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  • From: dave.kathy AT att.net
  • To: "Dave Campbell" <market-farming AT lists.ibiblio.org>
  • Subject: [Market-farming] Growdays in EXCEL
  • Date: Fri, 09 Jan 2004 23:46:52 +0000

Hi, all!

The demand for Shelly Elliott’s EXCEL spreadsheet that logs field activity
prompts me to offer a spreadsheet of my own, one that tracks growing days
during the year. My spreadsheet essentially calculates degree-days, adding to
the cumulative total on any day when the average temperature exceeds 50
degrees. A killing frost (<32 deg) resets the total to zero. A warmish day
when the average doesn’t reach 50 deg is counted as neutral; it doesn’t kill
plants, but they don’t grow, either. Horticulturalists interested in
particular plants may fine-tune and use some cut-off other than 50 deg, but
50 appears to be a good general number.

The reason to do this is that different species of plants and insects
flourish in response to degree days. The index, therefore, is independent of
the calendar, or, in other words, of the weather in a particular year. I
wrote my program to use for beekeeping, to track when honey flows start for
different blooms (locust, alsike, sweet clover, buckwheat, goldenrod, …), but
it also is good for IPM planning (when to expect white flies, flea beetles,
Colorado potato beetles, …) Each day you enter low and high temperatures,
comments (if any) on what plants have started blooming and what bugs are
showing up, and (optionally) rainfall. The program graphs daily temperatures
and weekly average temperatures, cumulative yearly growdays, and cumulative
yearly rainfall. Like all logging programs, its only useful if you keep it
up day by day, so if you are not likely to do that, forget it! Yes, it’s a
pain for the first year, but after a couple of years patterns start to emerge
and it turns into a strong tool. Or so I’m told!

Anyway, now is a good time to start growday record keeping for CY2004. I
wrote my original program for Quattro Pro, but I’ve translated it to EXCEL,
too. (The EXCEL graphs are still kinda shoddy, but they are usable.) Size:
380 KB in EXCEL. I’ll share it free with those who want it: email me
privately at

dave.kathy AT att.net.

Dave Campbell
Tiffin IA





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