Are we using water wisely?

By Selena Randall

I passed by gardens at the University of Manitoba on a rainy day last week, and was surprised to see that maintenance staff were setting up sprinklers to water the lawns and flowerbeds – surely this was unnecessary and they could be doing something else? Is it effective? Do you ever think about how much water you use on your gardens and where it comes from?

In our garden, we use a trickle irrigation system to water much of our vegetable garden, and only when we’ve had a few days without rain and the plants need it. We use a timer and typically run this in the morning, when the water in the hoses is cool, and when evapo-transpiration from the plants is low. This means most of the water reaches the roots. Other plants are watered from rain barrels using a watering can, if we have had a few days without rain. We surround the plants with a bark mulch to retain as much water as possible.

Green grass looks more attractive than yellow-brown, and lush grass is more comfortable to walk and sit on, so it’s not surprising that we want to keep it looking good. But there are some things we do that make our efforts inefficient.

In the growing season it’s tempting to cut the grass as short as the mower allows, to reduce the time until the next cut. However, this encourages shallow root growth and makes the grass vulnerable to water loss from the surface of the soil. But did you know - setting the mower blade higher, encourages deeper root growth and keeps the grass roots in the cooler, wetter zone, where drying is less frequent. Our by-laws allow us to grow our grass to 6” (15cm) length, so this doesn’t have to mean more frequent mowing!

We also tend to water frequently and in short bursts, which wets the surface but doesn’t necessarily reach the root zone effectively. But did you know – there’s a whole science around lawn watering. For lawns, knowing your soil, and calibrating your sprinkler to deliver enough water to reach the root zone (which will mean doing some timed trials and digging holes to find out where the root zone is) will make the most of your efforts. There are websites that can advise – for example http://sip.mesonet.org/

And we often water in the evenings, when we have more time after work.  But did you know - watering in the evening can leave water on the leaf surfaces. This is added to by overnight dew, and excess water collects in the root zone and encourages fungus growth and diseases. This can be reduced by watering in the early morning, so the early morning sun dries the leaves.

We try to cover a broad area with our sprinklers, blasting the water into the air to reach as far as it can. But did you know - 20% of the water from our sprinklers evaporates before it even reaches the ground, making this method pretty ineffective. For flower and vegetable beds targeted watering can be much more effective.

Grass is pretty resilient – remember how quickly it turns green after the snow is gone? I just rely on rain to water my grass (and its healthy weed population), and I accept a few weeks when it looks less healthy (and I need to mow it less), knowing that at the first sign of rain it will quickly bounce back.