Is Overhead Watering Bad For Plants?
When you’re starting a new garden or have grown to a size where an irrigation system is necessary for success, you must decide which type of system you’ll choose. Join organic farmer Jenna Rich as she shares what she’s learned about overhead watering and if it is, in fact, bad for plants.
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When we started our small-scale farm six years ago, we didn’t have much money to spend on fancy irrigation systems or greenhouses. It all began with us dragging heavy hoses and watering cans around, bringing trays indoors each night when the weather was dangerous for seedlings, and praying our transplants would survive the unexpected cold springtime temperatures.
After a couple of years, we upgraded to drip irrigation, and that’s the method we have continued to use every year. That said, overhead watering is a perfectly acceptable method for watering. But is it bad for plants? Let’s discuss the method further to find out.
The Short Answer
The short answer is no, but in some instances, overhead watering can be bad for plants. Although overhead watering is a quick and easy method, many gardeners have opted for watering at the root for reasons we’ll discuss here.
Let’s get into what overhead watering is, and in a bit, we’ll introduce an alternative that may work better for your garden. Each has its advantages and disadvantages.
What is Overhead Watering?
Overhead watering is exactly what it sounds like. It’s a garden watering system that mimics natural rainfall by watering plants, the surrounding soil, and everything else in its path. Typically, the system consists of pipes, a pump, and sprinkler heads every few feet that point downwards, watering the crops below.
Sprinkler systems hook into a stable plastic hose on the ground and shoot up, casting an umbrella of water up and overhead. Overhead watering also includes methods like using a can or hose.
Some large-scale operations use overhead watering to germinate cover crops and mist crops in greenhouses on an excessively hot day.
Benefits of Overhead Watering:
- Wide broadcast decreases the chance of plants not being watered.
- The entirety of the system is visible, so spotting trouble is quick and easy.
- Sprinklers have different settings and can be customized to your needs.
- Provide frost control in cold climates.
- Increased chance of even germination for cover crop or grass seed.
Disadvantages of Overhead Watering:
- Too much water can cause erosion and loss of nutrients, including expensive amendments and compost you may have added.
- Evaporation occurs, especially on hot, windy days.
- The chance of run-off and puddling increases.
- Too much water in the soil can lead to soil diseases like root rot or the lack of oxygen to roots that may cause death.
- The risk of fungal diseases like powdery mildew increases due to wet foliage.
- Gardening supplies and items like row covers mistakenly left out become muddy and soggy, creating a mess.
- Increased water waste.
The Long Answer
The long answer is no, it’s not necessarily bad for plants, but there is an alternative that many gardeners prefer over overhead watering. How you water your garden relies on personal preference, space, and the cost of setup. You will likely find as many gardeners who swear by overhead watering as you will who say drip irrigation is the way to go.
An Alternative Method – Deep Watering
Deep watering is another term for a drip irrigation system that places drip lines directly on the soil surface close to the plant base. When the water drips out, it goes directly down into the soil to the root system. There is no exact definition, but most growers agree deep watering is when water reaches at least six to eight inches below the soil surface.
Systems include a main header for each area that connects to pliable tubular lines that can be spaced out as needed. When fewer lines are necessary in the off-season, you can use plugs in the main header to downsize as needed. Each line features drip emitters ranging in frequency from 6-12 inches. The emitters face up so the water pools on top, spilling over onto both sides equally.
Benefits of Deep Watering
The benefits of deep watering include lower disease risk, more efficient water use, encouragement of deeper root systems, plant stabilization, and possible weed suppression.
Decreased Risk of Fungal Diseases
If you’ve been gardening for any length of time, you know wet conditions allow certain diseases to thrive. These include but are not limited to Verticillium wilt, Septoria leaf spot, powdery mildew, and root rot.
Deep watering delivers water right at the base of plant stems, allowing it to soak in immediately without the chance of lingering on foliage or the soil surface. Fungal spores that are spread by way of water won’t have a chance to do so when there is no excess water to travel through.
Water Conservation
When water evaporates from plants due to wind or sun after overhead watering, it’s not absorbed into the plant’s root system. Therefore, it’s hard to gauge how much water reaches the roots. Remember that ideally, the top six to eight inches of soil get penetrated with water each time you irrigate for proper plant watering.
Pro tip: Invest in a simple but effective moisture meter. Check levels before and after watering and take note of them.
