The necessity to irrigate when growing potatoes

June 26, 2023

The amount of rain during the growing season between a dry year and a wet year is of the same order of difference. Besides, within a growing season, even if the total amount of precipitation is average, prolonged dry or wet spells may occur, which are growth prohibitive.

Water availability

Crops differ much in water availability within a few kilometers because of differences in occurrence of rain storms in summer. Even when over a certain period statistically the amount of rainfall is average or sufficient on average, there is considerably more benefit from a continual light rain than from a rain-burst followed by runoff and drainage. So, there is not much prediction possible regarding expected precipitation among years, sites and rainy seasons. There are, however, some certainties. Where growers produce crops in winter after the monsoon they are sure there will be no rain and they rely fully on irrigation. After winter in temperate climates when precipitation exceeds evapotranspiration the soil is saturated with water and initially no irrigation is needed. In East Africa and the highlands of continental South Asia, when growers take the risk to plant before the peak of the rainy season they are sure that the crop will not suffer from drought albeit more likely from late blight. In the rain-fed High Veld in South Africa, rains are so irregular and vary so much in intensity that growers in the largest part of the area rely on irrigation. The same is true for the latter part of a spring crop and the early part of autumn crops in Mediterranean climates that are subject to very mild somewhat rainy winters and hot summers.

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