Field evaluation of rice (Oryza sativa L.) agronomic traits for early planting in Arkansas

An early planting date study of rice (Oryza sativa L.) was conducted in 2005 and 2006 which included divergent rice cultivars in order to identify agronomic traits that help in selection for stresses that are frequently encountered before optimal planting dates. Planting dates (PD) for both years began 02 March and were spaced approximately two weeks apart. The research objectives were to determine the effects of early planting on (1) plant growth and development (days to emergence, plant stands, days to 50% heading, plant height and lodging); (2) rough rice grain yield (RRGY) and selected yield components [(number of panicles/m2, percent filled grains (% FG), percent effective tillers (% ET), thousand kernel weight (TKW) and harvest index (HI)]; and (3) milling quality (total and head rice yield, TRY and HRY) and grain quality (rough and brown rice grain length, width and length to width ratio).;PD did result in reduced grain yield at PD 1. In general, the earliest PD resulted in the numerically highest number of % FG and TKW with both being affected by a genotype by environment interaction but TKW was the least affected. % ET and HI were only affected by a cultivar main effect. Average HRY ranged from 52% in PD 2 to 55% in PD 4. Amylose was not affected by early planting.;PD 1 resulted in a 19 d delay in 50% emergence compared to PD 4. Early planting resulted in visually reduced plant stand in PD 1 and there was a general trend toward higher stands at later PD. The earliest PD resulted in a 28 d delay in 50% heading from emergence (DFE) compared to PD 4. Plant height was not affected by early planting and plant lodging was affected by a significant genotype by environment interaction due to untimely harvest of plot in PD 1.