Improved seeding technologies demand high quality seed

Posted by Duncan Ag, courtesy of Professor John Hampton on 17 July 2014

Improvements in seeding technologies for crop and pasture establishment have delivered increasing environmental and financial benefits through:

  • better preservation of soil structure
  • improved soil organic matter
  • reduced soil erosion
  • improved soil aeration
  • improved water use efficiency
  • reduced fuel use.

Seeders are now available which are equally suited to both conventional cultivation and reduced tillage. Unfortunately, seed quality can fail to match the performance capacity of the seeding equipment which – together with the operator - often get blamed for disappointing plant establishment.

So, why may a seed line have emergence problems?
The obvious answer is poor germination. While seed lines with poor germination do exist, it is unusual for them to be used in New Zealand because the vast majority of seed lines have high germination (≥ 90%). But large emergence differences can occur even when high germinating seed lines are sown, as reflected in the following table.

Field emergence of nine forage and nine vegetable brassica seed lines all with a germination of 91% or higher following three sowings at the same site:

 Sowing no.

10cm soil temp

Forage Species Field Emergence

Vegetable Species Field Emergence

 

 (oC)

Mean (%)

Range (%)

Mean (%)

Range (%)

1

4.4

72

16-92

64

29-79

2

8.7

72

42-89

67

55-80

3

9.2

69

6-85

79

71-87

In the presence of seed bed stress (in this case low temperature) some high germinating seed lines struggled to emerge while others did not. The reason for these differences is due to another seed quality component – seed vigour.

Seed vigour determines the ability of the line to cope with environmental stress. Differences in the vigour of high germinating seed lines can be explained by the process of seed ageing, or physiological deterioration. This deterioration can begin before seed harvest and is particularly influenced by high temperature during seed development. Seeds lose vigour before they lose the ability to germinate. Seed lines which have high germination but emergence problems are low vigour lots, while those with good emergence are high vigour lots.

It is important to note that if seed bed conditions are benign (i.e. no stress), then both low and high vigour seed lines will be expected to have good emergence. Only when seed bed stress occurs will seed vigour have a major impact on emergence.

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