Agriculture Reference
In-Depth Information
Summary of procedures for conductivity test:
1. Determine the moisture content; if <10% or >14%, adjust it according to AOSA Seed Vigor
Testing Handbook.
2. Count and weigh the appropriate number of seeds and soak for approximately 24 h in distilled
water at 20 or 25°C.
3. Measure the electrical conductivity of the electrolytes in the steep water and report it per gram of
seed (µS/cm/g).
Cold Test
The cold test of corn is the oldest and most popular vigor test in the United States (Ferguson-Spears, 1995;
Baalbaki and Fiedler, 2008; Tables 8.3, 8.4) and can be used for other crops such as soybean (Zorilla et al.,
1994), onion (Bekendam et al., 1987), and sweet corn (Wilson and Trawatha, 1991; Borowski et al., 1991).
It is used as a routine vigor test on dry edible beans in Michigan. Differing perspectives exist concerning
how to conduct and interpret data from a cold test (Gutormson, 1995; Nijenstein, 1995). Cold test results
are dificult to standardize among laboratories. Part of this is attributed to variability in soil moisture con-
tent where reductions in seed germination occur above 34% soil moisture content (Nijenstein, 1988). Small
differences in temperature during the cold test also adversely affect results. Bruggink et al. (1991) reported
that 8.8°C was most effective for detecting vigor differences in corn and above 15°C, no differences were
detected. The use of temperature regimes inappropriate for the crop being tested is another factor that may
limit the cold test's effectiveness. One approach to making the cold test more widely applicable to many
crops is establishing speciic temperature regimes for speciic crops and varieties. Despite these issues,
the cold test remains valuable and standardization efforts are continuing. When soil type and soil moisture
content varied, ranking of nine corn seed lots did not change even though standard germination percentages
were affected (Nijenstein, 1986). Byrum and Copeland (1995) found that under carefully controlled condi-
tions, cold test results from various laboratories had as little variation as standard germination test results.
Today, the cold test is performed on almost all seed corn sold in the United States.
Cold test results have been successfully used to assess ield performance and the test has the ability to
rank seed lots based on vigor differences. Several studies have repeatedly demonstrated the close associa-
tion of cold test results with ield emergence of corn (Bekendam et al., 1987; Martin et al., 1988; TeKrony et
al., 1989), soybean (Zorilla et al., 1994), cotton (McDonald et al., 1978), carrot (Pereira et al., 2008), squash
(Casaroli et al., 2006) and rice (Patin and Gutormson, 2005).
Beyond assessment of ield performance, other uses of the cold test include:
1. Evaluate fungicide eficacy;
2. Select genetic material demonstrating an ability to germinate in cold, wet soil;
3. Evaluate physiological deterioration resulting from prolonged or adverse storage, freezing injury,
immaturity, injury from drying or other causes;
4. Measure the effect of mechanical damage on germination in cold, wet soil;
5. Select seed lots for early spring planting; and
6. Provide a basis for adjusting planting rates for individual seed lots.
Many different methods are used for conducting the cold test among laboratories. All methods gener-
ally expose seeds to cold temperatures (10°C) in non-sterile ield soil at approximately 60-70% of water
holding capacity for 7 days when the seeds are removed for a grow-out period of 4 to 7 days at ideal germi-
nation conditions (25°C for corn). During the cold period, microorganisms present in the non-sterile ield
soil colonize low quality seeds which are weakened during germination at favorable temperatures resulting
in low germination percentages. To accomplish this, varying seed:soil contact approaches can be used.
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