Irrigation
Impact of dry conditions on potato yield

Potatoes are a cool weather crop that require about one inch of water a week to produce the highest possible yield. There are two main reasons that potatoes are more sensitive to water stress than most other crops: they have a shallow root system, with most of the roots in the top 12 inches of soil. And soil type: potatoes do well in sands and sandy loams, soils that have low to medium water-holding capacity.

Irrigation is required to keep the available soil water in the root zone above the allowable depletion level. Photo By Rosalie I. Tennison.

High yields of high quality potatoes can only be achieved by maintaining high levels of available soil moisture throughout the growing season. Without regular rainfall, frequent irrigation is necessary. Soil moisture becomes critical when the available soil water drops below 60 to 65 percent. The impact of water stress will depend on the severity, timing and duration of moisture stress.

Table 1 shows the crop growth stages of potatoes and the amount of available water required for a high yield of good quality potatoes. Research in the US has shown that yield losses will occur if available soil water drops below required levels for more than five days.

If there is insufficient rainfall, irrigation is required to keep the available soil water in the root zone above the allowable depletion level. This ensures that the crop will not suffer water stress and will produce maximum yield.

For more information on dry conditions and low water, visit the web site at www.ontario.ca/crops and click on the ‘Adverse Weather’ button. -end-

*Eugenia Banks is a potato specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs in Guelph.