|Mitchell, Robert - Rob|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2011
Publication Date: 1/27/2012
Publication URL: http://handle.nal.usda.gov/10113/54072
Citation: Mitchell, R., Vogel, K.P. 2012. Germination and emergence tests for predicting switchgrass field establishment. Agronomy Journal. 104:458-465.
Interpretive Summary: Switchgrass is an important warm-season grass for use as a potential bioenergy crop in the USA. The economic viability of growing switchgrass for bioenergy hinges on successful stand establishment in the seeding year. The main causes of poor or failed switchgrass establishment are lack of rainfall during the establishment period, weed competition due to poor weed control practices, improper planting procedures including seedbed preparation and planting depth, and poor seed quality. All factors except rainfall can be addressed by management. Our objective was to evaluate different seed quality tests for their ability to predict actual field establishment to reduce risks of catastrophic failure during switchgrass stand establishment. Functionally, a seedlot establishment test is the pure live seed for a seedlot based on the number of seeds per ounce for that specific seedlot. Our working hypothesis was that seeding switchgrass based on seedlot establishment tests will increase the ability to reliably establish switchgrass stands when compared with existing practices, regardless of the quality of different seedlots. The pure live seed method was a poor predictor of field establishment. A simple seedlot test such as the number of seeds per ounce that emerge through 1.5-inches of sand was the best predictor of field establishment and provides significant benefits in both stands and initial biomass yields with little additional cost. Stands on which planting rates were based on seedlot establishment tests that included stress tests were better predictors of establishment than the standard pure live seed method. Switchgrass seeding rates based on seedlot establishment tests are recommended to reduce risks of failure during stand establishment.
Technical Abstract: The effect of switchgrass (Panicum virgatum L.) seed quality tests on field establishment has not been addressed. Our objective was to evaluate the ability of seed quality tests to predict field establishment. Standard Association of Official Seed Analysts (AOSA) tests are based on the percentage of seeds in a seedlot that germinate under standard laboratory conditions whereas the Seedlot Establishment Tests (SET) are based on the number of seeds that emerge g-1 of seed using different germination or stress test conditions. SET was determined using six laboratory tests and the results validated in three replicated field trials. Treatments were: 1) AOSA pure live seed (PLS) test assuming 858 seeds g-1; 2) AOSA test with no pre-chill; 3) AOSA test with pre-chill; 4) heat stressed at 50 oC for 12 h; 5) emergence from 4 cm of sand; and 6) heat stressed plus emergence from 2 cm of sand. Data from non-control tests were on a SET/g basis. Field trials were seeded at 200 PLS or SET/m2. Seedlots differed for all laboratory tests. Field establishment differed by seed quality test on which seeding rate was based. The PLS method was a poor predictor of field establishment. The SET using emergence from 4 cm of sand was the best predictor of establishment. Stands on which planting rates were based on SET that included stress tests were better predictors of establishment than the standard PLS method. Switchgrass seeding rates based on SET are recommended to reduce risks of failure during stand establishment.