Guayule (Parthenium argentatum Gray) is a desert adapted shrub, and a source of domestic natural rubber. Guayule requires fewer production inputs (namely water, fertilizer, and pesticides) to produce economic yields than typical crops grown in the southwestern United States. This is of immense importance due to the recent reduction in access to Colorado River water for irrigation in Central Arizona. Growers are now making decisions to alter crop rotations and fallow large portions of their land. This low water use crop may provide an attractive alternative cropping solution. While guayule has been grown at some level in the US since the early 1900’s there are still many questions around the most economical practices for its production. The first study in this thesis clarifies the role of nitrogen fertilizer in guayule growth and developed a field tool for diagnosing nitrogen deficiency. The second study developed a clearer understanding of the different root systems guayule produces when grown by transplanted seedlings versus direct-seeding into the soil. Together they increase our understanding of how to best grow this crop
