ISSUE 1    May 4, 2006


In many parts of eastern ND planting has been put on hold after the inch-plus of rain received over the weekend. Many farmers were just getting into their fields for the first time when this rain came, so small grain planting will be competing with corn planting when soils finally dry. Any additional rain (and some is in the forecast) could delay planting even further. What are the implications of planting small grains and corn late?

Optimum planting date for small grains

Small grains are cool-season crops that are most productive when they grow and develop during cool weather. The development of high yield potential in small grains is particularly favored by cool temperatures during vegetative and early reproductive development. Planting early helps ensure that these crops will develop under cooler, more favorable conditions. The optimum and last planting dates for small grains are summarized in the following table.

Avg. optimum and last planting dates for small grains in ND

Region of the state


Last Planting date

So. of Hwy 13 and 21

2nd week of April

2nd week of May

South of I-94

3rd week of April

3rd week of May

South of Hwy 2

4th week of April

4th week of May

So. of Canadian Border

1st week of May

1st week of June

As a general rule, yields decline by about 1% per day delay after May 15th. Late planted small grains often have higher protein, so nitrogen levels can be adjusted downward to more closely match the lower yield potential of a late planted crop.

Optimum planting date of corn

The optimum planting date for corn for the entire state is May 1st. In most regions and years there will be minimal difference in yield and moisture at harvest between corn planted between May 1st and May 10th. Unlike small grains, corn is a warm season crop and has limited growth when temperatures are below 50 F. Early planting (near May 1st) is recommended for corn, not because of the impact of late planting on yield potential, but because every possible heat unit is needed to enable the crop to reach maturity and to dry sufficiently in the fall so that minimal post-harvest drying is needed. The recommendation is to stay with a full season hybrid through May 20th. Switch to an earlier maturing hybrid when planting after that date.

Hopefully conditions will allow for a rapid return to the fields. If planting is delayed further, however, the question of which crop should be planted first, may become important. I think there are strong "biological" reasons as outlined in the above paragraphs to support the decision to start with either small grains or corn. Consider factors such as the relative importance of each crop in your overall farming system, their likely harvest price, the weather forecast and which field will be ready for planting first in making a final decision.

Joel Ransom
Extension Agronomist/Cereal Crops



There is a lot of interest in planting soybean early but how early is the question and yet not take on a lot of risk.

One of the biggest advantages of early planting is that it provides a longer planting window for attaining maximum yields. University agronomists in other states have reported that the newer soybean varieties are more tolerant of adverse, early-season conditions than older varieties. In North Dakota soybeans planted from May 1 to May 15 in most years will have comparable yield if the maturity rating is the same. Soybean planted in late May and early June usually have lower yield potential than soybean planted in early May.

The primary risk of early-planting is that the beans will be damaged by freezing temperatures. This risk is mitigated to some degree by the fact that germination is delayed under cooler soil temperatures. Soybean tissue is also more resistant to freezing temperatures than corn tissue. However, the corn growing point remains below ground for several weeks or more while the terminal bud or growing point of the soybean is exposed early upon emergence. Typically, temperatures must reach 28°F for damage to occur if soybean are just emerging at the cracking stage or cotyledon stage and can with-stand some frost. At the unifoliate and 1st trifoliolate leaves, soybeans are very vulnerable to killing frosts at or below 32 F. There is also risk that soil-borne diseases may damage soybean seed planted into cool soils.

If you decide to plant soybean in the 1st week of May, you should consider the following recommendations:

• Don’t plant unless the soil is dry enough to support equipment. Shallow soil compaction will haunt you the remainder of the growing season.

• Soil temperatures of the seed bed should be at minimum 46-48 F or warmer if at all possible. A chilling injury can occur to germinating soybean seed if soil temperatures are below 44 F. This can result in poor seedling vigor and reduced plant population.

• Plant seed that has been treated with a fungicide if planting into cool soils and if no-till seeding.

• Plant high quality seed that was grown in 2005. Don’t use old seed!!

