No abstract

Hail storm damage to the cotton (Gossypium hirsutum L.) plants can destroy vegetative and reproductive structures, modify canopy architecture and impact lint yield. Field studies were conducted at University of Arizona Maricopa Agricultural Center in 2011, 2012 and 2013 to examine cotton plant architecture changes and compensatory growth in response to removal treatments of uppermost nodes on main stem (terminal bud removal, 2 node removal and 4 node removal) as simulation of hail damage at the node 2, 4, 8, 12, 16 and 24 growth stages. Main stem node removal caused significant decrease in leaf area and biomass, especially at early growth stages. However, significant lint yield reduction only occurred by removing 2 nodes at the node 4 stage and removing 4 nodes at the node 8 stage in 2011, removing terminal bud at the node 12 stage in 2012 and removing terminal bud, 2 nodes and 4 nodes at the node 8 stage in 2013. The lint yield reduction did not exceed 13 % in all three growing seasons. Yield loss due to main stem node removal was mainly compensated by increased boll number on the vegetative branches at early growth stages and on fruiting branches at late growth stages. Yield compensation from vegetative branches increased with number of main stem nodes removed. This study suggests that the cotton crop has a strong compensatory ability to plant structure damage due to its indeterminate growth and longer growing season in the region.

Th e plant root system is earmarked as key to the next Green Revolution. Field experiments were conducted in 2010-2011 and 2011-2012 to determine the impact of N management system on root growth in cultivar Pavon 76 (Pavon), bread wheat (Triticum aestivum L.), and wheat-rye (Secale cereale L.) translocations Pavon-1RS.1AL (1RS.1AL), and Pavon-1RS.1BL (1RS.1BL). Th e three genotypes were examined under organic N (manure) and synthetic N fertilizer regimes each at a high and low rate, and an unfertilized control. Th e translocated genotype 1RS.1BL had 23 and 9% higher total root biomass than Pavon in the 2010-2011 and 2011-2012 growing seasons, respectively. Compared to Pavon, root mass of genotypes 1RS.1AL and 1RS.1BL was 23.3 to 55.9 g m -3 higher in the top 40 cm of the soil profi le and 15.1 to 31 g m -3 higher in soil profi les below 40 cm. Th e 1RS translocations also had higher root dry mass than Pavon under synthetic N, low organic N and the unfertilized control. Mean genotype grain yields for both growing seasons ranged from 3.8 to 4.1 Mg ha -1 and there were no diff erences between 1RS lines and Pavon. Th ese studies show that the root system was enhanced without a subsequent loss of yield in a high yield potential environment; similar research is needed for low wheat yield potential environments.