• Korean Journal of Soil Science and Fertilizer
• /
• v.50 no.6
• /
• pp.674-683
• /
• 2017

The frequency and intensity of soil moisture stress associated with climate change has increasing, and the stability of field crop cultivation has decreasing. This experiment was conducted to investigate the effect of soil moisture management method on growth and yield of corn. Soil moisture was managed at the grade of WSM (wet soil moisture, 34.0~42.9%), OSM (optimum soil moisture, 27.8~34.0%), DSM (dry soil moisture, 20.3~27.8%), and ESM (extreme dry moisture, 16.6~20.3%) during V8 (8th leaf stage)-VT (tasseling stage). After VT, irrigation was limited. The treated amount of irrigation was 54.1, 47.7, 44.0 and 34.5% of total water requirement, respectively. The potential evapotranspiration during the growing period was $3.29mm\;day^{-1}$, and upward movement of soil water was estimated by the AFKAE 0.5 model in the order of ESM, DSM, OSM, and WSM. We could confirm this phenomenon from actual observations. There was no significant difference in leaf characteristics, dry matter, and primary productivity depending on the level of soil moisture, but leaf development was delayed and dry weight decreased in DSM. However, dry weight and individual productivity of DSM increased after irrigation withdrawal compared to that of OSM. In DSM, ear yield and number of kernels per ear decreased, but water use efficiency and harvest index were higher than other treatments. Therefore, it is considered that the soil moisture is concentratedly managed before the V8 period, the V8-VT period is controlled within the range of 100 to 500 kPa (20.3~27.8%), and no additional irrigation is required after the VT.

• Journal of Bio-Environment Control
• /
• v.4 no.2
• /
• pp.188-194
• /
• 1995

This study was carried out to investigate the effect of NH$_4$H$_2$PO$_4$ on pH stabilization in deep flow culture system using tap water, and to determine the optimum range of NH$_4$H$_2$PO$_4$ in culture solution. The pH of tap water is 7.5. The higher the concentration of NH$_4$H$_2$PO$_4$ was, the more the pH of nutrient solution was decreased. In NH$_4$H$_2$PO$_4$ 4/3-5/3 me/$\ell$, the pH of nutrient solution was 6-7.5 during the experiment. The highest brix(%) was obtained in NH$_4$H$_2$PO$_4$ 5/3-6/3 me/$\ell$. Leaf length, leaf width and stem-base diameter were highest in NH$_4$H$_2$PO$_4$ 2/3 me/$\ell$. The L and b＊ values were highest and the a＊ value was lowest in NH$_4$H$_2$PO$_4$ 8/3 me/$\ell$. Toxicity symptom of ammonium appeared in NH$_4$H$_2$PO$_4$ 8/3 me/$\ell$. It suggests that there was the relationship between leaf color and growth condition. It was concluded that NH$_4$H$_2$PO$_4$ 2/3 me/$\ell$ was good before harvest stage and NH$_4$H$_2$PO$_4$ 5/3-6/3 me/$\ell$ at harvest stage.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.24 no.4
• /
• pp.69-79
• /
• 1982

