Abstract
The dry matter production of orchardgrass (Dactylis glomerata L.) sward under various conditions of air temperature and radiation were estimated and analysed in this paper. Based on CO_2 balance of the amount of photosynthesis and respiration in community, the dry matter production and crop growth rate under various conditions of air temperature and radiation were calculated from eq. (8) and (9) which were examined in the previous paper 7. The constant values of eq. (8) and (9) were estimated from the experimental results of pot cultivations which were carried out under various conditions of air temperature and radiation. The results are as follows; 1. The rates of leaf area production, photosynthesis in single leaf and respiration were influenced heavily by the variation of air temperature. The rate of leaf area production showed the greatest value at 20℃. The rate of photosynthesis in single leaf decreased at low air temperature below 15℃. The respiration rate of plant increased with increasing of air temperature (Q_<10>=1.65). 2. The influence of air temperature on the dry matter production varied complexly in connection with the regrowth stage after cutting. In this experiment, the dry matter production in community showed the greatest value at 16℃ and this temperature scarcely varied under various conditions of radiation. 3. Among the many factors which were related with dry matterr production, the amount of photosynthesis in community was influenced heavily by the variation of radiation. The dry matter production in community increased with increasing of radiation. But the productive efficiency per a unit radiation showed high value under the low radiation and decreased with increasing of radiation. 4. The periods from the day of cutting till the day when the maximum crop growth rate (CGR max) was showed were calculated from eq. (12). These periods affected by air temperature and radiation. The shortest value of these periods showed at 18℃-20℃ and under the highest radiation.
