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Doctor of Philosophy (PhD)
Plant, Soil & Insect Sciences
Year Degree Awarded
Stephen J. Herbert
Agronomy and Crop Sciences
Switchgrass (Panicum virgatum L.) is a C4-grass indigenous to North America being considered as the “model” energy crop. Switchgrass is difficult to establish and first-year stand failure often challenge the large scale production of switchgrass. Reliable establishment methods and effective weed management practices to produce a harvestable biomass in the establishment year are required. Also, to maximize the economic viability of switchgrass production, appropriate nutrient management and harvests are needed. Thus, we conducted researches to improve switchgrass establishment and production. These studies ranged from finding the most promising switchgrass variety to adjusting switchgrass seeding rate, determine the most appropriate seeding date, seeding methods, weed management, nitrogen application, and harvest management.
Currently Cave-in-Rock is a highly suggested upland variety for northern region of United States. Results of our variety trials both at establishment and production level indicated that Carthage and Shawnee could also be considered as promising varieties in northern regions of United States. In a four-year study, Carthage consistently produced higher biomass yield compared with other varieties. A vigor test trial was suggested for adjusting switchgrass seeding rate and we found significant differences between the required seeding rate for producing acceptable first-year biomass in fertile soils and marginal soils. While approximately 7 kg ha-1 seeding rate might be sufficient for fertile soils, 14 kg ha-1 might be required to produce enough established seedling for the same biomass production in a marginal soil. An early planting of switchgrass was not as effective as a late planting in weed suppression but plants were more advanced morphologically thus, produced acceptable biomass yield with root system which ensures successful second-year production. Among cover crops, oat outperformed others (Fallow and Rye) with both suppressing weeds and improving switchgrass establishment. Results suggested drastic differences between no-till planting and seeding with cultipacker seeder where no-till planting into oat produced significantly higher biomass yield compared with cultipacker seeder. A firm seedbed is also another desirable method of planting where significantly improved switchgrass establishment and production was observed with 2 times rolling/cultipacking after seeding. Our findings indicated that application of herbicides is strongly required in the establishment year where a Broad Spectrum application of atrazine, quinclorac, 2,4-D, and dicamba improved switchgrass establishment through effective control of weeds. We found a late-fall harvest could improve switchgrass quality for combustion (less moisture, ash, and nutrient content) without yield reduction for many years. When switchgrass was harvested in late-fall, no response to N application was found.
Overall, it is proposed that a no-till planting of switchgrass into oat cover crop with herbicide application planted in early-June could provide a successful stand and later, a late-fall harvest without any N application could maintain crop productivity with acceptable biomass yield and quality for several years.
Sadeghpour, Amir, "ASSESSING BEST MANAGEMENT PRACTICES FOR IMPROVING SWITCHGRASS ESTABLISHMENT AND PRODUCTION" (2014). Doctoral Dissertations. 128.