Development of the variable rate management in proportion to the specific variation of soil and crop growth properties and yield on village farm

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An on-farm experiment was carried out at the paddy fields located in Ohnishi, Sakurai, Nara Japan In Ohnishi, the unit area of the paddy fields that are cooperatively managed by farmers is about 38 ha, and about 380 paddy fields. The cropping system of these fields has been three cropping in two years.1.The multivariate analysis clearly demonstrated the high contribution of the agronomic factors (soil fertility factor, early growth factor, N dressing and uptake factor) as yield-limiting component factors. The agronomic factors (soil fertility factor, early growth factor, N dressing and uptake factor) could control about 77.1% of the spatially structured variation of the brown rice yield.2.The uniformity of the cropping system, the cultivation method and the land utilization among fields influenced spatial dependences. Maps of Npf, which were generated by interpolation among estimated values by block kriging, will be made available to the farmer to apply top-dressing at optimal rates depending on the plant condition.3.The proper management of variable rate seeding in proportion to the soil moisture percentage on dried soil basis at seeding in the wheat field may be able to control the number of panicles in the field to bring the adequate average wheat yield. This variable rate management may control 42.7% of the controllable proportion to total variation of wheat yield in the field.