Watering to much or not enough

For the last three years I water when the MM looks dry and sometimes I stick my finger into the mix and then I water. I've always felt like I was over watering but never sure. This year I bought a moisture indicator from Rapidtest and my eyes are finally open. When I thought the garden was ready to water a check with the meter showed plenty of moisture almost everywhere. I have more than halved my watering and the plants seem to be quite happy. We will see how the plants continue to mature and what will happen with the yields.

I too have trouble gauging the moisture... and have been using my finger to figure it out....
I'm still not sure... and I don't want to mess it up after all the effort I've put in with MM and fencing

How do you water your garden?
(I just ordered a drip system, but am rethinking it)

I found that I was not watering nearly enough.  Now that I'm giving them more, the plants are really taking off!

But my slope makes sure everything drains well too...

We've had conflicting feedback on moisture meters.  Some folks like them; some folks can't get repeatable readings.  I tried one that appeared to work in native soil, but didn't work in MM.  

If you know for a fact that you have good drainage, you won't over-water properly made MM.

Learning how to keep MM moist throughout its depth takes some practice.  Water will run out the bottom of a box when the MM is properly saturated and also when it is too dry!  Sticking your finger to the bottom of the box is the simplest way to test for moisture.

I've read quite a few times, and been told by our master gardeners too, that over-watering is the most common garden mistake. It often goes hand in hand with another problem, light watering, which one of our instructors refers to not as watering, but as psychotherapy. It makes you feel good and like you're doing something, communing with nature or whatever, unwinding after work in the garden, but doesn't necessarily do much for the plants. It's best to water deeply and less often, as that encourages roots to grow deeper to find water, which makes for a stronger plant that also has better drought resistance. (Deeper roots mean the plant is more likely to find water when it really needs it, and less likely to dry out. Bonuses are that that bigger roots can also better find and absorb water and nutrients throughout the growing season, as well as make a plant less susceptible to being lastingly damaged by heat.)

In the master gardening greenhouses and on their outside plants too, the local MG's use moisture meters religiously. Using them thousands of times over the last few months doing greenhouse work, they seemed to confirm their worth. They regularly showed, for instance, that plants and seedlings in less than ideal spots got watered less and in comfortable places that were easy to reach got watered more. Human nature revealed ... we can be kinda lazy and inattentive, even MG trainees. This is the kind of thing that is all too easy to overlook in our own gardens or greenhouses at home. We're all human beings, after all. That soil that "looks" okay; that plant that gets watered too much because it's up close or too little because it's further away ... the moisture meter is a good way to protect our gardening interests from, well ... ourselves!

That's not to say you can't get a bum moisture meter. I did. It registered the same in every type of soil no matter how wet or dry it was ... including in a glass of water: dry. So I returned it after getting and testing another.

Tip: Thoroughly wipe off the meter's probe after each insertion into the soil. Otherwise you may mistake the reader for being unreliable when really the unreliable one is YOU.

I have a feeling that the MM is not moist at the bottoms of the pots, even though I water daily, and the water runs out the bottoms. I checked a pot tonight, down about 5 ", and it was dry, and I had just soaked it! I may have to re-hydrate the MM by using trays/saucers for a day or two. I learned that leaving the trays under the pots leads to stinky roots and mix, but I think for a few hours it will be okay.

Sounds like many of us have the same experiences. I know that you can't over water the MM if you have good drainage but under my boxes the soil (?) is heavy clay. This could become saturated and not drain as well. The moisture meter ranges from a high od 9.9 and a low of 0 so I look at it like a percentage of saturation and water when the meter says below 3.5 or 4. I don't know if this is correct or not but I don't think keeping the MM at 9.9 all the time would be a good idea.

Marc,

Would you share your opinion on drip irrigation vs. sprinkler, hand held hose watering?

shegardens wrote:Marc,

Would you share your opinion on drip irrigation vs. sprinkler, hand held hose watering?

