ISSUE 2   May 21, 2009

SOYBEAN PLANTING CHALLENGES

This season, planting has been delayed for the small grain and corn crops. However, soybean planting is still timely. Soybean is susceptible to frost and prolonged exposure to near freezing conditions in both the spring and fall. Ideally plant soybean after the soil has warmed to 50 F and air temperatures are favorable. Table 1 provides a comparison of major crops as they respond to cool temperatures and how many days it takes for plants to reach physiological maturity.

Table 1. Resistance of selected field crops to frost at different development phases and days to physiological maturity.

 

Harmful Temperature in Fahrenheit

 

Germi-nation

Early growth

Flowering

Seed Set

Seeding to physiological maturity

( F)

(days)

Spring Wheat

14-16

22-25

28-30

25-28

83-98

Barley

18-19

25-27

28-30

25-28

70-85

Peas

18-19

22-25

27-28

25-28

95-99

Canola

18-19

24-26

27-28

27-28

75-85

Corn

27-28

30-32

28-30

27-28

85-110

Dry Beans

21-23

30-32

27-28

25-27

80-98

Sunflower

21-23

22-25

27-28

27-28

88-105

Safflower

21-25

22-25

27-28

25-27

80-95

Flax

19-23

24-26

27-28

25-28

80-95

Soybean

25-27

30-32

27-28

27-28

90-110

Buckwheat

28-30

32

28-30

28-31

70

Selected data adapted from Ventskevich. and Pro Crop 2008 http://www.ag.ndsu.edu/procrop/procrop.htm .

Each soybean variety has a narrow range of north to south adaptation. Soybean yield and quality are affected if a season-ending freeze occurs before a variety reaches its physiological maturity. Therefore, select varieties which are adjusted for the length of the local growing season. Dates of soybean variety maturity, as listed in ND yield performance tables, indicate physiologically maturity. Usually harvest takes place approximately 7 to 14 days after the soybeans are physiological mature.

Relative maturity ratings are also provided for many of the varieties entered in the NDSU trials. These ratings consist of a number for the maturity group designation such as: (000, 00, 0 or 1) followed by a decimal, l these indicate maturity rankings within each maturity group.

Soybean variety selection should be based on maturity, yield, lodging and disease reaction. Comparative maturity and yield for soybean varieties can be obtained from a current copy of NDSU Extension Service publication A-843, "2008 North Dakota Soybean Variety Performance Testing" or at the following NDSU Extension web-site: http://www.ag.ndsu.edu/pubs/plantsci/rowcrops/a843.pdf.  

Wet soil conditions and less than ideal seed bed conditions may result in compaction and inadequate seed to soil contact. Soybean producers need to make sure the seeding furrow is closed and seed is covered without compacting the soil. Soybeans are well suited to a no-till planting system. Not working the ground before seeding during this wet period will reduce labor and the chance that compaction will take place during cultivation. If soybeans will be planted in fields that have been flooded this year, it may be necessary to remove debris and mix in the soil deposits (from the flood) into soil before planting.

Soybeans are sensitive to planting depth. The depth of the seed can be varied depending on the soil type, moisture and temperature. Some wetter soils tend to crust and soybeans should be placed shallower than under perfect planting conditions , so the seed can push through the soil surface a little easier. More seeds in the row (such as in wider row spacings with similar populations) will also help the germinating seed to push through the soil surface and emerge more uniformly. Soybean plants emerge best when seeds are planted 1 to 1.5 inches deep.

Row planters have better depth control than grain drills and accurate placing of the seed will result in more even distribution of the seed and uniform germination. Air-seeders can bounce and sometime soybean seed ends up near the surface of the soil. This seed may germinate but often will not develop into a viable plant. Planting speed can greatly affect seed placement. Drive no faster than a speed which will permit uniform seed depth control.

