Watering a no dig garden

by cakedude - brenda
(glendale, AZ)

Watering our new no dig garden sufficiently is our dilemma. It seems like once all the layers are in place the compost almost acts like a seal to keep water from draining evenly down into the straw layer.

How do we keep the lower layers moistened? How much and when do we water?

Also, we're in Arizona. What can we anticipate watering-wise during the summer 110-plus degree days?

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Megan replies... A slight waxy watertight barrier sometimes forms on organic matter on the soil surface when it dries out. Whether you're trying to water a no dig garden, or even a lawn or indoor pot plant, you can get this annoying problem of the water running off without soaking in.

To the rescue comes soap. Use a biodegradable laundry powder, mix roughly a small spoonful in a can of water, or sprinkle powder very sparsely over soil. The harmless and (beneficial in small doses) surfactants, carbonates, citrates, silicate and zeolites in it act as wetting agents and have moisture retention properties.

Also make sure your garden has a good top mulch layer. This should be organic, reasonably dried — straw, leaves, grass, or any mix which can include bark, pine needles, shredded branches, corn husks etc.

Watering the layers of your no dig garden as you put them down saves some effort later, and then it's important to keep plants growing and healthy by not letting the soil dry out. The mulch and layers of humus and in fact all the materials that go into building your garden will create a rich growing medium with good water retention abilities.

When watering a no dig garden, give it a good deep soak, preferably early morning before the sun evaporates the water as you put it on. Don't give little sprinkles every day as that just encourages shallow plant roots. If practical, lay soaker hoses through your garden and drip feed water every few days.

Seeds and seedlings need constant moisture, but established plants will have deeper roots, so even if the surface is dry, as long as the soil is moist about 3 cms (1 inch) below the surface, then no need to water that day. Poke your finger in and test — in the soil under the mulch.

As a very rough guide, space out some cans or containers around if you've got a sprinkler on, and when there's at least 3cms (1 inch plus) that should be enough. Again, poke your finger in or dig down with a trowel and make sure there's plenty of moisture in the deeper layer, where all the roots are.

Many gardeners when watering a garden, practice an intermittent system that encourages water to go deep. To do this turn on your sprinkler for say, 30 minutes or 1 hour or about the length of time it takes to fill 1-2cm of water in containers. Then turn off and come back and finish watering later, or use an irrigation timer to turn on and off.

This allows the soil to "breathe" and the water to sink downwards without running off. Otherwise continuous flooding of the top layer can cause an anaerobic condition, blocking the pore spaces in the soil and even killing off the tiny root hairs that are useful for rapid absorption of moisture and nutrients.

The magnificent book "Roots Demystified" by Robert Kourik, explains all this information and vastly more. I find his book better than any gripping novel to have on my bedside table! Go to Roots Demystified to have a look.

Arizona... 110 plus degrees, crikey! That's tough weather, so you'll have to source the most suitable plant varieties that are native or bred to withstand your climate.