Fig. 3. Predicted grain yield of rice as affected by Zn fertilizer source and application rate during 2000 at the Pine Tree Branch Station (PTBS) and Rice Research Extension Center (RREC). For reference, the mean grain yields for the unfertilized controls (0 kg Zn ha^–1) are shown as . For the RREC, mean grain yields are shown as • for zinc sulfate 31% Zn (ZnSul31), for zinc lignosulfonate 10% Zn (ZnLig10), for zinc oxysulfate 20% Zn (ZnOxy20), and for zinc oxysulfate 36% Zn (ZnOxy36). For the PTBS, standard errors were 209 for intercept, 52.2 for linear coefficient, and 2.6 for quadratic coefficient. For the RREC, standard errors were 270 for intercept, 67.2 for linear coefficient, and 3.3 for quadratic coefficient.