The right amount of moisture is key in your onion patch. When watering your onions, there is a fine line that must not be crossed when it comes to the amount of water your onions need. Onion plants require adequate water to produce high yields, but it doesn't take much over watering for your onions to become diseased and rot in the ground. There are several methods to watering your onions including furrow irrigation, drip tape, and overhead watering. We prefer furrow and drip tape irrigation systems as overhead watering can promote the spread of disease in your onion crop.
You will want to water occasionally but thoroughly, applying about one inch of water each time. We recommend using the "knuckle rule" to tell when it's time to water. Stick your finger into the ground near the plants; if you can't feel moisture up to your first knuckle, it's time to water. In a typical 12 week growing season, we recommend irrigating with one inch of water once or twice a week depending on the amount of rainfall received.
The furrow irrigation method encompasses "flooding the beds" in the furrows and allowing the plants to soak up water slowly and thoroughly. As a general rule, when the top of the bed is totally darkened by moisture, you have provided enough water to your onions. Furrow irrigation is the main method of watering used on our farm. Check out our video below to learn more about furrow irrigation.
Some onion growers use a drip tape irrigation system to water their onions co nsistently and uniformly. Drip tape is a series of punctured tapes buried in the ground that deliver water directly to the plants' roots. This helps avoid fungal diseases caused by overhead watering. For those of you interested in using a drip tape system, be sure it's designed and deployed properly to water your onions evenly. Uneven watering can result in decreased yields. Areas that are too wet will promote leaching and disease.Install drip tape down the center of your onion beds between the rows of onions at a depth of 3-4 inches (emitter space should be at least 12 inches). With drip tape, you will still follow the "knuckle rule" to know when it's time to water.