A Demonstrative Study on Rice Culture Management based on Leaf Color of Rice Plant

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A three-year project aming at stable-high-yielding cultivation of rice by developing a cultivation calendar which schedules the cultivation management using leaf color meters has been completed. The leaf color meters used for this experiment were SPAD-501 and SPAD-502. A field experiment was conducted. Lab tests using soil bins were conducted. The DSSP and the conventional transplanting method were tested.Initially, the measurement on the leaf color was taken only for the ear leaf. During the experiment it was found that the maximum value among the values of leaf color taken from the upper three leaves including the ear leaf substantiates the SPAD value. Those SPAD values were used to develop the cultivation calendar. It was also found that broad differences in leaf color between varieties were exist even under the same cultivation condition. However, the difference in leaf color due to the varietal difference can be compensated by using appropriate conversion factors. The future task should be the determination of those conversion factors for every variety of rice. The cultivation calendar developed based on SPAD values much differs from the ones based on the Fuji leaf color scale. The key points that the newly developed cultivation calendar includes are to have more number of stalkes per hill than conventional and to maximize the number of grains per head. This originates the difference in the leaf color management between the newly developed method and the conventional method based on the V shape theory. Some demonstrative operation to prove the effectiveness of the newly developed method were conducted using some commercial rice production fields. A high yield has been expected.For the future study the following management is expected to develop. A reduced-top-dressing-management to control the leaf color according to the newly developed cultivation calendar must be developed.