Corn seedling emergence
Germination testing, especially the cold test, is probably the best predictor of successful emergence in the field. Comparing lab results with field emergence percentages is not easy because of the other variables involved in success. Cold tests are the best to reflect growth in the low temperatures that most corn seed faces when planted in temperate zones. Damage or weakness of cellular membranes during imbibition will show that some seed are not germinating as quickly as the less damaged seed.
Slight differences in soil micro-environments within a few feet in the field can have a drastic effect on the weaker seed. Tighter soils can have oxygen deficiencies, higher water content and more resistance to growth of the coleoptile as it pushes upwards. Minimum tillage debris on soil surface prolongs the colder temperature. Small differences in planting depths and consistency of seed drops with planters also make field assessment of field germinations of multiple seed lots difficult.
Ideally a germination lab should consistently compare its results with field emergence. This is not easy because such a test should include multiple replications within a field and across several fields. Comparison of lab tests on referee samples by 20-40 public and private labs usually show warm test variance of 4-5% on generally high germinating seed and of up to 10% on cold tests. Some of these are ‘official’ labs that prescribe to similar methods but subtle differences between labs, or even among samples apparently account for the differences in results. The complexity of comparing with field results further inhibits the development of the perfect lab test for predicting field emergence in all conditions. On the other hand, poor performance in most cold tests suggests that a seed lot is more likely to have field emergence problems. A company eventually attempts to establish acceptable cold test result standards from a lab that is most frequently associated with reliable field emergence. It is important that the standard is relevant to that lab tests and not necessarily to other labs.
Seed companies and growers agree with the desire that seed germination quality should not be a factor in performance of the hybrid but predicting this is not perfect.
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About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.