The objective of this study is to contribute to drainage planning in the most realistic and economical way by establishing the relationship between rice yield reduction and overhead flooding by muddy water of each growth stage of paddy, which is the most important factor in determining optimum drainage facilities. This study was based on the data mainly from the experimental reports of the Office of Rural Development of Korea, Reduction Rate Estimation for Summer Crops, published by Ministry of Agriculture and Forestry of Japan and other related research documenta- tion. The results of this study are summarized as follows 1. Damages by overhead flooding are highest in heading stage and have the tendency of decrease in the order of booting stage, panicle formation stage, tillering stage, and stage just after transplanting. Damages by overhead flooding of each growing stage are as follows: a) It is considered that overhead flooding just after transplanting gives a little influence on plant growth and yield because the paddy has sufficient growth period from floo ding to harvest time. b) Jt is analyzed that according to the equation y=11 12x 0.908 which is derived from this study, damages by overhead flooding during tillering stage for 1, 2, 3 successive days are 11.1 %, 20.9%, and 30.2% respectively. c) Damages by overhead flooding after panicle formation stage are very serious because recovering period is very short after damage and ineffective tillering is much. Acc- ording to the equation y=9. 58x+10. Ol derived from this study, damages by overhead flooding fal 1,2,3,5 successive days are 19.6%, 29.2%, 38.8%, 57.9% respectively. d) Booting stage is the very important period in which young panicle has grown up almost completely and the number of glumous flower is fixed since reduction division takes place in the microspore mother cell and enbryo mother cell. According to the equation y=39. 66x 0.558 derived from this study, damages by overhead floodingfor 0.5, 1, 3, 5 successive days are 26.9%, 39.7%, 72. 2% and 97.4%, respectively. Therefore, damages by overhead flooding is very serious during the hooting stage. e) When ear of paddy emerges, flowering begins on that day or the next day; when paddy flowers, fertilization will be completed 2-3 hours after flowering. Therefore overhead flooding during heading stage impedes flowering and increases sterilizing percentage. From this reason damages of heading stage are larger than that of booting stage. According to the equation y-41 94x 0.589 derived from this study, damages by overhead flooding for 0.5, 1, 3, 5, successive days are 27.9%, 63.1 %, 80.1%, and 100% 2. Considering that temperature of booting stage is higher than that of beading stage and plant height of booting stage is ten centimeters shorter than that of heading stage, booting stage should be taken as a critical period for drainage planning because possi- bility of damage occurrence in booting stage is larger than that of heading stage. There-fore, it is considered that booting stage should be taken as critical period of paddy growth for drainage planning. 3. Overhead flooding depth is different depending on the stage of growth. In case, booting stage is adopted as design stage of growth for drainage planning, it is conside red that the allowable flooding depth for new varieties and general varieties are 70cm and 80cm respectively. 4. Reduction Rate Estimation by Wind and Flood for Rice Planting of the present design criteria for drainage planning shows damage by overhead flooding for 1 to 2, 3 to 4, 5 to 7 consecutive days; damages by overhead flooding varies considerably over several hours and experimental condition of soil, variety of paddy, and climate differs with real situation. From these reasons, damage by flooding could not be estimated properly in the past. This study has derived the equation which shows damages by flooding of each growth stage on an hourly basis. Therefore, it has become possible to compute the exact damages in case duration of overhead flooding is known.

• Current Research on Agriculture and Life Sciences
• /
• v.22
• /
• pp.1-12
• /
• 2004

Pod-edible bean or snap bean is a fairly new crop to domestic farmers but the national demand is steadily increasing in recent years along with the development of western food business and change in dietary patterns. At the same time, much efforts are being made to export it to foreign country, mainly to Japan. The amount of seeds introduced from outside is also continuously increasing along with the enlargement of area planted for the crop. Hybridization breeding for the crop has already been started to supply the cheaper and better seeds which will reduce the seed costs and foster the higher income to the farmers. In this experiment, several technologies related with the production of quality seeds are preliminary investigated. Some of the results obtained are summarized as follows; 1. Highly significant interaction was recognized between planting dates and no. of pods per plant and no. of branches but no interaction between planting dates and plant height and no. of nodes on main stem. Days to maturity was proportionally reduced to later planting dates. 2. Rate of viviparous pods and seeds was gradually increased in later planting dates but rate of germination was increased in earlier planting dates with lower germination rate in white seed coat grains than in colored seed ones. 3. Seed yield was higher in the earlier planting dates with a great deal of varietal difference. Early to mid April was considered to he the optimum planting dates for snap bean in Kyungbuk area. High correlation was recognized between seed yield and no. of pods per plant, no. of seeds per plant, and 100 seed weight. 4. Days to flowering was three and seven days longer in Cheongsong, high mountainous area than in Kunwi, somewhat prairie lowland. One hundred seed weight was also higher in Cheongsong than in Kunwi. Rate of viviparous grains, pods, and decayed seeds was higher in Cheongsong but, at the same time, the rate of germination and seed yield was also higher in Cheongsong. 5. One hundred seed weight of KLG5007 increased continuously up to 35days after flowering and decreased thereafter but that of KLG50027 increased to 40days after flowering and slowly reduced thereafter. The content of crude oil reached to maximum at 40 days after flowering and reduced thereafter. The rate of germination in Gangnangkong 1 was the highest, 89.3%, at 35 days after flowering and reduced thereafter while that in KLG50027 reached to maximum, 70.7%. at 40days after flowering and reduced thereafter. Thus, the optimum harvesting time for snap bean was considered to be 35~40days after flowering. 6. The snap bean pods at yellow bean stage easily became viviparous ones under saturated moisture conditions for 24 hours at $25{\sim}30^{\circ}C$. Therefore, it is recommended to harvest pods somewhat earlier than yellow-bean stage and let them do post maturing, especially when it is to be rained.

