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Publication #HS713

Seed Quality and Seeding Technology1

Bielinski M. Santos2

Seed

Quality seed is defined as varietally pure with a high germination percentage, free from disease and disease organisms, and with a proper moisture content and weight.

Quality seed insures good germination, rapid emergence, and vigorous growth. These aspects translate to a good stand (whether greenhouse or field). Poor quality seed results in "skips," excessive thinning, or yield reductions due to overcrowding, all of which diminish profitability.

Vigor is often implied when discussing seed quality, and most growers have come to use the terms "quality" and "vigor" interchangeably. "Vigor" is defined as those properties that determine the potential performance of seed during germination and establishment. Seed vigor is generally related to yield in vegetables. Therefore, high-vigor seed should be used in all instances to ensure good stand establishment under varying field conditions.

Different seed lots sown in the same environment may act differently, and seedbed factors (temperature, water content, etc.) strongly affect seed performance. Fluctuations (airspace, moisture, temperature, etc.) in the seedbed environment are the most important factors in determining final seedling emergence. Furthermore, large seeds of a particular species frequently produce more vigorous plants and uniform stands than small seeds.

Most seeds are fairly hardy; however, seeds in the bean and pea family (snap, lima, southern pea, English pea, etc.) are fragile and should be handled with extreme care. Dropping these seeds from any height while loading or unloading or pouring into seed hoppers will crack their seed coats and decrease germination.

National and international seed companies strive to provide high-quality vegetable seed through various milling processes and stringent disease screening. These techniques reduce the total tonnage of raw seed but increase the overall quality. Federal minimum germination standards regulate the seed industry (Table 1). However, most companies attempt to exceed these minimum standards.

Organic Seed and Sources

Seed used for organic vegetable production must meet specifications of the USDA's National Organic Program. Recordkeeping is required for growers during all phases of organic production, as is certification by an accredited certifying agency. Use of conventionally produced seed is allowed only when preferred cultivars are not available from organic sources. In no case are seeds treated with non-approved substances, or seeds of genetically modified organisms or derived from artificial seed technologies, allowed in organic production.

Primed Seed

Improved seed quality and vigor may be obtained with primed or enhanced seed. Primed seed is biologically altered through the addition of just enough water (and often some hormones) to allow the seed to undergo the early stages of germination without actually germinating. In this "primed" state, seed will germinate more rapidly and emerge more uniformly over a greater range of tem- peratures and soil moisture conditions. This translates to greater seedling vigor, uniformity, and rapid establishment.

Primed seed is best suited for direct seeding where adverse conditions may prevail during germination and emergence. However, enhanced seed use in the greenhouse is also cost effective. Uniformity of emergence alleviates "playing catch-up" within a flat due to uneven emergence. Rapid emergence means production programs (fertilizer, pesticides, etc.) can be quickly implemented. The reduction in wasted space from poor germination and in labor for thinning overseeded flats increases production efficiency. Greater efficiency means greater profitability.

Seed Storage

Care must be taken with seed to avoid injury and provide proper storage. Unused seed is best stored if the hermetic seal has not been broken. However, if open cans are to be stored, it is best to seal these cans in ziplock bags and store at 40°F-50°F preferably in a refrigerator used solely for seed storage. High temperatures and humidity are very harmful to seed. Humid conditions lead to increases in seed moisture, which reduce shelf life. Under proper storage conditions, vegetable seeds can remain viable for several years. The relative life expectancy of vegetable seed is presented in Table 2.

Field Seeding

Prior to seeding, the field should be leveled and worked to obtain a fine textured soil, free of clods and debris. Seedbed firmness, depth of planting, and available moisture are important considerations. Treated seeds should be used for protection against soil-borne diseases and insects during germination and seedling development. New seed film-coating techniques apply fungicides and pesticides in "no dust" formulations, which decrease the potential for worker injury by reducing absorption and inhalation risk.

See Table 3 for the number of seeds per unit weight for the individual crops.

Direct seeding can be accomplished with a variety of planters. The particular type of planter used will depend on the grower's preference, field conditions, equipment, and experience. Tractor speed is the key to success or failure of many stands. Lower speeds reduce injury to seeds (especially bean and pea) as they pass through the planter. A planting speed of 2-3 miles per hour is preferable.

