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Late winter crop planting decisionsBy D. Bruce Bosley CSU Extension Agent, cropping systems Colorado Several area farmers have asked about planting winter wheat in March for a grain crop this summer. Wheat looks good based on current and contract market prices. The question behind the question is: what are the risks of planting winter wheat at this time. The risk for planting winter wheat in March is will it have enough cold temperature hours to vernalize and just as importantly, will the wheat develop seeds sufficiently before the hot dry temperatures stop wheat grainfill. Some plants will not flower until after they have been exposed to cold temperatures. This exposure to cold temperatures, resulting in physiological changes in the plant, is called vernalization. Not all plants have a vernalization requirement, and the degree of vernalization required can vary within a species. Vernalization days are a measure of cold temperature, similar to growing degree days as a measure of warm temperatures. Contrary to popular belief, the best vernalization temperatures are in the 40 F to 50 F range, not at colder temperatures. Vernalization is a biological process and plants have to be biologically active--not frozen--for it to occur. Winter wheat does have a vernalization requirement. Most spring wheats do not, or they have very low vernalization requirements. Winter wheat seed is preferred over spring wheat because it is easier to obtain especially if the farmer has stored wheat stored on farm but also because very little spring wheat is planted in Northeast Colorado and adapted spring wheat seed varieties are usually hard to find. Assuming satisfactory field conditions, you can safely plant any winter wheat before January 1st in Northeast Colorado with minimal risk. After Jan. 1, the answer depends on how much yield you are willing to lose, and how much risk you are comfortable with. Some farmers have successfully planted winter wheat in January and even into mid February and have gotten decent yields especially when early summer temperatures remain cool. The few that have planted side by side with spring wheat have reported better yields with winter wheat with early plantings. By early March vernalization may still be possible but the late planting will delay wheat flowering and grainfill by weeks and very probably set this critical development stage into the weeks where when heat stress injury are likely. Perhaps this is a good time to re-evaluate your planting options for spring crops. The high prices for wheat and corn are driving the acreages up for both crops and taking acres away from millet, sunflowers, annual hays, and other suitable crops. This may be a good opportunity to plant against the trend and place your bet on crops that are likely to be in short supply and consequently will also have a high market price. Please contact me, Bruce Bosley, about this or other cropping systems or natural resources topics at 970-522-3200, extension 285 in Sterling or 970-542-3540 in Fort Morgan. 3/10/08 Date: 3/5/08
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