How Much Water Is Enough?

For most of a growing season there isn’t a need to water gardens in Ireland, but when the weather is dryer than usual, how can I tell when to start watering? How much water is enough? There is a significant difference between watering to prevent the soil from getting too dry and watering to maintain a high level of moisture in the soil, and what does that look like over a dry season?

[Sylfirus]

In france we had no rain for somthing like 40 days, every lawn non automatically-soaked burned down, its crazy, feels like africa.
Your Channel seems to be serious business, i love that as the mad scientist i am. Keep up
+1 sub

[debrariley]

I really like the format of your videos, your voice both tone and speed are both easy to listen to so that it doesn’t overwhelm the content . I also like the recognition of your errors, this is so good for us all to learn from. They are all so informative... even the rat video was interesting.

[BigAlSparks]

Another outstanding lecture from the professor of gardening! Thank you for the wealth of information and observations you share!

[donnaflores]

Thank you for the information. I like the way that you approach problems in a systematic manner and do not rely on what people have done before. This scientific approach leads to many wonderful discoveries in the garden.

[MAMDAVEM]

Recently I started growing Tomatoes using Deep Water Hydroponics. Every couple of days I need to top up the nutrient reservoir with makeup water to account for transpiration (there is very little evaporation due to it being a closed system) . Your video made me realise that the watering that I need to give to my Tomato plants that are growing in soil containers probably need to roughly match the top up water I need to give my hydroponic grown tomatoes.

[ecospider]

I always see people transporting live trees and shrubs in the back of their truck in covered and wonder how many die do to drying out. People don’t think of how much water is lost into the air through the leaves. Thanks for the terminology for this “evapotranspiration”

[Gandalf-The-Green]

You Sir are an inspiration, that is just plain and indisputable. I quit university just before my biology master, and in one of the first semesters we went to the main BASF plant where the PR guy told us: "Well, organic farming is jolly well, a nice idealistic thing, but you are not going to feed the world on it". I knew at the instant that he was lying. It is in fact a fat obese lie that I have heard all over again ("mankind would have never gotten so numerous without anorganic fertilisers"). I really like to redirect doubters to your channel to see what you grow, how many people could be sustained by your work. My dry soil above some 8 meters of limestone is just barely good enough for home use vegetables, but I can grow figs and grapes and strawberries and hardy kiwi plants and herbs to sell, and that is something at least, and combined with honey and quail eggs it is quite acceptable for a side income. I would love to do more vegetables but in the end will have to do more beekeeping or quails/chickens for an income. Greetings from South Germany, apparently now the new northern Sahara border.

[fxm]

This is great information. I hadn't realized that evapotranspiration was such a big factor in how quickly the soil dries out. Even if I don't follow the hard data as closely as you do, simply including the idea of evapotranspiration to my mental model of what's going on in the garden is sure to help. Thanks, Bruce!

[myounges]

With all the land you have it could be interesting to invest is some rain harvesting techniques. Start with a water deposit at the end of your gutter drains.Then attach a dropping hose to these deposits, hopefully the land level is correct and help with the manual labor of watering.

[MrShanePhoto]

Really interesting. I've a 100m square allotment in dublin and I maybe did 10 to 20 watering cans every second day. It's amazing to see how short I was looking at your numbers. Need to get hay for next year. Way more mulch. Thanks

[JamieTannerPresents]

mulch reduces the need for watering very well in my gardens!

[portiaholliday]

Planting into an understory greatly saves water. I use Gill Over the Ground and wild strawberries. They keep my soil very moist. I just planted Brussels into a bed of Alfalfa. I am looking forward to this going well. I am comparing it to a bed covered with coffee grounds which also keep the soil moist.

[Dzloof]

Thank you for your dedication to provide precise data on what is necessary.

[lucasa]

That's why food forests work so well. A forest floor is so much less dry. And combine the right types of plants and you can keep your soil healthy and full over everything your crops need.

[michaelmcclafferty]

We have an allotment around 100m2 in Burghead in north-east Scotland without a mains water supply.
We found 2018 very challenging to keep our plants going. We are trying to adopt a no-dig method but this needs a lot of compost.
After build four cubic metres 4x4 bins we need even more than that to keep 10 raised beds going.
That said, the results and low weed maintain ancestors are worth it. The water retention is good but still needs visits at least every day in late spring and early summer.

[nickstraw]

Yet more pertinent and thoughtful questions Bruce. I think most people without irrigation in western Europe have come to the same conclusions, but nice to have some quantative data.
Thanks again.

[Jason-kgrs]

Thanks for the informative video, how much to water is always a conundrum here too. I find for me it varies with the type of plant and what phase of life it is in as well, for instance my beans are in full production right now so I am watering them heavier than I would the early season. Here in the mid west the old general rule of thumb is an inch of rainfall weekly, I loosely follow this rule, but you always have to leave room for flexibility. Thanks again I'm going to look into the formula you showed and check for some similar websites for my region to see if I can improve.

[booswalia]

I find a good mulch with some leaves, straw or hay keeps the garden from drying out.

[nickstraw]

I am in the east of England (the area of UK with the least rainfall in a normal year), and like much of western Europe the very dry early summer was a trial. We have been practising No Dig for a couple of years. As mentioned, the hardest part is getting enough mulch - and in the UK, compost seems favourite. This means making your own, unless you want to spend more on your veg thaan it would cost from a farmers market.
We have a decent sized plot for here - about 2/3 acre, and about a regular sized allotment plot is actually used for food growing. There is a large piece of grass, which provides lots of "greens". This fires up the heaps very well, but you do need to balance with "browns" to stop the whole lot turning into a rather nasty slimey mess. I use whatever I can get, obviously all the prunings and kitchen waste, combined with horse manure and stable straw. Yesterday's pile was mixed with a whole lot of shredded bank and insurance paperwork. This am, 14 hours after dropping the lid on, it was reading just under 60C. I will have to turn it next week.
In a normal season, we get two cuts a week, and making compost like I do becomes a chore. But at least I don't have to dig or barely weed. Most of our veg got by with just minimal watering, but we do now have quote deep (raised) beds.
The horse manure I store in a separate "bin" about 2cuyds. And I try to leave it for a long as possible, at least a year, ticking over at about 50C. As mentioned, some fresh stuff gets used in making the regular compost, and despite horses having not very efficient digestion unlike cows, we see no extra weed pressure. We do get a few volunteer tomatoes, a couple of which we allowed to develop and will be producing well in a week or two. After all the heat, it has now cooled down and is probaly below average temps and high humidity, so blight may rear its ugly head.

So far the No Dig has worked well for us. It certainly is not NO Work, but the annual dig or even forking over after crops is not missed. The biggest bonus for us is the lack of weeds and most of the plants are healthy and seemingloy more self reliant.
An additional bonus of havesting plants by cutting off at ground level is that some come again like the Chelsea chop. This year the florence fennel gave us a big crop, but now is coming again, each root has 4 to 6 new small bulbs, harvestable again in a couple of weeks. As an aside, fennel can be a bit of a thug. We had one for the seed in the herb garden and we still find shoots several years later.

Someone mentioned swales. My plot and from the look of Bruce's, are both very flat. I don.t see any value in swales in these circumstances, especially in free draining aluvial/peat soils.

[DovidM]

Another very useful video.

I have wondered if my warm season cover cropping was causing moisture loss through evapotranspiration. Digging holes in parts of the field with no cover crop and those with a cover crop seems to indicate drier conditions where cover crops are grown. However, the results are not day and night, and, in years without drought, it seems worth it still to sow warm weather cover crops since I am still building soil structure.