Much of the state has experienced hot, windy weather recently. From my interactions, some individuals appreciate the drying weather and others are praying for rain and a reprieve from the wind to get some spraying done. Although growth stages of crops vary from region to region, many fields may experience some stress due to wind and heat. However, if moisture is still present in the root region, warm-season crops like corn and soybean are likely experiencing a growth spurt while cool-season crops like small grains may struggle in the heat.
When we have hot weather during this part of the growing season combined with winds, we can see a few negative things develop, especially in dryland crops:
Small Grains — wheat and oat fields may be flowering (pollinating) at this time or just beyond this growth stage. Heat and pollination of these cool-season crops is not a positive combination and can negatively affect grain fill and consequently, yield. Extended periods of strong winds can also be hard on these plants and cause extra environmental stress that is conducive to bacterial leaf infections; fungicides are not effective for bacterial infections, leaving a producer to hope for the best in these situations.
Corn — according to the June 15 NASS (National Agricultural Statistic Service) report, corn emerged in South Dakota is at 98% (ahead of last year’s 50%). With most SD corn being in the vegetative growth stage, this heat wave is a welcome site. Corn accumulates about 1,300 heat units (growing degree days) during the vegetative growth stage prior to pollination. A “growing degree day,” is a measure of heat accumulation; it is calculated by subtracting 50 from the daily average temperature. As long as sufficient moisture is present in the root zone, established corn should continue to thrive as growing degree days accumulate. At early growth stages, it is important to protect the mesocotyl; this is what the plant lives off of until the 4-5 leaf growth stage when nodal roots develop and the growing point moves above ground. Strong wind isn’t a great asset at this stage of growth, but most corn is well enough established to withstand winds and stand back up if slightly lodged after a storm. Check out the ‘Degree Days Tool’ to see the accumulated growing degree days in your area at climate.sdstate.edu.
Soybean — with NASS reporting soybeans emerged at 86%, we’re well ahead of last year’s 29% emergence at this time. Much like corn, soybeans are a warm-season crop that like the heat as long as adequate moisture is present in the root zone; as a photoperiod (day-length) sensitive plant, timing of soybean flowering is highly dependent upon planting date and weather. They are a bit fragile to wind and weather events at this stage as the growing point emerges initially with the plant and stays near the soil surface. Although most soybeans are still quite small, they can be subject to extensive wind or storm damage if the growing point is affected. Keep in mind that row crops don’t use a lot of moisture this early in the growing season, but it is still an important factor in crop development.
Alfalfa — as a cool-season crop, alfalfa comes up early in the spring and many eastern South Dakota growers have already put up their first cutting of hay. In more arid western SD climates, producers may still be waiting to begin the first cutting. Although it’s technically a cool-season crop, alfalfa can grow in a wide range of temperatures beginning at 46°F and extending to over 100°F in some cases; however the ideal shoot growth happens between 72 and 76°F. At extremely hot temperatures, water becomes the limiting factor to keep production up.
There’s always a lot to do this time of year, but worrying often makes the top of the list for many farmers. We can’t do a lot to avoid issues created by heat and wind stress in our crops at this point, but it’s good to have an understanding as to what’s going on in your fields. Now is the time to scout fields and watch for pest problems that may arise. Insects are on the move in field crops in South Dakota and farmers should be monitoring populations and thinking about post herbicide applications as well.