How much water and fertilizer do I need

dlnkbrown1974March 10, 2011

I've raised tomatoes for several years but not mastered it yet. I plant 72 plants each year which is mostly heirlooms. I plant them on a raised row covered with black plastic with a soaker hose. This year I plan on using a solid hose with two half gallon emitters per plant. Does that sound ok? Last year I think I put to much calcium nitrate. A lot of my tomatoes were white and coarse inside. I usually fertilize weekly switching between calcium nitrate and mircle grow. I need help knowing how much fertilizer and water is needed.

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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

You are going to get many differing opinions and that is about all any of us can do is give you our opinion - for what they are worth. The more details you can give us the more help we could be.

I'd need to know how close together you are planting them. It is difficult to imagine one long mounded row with 72 plants in it so I'm assuming multiple rows. If so what is your plant spacing? Hopefully approx. 3 feet apart.

Personally I would never use calcium nitrate (too much salt) unless I knew for a fact that my soil was calcium deficient - which is very rare - and if it was deficient then there are many other calcium supplements that would be more beneficial. Consider a 1x application of dolomite lime IF your soil pH isn't already alkaline.

I also won't use MG because of all the salts it contains and deposits in the soil but that too is just my opinion. Do some research into the many alternative fertilizers that are available and discussed here and keep the need for micro-nutrients up front.

But regardless of the type of fertilizer you choose to use, feeding weekly is overkill. Every 2 weeks with a dilute feeding of some kind - maybe - depending on how much soil preparation and amending was done up front and how the plants are performing. Timing of application is as vital as the type used.

As to water? There is no absolute formula as it all depends on your soil type and weather. I am on about the same latitude as you and if I used black plastic without a heavy layer of mulch on top my plants would be heavily stressed from the heat. So I'd suggest that if you want to use the plastic be sure to cover it well once the soil temp has topped 65. Also the mounds will dry out faster than direct in-growth.

Two half gallon emitters per plant should work fine depending on how they are spaced - don't set them right at the base of the plant but at what would be the drip line of an established plant - say 12-18" out either side of the stem. And how often do you plan to water? How long to set the timer for? It is consistent soil moisture levels you are shooting for so you need to have access to the soil 6" deep to access moisture levels and you will need to experiment with the frequency and duration (varies with weather) until you get a good balance.

My soil is very well amended with lots of organic matter and my gardens (no mounds) are heavily mulched with 6-8" of hay and straw so the times and durations I use wouldn't be of any help to you. But I'd suggest you might try the old cat food can test.

Take an empty tuna or cat food can or 2 and bury them so the top sits flush with the soil and 1 of your emitters drip directly into it. Time how long it takes to fill the can (your plant will be getting 2x that much with 2 drippers) and begin by running your system that length of time 1x per week.

Put up a rain gauge and if you have rain cut your watering by that much each week. As the temps increase - depending on whether you mulch or not - and the plants grow you may have to increase the frequency but the time should remain fairly constant. 24 hours after you water dig a 6" deep hole near a couple of the plants and note the soil moisture levels. Use your hands, feel it, squeeze a handful of it, note its color. Check it again 24 hours later to get a sense of how quickly it is drying out. You need to develop a good sense of what your soil feels like when it is at the ideal moisture level of cool to the touch, only slightly moist, doesn't clump and crumbles easily, and darker in color than the top soil.

I hope this is of help to you but keep in mind that your garden is unique and adjust accordingly.


    Bookmark   March 10, 2011 at 7:00PM
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gardningscomplicated(southeast michigan - 5b or 6?)

I almost never water, because we typically get too much rain. And last year, after lots of research and discussion, I decided to just throw some cut weeds on top my beds. And I did a little experimenting with weed teas. Also, one of my gardens already had compost and straw from the year before. This year I'm going to do the same, but get started earlier with the teas. At least that's what I'm currently planning. One of my main goals is to provide a good environment for earthworms (and other natural fertilizer producers), and let them do the rest of the work.

    Bookmark   March 10, 2011 at 10:42PM
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Thanks digdirt for your information. My plants are spaced 4 feet apart and rows are 6 feet apart. What type of fertilizer would you use in the drip line? I plan on adding lots of cow manure and tilling in soil soon.

    Bookmark   March 11, 2011 at 9:49PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

What type of fertilizer would you use in the drip line?

Any water soluble works ok. I prefer to use organic based ones and ones that provide good levels of micronutrients as well but there are many different ones of both organic and synthetic available. They do vary as to frequency of application.

Check out,, and for starters.


    Bookmark   March 12, 2011 at 11:42AM
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