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Irrigating Vegetable Crops

Most vegetable crops require a uniform supply of moisture throughout the growing season. The average rainfall in Ontario is 70 mm/month during the growing season. This provides only 65% of the water needed for optimum yield.

Vegetable crops vary in their response to irrigation. Shallow-rooted crops, such as potatoes and celery, require frequent, light irrigations. Intermediate and deep-rooted crops such as cabbage, melons, tomatoes, and sweet corn can use water from a greater volume of the soil profile and do not require irrigation as frequently.

We know irrigation is a benefit on light soils and in dry conditions, but properly scheduled irrigation can pay in other conditions as well. For example, recent Ontario research on processing tomatoes showed yield increases of up to 81% on a range of soil types with the use of properly scheduled irrigation. Irrigation increased yields in both wet and dry years and on sandy soils as well as on clay loams.

The maximum benefit from irrigation is achieved when the proper amount of water is applied at the right time, minimizing moisture stress while avoiding overwatering. Most vegetable crops have growth stages during which drought stress can severely reduce yield and quality. Irrigation is especially important during these critical growth periods.

Irrigation can be scheduled based on routine soil moisture monitoring or through calculation (the water budget method).

More details can be found in OMAFRA's Vegetable Production Recommendations, in the Best Management Practices manual Irrigation Management, and in OMAFRA factsheets, including Irrigation Scheduling for Tomatoes - An Introduction (Order # 08-011). These publications are available through Service Ontario (1-800-668-9938 or www.publications.serviceontario.ca). You can also access the irrigation factsheet online at http://bit.ly/XtVHn and the infosheet, Irrigating Vegetable Crops, Note: bit.ly shortcut URLs are case-sensitive.