• The Korean Journal of Mycology
• /
• v.37 no.1
• /
• pp.117-119
• /
• 2009

Rhizopus soft rot caused by Rhizopus stolonifer occurred on strawberry (Fragaria ${\times}$ ananassa) in the plastic boxes in Jinju City Wholesale Market of Agricultural Products at Gyeongnam province in Korea on April 2008. The infected fruits were rapidly softened, water soaked and finally rotted. The symptoms were mainly occurred through wounds at harvest time. The colony color was white, cottony to brownish black after fully matured and numerous sporangiospores were formed on sporangia. The optimum growth temperature of the fungus was $30^{\circ}C$ on potato dextrose agar. Sporangia were globose or hemispheric shape of white color at initial stage and gradually changed with black color of $82{\sim}195{\mu}m$ in size. Sporangiophores were $12{\sim}25{\mu}m$ in width. Columella were hemispheric in shape, and $70{\sim}92{\mu}m$ in size. Sporangiospores were irregular round or oval in shape, brownish-black in color and $9{\sim}21\;{\times}\;7{\sim}8{\mu}m$ in size. This fungus formed stolones and rhizoid on PDA. On the basis of symptom, mycological characteristics and pathogenicity of the fungus, the causal fungus was identified as Rhizopus stolonifer (Ehrenb.) Vuill.

• Korean Journal of Agricultural Science
• /
• v.25 no.1
• /
• pp.19-25
• /
• 1998

This study was conducted to develop an appropriate postharvest technique to extend the shelf-life of an early cultivar, 'Tsugaru' apples. The general quality of stored fruit was more affected by maturity at harvest than postharvest treatments. When firmness and internal quality were considered, fruits harvested at the medium stage of color development showed better results. Between postharvest treatments examined in this study, a simple polyethylene film(PE) wrapping (30um) was excellent on inhibition of weight loss but this treatment revealed no clear effect on other quality factors including firmness and acidity. Ethylene scrubber(ES) in polyethylene wrapping showed a positive effect on keeping fruit quality in general. Especially acid content was higher in fruit stored with PE + ES, thus, fruit seemed to be better in freshness. A physiological disorder was observed regardless postharvest treatments. The symptom was associated with incidence of pitting on surface and breakdown of the effected tissue. And much more symptoms were developed near the calyx end. Thus, future studies concerning 'Tsugaru' storage should include an examination of the optimum storage temperature.

• Korean Journal of Soil Science and Fertilizer
• /
• v.43 no.5
• /
• pp.637-643
• /
• 2010

For enhancement of apple productivity, the calcium fertilizers to increase the calcium content of fruit, and reduce the incidence of bitter pit in apples are applied. Crushed oyster shell contains a plenty of calcium carbonate, and a very small amount of boron, ferrous, and manganese. A field study was conducted to determine the optimum level of crushed oyster shell for soil nutrient management, and its effect on the induction of bitter pit in cultivar 'Gamhong' apple. The application of crushed oyster shell increased organic matter, available phosphate, and exchangeable cation concentration in soil. We found a significant positive correlation between soil pH, and application level of crushed oyster shell in both top, and subsoils. The incidence of bitter pit in apple fruit at the harvest stage was significantly higher in non treatment and calciummagnesium carbonate treatment than on over applications 4 Mg $ha^{-1}$ for crushed oyster shell. However, the optimum level of crushed oyster shell was 2 Mg $ha^{-1}$, especially considering the soil Ca content, soil pH, fruits weight, and yield. Our results show that the crushed oyster shell can be effective in restoring the soil nutrient balance, and inducing the bitter pit in apple fruit.

