 liter bottle, which makes 112 gallons of fertilizer at “normal“ strength. For about $12.

So even if I did normally just water, and only add the fertilizer once a month, if it makes 112 gallons and I want to add enough to penetrate the root zone once a month, I need about 400 gallons of solution.

So say I need four bottles every month. Just using May to August, four months, times four bottles a month, that’s 16 X $12, which is $192!!!!!

I realize that is one example, but I didn’t get much different a monetary result if I use something as simple as Miracle Gro either.

Well, I guess it's a matter of the recommended application rate. When I fertilize ONCE, with liquid fertilizer, I sure don't apply as much liquid as I do when I water ONCE. Again, it sounds like your confusing irrigation with fertilizing. You're saying that when you fertilize once, you need 400 gallons of fertilizer? How many acres are you fertilizing?

I think you have to take the recommended application rate (gallons per square foot, per unit time), and make sure that amount of fertilizer gets in your soil in that length of time.

Maybe I’ve been doing liquid fertilizer wrong. I just assumed you had to get it into the root zone just like when you water. If it only soaks an inch or two in how good is it?

OK, here’s what confuses me. Making an example up on the fly here.

Say a particular planting needs 5 lb of Nitrogen at this time.

If you’re using a 10-10-10 granular fertilizer, then you know you need 50 lbs of that particular fertilizer to end up with the right amount of N.

How does that translate when using a liquid? Assume the liquid also had the same Guaranteed Analysis in this example (say it’s a 10-10-10 liquid). It can’t just be 50 lbs of the liquid solution? Yet 50 lbs of the concentrate definitely isn’t right.

That’s probably why I’m looking at this wrong.

I think what you are asking about is what is called "fertigation" - drip irrigation watering that incorporates fertilizer. It is often referred to as "spoon feeding nutrients".

If so then first you have to understand how drip irrigation works - very slow delivery of water over several hours of time. It is the amount of time used that determines how deep the water gets and nothing is worse than running a drip system for the 20 min 2x a day one sees folks doing.

So if you Google that term you'll discover that miniscule amounts of the water soluble fertilizer is used each time. The goal is nothing like weekly or monthly feedings - a big dose of nutrients all at one time. Rather the goal is to maintain a consistent LOW-dose level of soil nutrients.

Your fertilizer of choice needs to be relatively high dose (20-10-20 is common) as it is first diluted to approximately 1/4-1/8 the normal strength (depending on the siphoning/injector system used to connect to the drip system) and then further diluted as it is delivered by the water running through the drip system. If you use low-dose fertilizer to begin with then yes you will go through a lot of it.

A "bottle, which makes 112 gallons of fertilizer at “normal“ strength." would likely last all season in the average garden when fertigation is used - assuming an NPK rating of 10-10-10 minimum.

The only fertilizer products I find on the Drip Depot website is AlgoPlus - ok but not great for vegetables and it is relatively low dose at 6-6-6. Diluted to 1/4 strength you'd be feeding 1.5-1.5-1.5 with each watering.

Make sense?

Dave

My garden is 50 X 45.

You could ask the same question about solid fertilizer that you sprinkle on top. How does it get down to the roots? Once it dissolves it slowly percolates deeper into the soil. The more irrigation water is applied to the surface, the more it is diluted and the further it penetrates into the soil. Successive irrigation "washes" the applied fertilizer down deep. By that token, highly water soluble liquid fertilizer components like nitrates get washed out of the soil entirely. They just keep getting washed deeper and deeper until, boom, you're in the water table, and they're gone.

You bet that if you sprinkle liquid fertilizer on the soil for a few minutes, it sure isn't going to immediately land where the roots can get to it.

Doesn't much matter if you do it slowly, or you do it fast. The goal is to establish a reasonably stable plant-friendly concentration of fertilizer in the soil.

If you soak your whole bed, to depth, with liquid fertilizer, that won't be plant friendly. You'll fry your plants, and yes it'll cost you lots of bucks. By the same token, you can't grow hydroponically in liquid fertilizer. Liquid fertilizer is concentrated nutrient.

Good info.

So, how do you do the “how much” calculation? How to know based on the N/P/K, how much is XXX lbs of N per acre or whatever?

