Rice (Oryza sativa L.) research field plots are likely to have nearly compl
ete weed control whereas normal farmer field-grown rice often have consider
ably greater weed populations. Consequently a disparity might exist between
nitrogen (NZ requirements for producing maximum yields, in weedy (such as
in some farmer fields) versus weed-free rice (such as field research plots)
. We conducted a 2-year field study at Keiser, AR.. Using paired plots, we
compared weed control effects, at several preflood N rates (0-112 kg N ha(-
1)) on yield, yield components, harvest index and weed weights. Rice yield
responses to preflood N fertilization were similar with and without weed pr
essure. Consequently, N fertilization recommendations based on research plo
ts with little or no weed pressure are valid for research plots and grower
fields with much greater levels of weed pressure.