| Agricultural intensification is often posited as a critical strategy to meet growing food demand and reduce world hunger. However, agricultural intensification also comes with downsides. This dissertation seeks to better understand the role of agricultural intensification in meeting the dual food and environmental challenges. Chapter 2 examines the effects of nitrogen (N) fertilization and conservation tillage on measured soil organic carbon (SOC) stocks in the agricultural soils of the United States. N fertilization positively affects estimated SOC, but the magnitude differs due to varying cropping systems: when cropping frequency increases one, measured SOC under fertilized treatment increases by 6.5%. Conversion from conventional tillage to no tillage increases SOC stock. Moreover, the longer the time in no tillage, the greater the amount of SOC compared to conventional tillage. This study confirms that adoption of N fertilization and conservational tillage can potentially increase measured SOC if management practices are designed properly. Chapter 3 explores the relationship between changes in agricultural yield and cropland area. The yield-cultivated area dynamics are evaluated under the context shaped by variables that can potentially affect cropland extent. Cropland area increases at a much lower rate than total agricultural production; however, actual declines in cultivated area only occur between 1980 and 1985. The amount of CRP area has a positive impact on land-sparing, whereas USDA farm subsidies and agricultural commodity prices negatively impact land-sparing. In Chapter 4, I analyze the spatial patterns of agricultural expansion and crop rotation systems in the Midwest Corn Belt during 2006-2013 when there is a doubling of corn and soybean prices. I find that corn and soybean continuously expand whereas most other crops shrink. Grassland is the most affected, with a total net loss of 3.9 million acres. Grassland loss is mainly concentrated along the western margin of the Corn Belt, an area with higher levels of drought risk. Wheat to corn/soybean conversion occurs in top wheat-producing states, totaling 2.5 million acres. With respect to agronomic practices, the amount of corn planted on corn increased by 23% between 2006 and 2013, whereas the amount of continuous soybean cropping fluctuated over time. |
