Heating-Degrees and Planting

In the US west (west of the 100th Meridian, or roughly the 20″ rainfall line), we worry more about drought than anything when we consider crop success or losses. Moisture, then too much heat, then frost seems to be the usual priority list.

Not this year. It is too cool to plant cotton, and maize is . . . interesting, based on the hybrids commonly grown in this area. The winter wheat looks OK, or did as of Sunday afternoon’s windshield survey.

When we talk about energy use in a building, we refer to “heating degree days,” based on a temperature of 65 F. In theory, at that temperature, a building uses the minimum amount of energy to be heated or cooled. However, I have heard it used in agriculture, as a short-hand for growing degree days. Growing degree days refers to the amount of heat energy needed for plants and insects to germinate, grow, and mature. They are very, very important in thinking about yield development and what type of seed to plant, if you are in an area that has a comparatively short growing season.

Different plant species have different GDD optima, but most food crops (corn, many wheats, soybeans, sorghum) do better above 50-55F, and growth levels off above 85F or so. Cotton needs a minimum of 60F, while alfalfa can take 41F. Soil temperature is also important, because if the soil is below a certain temperature, the seeds won’t germinate. They stay dormant, then rot if there’s enough moisture. There’s a “sweet spot” for ideal planting conditions, and then again for ideal growing conditions. Too hot and things can bake if the weather is dry, plus bugs get a head-start. Too cool and growth is slow and yields don’t reach their best level. Different pest plants also do better under different conditions. (Some places in the US and elsewhere have fields underwater. Unless you grow rice, that’s not a great situation, and even then you need the water to recede from time to time.)

Right now, the Texas Panhandle has been cool and dry. Too cool for cotton to be planted, and for most of the maize (corn) hybrids that are common in the area. If a farmer usually plants 120-day corn (estimated days to maturity and harvest), switching to 90-day corn can’t be done quickly. First you have to find someone with the seed, then get it down here, and so on. We’re pushing the northern edge of cotton growth up here, because we are cooler than where cotton usually grows (Deep South, South Plains). With cool soil and chilly weather, the farmers can’t get seed into the ground. This pushes back maturity and harvest, and no one wants unripe cotton to get hit by a freeze or snow (like October of 2019.) Ditto food crops.

Traditionally, US farmers worried about drought and heat, while Europe worried about cold and wet. This spring? Lots of the US and Europe are cold and wet. Solar energy output is low, which doesn’t help things like tomatoes. Anecdata about hone-grown tomatoes suggests that people are having to use cold-climate tomato breeds farther and farther south, and have been for the last decade or so. Canada has lost a lot of its grain to cold and wet weather the past few years. Global warming? Perhaps, but certainly not this spring, based on the weather patterns, and it is year-to-year that we produce food and fiber.

The High Plains region had a hard freeze the past two nights, with high temperatures in the 40s-50s. Things are supposed to warm over the next few days, then cool again. The Midwestern grain belt? Cool and damp. I haven’t been watching grain futures to see what the market thinks, but I would not be at all surprised to see futures prices start going up if the planting prognosis continues to be less than great.

I like cool weather for being out and about in. It’s not so great for agriculture.


9 thoughts on “Heating-Degrees and Planting

  1. Not so great for agriculture, yes indeedy.
    That hard freeze slopped over into this part of East Tennessee; yesterday morning got down to 25°​F, and this morning was kinda frosty. Good thing I hadn’t yet planted anything out (owing to being behind schedule on just about everything).
    The next-door neighbor had planted things out a few days earlier, and hastily put coverings over his plants. Another neighbor, across the road, had planted things out in early March; that didn’t go well.
    It figures: the year everybody decides to have a victory garden is the year we get late frost.

  2. What global warming? Oranges used to be grown in southern Georgia and Alabama. Now they don’t grow north of Orlando.
    The current solar minimum isn’t helping, either.

  3. I had that discussion with a friend, the other evening. His warm-climate favorites have grown and produced less, for about a decade now, in a steady trend. I have time to put in more cool-season garden stuff, and am looking hard at a July/August cold-season set. Winter squash and pumpkins – not just for decoration, now.

  4. My efforts to establish a raspberry bramble and grapevines continues to be cursed. (At this point, it’s kind of funny. Maybe next year, the 8th? time will work.)
    And I’m pretty sure the hydrangeas are pushing up daisies.

    But the roses came through.
    I hadn’t transplanted the tomatoes or cucumbers outdoors yet.
    The annual climbers and ground covers are still inside.
    The planted seeds in the flowerbeds or lettuce container hadn’t quite come up yet.

    So, overall, not too bad.

  5. Whike testifying to water over temp concerns out here-and we’re actually normal for temps, but our growing season is very short, with last frosts regularly in June-I’ll share this regular stop-off of mine: https://droughtmonitor.unl.edu/CurrentMap.aspx

    We personally are only a little drier than average, but most of the west? Well, this is going to be an interesting year. Cold plus no water is a good recipe for crop failures. Expect the feud with California to intensify.

  6. Zone 1 here. We expect most(!) hard freezes to be over in June, barring the usual 2-3 that show up late. This year, we’re getting seriously cold weather. Medical issues prevented me from getting out the rain barrels, but it’s been a fairly dry month. The county records say we’ve had 0.17″ so far, about half of which was snow. Further south in California, in the high country north of the Sierras, the monthly total is a trace.

    The same medical issues say we won’t be doing any outside gardening this year, but $SPOUSE will start tomatoes indoors for our greenhouse around May 1st with transplants June 1st or so. Last year was awkward; June was exceptionally cold, while July was exceptionally hot. The greenhouse does a better job at retaining heat than shedding excess, and the plants suffered. We usually use three varieties of tomatoes, two cold weather varieties and a random Roma. Siberians (allegedly an heirloom variety) and Siletz (an Oregon hybrid with largish fruit) do well when it’s cold.

    We’re hoping for consistency. Not counting on it.

  7. We haven’t been able to plant “summer” varieties of tomatoes in the Central Valley of California, but it’s not due to any change in the weather. It’s because the air here is dry enough that there can easily be a 40-degree difference in summer between daytime high and nighttime low. Summer varieties of tomatoes stop ripening when the temperature drops below about 70 degrees, which happens almost every night. (110-degree days happen, but not too often.)

    Evaluating climate change is very tricky because the effects are apparently very, very spotty. Some areas get warmer while others get cooler.

    • And that’s before you toss in 1) urban heat islands growing up around reporting sites and 2) decreasing numbers of reporting sites because of lack of funding, lack of repairs, lack of locations, and other things. So fewer data points over a larger area, which leads to “fuzzier” data. At one point, Arctic temperatures were tracked and reported from one point, and all other data were extrapolated from that and from space-based equipment. SIGH.

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