BTW, true fertigation probably isn’t what I want - if it’s rainy I won’t be watering, and therefore not fertigating either, so doing a once a month or so feeding is better.

With regard to "how much is enough?", I really have no clue. Maybe there are instructions on the product? I just mix up a gallon of MG, and spread it over a couple of square yards every few weeks. If you come up with a rule like that, you should be able to calculate the concentration to use in your mix.

Yeah, I have realized that if I have just a regular sprayer, I can put enough fertilizer down once a month easily enough without messing with the Need to run it through the drip system.

hairmetal, I would like to know why you have 'quickly' it seems to have hitched onto the drip irrigation thing. Are you going to lay down plastic mulch? You said you had a 50x45 garden. To me that is a small garden.

Buying the supplies you need sounds like a bit of cost. Anyway it is your garden and like for me, it is my hobby.

Because one of these times I had to water last year, I used the oscillating sprinkler and ran my well dry (for a few minutes, but still, it spooked me).

Plus my wife and I both work, we have kids, we have daycare, we have lives outside of the garden.

It just seems like it would be more convenient to be able to turn it on and leave it for a while.

Ok so no one has really answered this question effectively yet. Let me start by saying I am a full time vegetable farmer on ten acres using fertigation on everything.

The size of your plot will have a significant financial start up cost, but it will be worth it in the long run. Most of the initial investments are one time purchases like mainlines, valves, pressure regulators, end closures, timer, TDS meter, fertilizer injector, and pressure gauges for the mainline

There are several questions I would need to know for sure to effectively respond, but here is a basic rundown.

You will need for starters, a TDS meter available for $20-30 at most home improvement stores. You will need to know your gpm from the well pump, and as close to exactly how many feet of drip tape you have.

Are you laying under plastic or mulch? Burying the drip tape? Laying on top of the dirt?

Do you have a 7 day timer?

.25gph drip is a little lower than most standard vegetable tapes. Usually .34 or .45 is used on gardens, because 1 hour a day for 7 days is 1” of water like most plants require.

However, how you lay the drip tape affects how long you run the system.

With most liquid fertilizers imjected through an EZ flo system, the target is to get to around 700ppm over your usual ppm. So if you use a TDS meter and it reads 100ppm with just the water, you will need to adjust the fertilizer input to get a reading of 800ppm.

This is done different ways you can adjust the mixing rate on the EZ Flo, you can adjust the fertilizer solution before adding it to the system, or you can adjust the values higher or lower with an inline ball valve, but that’s a more advanced method so skip that one.

How you design the system using the timer will change how you need to adjust the values if you run it for 4 hours every five days, you will want a slightly higher value, say 850-900ppm as compared to around 700 with an everyday watering. At no point with fertigation should you be running straight water once crops are starting to bloom. Allow the rain to be your fresh water source, and use the drip for maximum value

When it comes to fertigation, you cannot just guess with it. It is absolutely critical to know all components of your system, but the yields compared to traditional growing are not even comparable. I’m talking 3-4 times greater yield on most plants!!!

your EZ flo will come with a standard set of instructions but they don’t mean anything until you know all those other factors listed above. You may have to install a white flo disc or a red flo disc, or you may have to run the garden in multiple zones.

Probably the most critical thing though of anything, is to remember with drip you are thinking in terms of hours, NOT minutes. Running in minutes will cause crops to die.

I recommend you check out Urban Farm Fertilizers if you are going to be using an EZ Flo system as the numbers above are based on my uses on nearly every vegetable crop available for consumption by the public.

Youll also need some food coloring to add to the EZ Flo system so you can see when you run out of fertilizer.

As far as how much...you have to know the numbers above. Period. Generally with my mainline ez Flo system it is diluted one gallon of fertilizer to 2800 gallons of water to achieve the correct ppm. For cover crops and leafy stuff it’s diluted even further to nearly 7000 gallons to one gallon fertilizer.

Let me know if you need anymore help with this set up.

A very simple "back of the envelope" calculation for Foliage Pro:

One gallon of Foliage Pro runs around $40. The suggested rate of application for every watering is 1/4 tsp of fertilizer per gallon of irrigation water, which would mean 3,072 applications (762 tsp in a gallon *4) for the whole gallon of fertilizer. Thus, 3,072 gallons of irrigation would cost you about $40. That doesn't seem overly expensive.

-Brett