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Optimum Planting Dates for Small-Grains (5/11/17)

Planting in a timely manner can be an important determinant of yield.

Optimum Planting Dates for Small-Grains

Planting in a timely manner can be an important determinant of yield. Unlike other yield-enhancing inputs, planting at the optimum time usually does not cost more than planting late, so it can provide extra profits to the farm. Given the variability in weather, it is not possible to know what the best planting date will be in a given year. Research, however, has identified the period that will give the best results with the highest probability. Table 1 summarizes our current recommendations for optimum seeding dates for small grains.

joel table 1

April this year was cold and wet so planting of small grains was delayed for most of the state. In fact, by May 1st only 18% of the spring wheat and 13% of the durum was planted. This past week planting progress jumped to 45% and 24% for spring wheat and durum, respectively, nearly on par with the five-year average. Given the dryer weather, I would estimate that much of the small grains area will be planted this week.

Research has shown that delays beyond the optimum period indicated above can result in yield losses of 1% per day of delay. This is not always the case. Nevertheless, because small-grains are cool season crops, they develop their highest yield potential when they develop under cooler temperatures, especially during vegetative and early reproductive stages. Cool weather enables larger spike development. In high yielding environments like the desert southwest, spike size can be 50% larger or more than what we normally see because of favorable temperatures during early spike development. High temperatures during grain filling also reduce the amount of photosynthate that is available during kernel development reducing the grain size and in some cases grain numbers.

I have summarized the effect of planting date on durum yields. These data are from Dr. Shana Forster’s recently completed Ph.D. research. The rate of yield loss varied by environment, but over the four environments the rate of loss when planting was delayed beyond the optimum was similar to what we indicate in our current recommendation. Hopefully, the remaining area to be planted to small grains will be seeded shortly, thus positioning the crop into a reasonably favorable environment for high yields this year.

joel table 2

Joel Ransom

Extension Agronomist for Cereal Crops

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