Water Requirements in Horticulture Crops - Frequently Asked Questions

How much water does my horticulture crop require? When is the best time to water (when is adequate moisture critical)?
The amount of water used by a particular crop depends on a number of factors, including crop growth stage and environmental conditions (temperature, wind, relative humidity). The speed at which soil moisture is depleted depends on crop use and the soil type (sand, clay, etc.). Applying adequate amounts of moisture requires a basic understanding of soils and the general water use of the crop. Moisture stress/excess can influence crop yield and survivability (over-wintering).

Table 1: Critical periods and water requirements of Fruits and Vegetables

VEGETABLES
CROP	CRITICAL PERIOD		WATER REQUIREMENTS
Asparagus	During establishment During harvest		Apply approx. 50 mm after harvest Apply 25 mm at the end of the season Apply 25 mm every 10 days (depending on precipitation)
Beans	During flowering and pod set		Apply 25 to 38 mm per week during peak use period*
Carrots	General growth and root fill		Will use 4 to 6 mm per day during peak use period
Cole Crops (Broccoli, Cabbage, Cauliflower)	Head formation and enlargement		Will use 380 to 500 mm during the season*
Corn	Tasseling, pollination and ear filling		Will use up to 6 mm per day (during peak use period) Will use up to 510 mm during the season*
Cucumbers	Flowering, fruit set and development During rapid growth and fruit sizing		Apply 25 mm after seeding/transplanting Don’t allow to dry out during critical period Will use approx. 200 to 250 mm during the season*
Eggplant	Flowering, fruit set and enlargement		Apply 25 mm per week*
Garlic	Bulb formation and enlargement		Apply 25 mm per week (minimum)*
Lettuce	Germination and throughout growth		Don’t allow soil profile to become depleted
Muskmelon/ Cantaloupe	Flowering, fruit set and development		Apply 25 mm after seeding/transplanting Don’t allow to dry out during critical period
Onions	Bulb formation and enlargement		Will use 4 to 5 mm per day (during peak use) Apply 25 mm per week* Will use 350 to 500 mm during the season*
Peas	Flowering, pod set and fill		Will use 5.5 to 6 mm per day (during peak use) Will use 375 mm during the season*
Peppers	Flowering, fruit set and enlargement		Apply 25 mm per week* (depending on soil type)
Potatoes	Tuber initiation and sizing		Will use 5.5 to 6 mm per day (during peak use) Will use up to 550 mm during the season*
Pumpkins	Flowering, fruit set and development		Apply 25 mm after seeding/transplanting Don’t allow to dry out during critical period
Radishes	Root fill		Don’t allow to dry out
Tomatoes	Flowering, fruit set and enlargement		Apply 25 mm per week*
Zucchini	Flowering, fruit set and development		Apply 25 mm after seeding/transplanting Don’t allow to dry out during critical period

FRUIT
CROP		CRITICAL PERIOD		WATER REQUIREMENTS
Strawberries (June bearers)		After planting (during establishment) During flowering, fruit set and fill		Don’t allow soil to dry out Apply 6 to 8 mm every 2 days* Apply 25 mm per week after mowing (renovation)*
Strawberries (Day neutrals)		After planting (during establishment) During flowering, fruit set and fill		Don’t allow soil to dry out Apply water in frequent, light applications Initiate field cooling to improve fruit set in high temperatures
Raspberries		After planting (during establishment) During flowering, fruit set and fill		Will use approx. 5 to 8 mm per day (during peak use period) Apply 25 to 37 mm per week from blossom to harvest*
Saskatoon berries		After planting (during orchard establishment) During flowering, fruit set and fill		Will use 160,000 to 180,000 litres per acre per year
Currants/ Gooseberries		After planting (during orchard establishment) During flowering, fruit set and fill		Ensure supply of approx. 25 mm per week

* Including precipitation

Tips for reducing water application requirements

Use some form of mulch [plastic, organic (straw, bark, shavings)]
Apply the water either directly to the plants (through a drip system) or using a lower pressure applicator (versus sprinkler application)
Apply water in the early morning or evening when temperatures are lower (to reduce evaporative losses)
Provide adequate nutrients to ensure healthy, deep-rooted plants which maximise water use within the soil profile

Prepared by Robert Spencer, Ag-Info Centre, Alberta Agriculture and Rural Development

For more information about the content of this document, contact Robert Spencer.
This document is maintained by Mary Ann Nelson.
This information published to the web on August 5, 2003.
Last Reviewed/Revised on November 27, 2013.