• Korean Journal of Weed Science
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• v.12 no.3
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• pp.200-222
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• 1992

The results of recent researches for improvement of seedling stand in direct seeded rice on the dry paddy in Korea were summarized as the following ; a variety to be cultivated should be chosen the characteristics of high percentage germination under low temperature, shorter period of shoot emergence, and better growth of the mesocotyl and shoots. Meanwhile, there was 40% increase in seedling stand at the treatment of removal of the seed awn under using the drill seeder. After seeding the rice seed covered with soil of 3cm depth was better seedling emergence and also there was the hightest seedling emergence at the 70% of moisture content of the soil. In addition, the application of the Release containing GA 10% enabled to increase the seedling stand and furthermore it was effective under deep seeding depth. The optimum seeding date should be seeded around May 10 when mean air temperature is above 12-13$^{\circ}C$ so that may establish more less 70% in seedling stand. Based on an appropriate seedling stand of 150/$m^2$, the optimum seeding rate was 5kg/10a. It was the best in seeding method using drill seeder and the most desirable recommended seeding method was the drill seeder in terms of seedling stand. In order to improve seedling stand water management was more effective in canal irrigation and in drainage at 6hr after irrigation following by the seeding process. On the other hand, for the increase of seedling stand under flooded condition a variety might have characters being better germination at low concentration of dissolved oxygen and vertically deeper growing of the crown root. Also, seedling stand was able to increase with the seed coating of $CaO_2$in the flooded soil. It was possible to be seeded on the early part of May being mean air temperature of avove 10$^{\circ}C$ and the optimum seeding rate was 5kg/10a. For an effective water management water would be flooded up to 3cm depth for 2-3 weeks after seeding. The rice plant grown under the direct seeded cultivation might be not so much strong in lodging resistance compared to that grown under the transplanting and moreover direct seeded rice cultivation under flooded condition would be more weak growth of the rice plant than that on dry paddy. Meanwhile, the lodging would be affected by the seeding rate, the soil depth after seeding. and seeding method even in the same variety. In particular, roots in the lodging pattern of direct seeded rice cultivation under flooded condition were largely distributed on the soil surface so that resulted easily in the lodging. In general, the lodging resistance would be greater as seeding rate and amount of N fertilizer application are lower and soil depth after seeding is higher. Among the introduction of different seeding method the high ridged drill seeding method on dry paddy soil resulted in the lowest in the lodging index and also it was lower in the drill seeding method than in the scattering seeding method under flooded condition. In case of more than 150 seedlings per $m^2$ there was a severe lodging due to high lodging index at the 3rd and 4th internodes. The effective lodging prevention was able to at the treatment of the Inabenfide at 45 days before heading and the Uniconazol at 15 days before heading which caused the shortage by 10-15cm in culm length. Also, fertilizer management using split application of nitrogen would be contributed the reduction of lodging at the rate of 20-30-20-20-10%(basal-5th leaf stage-7th leaf stage-panicle initiation stage-heading stage) on the dry paddy soil.

• Journal of Korean Society of Forest Science
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• v.108 no.4
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• pp.592-599
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• 2019

This study aimed to develop an equation for estimating stem volume for Larix kaempferiin South Korea using independent variables, diameter at breast height (DBH), and height as being closely associated with stem volume. Analysis was conducted on the growth performance of 2,840 Larix kaempferi samples across South Korea after felling them and gleaning diameter data according to both stem height and stem analyses. In order to test the fitness of six different stem taper equations, empirical assessment was conducted for fitness index (FI), bias, mean, and absolute deviation (MAD), and coefficient variation (%CV). The two selectedmodels found to be optimal were the following: model one (V=a+bDBH²), established by employing DBH only; and model four (V=a+bDBH²H), established by utilizing DBH and height, respectively. The findings of non-linear regression indicated statistical significance (p < 0.05) in a and b, which were the coefficients for the intercepts and slopes of the models. The FI of the models ranged between 94% and 99%, and the bias was close to zero, while MAD ranged from 0.01 to 0.05, and %CV from 5.97 to 14.43, indicating a high level of fitness. Thus, using the suggested models, the basic information necessary for forest management was obtained, and an estimation of the stem volume was effected without delay soon after effecting DBH and height measurements.