La Niña is a climate phenomenon which continues impacting most of the U.S. crop growing regions this year. Continuing to play out far west of us in the Pacific Ocean are prolonged cooler-than-normal sea surface temperatures. With such La Niña events, strong winds push warm waters toward Asia, with sea upswelling increasing off the Americas’ West Coast. This means that cold, nutrient-rich water rises to the Pacific surface, which in turn pushes the jet stream northward. As a result, southern and western states tend to experience drought while the Pacific Northwest and Canada see heavy rainfall and flash flooding. What’s been occurring since late spring 2022 is a blockage of moist air originally destined for the U.S. West Coast. This deflected potential precipitation never becomes rain to moisten parched Western states. How much further east La Niña’s scorching misbehavior meanders is a work in progress.
The July 5 U.S. Drought Monitor map showed continued severe drought in many western ag regions. This snapshot picture wouldn’t change much if retaken today. But drought conditions have dramatically spread into large areas east of the Mississippi River, particularly the Southeast. Parts of the Midwest, all of Indiana and Kentucky (prior to that state’s end of July flooding) and much of New England are now designated drought areas. With continued tight grain and forage supplies, these extensive drought conditions are expected to impair future U.S. milk production capacity. Growers fortunate enough for their fields to dodge these moisture deficiencies can look forward to the double bounty of good yields and near record-high prices.
The dry weather is producing spotty crops. For example, one area will have rain and decent crops while just a mile away the crop is struggling from water shortage. We observe that, regardless of weather, farmers that rotate crops frequently – and build their soils’ structure and organic matter with intensively managed winter forage – are better off. Their crops do much better, despite unfavorable conditions. But overall, it appears that La Niña has reached farther east than many experts predicted.
Whether or not the very hot, dry weather of late July that hit the Northeast was “little girl”-based or empowered some other way, one thing was certain: Temperatures exceeding 85º F are not productively used by corn crops. The baseline for calculating growing degree days (GDDs) is 50º. A day whose starting temperature is 55º and peaks at 85º will average 70º, meaning that 20 GDDs were accrued that day. A day that starts out at 55º and peaks at 95º will not earn any additional GDDs for the extra 10 degrees (95º minus 85º). Not only that, other problems will occur if moisture and potassium (the moisture regulating mineral) are deficient.
Fortunately, there are grass family plants that some refer to as hot climate summer annuals (HCSAs). This grouping, which includes sorghums, sudangrasses, their hybrids and millets, can utilize all the extra GDDs generated past the 85º ceiling. Sorghums, for instance, have been shown to keep performing at temperatures of 110º. Case in point: I advised a farmer (Bill) who this year planted sorghum/sudan (SS) and Japanese millet on separate parts of a 12-acre piece of upland soil. The field, planted in mid-June (when soil temperature finally hit 65º consistently), was soil-tested: pH was 5.9 and phosphate level was very low. SS was drill-seeded at 33 lbs./acre, and millet was drill-seeded at 25 lbs./acre. I examined the stand on July 25 and both the millet and the SS were about waist-high. I suggested that he mow the stand a week later. But by July 29, benefiting from high humidity and 90º-plus temperatures, both crops were chest high, so he mowed them; Bill round-baled them Aug. 1. Mowing them this early rather than allowing them to head out – millet would have needed another three weeks, SS four weeks – gives the crops’ regrowth seven weeks before the first killer frost is expected to hit. We both look forward to a decent second cutting. When I looked at this stand on July 25, the millet generally appeared a little greener than the SS; millet is more tolerant of lower pH and lower phosphate.
After harvesting the second cutting of HCSAs next month, Bill will be able to plant winter forages. One possibility is to plant 50 lbs./acre each of oats and winter rye. If that’s done after the second cutting of HCSAs, there will be no chance to harvest winter forage this autumn. The oats will freeze to death and thatch over the rye, which should survive beautifully till spring. At that time, rye can be harvested a week or 10 days earlier than perennial mixed hay first cutting. The other option involves planting spring oats plus winter triticale but forfeits a second cutting of HCSAs. Based on Cornell research involving cooperating farmers, three bushels of oats planted with 80 pounds of triticale before mid-August will give an oat/triticale harvest at the end of September. If you mow the oat/triticale stand, leaving at least four-inch stubble, the triticale will continue to grow into autumn after oat harvest. Fertilizing the triticale as normal next spring results in two very high-quality forage crops in one planting – one in autumn, one in spring. It can be followed by corn or a no-till legume seeding.
I’m often asked about prussic acid threat associated with sorghum – and to a lesser extent with SS and sudangrass. If grazed at a height less than 20 inches, there exists a possible threat of hydrogen cyanide-prussic acid poisoning, particularly if the grazed forage in question is aftermath. When these HCSAs are made into baleage or haylage, the ensiling fermentation process chemically renders the prussic acid harmless. Millets pose no prussic acid threat, period.