I'm not knowledgeable in that regard compared to many if not most of the people here, and I'm sure some of them will help you out, so I'd best leave answering that to others. I'll only comment that, as I recall, a very large majority of water goes to evaporation when using sprinklers, so sprinkler use takes much more water and for some will be much more expensive than using drip irrigation. In some places with shaky water supplies, using sprinklers is actually forbidden because it is so wasteful. Also, it's not just watering style but the time of day that can make a difference in effectiveness and economy.

johnp wrote:For the last three years I water when the MM looks dry and sometimes I stick my finger into the mix and then I water. I've always felt like I was over watering but never sure. This year I bought a moisture indicator from Rapidtest and my eyes are finally open. When I thought the garden was ready to water a check with the meter showed plenty of moisture almost everywhere. I have more than halved my watering and the plants seem to be quite happy. We will see how the plants continue to mature and what will happen with the yields.

Remember to keep the tip end  1inch ( 25 mm ) of the probe bright & clean by giving it a gentle rub with steel wire wool or a green pan scrubber to remove any oxide on it , as the oxide  prevents an accurate reading due to its higher electrical resistance .

Plantoid, thanks for that advise on cleaning the tip.

plantoid wrote:

Remember to keep the tip end  1inch ( 25 mm ) of the probe bright & clean by giving it a gentle rub with steel wire wool or a green pan scrubber to remove any oxide on it , as the oxide  prevents an accurate reading due to its higher electrical resistance .

Plantoid, I think last year you mentioned this and also mentioned wiping the tip of the probe with something (maybe vinegar) ??? But I can't remember what liquid you said to use.  I bought a new probe this year and want to make sure it is reading correctly.

I'm trying an experiment.  Last year I over watered one bed so much it killed the beneficial soil bacteria and encouraged root knot nematodes.  

I've always been told that vegetable plants need about "an inch of water a week".  But for me, that's really hard to estimate as I stand there with my hose, turn on my watering grid system.  And, my tendency is to over water because I'm never sure I've watered enough -until it's too late.

So - I just purchased an inexpensive but highly rated "water meter" for my hose.  It registers how much water actually goes through the hose during a watering session.

Hopefully, by calculating the number of gallons required to give the plants an inch of water per bed - and using the hose meter to check how much is going on the bed, I should be able to start judging better when I have watered correctly.

For example an inch of water in a 4x4 bed is 9.97 gallons.  So if I need to give the bed an inch of water each week and I water twice during the week, I can give the bed 5-gallons each time.  

Once I've done this a few times, I think I should be able to set the timer on my watering system much more accurately.

What type of meter did you get? I've thought about doing something similar, although I really don't need another garden gadget!

Hi boffer,

I got this one:   http://www.amazon.com/gp/product/B007NHRSOY/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1 

The $42 price wasn't bad and it has a 4 out of 5 star rating.

My concern is mostly when I water with my grids, because I can't tell how much water is actually going into the box since it disappears so quickly in the MM. 

They're on timers but, I find that sometimes I've accidentally watered way too much.  I thought I would time how long it takes to provide the appropriate number of gallons then set the timer accordingly.

I'll see how it goes when the meter arrives.

I water with a hose so I just took a 6 gal. bucket and timed how long it took to fill. With no other hoses running it took one minute to fill or 6 gal. per minute. A little less than a min. for a 4x4 box twice a week. I still check with the moisture meter, just in case.

johnp wrote:I water with a hose so I just took a 6 gal. bucket and timed how long it took to fill. With no other hoses running it took one minute to fill or 6 gal. per minute. A little less than a min. for a 4x4 box twice a week. I still check with the moisture meter, just in case.

So how do you convert 6 gal per minute into 1 inch in a 4 x 4 box (or 1.33 sq ft).  You are saying that 6 gallons is proper watering amount for a 4 x 4 twice a week.??? (depending on weather, temps etc).

