Pokhrel, Pramod (2020-06). Agronomic Performance and Modeling of Bioenergy Feedstock Crop Growth and Development in the Texas Rolling Plains. Doctoral Dissertation.
Thesis
Energy canes (Saccharum spp. hybrid) and energy sorghum (Sorghum bicolor L. Moench) have the potential to adapt in broader agroclimatic conditions and produce higher biomass yield. The first study was conducted to evaluate the agronomic performance of four energy cane genotypes (TUS11-62, TUS11-58, TCP10-4928, and Ho 02-113) in the Texas Rolling Plains. The results showed that the average biomass yield of plant cane, first ratoon, and the second ratoon were 20.16 t ha?1 , 40.37 t ha?1 , 26.4 t ha?1 respectively. Feedstock genotype did not affect biomass yield except plant cane in 2016. Severe winter kill resulted in the yield decline in the second ratoon. The second study was conducted to test the feasibility of the Decision Support System for Agrotechnology Transfer (DSSAT) - CANEGRO model to simulate the growth and development of energy canes. Among all variables measured, model predictions were best for stalk height and aboveground biomass yield. The simulated biomass yield and stalk height were within +-15% to observed values. The third study was performed to simulate the effect of change in climatic variables on biomass yield of energy cane in the Texas Rolling Plains. An increase in temperature and decrease in precipitation decreased biomass yield. Simulation results showed that the aboveground biomass yield of plant cane ranged from 11- 14 t ha?1 in irrigated and 4-9 t ha?1 in rainfed conditions and first ratoon ranged from 24 - 38 t ha?1 in irrigated and 10 - 21 t ha?1 in rainfed conditions respectively. Yield loss was higher when daily maximum and minimum temperature increased by 2?C and precipitation decreased by 20%. The fourth study was conducted to evaluate the biomass yield and canopy characteristics of energy sorghum cultivars; ES 5140 and ES 5200. Additional water input (67%) in high irrigation treatment increased the plant height by 30%, water use efficiency (WUE) by 42%, and final biomass by 100% compared to low irrigation treatment. A strong linear relationship between leaf area index (LAI) (R2 = 0.82) and exponential relationship between LAI and normalized difference vegetation index (NDVI) (R2 = 0.82) were observed. Both sorghum hybrids showed similar light interception characteristics (light extinction coefficient of 0.41 in ES 5140 and 0.42 in ES 5022).
