Weather Forecast



One-half + one-half = 1, right? Not always

I talked with a farmer today who received two separate shots of rain over the past two days. One brought a little more than half an inch of preciptation, the other a little less than half an inch.

"It was about an inch total. And it helped. But getting it all at once would have been better," he said.

If you're not involved in ag, that probably doesn't make sense. Even the most mathematically challenged among us know that one-half plus one-half equals one. But those of us familiar with farming understand what the farmer meant: a single bigger shower usually helps crops and pastures more than several smaller ones over multiple days.

I'm a journalist, not a horticulturalist or agronomist. So please don't be too hard of this simple explanation of why the one, bigger rain is better:

What matters is how much rain sinks into the soil where growing plants can utilize it. Preciptation lost to evaporation, before it can sink in, doesn't help the plants or the farmer. Typically, there's less evaporation -- and therefore more benefit -- from a single, bigger rain.

Quite a few factors determine how much a single shower, or a combination of showers, benefits crops and pastures. Again, go easy on this non-scientist, but the list includes: Does the rain come hard or gently? What's the temperature? Does the sun come out right away or do clouds remain? Is the soil crusted on top (making it harder for moisture to sink in)?

The best, most useful rains usually come slowly and gently, at night -- or if they fall during the day are followed by cool temperatues and overcast skies. 

My two takeways:

1. Though two half-inch rains aren't as helpful as a single one-inch rain, they're better than one half-inch rain. Part of farming is appreciating the rain you get, even when it's less than you want.

2. Sometimes one-half plus one-half equals seven-tenths or three-quarters or some other number less than one. The math is faulty, but it's true nonetheless.