To chit or not to chit?

Chitting potatoes - the process of laying seed potatoes out in a dry, airy place out of direct...
Chitting potatoes - the process of laying seed potatoes out in a dry, airy place out of direct sunlight to sprout - is an easy way to ensure a bumper start to the season. Photo: Getty Images
Depending on which spuds you like, sprouting them early may not be necessary, writes James Wong. 

As an unapologetic science geek who finds trawling through the data of agricultural trials fascinating, I am forever curious as to whether age-old horticultural techniques are actually supported by good evidence. One of the most commonly debated is that of chitting potatoes. So, with thousands of home-growers across the country starting to do this right now, I thought I'd take a look at what the science says.

Chitting potatoes is the traditional practice of placing seed potatoes in a light, frost-free spot in late winter to encourage sprouting. The argument is that this process artificially elongates the growing season, resulting in an earlier crop and greater yields. However, for home-growers low on space this can mean windowsills covered in egg cartons of shrivelled-looking spuds which, aside from not being exactly ornamental, can take away prime ``window front'' real estate for growing seedlings. So does this claim stand up to the scientific test?

The answer is surprisingly complex. Despite being claimed as a fact, there have actually been surprisingly few scientific trials that have investigated the issue. A scan of the scientific databases pulled up less than half-a-dozen peer-reviewed papers on the subject. The trials I could find also tended to be small-scale, run on only a limited range of varieties for a short period. This means that the results are often contradictory, even within the same trial.

For example, a two-year trial published by the Department for Environment, Food and Rural Affairs in the early 2000s found conflicting results from one year to the next. In 2001, chitting had no real effect on crop development, but in 2002 the exact opposite was noted. To make matters more confusing, they only tested two varieties of spuds, meaning it is difficult to extrapolate this out to other potato varieties. It was notable that there was more of a difference between potato varieties than whether the tubers were chitted or not.

Other studies, such as one conducted in Canada in the 1980s, have reported on average a 30% increase in potato yield. This finding was replicated more recently in a UK trial in 2016, which found a similar yield boost. However, the effect of cultivar choice still seemed to be as important a factor in yield, if not more so.

It is worth noting that such trials where an increase in yield is reported tend also to report that the chitted plants produce fewer, larger spuds as the cause of the total yield increase. Great if you like the big boys for baking, a shame if you like the tender, baby ones for salads.

Across the board, it seems as if chitting can indeed increase yield. Not a bad exchange for a practice that is so easy to do and is essentially cost-free. However, if it's yield you are going for, other factors such as variety can be just as important. If, on the other hand, yield doesn't matter and it is smaller, new spuds you are after in exchange for less work and more windowsill space, ditch the chitting altogether. It's entirely up to you.

 - Guardian News and Media


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