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  • Writer's pictureLynn


Irrigation Best Practices

I learned this adage in my Master Gardeners class this year on roots and irrigation. And it will forever change my gardening life: “water the soil, not the plant” and its companion“feed the plant, not the soil.” Different plants have different root depths and because of this, they have different watering needs. Let's take tomatoes as an example. Tomatoes were my gateway obsession in vegetable gardening.

Every year I learn something new about what to do more of or less of, but this year’s lesson fell into the never do again category making me feel bad for every tomato I’ve grown in years past, despite how well many of them still did. It turns out that the roots of a tomato plant spread to six feet deep and six feet wide and like almost all plants the most fragile part of their root system is the 6-8 inches around the base of their stem where the roots are closest to the surface.


Furrow Irrigation in my Vegetable Beds
Furrow Irrigation in my Vegetable Beds

Never till or disturb the tender roots around the stem and base of the plant and water as widely and deeply as possible to get to that wider system of roots—“water the soil, not the plant!” I was doing just the opposite, I was digging a foot wide basin at the base of each tomato for watering, and, adding insult to injury, I was churning and loosening that soil each time for better water uptake. So I’m trying furrow irrigation this year in all of my tomato and veggie beds, watering and feeding them straight up the middle. This also avoids getting any unnecessary water on the leaves and lower foliage of the plant, which increases the chances of leaf mold and other diseases.

Furrow Irrigation for Your Veggies

To use Furrow Irrigation simply dig a trench down the middle of the full length of your raised bed, or between rows with your veggies planted on either side. To water your plants flood the furrows with water using a handheld hose, a watering can, or a soaker hose on a timer. This is also an easy way to apply fertilizer to reach the lower roots. My favorite is to put a few handfuls of worm castings around each plant and other fertilizers along the bottom of the furrow so that between watering them and the rain it slowly works its way down to the deeper roots allowing your vegetables to develop a deeper root system. It also allows you to water your plants less frequently and more deeply.

Basin Irrigation around a new Grape plant
Basin Irrigation around a new Grape Plant

Basin Irrigation for your Trees

The same lesson goes for your trees, grapes, and blueberries. Never till or disturb the tender roots around the stem and base of the plant and instead of water the soil out at the leaf line of the plant. One of the best irrigation methods for doing this is Basin Irrigation. Dig a donut-shaped basin out several feet from the center staying clear of digging within a foot circumference or more out from the tree’s center. That is where all of its most vulnerable crown roots are closest to the surface. The goal is to fill the outer circle with water 💦 from your watering lines, a bubbler, or hose to reach the outer tree roots always avoiding watering or mulching the roots closest to the center which are more vulnerable to root rot and disease.

Signs you are Watering too Much or too Little

Vegetables need consistent watering to thrive. This is particularly true for peppers, tomatoes, and other fruits. Infrequent or inconsistent watering can result in cracking in the fruit, poor yields, and smaller fruit of root systems. As a rule, you will need to water your vegetable beds one to three times a week in the heat of the summer and once or twice in the spring and fall, depending on what you are growing and how deep it’s roots are.

Top Five Watering Tips

  1. Mulch your plants will also help reduce evaporation and help retain the water longer between waterings.

  2. Water in the morning before the sun is too high to reduce evaporation and allow the water to penetrate the soil deeply.

  3. Water deeply and less frequently—2-3 times a week in the summer months.

  4. Water the soil, not the plant and feed the plant not the soil

  5. Overwatering is just as bad as underwatering. The roots of most plants need a 50/50 mix of oxygen and water to thrive. Too much water and they literally drown without oxygen. For most fruit and vegetable gardens use the rule of thumb of 1-2inches, 2-3 times a week. To adjust your watering to meet the needs of vegetables of different root depths use the following key. On average one gallon of water adds 1.6 inches of water when applied to 1 square foot of soil. Either set your irrigation system or if you are using a hose use a gage to make sure you are not over or under-watering.

Don’t Be Fooled

Just because a plant looks wilted in the heat of the day doesn't mean that they need more water. This is especially true for plants like zucchini and summer squash which have naturally adapted to the heat by wilting to reduce the surface space of their leaves to the sun in order to reduce evaporation. If plants wilt in the hottest part of the day visit them again in the evening to see if they have bounced back in the coolness of the evening. If they have don’t water them outside of your regular cycle.

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