Kothari, Kritika (2019-04). Assessing Climate Change Adaptation Strategies for Major Crops in Texas: A Case Study in Two Regions. Doctoral Dissertation.
Thesis
Agriculture is arguably the most vulnerable sector to climate change (CC). Producers in Texas not only face challenges from CC, but also from dwindling irrigation water supplies. This study was aimed at assessing the CC impacts on crop production and evaluating adaptation strategies in two agricultural regions in Texas: Texas High Plains (THP) and Edwards Aquifer (EA) region. Crop yield and irrigation water use for sorghum, cotton, winter wheat, and corn (for EA region only) were assessed under multiple CC scenarios using the CMIP5 climate data projected by nine Global Climate Models. Special emphasis was placed on grain sorghum in the THP because it was not studied well before despite its lower water requirement. Scenario-based analyses were conducted using the Decision Support System for Agrotechnology Transfer (DSSAT) model at Bushland, Halfway and Lamesa in the THP, and with the Soil and Water Assessment Tool (SWAT) model in the Lower Medina Watershed in the EA region. Optimum thresholds to start and stop irrigation for grain sorghum in the THP were found to be 50% and 85% of plant available water content, respectively. Deficit irrigation during early reproductive stages optimized irrigation water use efficiency. Simulated sorghum yield and irrigation water use in the mid-century (2036-2065) decreased within 2-14% and 3-9 %, respectively in the THP compared to the baseline (1976-2005). Cotton and winter wheat yield increased (2-21%) at Bushland and Halfway and decreased (2- 7%) at Lamesa. Cotton irrigation water use increased (5-8%) and wheat irrigation decreased (0.4-5.5%) at all sites. The differences across sites were attributed to the differences in soils and climate. Among the genetic traits tested, high yield potential was found to be beneficial for most crops and sites, and long maturity cultivar increased irrigation water use significantly. Changing root physical and hydraulic properties had mixed effect across sites and crops. For the EA region, increase in yield (5-47%) and reduction in irrigation water use (23-42%) was simulated for the four crops considered, mainly due to CO2 fertilization. Out of the heat tolerance and deep rooting adaptations evaluated, increasing root depth by 20% percentage showed substantial benefits.
