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Planting Small Grains and Corn - 2020 (04/30/20)

Optimum Seeding Dates of Small Grains, Optimum Seeding Rates of Spring Wheat, Optimum Seeding Dates and Planting Recommendations for Corn

Optimum Seeding Dates of Small Grains

Due to unfavorable soil and weather conditions, planting has just now started and only in some regions of the state. As of April 26th, only 5% of the spring wheat area and 2% of the barley area had been planted, compared to 18% and 13% for the five-year average. Planting small grains early in the season is considered desirable, as it allows these cool season crops to grow when temperatures are more favorable to the development of high yield. Table 1 summarizes our current recommendations for optimum seeding dates for small grains. These dates are based on trials conducted at Research Extension Centers averaged over multiple years. Yield losses are estimated to be 1% per day after the optimum recommended planting date. Nevertheless, when looking at data USDA data for the entire state, I found little relationship between when 50% of the spring wheat was planted and yield. As an example, last year we reach 50% the spring wheat crop planted on May 15th, about 5 days later than the average of the past 10 years, yet the statewide yield was 49 bu/acre, well above the average yield for the same period. Planting date alone is obviously not the only determinant of yield in a state where drought stress is common. In most seasons, planting on or before the recommended optimum date will enable higher yield potential than when planting later.


         Table 1. Recommended optimum seeding dates for small grains in North Dakota.


Optimum date

Last Planting Date

South of Hwy 13 and 21 & north of SD border

2nd week of April

2nd week of May

South of I-94 & north of Hwy 13 and 21

3rd week of April

3rd week of May

South of U.S. Hwy 2 & north of I-94

4th week of April

4th week of May

South of Canadian Border & north of Hwy 2

1st week of May

1st week of June


Optimum Seeding Rates of Spring Wheat

I occasionally get questions about the optimum seeding rate of new wheat varieties. After several years of research on the potential interaction between varieties, seeding rates and environments, the answer is, unfortunately, it depends. The optimum seeding rate can vary somewhat from variety to variety but also from environment to environment. I have developed the following guidelines, based on the results of this recent research that I use when formulating seeding rate recommendations: 1- First, it is important to use seed numbers per acre not bushels per acre for the basis of a seeding rate. Seed weight varies considerably between seed lots. If you seed by weight without taking into consideration seed weight, you may be under-seeding or over-seeding without knowing it. Information on the number of seeds per pound can be found on seed tags or can be calculated by counting a thousand seeds, weighing them on a kitchen balance and doing some simple math. 2- Start with a base seeding rate of 1.5 million seeds per acre, which was the average economic optimum rate over environments and varieties. 3- For environments where yield will likely be less than 50 bu per acre, reduce the seeding rate by 100,000 seeds (i.e. 1.4 million seeds). 4- For varieties that are rated 5 or higher for straw strength, reduce the seeding rate by 200,000 seeds per acre. 5- For higher yielding environments (> 50 bu per acre) and when using a variety with good straw strength that produces few tillers, increase the base rate by 100,000 per acre. These seeding rate recommendations are for the number of live seeds so you will need to adjust for the germination of the seed lot. In our research plots we observed that on average about 15% of the seeds did not establish seedlings. Accordingly, there is no need to adjust seeding rates upward to accommodate seedling mortality, unless for some reason you feel mortality rates will be higher than the 15% mentioned above.


Optimum Seeding Dates and Planting Recommendations for Corn

There was no report of corn planting in the most recent USDA-NASS report. The five-year average for this period is about 7%. The optimum period for planting in corn is during the first two weeks of May. This is narrow window given the likelihood of rain or cold or wet soils precluding planting during some of those days. Over the last 10 year, typically only about 50% of the corn acres are planted by the May 15th; last year we reached the 50% mark on May 23rd. After May 20th, we recommend a switch from a full season hybrid to an earlier maturing hybrid. Last year illustrated the risks of staying with a full season hybrid when planting is delayed, as many late-planted full season hybrids did not reach maturity before the end of the season resulting in low test weights and very wet corn.

Because corn is a warm season crop, it does not grow when temperatures are below 50 degrees. It is not uncommon for soil temperatures to be below 50 degree in early May. Though we accumulate very few corn growing degree days in early May, most seasons planting in early May will result in better yields and an earlier maturing crop than waiting for a period of sustained warmer soil temperatures. The relationship between planting date and final yield for the state is not very strong (Figure 1). Three of the lowest yielding years were those that were planted after May 15. On the other hand, two of the three highest yielding years, 2018 and 2019, were planted on May 20 and May 23, respectively and had yields well above the trend line in this graph. Also, of note is that the final planting date for full insurance coverage for corn in North Dakota is May 25th except for Cass, Ransom, Richland and Sargent counties where the final planting date is May 31st.



One risk of planting in early May is that of imbibitional chilling injury to the seed. This injury can cause reduced stands and variable emergence timing. It most often occurs when the seed imbibes water that is less than 50 degrees shortly after planting. Seeds that are planted into cold soils that do not warm up above 50 degrees during the first 24 to 36 hours after planting, or if planted into soils receives a cold rain or snow shortly after planting.

Planting date is not the only determinant of yield and in fact only explains little of the yield in the above graph. This means that regardless of planting date management and weather after planting will determine ultimate yield. Establishing a uniform stand is a critical practice in developing a foundation for high yield. In addition to soil moisture and temperature, planting speed, and crop residues have been shown to impact corn emergence. Crop residues influence soil temperature (and uniformity of emergence), so make sure trash managers are working and properly adjusted. Seeding depth can also play a role in emergence variability. Seeding at 1.5 to 2 inches is generally recommended, but if the soil surface dries out, don’t be afraid to plant deeper if it places the seed in uniform moisture.

Joel Ransom

Extension Agronomist, Cereal Crops

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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