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

利用叶色仪制定水稻栽培管理日历的水稻稳产高产栽培三年计划已经完成。本实验所用的叶色计为SPAD-501和SPAD-502。进行了田间试验。使用土壤箱进行了实验室测试。对DSSP法和常规移栽法进行了试验，试验初期只对穗位叶进行叶色测定。在试验过程中发现，从上部三片叶（包括穗叶）中提取的叶色值中的最大值证实了SPAD值。这些SPAD值被用来制定耕作日历。在相同栽培条件下，品种间叶色差异较大。然而，由于品种差异而导致的叶色差异可以通过使用适当的转换因子来补偿。今后的任务应该是确定每种水稻的转换系数。根据SPAD值制定的栽培日历与根据富士叶色等级制定的栽培日历有很大差异。新开发的栽培日历包括的关键点是比传统的每丘有更多的茎数，并最大限度地提高每穗的粒数。这是新开发的方法与基于V形理论的传统方法在叶色管理上的差异。并在水稻生产示范田进行了示范操作，验证了新方法的有效性。在今后的研究中，还将提出以下管理措施。根据新开发的栽培日历，必须开发减少追肥管理以控制叶色。

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.