Studies are being done to determine the long-term effects on plants after the stress of drought conditions. Drought and other extreme weather are becoming more normal as our climate shifts, so knowing how well our plants can bounce back is important.
Encourages A Deeper Root System
Most plants have deep roots and seek water down deep in the soil. Deep watering will promote this behavior and help the plant to produce a strong, healthy root system. Deep root systems help stabilize plants, help them find the nutrients they need, and decrease the chance of drying out.
If you water properly each time you irrigate and the top eight inches are watered, irrigation can occur less frequently. This makes an irrigation schedule easier to maintain, and you can feel confident your garden has ample water.
Plant Stabilization
Deep watering encourages a strong root system by forcing it to go deeper to get water and nutrients, creating a strong anchor for plants. Strong stabilization supports plants against environmental stressors such as inclement weather like rain, strong winds, and snow.
A solid root system will help hold topsoil; some can even be used as a carbohydrate storage center for later consumption. Healthy soil is the first step to a healthy root system and will help to maintain moisture. Annual soil testing is recommended to ensure proper levels. Amend as needed.
Possible Weed Suppression
When you’re watering directly at the roots of plants, leaving the surrounding top layers of soil dry, tiny weed seeds present may have a difficult germinating. If they germinate, they’ll quickly perish due to lack of moisture. This is just a bonus to drip irrigation!
Disadvantages of Deep Watering
Like anything else in the gardening world, deep watering comes with its potential downfalls. Here are a few.
- Emitters deliver the same amount of water to each plant, even though some require more. Some water is wasted, while some plants are left wanting more.
- Drip lines are easily damaged by tools, harsh weather, overuse, or too much pressure.
- Lines can easily move out of place, so you should check each line before each irrigation session.
How to Decide Which Way of Watering is Right For You
You might be wondering now how to decide which way to irrigate is best for you. It all comes down to a few factors:
- Space both for off-season storage and spare pieces like fittings, clamps, and filters.
- Cost
- Crops you’re growing
- Garden layout and farm management practices
- Experience
- Soil type
- Clay-like soils tend to be slower to absorb water, making overhead watering a challenge. If you simply leave the system on, you may end up with puddling. Drip irrigation can be adjusted to drip more slowly, which may lend itself better to this type of soil. If you have clay soil, you might consider watering in small increments, no matter the method. Adding compost each year will help adjust the soil type and retain moisture more efficiently.
- Water will penetrate through sandy soil much quicker than thick soils, and it may dry out more quickly.
Maybe you’ve used both of these methods before, or perhaps you use a mix of the two, which is a great option! That being said, here’s just a little information on certain crops that may prefer one method of watering over another.
Crops That Benefit from Deep Watering
What you grow may help you select an irrigation system. Here are a few groups of crops that benefit from deep watering.
- Larger fruiting vegetables like peppers and eggplants during their flowering phase.
- Berry plants like blackberries and raspberries whose root systems are shallow and at risk of drying out.
- Crops with a high moisture content, like watermelons, cucumbers, globe radishes, strawberries, and celery.
- Tomatoes which are producing large quantities of fruit and are susceptible to a variety of fungal diseases.
- Root vegetables like potatoes, beets, daikon radishes, and carrots.
- Many annual cut flowers.
How Much is Enough?
You may think you’re watering enough, but knowing how much water makes it down to the roots is important. There’s a simple test to help you figure this out.
After you irrigate, the soil surface may appear dry, but remember that what’s more important is what’s closer to the root system. Stick a trowel into the earth eight to ten inches, then pull it up. Observe the moisture level on the trowel and measure how far down it is. Turn the irrigation back on if it’s only three or four inches. If it’s over eight inches, set your timer for less time the next time you irrigate. You can also install a water meter to measure just how much water you output in your garden if you want precise data.
The amount of time and frequency of watering should change throughout your season depending on the weather, so keeping ample records will be helpful to look back on in future years.
Key Takeaways
- Which irrigation system you choose for your gardening operation is mostly a personal preference.
- Each method has its pros and cons, and the right system is the one that works best in your setup.
- Ample watering without standing water in the soil leads to better productivity, better root systems, and overall better health and longevity.
- No matter which method you use, record-keeping is key!
Final Thoughts
Although overhead watering plants is a perfectly acceptable method for watering your garden, it’s not always the best for overall health and use of water. Many fungal diseases can be avoided by deep watering, and less is lost to evaporation when you water at the root. If you have the resources and space to support a drip irrigation system, it is the recommended method.
