Timing Matters When You’re Harvesting Potatoes

Larry_Alsum_portraitDuring harvest time, farmers have to balance a variety of factors before setting out to harvest their potatoes. If it’s raining — you don’t harvest. If it’s too warm out — you don’t harvest. If it’s too cold out — you hope you’ve already harvested. Mother Nature — as in everything with farming — makes life interesting.

Take this potato season. Depending on where you farm in Wisconsin, you may have had a late start because of the heavy spring rains (potatoes don’t do well in wet soils, they prefer well-drained loose soils). And now that it’s harvest season, the weather has been “too nice” for harvesting. For most of us across the state, we’ve enjoyed a very warm-to-mild autumn with daily temperatures in the high 60s to low 80s. “While that’s good for people,” notes Larry Alsum, President and CEO of Alsum Farms & Produce Inc., “it’s not great for harvest-ready potatoes.” Larry should know — he’s been growing potatoes for 30 years and is currently in charge of 1,800 acres in southeastern Wisconsin.

According to Larry, potatoes should be harvested when their pulp temperature is between 50-60ºF. Why? It helps protect the potato from a variety of soft and dry rot diseases. If a potato is harvested when it’s too warm outside and is then placed into cool/cold storage, the taters are more likely to suffer from storage rot. And storage rot can spread throughout the stored potatoes, destroying all of the tubers. Potatoes are also more likely to bruise if their pulp temperatures are outside the ideal range. Thus, timing is everything. In warm weather such as we are experiencing now, farmers have to hit the fields at dawn and harvest as much as possible before the day warms up.

If we were experiencing a cold autumn, the rush would be on to harvest potatoes in advance of really cold days and nights. As Larry notes, “Potatoes can handle a light frost at 31º to 32º, but if it gets into the 20s and the frost penetrates the hill, the tuber will go bad. It will shrivel and rot.”

As you all know, sometimes fall comes early to Wisconsin — and it stays. When that happens, farmers are faced with another problem: thin-skinned potatoes. As potatoes mature, their skin thickens. This is important because that skin protects the potato after it has been harvested. Most tuber diseases enter the potato through a wound in the skin — so good “skin set” is critical to having healthy, quality potatoes on hand. Generally, farmers have to allow 10-14 days for skin set before harvesting. If it’s a particularly cold autumn, that can be difficult.

As Larry puts it, “Right now the goal is to just to take advantage of every opportunity the weather gives us to put away the best quality crop we can. We start at dawn – when it’s cool, not cold and then we stop when the warm weather hits.” He adds, “Of course, we also know the cold weather is right around the corner, so we often find ourselves in a dilemma trying to time our harvests. Every day is a balancing act,” he concludes.

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