RICE RATOONING - IRRI books - International Rice Research Institute

52 RICE RATOONINGTable 6. Simple correlation coefficients between TNC percentage and main cropand ratoon yields in the Regional Uniform Nurseries, Beaumont, Texas, 1977-78.TestMain cropyieldRatoonyield1977Group IGroup IIGroup IIIGroup IVGroup VCombined Groups1978Group IGroup IIGroup IIIGroup IVGroup VCombined Groups% TNC% TNC% TNC% TNC% TNC% TNC% TNC% TNC% TNC% TNC% TNC% TNC-0.439**-0.365*-0.351**-0.016-0.261*-0.305**0.015-0.1670.116-0.044-0.315**-0.239**-0.2430.262–0.347**–0.0940.462**0.279*–0.219–0.289***Significant at the 5% level of probability, **significant at the 1% level of probability.Although our investigations indicate that TNC percentage in the straw at maincrop harvest generally is not an effective indicator of ratooning potential under thecultural practices and climatic conditions common to the U.S. Gulf coast, we believethat the subject merits further testing. It may be that a different sampling time, ornitrogen level, or variations in cultural practice other than those under which ourstudy was conducted might provide more satisfactory results.Since the establishment of ratoon cropping with the release of Belle Patna in1961, average ratoon crop yields in both research plots and farmers' fields haveremained relatively constant in Texas and Louisiana. However, preliminaryindications are that the newly released, high-yielding semidwarf cultivars Lemontand Gulfmont may have significantly better ratoon crop potential under a high levelof management than Labelle and other current nonsemidwarf cultivars. Thepreviously cited 1985 data from Louisiana (7), data in our other paper presentedhere, and new data from other disciplines at Beaumont support this projection. Thesemidwarf cultivars may not have inherently higher ratoon crop yielding ability, buttheir high nitrogen-responsiveness and extreme lodging resistance may allow themto be fertilized for maximum yield expression without the lodging that frequentlyoccurs with nonsemidwarf cultivars at high fertility rates.The development and release of Lemont and other semidwarf long-grain ricecultivars have resulted in significant yield increases across the Southern U.S. ricearea. To maximize the high yield potential of the new cultivars, a higher level ofmanagement is being applied, with emphasis on reduced unit cost of productionrather than yield per se. Preliminary economic analyses indicate that ratooncropping can dramatically reduce per unit production cost of the total crop. As aresult of this finding, research on all aspects of ratoon cropping is being expanded,with emphasis on breeding for superior, stable ratoon crop yields combined withhigh main crop yields, and on developing cultural practices that will maximizeproductivity. The goal is to raise average yields in Texas to 8.5 t/ha by 1991.