Availability of soil water is a critical constituent that determines the yield and quality of the potato crop. Too little water diminishes yields, induces tuber malformations, or increases the severity of common scab or Verticillium wilt after an infection has occurred.

Excess or poorly timed irrigation may decrease yields and quality, cause several disease problems in the field, storage, or leach nutrients from the root zone. Fluctuations in water availability favor disorders such as second growth and brown center or hollow heart and sugar end.

Efficient irrigation requires finding out how much available water the soil can hold. Available water is that portion of the soil water that can be withdrawn by plants. During the growing season, irrigation is needed when a certain proportion of the available water, the allowable depletion, has been used. The allowable depletion in a particular field varies according to soil type, stage of crop growth, amount of available water, weather conditions, and irrigation cost. Because potatoes are sensitive to water stress, the allowable depletion is no more than 30 to 40%. To minimize common scab infection, the allowable depletion is no more than 20% during tuber initiation.

At the moment, there are four common methods used in potato crops irrigation: overhead rain guns, boom irrigation, sprinkler systems, and drip irrigation.

Overhead rain guns are the main method of application and are cheap and versatile. They can be efficient but are prone to uneven application, which can lead to over-watering in some areas. They need correct management of pressure, nozzle size, and gun angle to account for variable application conditions.

Boom irrigation improves the uniformity of water application, especially for scab control, but use can be restricted due to topography, layout, ‘field furniture’, and soil type. High application rates can lead to run-off, soil slumping, and ridge erosion.

Sprinkler systems reduce the labor required during the season and offer improved uniformity and the ability to apply small doses frequently, but capital costs are higher. Sensitive soils are protected from structural damage.

You can read the rest of this article in your complimentary e-copy of Issue 4 of Potato Business Digital magazine, which you can access by clicking here.