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Drought Can Impact Soybean Germination


Published: Friday, May 17, 2013

The following is from Mike Staton, Michigan State University Extension soybean educator.

While most of the soybean seed sold in Michigan will have warm germination rates at or above 90 percent, there have been reports of isolated seed lots with warm germination tests as low as 80 percent.

The reasons for lower warm germination test scores are the drought conditions during the 2012 season and the low moisture content of the seed at harvest. Mechanical damage to the seed coat or the embryo is more likely to occur when dry seed is harvested and handled. Ask your seed supplier for the moisture content of each of your seed lots or test them yourself.

Soybean seed that is below 10 percent moisture is extremely fragile and is at risk of incurring additional mechanical damage during seed treatment operations.

Michigan State University Extension says the warm germination test is an excellent indicator of how the seed will germinate under ideal conditions. However, it does not predict how the seed will germinate and emerge in cool or stressful soil conditions. Some type of vigor test such as the cold germination or the accelerated aging test is required to determine this.

The vigor test results should not be used to estimate germination percentages of a given seed lot, but can be used to compare and rank the ability of different seed lots to germinate and emerge under stressful soil conditions. Vigor test results are not typically provided to producers with the seed. The main reason for this is that there is not an industry-wide standard for testing protocols and reporting results.

Vigor tests should be run on all seed lots having warm germination scores of 85 percent or less. This is important as seedling vigor deteriorates faster than warm germination. Samples can be submitted to the Michigan Crop Improvement Assn. in Okemos, Mich. The cold germination test takes 14 days and will cost $12 per sample. The accelerated aging test takes at least 10 days and costs $13 per sample.

Producers can use the vigor test scores to rank the seed lots and determine their planting order. Always plant your highest quality seed first and your poorest quality seed last. Avoid planting lower quality seed into cold, wet soils, poor seed beds or high residue conditions that may reduce seed-to-soil contact. Fungicide seed treatments will help protect the seed and preserve the existing quality of the seed. However, they cannot improve the quality of the seed.

Producers should always use the warm germination score listed on the tag to adjust their planting populations. A simple method for accomplishing this is to divide your desired harvest population by the warm germination score and then divide again by the warm germination score to estimate actual emerged seedlings.

For example, if seed having a warm germination score of 85 percent will be planted and a harvest population of 110,000 plants per acre is desired, then 152,249 seeds per acre should be planted (110,000 0.85 0.85 = 152,249).

While it is always important to handle soybean seed carefully, this becomes even more important when handling dry or poor quality seed. Operate all equipment used to transport bulk seed slowly and keep augers as full as possible. Reduce the height that seed falls from augers and conveyors and never drop bagged seed.

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