Watering Drop by Drop
By Steve Reiners, Professor and Chair, Horticulture Section, Cornell University, Cornell AgriTech. This is part of a series of columns that he wrote about vegetable gardening during the pandemic that ran Spring-Summer 2020. Read more articles from 2020 | Read later articles in this series.
June 19, 2020
It’s been dry in the Finger Lakes. We went from cool, wet conditions to hot and dry almost overnight. We need to think about watering our gardens earlier than normal.
If seeding directly in the garden, here’s a trick that speeds germination. Make your seed furrow to the appropriate depth – ¼ to ½ inch for small seeds and an inch for larger seeds. Then lightly water the furrow before planting so it’s nice and wet. Place the seeds and cover with the dry soil and pat down.
When prewatering like this, I’ve gotten bean, squash and cucumber seeds to come up within four days. Two advantages with this method. First it puts the water right where it’s needed by the seeds. Plus, watering after seeding can result in soil crusting, making it difficult for seeds to emerge.
As soon as the plants break through the soil surface, it’s time to water more deeply. Shallow watering encourages shallow rooting and makes the plants more vulnerable to drought .
Deep watering will encourage roots to “follow the water” leading to deeper roots and more productive plants. To sum up your basic watering strategy: Water less often, but longer when you do.
At this time of the year, apply at least 1/3 of an inch of water at least three times per week if it doesn’t rain. As plants grow and temperatures warm, increase the watering to 1/3 of an inch four times per week.
If you are using a sprinkler, simply place some cans or buckets around the garden and measure the water depth with a ruler. As a general rule of thumb, 100 square feet of garden space requires about 60 gallons of water to equal one inch. For that 1/3 of an inch, that’s 20 gallons.
Sprinklers are easy to use and can water the whole garden at one time. Unfortunately, they also wet the leaves. And as any plant pathologist will tell you, wet leaves equal disease. Pathogens spread easily when plants are wet.
So, if you use a sprinkler, water in the morning so that leaves can dry out through the day. Watering in the evening assures a long period of leaf wetness, practically guaranteeing disease.
Trickle or drip irrigation is an effective alternative for watering gardens. These systems apply water slowly through perforated hoses or tubes laid directly on the soil, which decreases the amount of water needed by 50 percent or more. Little water is lost to evaporation as it is uniformly applied slowly right at the roots. Leaves remain dry, diseases are reduced, and you can water at any time, day or night, whatever fits your schedule. You can even water while working in the garden.
Trickle irrigation is more costly and will take some time to set up. But the cost and time is a small price to pay for a system so easy to operate that it requires no more than turning on a faucet (or a timer) to water the entire garden. Many of the components can be used year after year so the cost beyond the first year is minimal.
There are basically two types of trickle irrigation. The easiest to use is the soaker hose. This is a rubber hose (manufactured from recycled tires) with tiny pores along its entire length. Water leaks out of the hose slowly and evenly - about 1/2 gallon of water per minute per 100 feet of hose. To provide 1/3 of an inch of water with 100 feet of hose, you’d have to run the system about 40 minutes to provide the 20 gallons.
Depending on your soil type, the water will spread about a foot across the top of the bed. Commercial growers will use plastic tubes (trickle tapes) with holes spaced evenly along its length. Although these can be used in the garden, for most gardeners, the soaker hose is easier. Combine a soaker hose with mulch and you have the perfect system. Trickle is great when used under plastic or organic mulches like straw or old leaves.
Soaker hoses can be reused. Simply take them out of the garden and store in a shed or garage. You may notice they seem less porous the second year, which may be due to salt buildup from hard water. Just soak the hose in some vinegar in the spring to make almost new.
This week in the garden:
One bright spot with the dry weather is we’ll have less diseases and weeds are less likely to germinate. But don’t get complacent. Keep ahead of the weeds by getting to them when they are small. This is a great time to plant summer squash, cucumbers, snap beans, sweet potatoes and beets.