Soil temperature, seed germination and the unusual spring of 2012

How do soil temperatures for 2012 spring planting compare with previous years?

Crop seeds (and potato seed pieces) germinate and grow based, at least partially, on soil temperatures. Seed will remain dormant until the minimum soil temperature for germination is reached. The seed germination process will be slow at or near the minimum soil temperature, compared to a more favorable, or optimum, soil temperature for germination. If seed germination is delayed by cold soil temperatures, pathogens including root rots and damping-off organisms have a better chance of infecting the seedling, increasing the likelihood of significant stand thinning and overall yield reduction.

There are big differences between “minimum soil temperature for germination” and “optimum soil temperature for germination.” These soil temperatures are good to know, and should be considered as useful factors to determine seeding date along with frost-free dates and typical growing season limitations. However, the realities of time management on the farm can often result in compromising what we’d like to do with what we need to accomplish. In other words, farmers try to be as timely as possible with planting dates.

Along with the big difference between minimum and optimum soil temperature for germination, there is also some variation between information sources about the soil temperatures for specific crops. Listings from university and governmental sources in Nebraska, Alberta, Canada and other locations were used to prepare the following unofficial table.

Soil temperatures for germination of selected crops

Crop

Minimum (°F)

Optimum (°F)

Barley

40

68

Oats

43

68

Canola

50

60

Alfalfa

48

77

Birdsfoot trefoil

45

79

Red clover

45

77

Orchardgrass

40

65

Timothy

40

65

Field corn

46

86

Pumpkin

60

85

Potato

45

65

Soybean

50

77

Dry bean

60

80

So, where are we currently with soil temperatures in Michigan? Has the early warm-up in March affected planting dates, and if so, how much? How do soil temperatures this year compare with previous years?

The MSU Enviro-weather program is a good place to look for answers to these important questions on a local or regional basis. Simply click on a weather station location on the state map near, or comparable, to your farm. This will take you to the webpage for that weather station with weather summaries and degree day tools for that location. From there, you can view tables under “Soil Conditions” giving daily soil temperature reports over your selected time period. You can also view growing degree day (GDD) accumulations and prepared GDD tools including GDD comparisons over the last five years and GDD accumulations specifically related to alfalfa and corn development. (The GDD base 42 tool is very useful for planning first alfalfa cutting – 750 GDD for alfalfa placed in vertical silo storage, 680 GDD for alfalfa placed in horizontal silo storage). You can also access the Alfalfa First Cutting tool by selecting “field crops” from the horizontal list at the top of the screen, then clicking on the folder next to “Alfalfa.”

Example of Ithaca soil conditions

2012

Air   Temperature
  (degrees F)

Soil   Temperatures at 2 inches
  (degrees F)

Soil   Temperatures at 4 inches
  (degrees F)

Rainfall   (in.)

Soil   moisture (in./in.) at 4 inches

Soil   moisture (in./in.) at 10 inches

Day

Date

Max

Min

Max

Min

Max

Min

Today

Since   4/15

Max

Min

Max

Min

Sun

4/15

72.3

55.5

59.3

52.9

57

52.3

0.48

0.48

0.245

0.21

0.366

0.364

Mon

4/16

67.6

38.8

58.6

49.6

57.7

51.5

0.51

0.99

0.278

0.236

0.451

0.366

Tue

4/17

55.1

33.7

54.4

45.1

53.1

47.1

0

0.99

0.267

0.253

0.398

0.39

Wed

4/18

65.3

32.3

54

44.5

52.6

46.5

0

0.99

0.257

0.244

0.39

0.387

Thu

4/19

63.3

43.2

57.2

49

54.8

49.6

0.04

1.03

0.248

0.239

0.387

0.385

Fri

4/20

46.3

37.5

52.2

45.4

52.6

46.8

0.53

1.56

0.295

0.236

0.468

0.385

Sat

4/21

49.8

32.1

51.8

42.1

50.2

44.1

0

1.56

0.296

0.281

0.466

0.399

Sun

4/22

51.2

30.9

48.7

41.7

48.1

43.8

0

1.56

0.287

0.272

0.399

0.392

Mon

4/23

58.5

34.2

50.8

40.8

49.3

43

0

1.56

0.277

0.26

0.392

0.387

Tue

4/24

60.3

38.6

51.2

42.4

49.6

43.7

0

1.56

0.265

0.248

0.387

0.384

Wed

4/25

64.4

33.6

54.5

43.1

52

44.7

0

1.56

0.253

0.242

0.384

0.382

Thu

4/26

55.2

35.7

52.6

46.9

51.3

48.4

0.02

1.58

0.245

0.238

0.383

0.382

Fri

4/27

57

28.3

53.8

42.4

51.6

44.4

0

1.58

0.243

0.229

0.382

0.379

Sat

4/28

48.4

34

49.5

44.9

49.5

46

0

1.58

0.233

0.224

0.379

0.377

Sun

4/29

61.1

27.8

54.3

41.5

51.8

43.5

0

1.58

0.226

0.217

0.377

0.375

Mon

4/30

51.7

38.8

50.6

46.6

49.9

47.3

0.35

1.93

0.245

0.217

0.375

0.375

Tue

5/1

54.9

45.9

53.3

48.7

52.1

48.9

0.01

1.94

0.244

0.235

0.375

0.375


Ithaca Historical Degree Day Summary (Numerical Integration method) from 3/1/2012 to 5/2/2012

Year 

Degree Days Base 42°F 

Degree Days Base 45°F 

Degree Days Base 50°F 

Dates evaluated

2007

342

261

162

Data from 3/1 through 5/2/2007.

2008

62

48

30

Data from 3/1 through 5/2/2008.
Missing temperature data for:
3/1 Midnight-1AM-4/25 10-11AM (1330 hours)

2009

281

205

115

Data from 3/1 through 5/2/2009.

2010

477

375

242

Data from 3/1 through 5/2/2010.

2011

211

154

87

Data from 3/1 through 5/2/2011.

2012

532

422

268

Current data from 3/1 through5/2/2012 3PM.
Missing temperature data for:
5/2 4-5PM-5/2 11PM - Midnight (8 hours)

Average of 4 years, not including current year

327.9

248.8

151.5

4 years with > 90% of data.


For more information, contact .(JavaScript must be enabled to view this email address), U.P. crop production educator, at 906-387-2530.