Floral Impotency Due to Cool Weather in Paddy Rice Plants in the Early-Season Culture Area : II. Countermeasure to the damage by fertilizer application

[摘要] The present study was conducted to develop the basal fertilizer application methods which mitigate the damage due to cool weather at booting stage by investigating the relationships between the changes in cool tolerance and light-intercepting characteristics with the methods of fertilizer application as basal dressing adding phosphate, potash, compost and soil conditioning materials respectively to the standard basal fertilizer. And the effect of improvement against the cool tolerance on the topdressing to deeper layer culture was also investigated. The results are as follows. (1) The addition of 6 kg/10 a phosphate or 60 kg/10 a fused phosphate and 20 kg/10 a calcium silicate (soil conditioning materials) to the standard basal fertilizer had an effect on the improvement of cool tolerance in combination with addition of compost (heavy nitrogen applicated condition), i. e. the increase of phosphate application had an effect on mitigating the injurious action of heavy nitrogen application against the cool tolerance. And it was judged that the increase of phosphate application promoted the reduction of leaf nitrogen content and leaf area index, and effected to decrease the sterility by the path of "Increase of nitrogen application → Increase of leaf area index → Increase of shaded percentage in the space of rice plants community → Obstruction of raising temperature at various points surrounding rice plants → Increase of the sterility" which discussed in our first report. (2) Under the ordinary weather condition, in spite of the rice plants in the topdressing to deeper layer culture was as large leaf area index as the standard fertilizer application, its shaded percentage in the space of rice plants community was smaller, and the light-intercepting characteristics maintained better, and the temperature of leaf sheath surface, in which the young panicle exists, raised higher than those in the heavy and standard fertilizer application. And nitrogen content of the rice plants was lower than the other applications at all times, and its C-N ratio in leaf sheath and culm before the booting stage maintained higher than the other applications although it was lower at the booting stage. From the above mentioned, the topdressing to deeper layer culture accelerates the cool weather resistance by improving the light-intercepting characteristics and the constitution of the rice plants.

[学科分类] 农业科学（综合）

[关键词] C-N ratio;C-N率;Compost;受光態勢;Cool-summer damage;障害型冷害;Early-season culture;深層追肥栽培;Light-intercepting characteristics;早期栽培;Methods of basal fertilizer application;堆肥;Phosphate;基肥施肥法;Topdressing to deeper layer;燐酸