AbstractsBiology & Animal Science

While silicon (Si) fertilization is widely practiced in paddy rice production, the establishment of critical soil Si levels has remained understudied. This study was undertaken to: 1) determine the critical soil Si level for rice production in Louisiana using different extraction procedures, and 2) document the relationship between plant-available Si and select essential plant nutrients in soil and their uptake by rice. Field trials were established at 12 sites across Louisiana from 2013 to 2015. Si was applied as silicate slag (SiO3, 14% Si) at the rates of 0, 1, 2, 4, 6, and 8 Mg ha-1. Agricultural lime was also applied at (2 and 4 Mg ha-1) to evaluate the liming effect of slag in the main treatments. Treatments were arranged in a randomized complete block design with four replications. Soil samples collected at harvest were analyzed for pH, soil Si, heavy metals and plant-essential nutrients. Rice straw and panicle were analyzed for Si content; while panicle was analyzed for heavy metals and plant-essential nutrients. Analysis of variance and correlation analysis were performed for all measured variables using SAS 9.4. Slag application significantly increased the soil pH up to 1.4 units (p<0.05) in several sites. Rice grain yield was significantly (p<0. 1) increased in several sites by slag application, with the highest average grain yield obtained at application rates ranging between 1-4 Mg ha-1. The critical Si levels in soil ranged from 11.8 mg kg-1 (0.01 M CaCl2) to 771 mg kg-1 (0.1 M citric acid). The Si content in rice straw was negatively correlated with the panicle P (r = -0.25), S (r= -0.38), As (r = -0.33) and Cd (r = -0.39) but positively correlated with its Mn (r = 0.35) content. In general, soils with high initial Si and pH gave minimal responses to Si fertilization, while the Si content of soils with low initial Si was increased. Soil Si did not interfere with the uptake of most plant-essential nutrients, but the decrease in As and Cd contents of panicle shows that Si fertilization could be essential for improving grain quality of rice. Advisors/Committee Members: Tubana, Brenda S. (chair), Motsenbocker, Carl (chair), Harrell, Dustin (committee member).