Survey and Evaluation of Paddy-Upland Rotation Production System

In the paddy-upland rotation system, soil pH had no yearly variation in continuous ricepaddy field, but when it was changed to be upland, the soil pH had the tendency to be lower as yearly cultivation of upland was increased. Available form of nitrogen content was higher in annual and biennial paddy-upland rotated field compared to continuous rice-paddy cultivation. Soil phosphate content was increased in paddy-upland rotation system compared to continuous rice-paddy plot. Content of soil organic matter showed the tendency to be decreased in rotated upland field especially the third year upland rotated. Soil pore ratio was increased as paddy field was rotated to be upland in both surface and deep soil compared to continuous rice paddy cultivation. Soil hardness in 20cm deep decreased as rotated upland cultivation was longer and the rotated paddy rice field after upland cultivation. Though there was no change of soil volume density in continuous rice paddy field, it was decreased in rotated upland. In the status of weed occurrence in paddy-upland rotation system, though gramineous weeds were dominant in continuous upland field cultivation, cyperaceae and broad-leaved weeds were higher and the gramineous weeds were lower in rotated upland cultivation from rice-paddy field. Though the occurrence of aquatic weeds were dominant species in the rotated upland field in the 1st year cultivation from paddy field, occurrence of aquatic weeds seemed to be diminished and upland weeds were increased in rotated upland field cultivation of the 4th year. Results of soybean productivity in paddyupland rotation system, it was increased 15% generally. Yield of wheat and barley increased, especially soybean-barley cropping system with low fertilizing. Barley yield seemed to be increased as rotated year was longer by 4 year of rotated upland in both sandy loam and clay loam in yearly variation. Maize yield increased in the 2nd and the 3rd year rotated upland cultivation from rice-paddy field compared to the yield of the 1st year. Generally rice yield increased in paddy-upland rotation system compared to continuous rice-paddy cultivation. Results of yearly variation of rice yield in the paddy-upland rotation system was various. One reported that rice yield was higher in order of the 3rd year the 2nd year the 1st year rotated rice-paddy cultivation from upland field, the other reported that the 2nd year rotated rice paddy field rotated from upland showed the highest yield compared to the 3rd year and the 1st year of paddy field cultivation. Optimum year of paddy-upland rotation in paddy-upland rotation system seemed to be 6 years (three years of upland plus three years of paddy rice) of 1 cycle. Because paddy-upland rotation of each upland and rice-paddy over 3 and 4 years is cultivation lead to decrease the soil fertility and increase the occurrence of weeds, diseases and insects.