In precision seeding, a single seed is planted at an exact plant spacing to achieve a uniform stand. Precision seeders vary in their approach to seed singulation (punched belts, vacuum plates, cups on armatures, etc.), and, again, choice depends on grower preference, seed to be planted, and seedbed conditions. Table 4 for the number of plants per acre at various row spacings.

Precision seeding requires uniformity in seed size both between species and within species. For example, large seed (snapbean) cannot be planted with the same belt/plate/cup as small seed (broccoli). Within species, two small seeds may be picked up where only one seed should fall. Sizing within seed lots may be accomplished during commercial separation or through pelletizing techniques. Pelletizing, where a seed is encased in a material that can be formed to produce a uniformaly sized pellet, has improved over the years to reduce the occurrence of slow and erratic germination compared to raw seed.

While pelletized seed is required by some precision seeders, many planters are capable of planting raw seed. Sized raw seed used in these planters has been an advantage for some growers. Plants from large seed will emerge first and grow faster than from small seed.

Tables

Table 1. 

Minimum official federal germination standards.1

Seed

(%)

Seed

(%)

Seed

(%)

Artichoke

60

Corn, sweet

75

Onion

70

Asparagus

70

Corn salad

70

Onion, Welsh

70

Bean, asparagus

75

Cowpea (Southernpea)

75

Pak-choi

75

Bean, broad

75

Cress, garden

75

Parsley

60

Bean, garden

70

Cress, upland

60

Parsnip

60

Bean, lima

70

Cress, water

40

Pea

80

Bean, runner

75

Cucumber

80

Pepper

55

Beet

65

Dandelion

60

Pumpkin

75

Broccoli

75

Dill

60

Radish

75

Brussels sprouts

70

Eggplant

60

Rhubarb

60

Cabbage

75

Endive

70

Rutabaga

75

Cardoon

60

Kale

75

Sage

60

Carrot

55

Kohlrabi

75

Salsify

75

Cauliflower

75

Leek

60

Sorrel

65

Celery/celeriac

55

Lettuce

80

Spinach

60

Chard, Swiss

65

Muskmelon

75

Spinach, New Zealand

40

Chicory

65

Mustard

75

Squash

75

Chinese cabbage

75

Mustard, spinach

75

Tomato

75

Chives

50

Mustard, vegetables

75

Tomato, husk

50

Citron

65

Okra

50

Turnip

80

Collards

80

   

Watermelon

70

1Adapted from Donald N. Maynard and George J. Hochmuth, Knott's Handbook for Vegetable Growers, 5th Edition (2006). Reprinted by permission of John Wiley & Sons.

Table 2. 

Approximate life expectancy of vegetable seeds stored under favorable conditions.1

Vegetable

Years

Vegetable

Years

Vegetable

Years

Asparagus

3

Corn salad

5

Parsnip

1

Bean

3

Cress, garden

5

Pea

3

Beet

4

Cress, water

5

Pepper

2

Broccoli

3

Cucumber

5

Pumpkin

4

Brussels sprouts

4

Dandelion

2

Radish

5

Cabbage

4

Eggplant

4

Roselle

3

Cardoon

5

Endive

5

Rutabaga

4

Carrot

3

Fennel

4

Salsify

1

Cauliflower

4

Kale

4

Scorzonera

2

Celeriac

3

Kohlrabi

3

Sea kale

1

Celery

3

Leek

2

Sorrel

4

Chard, Swiss

4

Lettuce

6

Southernpea

3

Chervil

3

Martynia

2

Spinach

3

Chicory

4

Muskmelon

5

Spinach, New Zealand

3

Chinese cabbage

3

Mustard

4

Squash

4

Ciboule

2

Okra

2

Tomato

4

Collards

5

Onion

1

Turnip

4

Corn, sweet

2

Parsley

1

Watermelon

4

1Adapted from Donald N. Maynard and George J. Hochmuth, Knott's Handbook for Vegetable Growers, 5th Edition (2006). Reprinted by permission of John Wiley & Sons

Table 3. 

Number of seeds per unit weight.