• Till the field or clear the residue away from the row to allow the soil to warm up faster and reduce the likelihood of frost damage.

• With the recent rains in some areas, don’t plant if the fields and soils are on the wet side. Soybean mudded in early will fail to establish good plant stands and may result in reduced yield potential.



Temperatures can drop to freezing and below freezing levels during the month of May in many regions of North Dakota and northwestern Minnesota. What type of frost damage will occur with some of our crops that are just emerging and in a vulnerable stage? Temperatures below 32 F will cause water in plant cells to freeze and resultant ice crystals will kill cells by damaging cell membrane systems. How different crop species react to freezing temperatures depends on where growth is taking place, where growing points are located, and if cells have built in systems to prevent ice crystal formation.

Seedlings hardened by continuous low night and day temperatures are more resistant than seedlings hardened by alternating high and low day and night temperatures. The recent cool nights may have helped some plants with the hardening process.

There are considerable cultivar differences in all crops and no research has been done on the cultivars we are currently growing with respect to frost tolerance.

Corn: Corn plants less than 8 inches tall (V5 or less) will recover from frost because the growing point is still below the soil surface and usually not damaged. Lethal cold temperature is a concern since a corn plant’s growing point region is relatively protected from the effects of simple frost while it remains below the soil surface. Lethal cold temperatures (28 F or less) can penetrate the upper inch or two of soil, especially dry surface soils, and kill plant tissue directly, including coleoptiles and growing points. Non-lethal injury by cold temperatures may cause deformed elongation of the mesocotyl or physical damage to the coleoptile in non-emerged seedlings, resulting in the proverbial "cork-screw" symptom and subsequent leafing out underground.

Historically very few corn fields have been destroyed by spring freezes. Damage to seedlings could be:

(1) complete killing
(2) injury so severe that the resulting seedling is weakened to the point where it will never develop normal growth and reproductive systems,
(3) injury evident but seedlings remain vigorous and complete recovery can be expected.

Environmental conditions before or immediately after a low temperature greatly influence the extent of freezing injury. If the temperature drop is gradual, plants are in better condition to resist injury and can stand surprisingly low temperatures. Similarly, slow rising temperatures after a frost and satisfactory soil moisture conditions are desirable to aid recovery. Drought, wind and high evaporation are likely to aggravate the frost injury and lessen the chances of recovery.

Soybean: Soybean are easily damaged by frost in the 28 to 32 F range. Temperatures of 28 F for any extended period of time can completely kill soybean plants (stems and leaves). During the early seedling or cracking stage (VE to VC), soybeans have some tolerance to temperatures of 29-30 F for short periods of time. If the seedlings have been somewhat hardened off by cool temperatures for several days, then temperatures as cool as 28 F can be tolerated at the cotyledon stage if at the temp for a few hours. Once true leaves emerge (V1 and V2), soybean become more susceptible to freezing temperatures at or below 32 F for any extended period of time. Unifoliolate leaf stage is slightly more frost tolerant than first or second trifoliolate stages.

Sunflower: Sunflower in the cotyledon stages can withstand temperatures as low as 26 F range for short periods if they are just emerging from the soil. Sunflower in the 2 to 6 leaf stages become more sensitive with each development stage and terminal bud damage can occur. The lower limit for sunflower in the 2-leaf or V2 stage is 27-28 F. For the 4 and 6 leaf stages, 29-30 F is the lower limit.

Also, tolerance to frost can be influenced by the hardening off process. When it is cool or cold for several days such as 33-34 F at nights, seedlings become somewhat accustomed to the lower temps, and plants should have better tolerance to lower temperatures. It’s going from warm temps to extreme freezing temperatures all at once that are the most injurious. Wet soils and some dew also help in reduction of freeze injury. Cold and dry conditions help add more to seedling injury.