Hi yolos,

One US gallon (UK is different) contains 231 cubic inches of water.  You can check this online easily.

If you have a 4x4 SFG it equals  48" x 48" or 2,304 square inches.   

To put water in the box 1" deep,  you need 2,304 square inches x 1" deep water which equals 2,304 cubic inches of water. (2,304 x 1")

Therefore the number of gallons of water you need for the box is; 2,304 cubic inches divided by 231 cubic inches in a gallon or approximately 10 gallons of water.  (2,304/231)

The time it takes a hose to provide 10-gallons of water will be different for everyone depending on water pressure and hose size.

Sorry if this was more info than you wanted.

(figure 7.5 gallons per cubic foot)

1.33 cubic feet x 7.5 gallons = 9.75 gallons

9.75 gallons / 6 gallons per minute = 1.6 minutes

1.6 minutes / 2 times per week = 0.8 minutes per watering session


I've done the same calcs for my wands' outputs.  What it does for me is to keep me honest.  

We all know that looking at how wet the surface of MM is does not give us a clue as to how well saturated all the MM is.   If I'm feeling lazy or rushed when watering, having a 'feel' for how long a box needs watered (mathematically) helps ensure that a box gets sufficient water for the moment.  Every second or third watering, I  use the finger test to the bottom of the box so I know for sure.

Both of you did it different than I did but the results are the same. With my hose a little less than a min. for a half inch. What I wonder is who came up with the statement that vegies need one inch per week? I have also read that somewhere but it seems to me that humidity, altitude and other variables would also affect the moisture level. I think I will just check the MM and water when it needs it. 

johnp wrote:...What I wonder is who came up with the statement that vegies need one inch per week?...

The one inch per week number is from the row gardening world.  I have no idea how applicable it is to SFG.   Since a lot of them water with sprinklers, it's easy enough to just set a tin can in the middle of the garden to physically measure the amount of water delivered.

Don't know if this relevant, but I'll mention it anyhow: When setting up a new box, it takes about 1 gallon of water to properly saturate a square foot (6 inches deep) of MM.

johnp wrote:... I think I will just check the MM and water when it needs it.

LOL +1  me too

Gloria

Thanks for posting the link to your water meter; I just saw it on the previous page.

Whoa Ladies and Gentlemen!  For what it's worth, I can't imagine Mel ever intended watering to be as complicated as what this thread is implying.  

I'd like to share my 4 year sfg experience.
New direct sowed seeds and seedlings, give the plants a little water from the little cup of bucket warmed water once or twice a day is all I've needed and certainly did not wet the entire bed down.  

Yes, hot climates will need more watering attention and maybe I missed something from the previous posts. I'm in Ohio.  But also remember warm water moistens, absorbs into the mix much easier than cold.  Don't risk washing away nutrients unnecessarily.  As the plants get bigger I imagine what it takes to fill themselves up with water.  Not what it takes to wet down the entire bed.  It doesn't take very much at all.  My largest 7 inch diameter broccoli plants would only get a cup to cup-1/2 of water per day or every other day.  It's very helpful to dig a depression around the stem of all the plants so water is going right to the roots where you want it.  I don't worry about the rest of the bed getting wet.  I'm absolutely no expert here, and I don't want to come off as a smart aleck, just sharing that its easier to do what I described rather than become a mathlete in order to water my 10 beds.  

Hi llama momma,

You're absolutely right - watering isn't intended to be complicated.  And, I wish I had the time to water my 400 square feet, square-by-square by hand like you do.

But I don't, and my drip grid system is very effective.  However, it's been difficult to determine how long it needs to run.  Because the system is flat on the ground, I can't put a put a tin can under the grid to measure output, so I needed a different way to easily determine how long I should let the grid run. This seemed like a good solution.  

For those who water each square by hand or with a hose - using a water meter is definitely overkill.  Just thought I would share my experiment in case anyone was interested.

Gotcha !