Abstract
1. Extremely early maturing barley, Saikai-kawa 24, was sown Sep. 1 and Sep. 8 in 1978 at Kyushu Natl. Agric. Exp. Stn., Chikugo, Fukuoka. Seed rate was 400 kernels/m2. Seed was drilled. The distance between the rows was 18 cm. The field was irrigated occasionally. Plants grew vigorously. Grain matured and was harvested in late Dec.-early Jan. Aphid, leaf miner and cutworm were controlled by insecticides. No serious diseases were observed. The area of 0.216 m2 (3 rows × 40 cm length) × 2 were harvested every 2 weeks excluding roots and the changes in the growth were traced. 2. Seed germination and seedling establishment were good. Plants headed 44-45 days after sowing. Culm length was 53-64 cm. Total dry weight (excluding roots) estimated by harvesting 1.62 m2 (3 rows × 3 m length) × 2 was 60.0-91.1 kg/a and grain weight was 32.1-43.4 kg/a. Total weight increased rapidly from 2weeks before heading to 6 weeks after heading. On 84 days after sowing (Sown Sep. 1: Nov. 24, sown Sep. 8: Dec. 1), total weight was near to the maximum value. Plants sown Sep. 8 grew better than those sown Sep. 1. Plants topdressed (basal dressing, 1.0 kg nitrogen/a, plus topdressing, 0.5 kg nitrogen/a) grew better than those not topdressed (basal dressing 1.0 kg nitrogen/a, only). 3. Maximum LAI was 3.30-6.13. Mean CGR during the rapidly growing period (Sown Sep. 1: Sep. 30-Nov. 24, sown Sep. 8: Oct. 7-Dec. 1) was 11.3-19.1 (g/m2/day). Mean CGR of 84 days after sowing was 8.1-13.9. NAR before heading was 4.32-7.76(g/m2/day). RGR before heading was 0.095-0.156 (g/g/day). The efficiency of solar energy utilization (Eu) was estimatcd calculating (dry matter production × 4000 cal/g)/(solar radiation). Mean Eu during the rapidly growing period was 1.63-2.93%. Mean Eu of 84 days after sowing was 1.09-1.99%. LAI, CGR and Eu values of plants sown Sep. 8 or topdressed were higher than those of plants sown Sep. 1 or not topdressed. 4. The values of CGR, RGR, NAR and Eu of late-summer sown barley were nearly as high as those of other high yielding summer crops and rapidly growing winter barley. It is concluded that the high dry matter production of late-summer sown barley was obtained because of the high growth rate resulting from the efficiently utilized solar energy and the high net assimilation rate from the beginning of the growth.
