Wednesday, November 15, 2006
285-13

An Evaluation of Early Season N for Rice Production on Clay Soils.

Timothy W. Walker, Mississippi State Univ, Delta Center, PO Box 197, Stoneville, MS 38776, Brian V. Ottis, Univ of Missouri, Portageville, MO 63873, Richard J. Norman, Univ of Arkansas, Plant Science Bldg 115, Fayetteville, AR 72701, and Jason Bond, Louisiana State Univ.-Rice Res. Stn, P.O. Box 197, Stoneville, MS 38776.

 

An experiment was conducted on clay soils in AR, MO, and MS for a total of six site years to determine the effects of applying early season (ES) N on rice at the 1- to 2-leaf growth stage.  More specifically, the objectives of this study were to quantify the differences in biomass production and N-uptake at the 5-leaf and panicle emergence (PE) rice growth stages, and yield among treatments.  Four ES N sources {ammonium sulfate (AMS), diammonium phosphate (DAP), urea (U), and none} were applied at the rate of 22.4 kg N ha-1 and combined with three PF N rates (101, 134, and 168 kg N ha-1).  Early season N was applied to Cocodrie rice at each location when the rice reached the 1- to 2-leaf growth stage.  Plots were flush irrigated within 2 d after application.  Plant samples were collected at the 5-leaf rice growth stage, oven-dried, weighed, and digested to determine total biomass and total N-uptake.  This was repeated at panicle emergence.  In addition to biomass, plant heights were measured at the 5-leaf growth stage.  Finally, at physiological maturity, rice plots were harvested and yields were adjusted to 12% moisture content.  Plant height and biomass at the 5-leaf stage was greater when ES N was applied at all locations.  From these data, it appears that the value of ES N applications is realized in producing greater biomass and taller plants at the 5-leaf growth stage which will allow growers to establish a flood sooner.  N-uptake data from the second year will help to draw conclusions as to the efficiency of early season N applications.