RICE RATOONING - IRRI books - International Rice Research Institute

192 RICE RATOONINGRatoon tiller regeneration occurred sooner and the ratoon crop matured7-10 d earlier when the postflood N was applied one-half at heading, all at heading,or all 2 wk after heading, compared with when the postflood N was applied at PD.Earlier ratoon crop maturity should improve chances for a better growing climateand reduce risk (10).Effect of N applied after main crop harvest on ratoon yieldTables 4 and 5 show the ratoon crop yield potential of both cultivars when the maincrop stubble is in good condition for ratoon crop production and N application ratesafter main crop harvest are 0, 56, and 112 kg N/ha. As N rate increased to 56 kgN/ ha, the ratoon crop yield increased from 0.3 to 0.9 t/ha. Maximum yield increaseto 112 kg N/ha for both cultivars was 1.1-1.2 t/ha. Good ratoon crop yields (2.6t/hafor Labelle and 2.8 t/ha for Lemont) can be obtained when main crop yields arerelatively low (Fig. 1, Table 1), N is applied only at preplant and just before flooding,and 112 kg N/ ha is applied after main crop harvest.CONCLUSIONSThe amount of N applied to main crop at the PD stage did not influence ratoon cropyields. Good ratoon yields (2.6 and 2.8 t/ha) can be obtained under Texas climatewhen main crop yields are relatively low (4.9 t/ha for Labelle and 7.5 t/ha forLemont), provided main crop stubble is healthy.Applying N at or near main crop heading rather than at PD increased ratooncrop yields but decreased main crop yields, resulting in only a slight increase in totalTable 4. Labelle ratoon crop yield as influenced by N applied immediately aftermain crop harvest at Beaumont, Texas.Main croppostfloodN timing aNo applicationPDPD and HdHdHd2N appliedafter main cropharvest(kg/ha)056112056112056112056112056112Average ratoon crop yield (t/ha),1984 and 1985Low main crop N1.82.32.61.72.42.81.72.62.91.82.52.71.82.32.7High main crop N1.12.32.81.62.42.71.72.52.91.82.52.72.02.62.8LSD (.05) = 0.2a PD = panicle differentiation, Hd = heading, Hd2 = 2 wk after initial heading.