Jung-Hun Ok

Effects of False Seedbed on the Preventative Weed Control in Organic Rice Paddy Field

This study was conducted to determine the weed control effect of false seedbed in organic rice paddy field. False seedbed is one of the preventative weed control method, especially effective in upland vegetable field. False seedbed frequency and methods were examined by varying the processing time in greenhouse and field condition in 2012 and 2013. In greenhouse experiment, shallow recultivation and harrow surface soil was effective to control weed up to 70%. Optimal processing time of false seedbed was when the weed was two or three leaf stages. Under field condition, one-time treatment of false seedbed was 61% of weed suppression rate and two-times of false seedbed treatment was 79% of weed suppression rate. Monochoria vaginalis was still troublesome weed after false seedbed treatment, but the occurrence of Echinochloa oryzoides was decreased after false seedbed treament. Results indicated that false seedbed treatment was very effective to lower early weed occurrence in rice paddy field especially Echinochloa spp. Weed control efficiency of shallow recultivation by weeder hollow and rotary tillage by tractor were 68%, 13% respectively.

Estimation of N Mineralization Potential and N Mineralization Rate of Organic Amendments as Affected by C:N Ratio and Temperature in Paddy Soil

Understanding N mineralization dynamics in soil is essential for efficient nutrient management. An anaerobic incubation experiment was conducted to examine N mineralization potential and N mineralization rate of the organic amendments with different C:N ratio in paddy soil. Inorganic N in the soil sample was measured periodically under three temperature conditions (20°C, 25°C, 30°C) for 90 days. N mineralization was accelerated as the temperature rises by approximately 10% °C -1 in average. Negative correlation (R 2 = 0.707) was observed between soil inorganic N and C:N ratio, while total organic carbon extract (R 2 = 0.947) and microbial biomass C (R 2 = 0.824) in the soil were positively related to C:N ratio. Single exponential model was applied for quantitative evaluation of N mineralization process. Model parameter for N mineralization rate, k, increased in proportion to temperature. N mineralization potential, Np, was very different depending on C:N ratio of organic input. N p value decreased as C:N ratio increased, ranged from 74.3 mg kg -1 in a low C:N ratio (12.0 in hairy vetch) to 15.1 mg kg -1 in a high C:N ratio (78.2 in rice straw). This result indicated that the amount of inorganic N available for crop uptake can be predicted by temperature and C:N ratio of organic amendment. Consequently, it is suggested that the amount of organic fertilizer application in paddy soil would be determined based on temperature observations and C:N ratio, which represent the decomposition characteristics of organic amendments.

Effect of Cover Crop on Weed Control in No-tilled Organic Soybean Field

전북 완주의 국립농업과학원 유기농업 시험포장에서 2015년과 2016년 콩 무경운 유기재배를 위해 피복식물을 이용한 잡초관리 시험을 수행하였다. 피복식물은 호밀 단파와 헤어리베치를 단파하는 처리와 혼파하는 처리를 두었다. 피복식물은 2014년 가을에는 경운 후에 파종하였으나 2015년 이후에는 무경운 파종하였고, 콩...

Effects of Long-Term Fertilization on Microbial Diversity in Upland Soils Estimated by Biolog Ecoplate and DGGE

Organic amendment practices can influence diversity and activities of soil microorganisms. There is a need to investigate this impact compared with other types of materials. This study was carried out to evaluate the long term effects of chemical and organic fertilizer on soil microbial community in upland field. During the last 11 years green manure, rice straw compost, rapeseed cake, pig mature compost, NPK, and NPK + pig mature compost were treated in upland soil. Organic fertilizer treatment found with high bacterial colony forming units (CFUs) as compared to chemical and without fertilizer treatment. There was no significant difference in the actinomycetes and fungal population. The average well color development (AWCD) value was the highest in green manure and, the lowest in without fertilizer treatment. Analyses based on the denaturing gradient gel electrophoresis (DGGE) profile showed that rice straw compost and pig mature compost had a similar banding pattern while rapeseed cake, NPK, NPK + pig mature compost and without fertilizer treatment were clustered in another cluster and clearly distinguished from green manure treatment. Bacterial diversity can be highly increased by the application of organic fertilizer while chemical fertilizer had less impact. It can be concluded that green manure had a beneficial impact on soil microbial flora, while, the use of chemical fertilizer could affect the soil bacterial communities adversely.

Photodegradation of Butachlor and Pyrazosulfuron-ethyl in Rice Paddy Water under Natural Sunlight

Received: 7 March 2014 / Revised: 13 March 2014 / Accepted: 6 April 2014 Copyright c 2014 The Korean Society of Environmental Agriculture This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.