Flax: Flax is quite susceptible when it is first emerging. It can, in come cases, tolerate temperatures of 27 F early on. After the seedlings have passed the two-leaf stage and are hardened off by cold exposure, they can withstand lower temperatures down to 20 F. Check to see if stem is turning black. Therefore, after 2-leaf stage and hardened off it can stand temps in low 20's and recovery is very promising.

Small Grains: Cereal grains will lose leaf tissue that freezes. New growth will follow as the growing point is protected below ground up to and before . In some cases the eventual maturity date may be delayed. However, several frosts will destroy leaf tissue and can weaken the growing cereal grains and may result in yield reduction.

Alfalfa: Alfalfa will be damaged by temperatures in the mid to low 20's. Growth of alfalfa is from the tip of the stem. With frost damage the top will bend over and growth of the terminal bud at the tip will cease. New growth then comes from other lateral branches.

Other crops: Temperatures of 32 F and below will injure or kill buckwheat or dry edible beans. Both canola and crambe will tolerate temperatures in the low 20's. Pulse crops such as field peas or lentils have good frost tolerance since growing points remain below ground in the seedling stages.

Duane Berglund
NDSU Extension Agronomist



Sugarbeet seeds will germinate and emerge over a wide temperature range with adequate soil water. In most years, soil temperature at the 4 inch depth at planting time in mid-April is about 45 F. However, unusually high ambient temperature in April has resulted in growers planting into a warmer seedbed. This means that the sugarbeet crop and all its weeds will emerge faster than usual. The following table gives approximate days to emergence at different soil temperature ranges.

Soil Temperature (F)

Days to Emergence


21 days or more


10-21 days


7-12 days


5-7 days



Sugarbeet growers in North Dakota and Minnesota will plant about 759,000 acres in 2006. American Crystal Sugar Company will plant about 510,000 acres, Minn-Dak Farmers Cooperative will plant 116,000 acres, and Southern Minnesota Beet Sugar Cooperative will plant 118,000 acres. Growers in Western North Dakota will plant about 15,000 acres for the processing plant in Sidney, Montana. North Dakota and Minnesota will plant about 759,000 acres of sugarbeet which is about 55% of the total US sugarbeet acreage.

As of May 1, American Crystal Sugar Company have planted 139,000 acres (28%), Minn-Dak Farmers Cooperative have planted about 92,000 acres (80%), Southern Minnesota Beet Sugar Cooperative have planted about 94,000 acres (80%), and Sidney Sugar Company have planted about 30,000 acres (80%). Growers are waiting for the rain to stop and for fields to dry to complete planting. Current soil temperature at the 4 inch depth at St. Thomas, Fargo, and Wahpeton are about 52 to 53 F; this means that sugarbeet planted into these soils will emerge in about 12 days.



It is sugarbeet planting time. Our research shows that maximum recoverable sucrose per acre correlates well with plant population.

Research done at North Dakota State University and the University of Minnesota showed that a plant population of 175 plants per 100 foot of 22 inch wide rows at the 6-leaf stage was ideal for maximum recoverable sucrose per acre. It is important that the plants be evenly spaced within the rows.

At lower plant populations of 100 to 125 plants per 100 foot of row, roots tend to be somewhat larger but there is generally a reduction in yield, and sucrose concentration decreases resulting in higher processing costs. Lower plant populations take longer for the canopy to completely cover the soil resulting in a more costly weed control program.

Higher plant populations of 225 plants per 100 foot of row result in too much competition among the plants and consequently smaller sugarbeet roots and lower recoverable sucrose per acre compared to plant populations of 175 plants per 100 foot of row. Defoliation becomes very difficult at such high plant populations. Sugarbeet fields with 225 plants per 100 foot of row should be thinned to about 175 plants per 100 foot of row.

Plan to have a good plant population of 175 plants evenly spaced per 100 foot of row for highest sugarbeet yield and quality. Growers who use 30 inch row spacing should aim for about 200 plants per 100 foot of row to get highest yield and quality.

Mohamed Khan
Extension Sugarbeet Specialist

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