Date of Award
Master of Science
Crop Production and Physiology
Eastern gamagrass produces low seed yields resulting in high seed costs. Nitrogen application and defoliation management have been found to increase reproductive tillers and seed yields for other warm-season forage grasses. This study was conducted to determine whether nitrogen and defoliation management could be manipulated to increase harvestable seed yields on two cultivars of eastern gamagrass. Cultivar had the greatest influence on seed yield of any treatment in this study. Pete produced greater total numbers of terminal and lateral inflorescences and cupules than Iuka in both years. Reductions in seed production occurred with spring defoliation in the cultivar Iuka for the first year of the study and Pete during both years. In 2000, lateral cupules for both cultivars were decreased by 20% during the peak seed load due to spring defoliation, but cupules shattered less rapidly from the defoliated plants. In 2001, cupule loads for spring-defoliated plants were not significantly different from non-defoliated plants. These results suggest that a pre-heading forage harvest can be taken if the producer is willing to accept moderate reductions in seed yield. Spring defoliation may delay seed shattering; so defoliated fields could be harvested later than non-defoliated fields. Addition of 56 kg ha−1 nitrogen increased seed load in the second year of the study. However, seed yield did not increase at nitrogen rates above this level. An increase in nitrogen from 112 to 224 kg ha−1 decreased cupule numbers. Optimal harvest time was approximately two weeks after terminal cupules began shattering. Seed harvested one week earlier than this had 5 to 15 percentage points more immature seed. Cupule numbers were 13 to 20% less if seed harvests were taken one week later than this date.
Bryce Micheal Lemke
Lemke, Bryce Micheal, "Maximizing seed harvest in eastern gamagrass (Tripsacum dactyloides L.)" (2002). Retrospective Theses and Dissertations. 20140.