In planting soybeans it is important to have an even distribution of the seed. Soybeans with low plant numbers per acre, but with regular distributed plants, can compensate. Plants fill in the non-planted areas. If there are skips in the field, plants will not have the ability to cover the open areas and yield potential will be lower. The recommended established soybean plant stand is 150,000 plants per acre. To achieve this producers should realize that often there will be 10-15% fewer established plants than live seeds planted.

Rhizobia bacteria are beneficial and live in symbiosis with soybean plant roots resulting in nodulation of soybean roots. If fields were flooded this spring, anaerobic conditions may have reduced the level of Rhizobia bacteria in the soil. A seed inoculant with the desired bacteria may be beneficial under these circumstances. Inoculants are also highly recommended when there is not a history of soybean production in a field.

Hans Kandel
NDSU Extension Agronomist, Broadleaf crops
hans.kandel@ndsu.edu

 

EMERGENCE OF SMALL GRAINS AND CORN -2009

Not only has planting been delayed this year, but abnormally cool, May weather has slowed the rate of emergence of crops that have been planted. According to the latest USDA Crop and Pest Report, only 28% of the barley, 27% of the durum, 31% of the spring wheat and 23% of the corn had been planted by May 17th this year. This compares to the average for the last five years of 85% for barley, 63% for durum, 87% for spring wheat and 75% for corn. Normally when planting is delayed, the rate of emergence is hastened because average temperatures are rising. Not so this year, May temperatures well below averaged. Crop growth rate, including germination and emergence is driven by temperature. In this article, I will describe how temperature impacts emergence. Less than 3% of the acreage was planted before May 1st this year, so the focus of this article will be on temperatures since the beginning of May.

Growing degree days (GDDs) are better correlated with crop growth than calendar days or average daily temperatures. GDDs for small grains are calculated using a base temperature of 32 degrees F and are easily obtainable for many locations in the state from the North Dakota Agricultural Weather Network (NDAWN) under the applications submenu at http://ndawn.ndsu.nodak.edu. After planting, barley requires about 176 GDDs before emergence occurs and 245 GDDs before reaching the first leaf stage. Factors such as depth of planting, soil blackness and soil temperature can of course influence the actual GDDs needed before emergence. Wheat takes slightly more GDDs (180) before it emergences and reaches the first leaf stage (252 GDDs). Base 32 degree GDD accumulations since the beginning of May range from about 330 in the south to 230 in the northeast, which indicates that the earliest planted barley and wheat are somewhere between early emergence and just beyond the first leaf stage. This corresponds to my own observations as I have driven through the state the past few days; small grain emergence is visible only in the earliest planted fields. Wheat/barley GDD accumulations from May 1st to May 18th lag 60-100 GDDs behind normal, meaning that early planted small grains took nearly 5 calendar days longer to emerge after planting than normal. This is not good news, as delayed planting plus slower emergence means that critical growth stages (i.e. early spike development and flowering) of wheat and barley are likely to occur when temperatures are warmer than ideal (assuming that we have a more normal summer from here on out).

The story for corn is no better. Typically, by this time of the year nearly a quarter of all the corn has emerged. Not even the earliest planted corn has emerged this year. Like for wheat and barley, there is a predictable relationship between GDDs and emergence in corn. Corn is a warm season crop and requires temperatures exceeding 50 degrees F before measureable growth can occur. Corn GDD accumulations, therefore, are calculated using a base temperature of 50 degrees F. Corn and barley/wheat GDDs cannot be used interchangeably. Corn requires about 120 corn GDDs before it emerges. GDD accumulations since the beginning of May range between 70 and 120 depending on the location in the state, and are running about 30 to 50 behind normal suggesting that corn emergence will be 4 to 7 days slower this year than normal. The warming temperatures associated with delayed corn planting does not have the same impact on yield potential development on corn as it does with small grains. However, delayed corn development usually means higher moisture at harvest and more cost of drying before grain can be put in the bin or sold.

Joel Ransom
Extension Agronomist for Cereal Crops
Joel.ransom@ndsu.edu


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