Crop

Seeds/unit weight

Crop

Seeds/unit weight

Asparagus

13,000 - 20,000/lb

Onion

 

Bean

 

bulb

105,000 - 144,000/lb

baby lima

1,150 - 1,450/lb

bunching

180,000 - 200,000/lb

fordhook lima

440 - 550/lb

Parsley

240,000 - 288,000/lb

snap

1,600 - 2,200/lb

Parsnip

7,500 - 12,000/lb

Beet

24,000 - 26,000/lb

Pea

1,440 - 2,580/lb

Broccoli

8,500 - 9,000/oz

Pepper

4,000 - 4,700/oz

Brussels sprouts

8,500 - 9,000/oz

Pumpkin

1,900 - 3,200/lb

Cabbage

8,500 - 9,000/oz

Radish

40,000 - 50,000/lb

Carrot

300,000 - 400,000/lb

Rutabaga

150,000 - 192,000/lb

Cauliflower

8,900 - 10,000/oz

Southernpea

3,000 - 4,200/lb

Celery

60,000 - 72,000/oz

Spinach

40,000 - 50,000/lb

Collards

7,500 - 8,500/oz

Squash

 

Cucumber

15,000 - 16,000/lb

summer

3,500 - 4,800/lb

Eggplant

6,000 - 6,500/oz

winter

1,600 - 4,000/lb

Endive, escarole

22,000 - 26,000/oz

Sweet corn

 

Kale

7,500 - 8,900/oz

normal, sugary enhanced

1,800 - 2,500/lb

Leek

170,000 - 180,000/lb

supersweet

3,000 - 5,000/lb

Lettuce

 

Tomato

 

leaf

25,000 -31,000/oz

fresh

10,000 - 11,400/oz

head

20,000 - 25,000/oz

processing

160,000 - 190,000/lb

Muskmelon

16,000 - 19,000/lb

Turnip

15,000/oz

Mustard

15,000 - 17,000/oz

Watermelon

 

Okra

450 - 550/oz

small seed

8,000 - 10,400/lb

   

large seed

3,200 - 4,800/lb

Table 4. 

Plants per acre at various between and in-row spacings.

Distance between rows (inches)

In-row spacing (inches)

2

4

6

8

10

12

14

16

18

24

30

36

48

Number of plants per acre

7

448,046

224,022

149,348

112,011

89,609

74,674

64,006

           

12

261,360

130,680

87,120

64,340

52,272

43,560

37,337

32,670

29,040

21,780

17,424

14,520

10,890

18

174,240

87,911

58,080

43,560

34,848

29,040

24,891

21,780

19,360

14,520

11,616

9,680

7,260

21

149,354

74,675

49,782

37,337

29,870

24,891

21,335

18,669

16,594

12,446

9,957

8,297

6,223

24

130,860

65,405

43,560

32,670

26,136

20,908

17,424

16,335

15,520

10,890

8,712

7,260

5,445

30

104,544

52,272

34,848

26,136

20,908

17,424

14,934

13,068

11,616

8,712

6,970

5,808

4,356

36

87,120

43,560

29,040

21,780

17,424

14,520

12,445

10,890

9,680

7,260

5,808

4,840

3,630

42

74,674

37,337

24,891

18,668

14.934

12,446

10,667

9,334

8,297

6,223

4,978

4,148

3,111

48

65,340

32,673

21,780

16,335

13,068

10,890

9,334

8,167

7,790

5,445

4,356

3,630

2,723

60

   

17,424

13,068

10,538

8,712

7,467

6,534

5,808

4,356

3,484

2,901

2,178

72

   

14,520

10,890

8,712

7,260

6,223

5,445

4,840

3,630

2,904

2,420

1,815

84

   

12,455

9,334

7,467

6,222

5,334

4,667

4,148

3,111

2,489

2,074

1,555

96

   

10,890

8,167

6,534

5,445

4,667

4,084

3,630

2,722

2,178

1,815

1,361

Footnotes

1.

This document is HS713, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date June 1995. Revised September 2007. Reviewed November 2013. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Bielinski M. Santos, assistant professor, Gulf Coast Research and Education Center, UF/IFAS Extension, Gainesville, FL 32611. The Vegetable Production Handbook for Florida is edited by S. M. Olson, professor, NFREC-Quincy, and E. H. Simonne, associate professor, UF/IFAS Extension.

The use of trade names in this publication is solely for the purpose of providing specific information. It is not a guarantee or warranty of the products named, and does not signify that they are approved to the exclusion of others of suitable composition. Use pesticides safely. Read and follow directions on the manufacturer's label.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.