Factors of the Occurrence of Straighthead of Rice Plants : I. The Occurrence of straighthead by the application of barley straws in paddy fields

The factors of the occurrence of straighthead of rice plants are vague yet. The purpose of this paper is to present the effects of the application of barley straws in common paddy fields on the occurrence of the straighthead of rice plants. The summary of the results is shown below. 1) Some plants with high percentage sterility occured in the test plots in which barley straws had been applied. 2) Numerous plants with high percentage sterility occured in the barley straws applied paddy field which was restored to the paddy field last spring after ten years use as an upland. 3) Abnormal rice plants with deformed panicles and spikelets occured in the test plot in which barley straws were applied two years before. Percentage sterility of them were high (Fig. 4). 4) Abundant typical symptoms of straighthead of rice plants were observed in a farmer's paddy field in which much barnyard manure had been applied. 5) From above-mentioned results, it was concluded that straighthead of rice plants occured not only in paddy fields which had been restored after at least more than several years use as uplands but also in common paddy fields in which much organic matter such as barley straws had been applied.