RICE RATOONING - IRRI books - International Rice Research Institute

N FERTILIZER MANAGEMENT FOR MAXIMUM RATOON YIELDS 191Applying main crop N at heading or 2 wk after initial heading rather than atPD tended to increase ratoon crop yields of Labelle by 0.1-0.4 t/ha and ratoon cropyields of Lemont by 0.3-0.7 t/ha at Beaumont and by 0.3-0.6 t/ha at Ganado.Along with the increase in ratoon crop yields where N was applied at or nearheading, there was a decrease in main crop yield, apparently because no N wasapplied at PD. N application at heading did not significantly increase total riceyields. However, since ratoon crop yields seem independent of main crop N rate andmain crop yield, it is reasonable to assume that a N application at PD followed by anapplication at or near heading would have increased ratoon crop and total riceyields.Table 2. N management effects on main and ratoon crop yields of Lemont grown at Beaumont,Texas, in 1984 and 1985.N fertilizer rate andTreatment application time a Total N Yield (t/ha)(no.)PP PF PD Hd Hd2(kg/ha)Main crop Ratoon crop b Total167 kg N/ha12345224 kg N/ha123455050505050676767676767676767679090909090050250006733.5000 00 025 050 00 500 00 033.5 067 00 671171671671671671572242242242247.58.58.48.08.18.18.68.68.28.6LSD (.05) = 0.51.91.72.02.22.41.71.82.22.12.20.259.410.210.410.210.59.810.410.810.310.80.5a PP = preplant, PF = permanent flood, PD = panicle differentiation, Hd = heading, Hd2 = 2 wkafter initial heading. b Ratoon crop yield when no N was applied at main crop harvest.Table 3. N management effects on main and ratoon crop yields of Lemont grown at Ganado,Texas, in 1985.N fertilizer rate andTreatment application time a Total N Yield (t/ha)(no.)PP PF PD Hd Hd2(kg/ha)Main crop Ratoon crop b Total167 kg N/ha12345224 kg N/ha123455050505050676767676767676767679090909090050250006733.50000255000033.5670000050000067117167167167167157224224224224LSD (.05)8.28.68.28.08.08.38.68.48.28.2= 0.52.22.42.32.82.71.92.42.82.83.00.310.411.010.510.810.710.211.011.211.011.20.5a PP = preplant, PF = permanent flood, PD = panicle differentiation, Hd = heading, Hd2 = 2 wkafter initial heading. b Ratoon crop yield when no N was applied at main crop harvest.