Potatoes need water early
Potato growers in southern Alberta know the value of keeping their crops well-irrigated as tubers develop.
However, the effect of short-term moisture stress early in the season before flowering, when the tubers are being initiated, is often overlooked. Research at the Agriculture Canada research substation at Vauxhall shows adequate moisture is important at all stages in crop development, including the critical pre-flowering period.
To establish the effect of short-term moisture stress at specific crop stages on yield and processing quality, irrigation water was withheld from plots of eight cultivars during each of five growth stages.
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It is currently recommended potato crops be irrigated when soil moisture reaches approximately 70 percent of field capacity (tension of 40 kilopascals). Moisture was withheld until soil moisture tension reached 80 kpa, at which time recommended irrigation practices were resumed.
Moisture stress in the early season (between two and six weeks after emergence) had as great an impact on marketable yield as lack of moisture during the tuber growth phase (eight to 10 weeks after emergence).
For example, a short-term stress as early as two weeks after emergence reduced tuber number and tuber yield. The reduction in tuber number increased the yield of large tubers, but this did not entirely compensate for the reduced tuber number.
Also, an increase in the number of large, oversize tubers is often associated with increased levels of hollow heart and tuber deformities. Early season moisture stress also increased levels of reducing sugars and, consequently, chips and fries were darker and less attractive.
Good moisture management should provide sufficient but not excess moisture. Excess moisture, particularly in the early part of the season, can result in decreased yield and increased levels of the verticillium wilt.
Growers should begin checking soil moisture levels shortly after crop emergence.
– Agriculture Canada
