ASA Southern Branch 2008 Annual Meeting
February 3-5, 2008
Dallas, TX
Monday, February 4, 2008 - 10:35 AM
Evaluation of Polymer-Coated Urea as an Alternative to Preflood Urea for Delayed-Flood Rice.
Bobby Golden, Nathan Slaton, Russell Delong, and Richard Norman. University of Arkansas, 1366 W Altheimer Drive, Fayetteville, AR 72704
Nitrogen fertilization of rice (Oryza sativa L.) in the direct-seeded, delayed-flood production system relies heavily on aerial application of N-fertilizer. The ability to apply N-fertilizer with ground equipment before seeding would benefit rice producers by reducing N-application costs. The research objective was to evaluate rice growth and yield as affected by several polymer-coated urea fertilizers applied preplant and compared to the standard practice of urea applied post-emergence before flooding. In 2007, three experiments were established on silt-loam soils. Three polymer-coated urea fertilizers (ESN, Polyon 41, and Polyon 42; Agrium Inc.) were broadcast at total-N rates ranging from 34 to 168 kg N ha-1 immediately before drill seeding ‘Francis’ rice. Urea was applied post-emergence 31-39 d after planting at identical total-N rates as the polymer-coated fertilizers. Grain yield was determined by harvesting the middle four rows of each plot. Each experiment was arranged as a randomized complete block design with a 4 (N source) × 5 (total N rate) factorial treatment arrangement plus two unfertilized controls (0 kg N ha-1). Rice grain yield increased non-linearly across N rates with all N source and site combinations sharing a common quadratic coefficient, all N sources within a site sharing a common linear coefficient, and each N source × site combination having a unique intercept that was different than zero. The linear coefficients suggest grain yields increased similarly among N sources within each site. At two sites intercept coefficients for urea were greater than for polymer coated urea fertilizers indicating yields were greater per unit of N applied as urea preflood. Nitrogen release curves show the evaluated polymer-coated urea fertilizers release N too rapidly (ESN) or slowly (P41 and P42) to maximize early-season growth of rice produced in the delayed-flood management system, but show promise for this technology.