Physiological response of agronomic crops to nutrient management and abiotic stress

In Oklahoma, where resource availability varies throughout the growing season, the growth and development of grain sorghum often depend on tillers influenced by delayed nitrogen (N) application and planting density. However, their combined impact remains insufficiently documented. This study aimed to evaluate the physiological response of sorghum to delayed N application and assess the role of planting density. Field trials were conducted over three years at Chickasha (21,2022), Bixby (2022), and Perkins (2023), testing three N application timings: at planting, 21 days, and 42 days after planting and two planting densities (52,000 and 77,000 plants ha-1). Results indicated no significant differences in growth or yield among N timings or planting densities. However, delayed N application reduced tiller counts and panicle dimensions. These findings suggest growers can delay N application up to 42 days after planting without significantly impacting yield, but further delays could reduce productivity. The second chapter focused on the germination performance and early growth of six cover crops: Barley, Rye (Elbon, Maton, Oklon), Triticale, and Wheat Ok Corral (control) under four temperature regimes (20C, 25C, 20C, and 25C) at 7 and 14 days after sowing. Germination trials measured hypocotyl length, root length, and surface area. Results showed that temperature significantly influenced germination and early growth, with optimal performance at 25C and 30C. rye Maton Exhibited the highest growth metrics, demonstrating strong adaptability, while Triticale and Wheat Ok Corral consistently showed lower performance, especially at extreme temperatures of 20C and 35C. These findings underscore the importance of temperature in early-stage growth and provide insights into selecting cover crops suitable for varying environmental conditions. The last chapter assessed whether outline notes improved note-taking confidence and reduced anxiety, particularly post-COVID-19. A survey among 264 pre-COVID and 277 post-COVID students in an introductory plant and soil systems course (PLNT 1213) revealed that outline notes with 30% blanks helped students stay focused during lectures. Post-COVID, there was a 42.5% decrease in note-taking anxiety, suggesting improved comfort in learning environments. The study highlights that structured course notes reduce anxiety and improve students’ confidence and focus, demonstrating the effectiveness of combining pre-made and handwritten notes.