• Journal of the Korean Society of Industry Convergence
• /
• v.20 no.5
• /
• pp.395-404
• /
• 2017

Cultivating soybeans in rice paddy field reduces labor costs and increases the yield. Soybeans, however, are highly susceptible to excessive soil water in paddy field. Controlled drainage system can adjust groundwater level (GWL) and control soil moisture content, resulting in improvement soil environments for optimum crop growth. The objective of this study was to fit the soybean growth data (canopy height and stem diameter) using Gompertz model and Logistic model at different GWL and validate those models. The soybean, Daewon cultivar, was grown on the lysimeters controlled GWL (20cm and 40cm). The soil textures were silt loam and sandy loam. The canopy height and stem diameter were measured from the 20th days after seeding until harvest. The Gompertz and Logistic models were fitted with the growth data and each growth rate and maximum growth value was estimated. At the canopy height, the $R_2$ and RMSE were 0.99 and 1.58 in Gompertz model and 0.99 and 1.33 in Logistic model, respectively. The large discrepancy was shown in full maturity stage (R8), where plants have shed substantial amount of leaves. Regardless of soil texture, the maximum growth values at 40cm GWL were greater than the value at 20cm GWL. The growth rates were larger at silt loam. At the stem diameter, the $R_2$ and RMSE were 0.96 and 0.27 in Gompertz model and 0.96 and 0.26 in Logistic model, respectively. Unlike the canopy height, the stem diameter in R8 stage didn't decrease significantly. At both GWLs, the maximum growth values and the growth rates at silt loam were all larger than the values at sandy loam. In conclusion, Gompertz model and Logistic model both well fit the canopy heights and stem diameters of soybeans. These growth models can provide invaluable information for the development of precision water management system.

• Journal of Bio-Environment Control
• /
• v.23 no.4
• /
• pp.309-313
• /
• 2014

This research was conducted to establish recommendable side shoot management methods in the growth and yield of tomato in winter. A cherry tomato, $^{\circ}{\times}Unicorn^{\circ}{\pm}$ (Monsanto Korea, Korea) was cultivated in coconut coir in the form of bag as substrate. There were four treatments related to side shoot removal methods; 1) To remove all side shoots and also each one of three leaves which gives shade to each cluster attached below (UP-FL), 2) To remove all side shoots and also each one of three leaves which gives shade to each cluster only with fruit attached below (UP-FR), 3) To remove all side shoots (AS-All), and 4) To remain two leaves of each side shoot coming from right below each cluster (AS-Part). The number of malformed leaves were more in UP-FL, UP-FR, AS-All, and AS-Part in descending order, which showed the severe the removal of leaves the more the malformed leaves. The malformed leaves were diminished after the development stage the second or third cluster bloomed. The yields until fifth cluster were not different among the treatments. Therefore removal of side shoots and leaves recommends not to be done severely in early growth stage when tomato plants are cultivated in winter.

• Korean Journal Plant Pathology
• /
• v.3 no.4
• /
• pp.252-260
• /
• 1987

Incidence of lettuce drop was observed throughout the growing season in the vinylhouse at the southern part of Korea, Kimhai. Occurrence of this disease was especially severe at the seedling stage. Number of sclerotia in surface soil $(30\times30\times5cm)$ was 22.0 at the seedling stage, and 5.3 at harvest in the infected area. Temperature for mycelial growth ranged from 5 to $30^{\circ}C$ with optimum temperature at $25^{\circ}C$. Sclerotia were formed fewer at low temperature, but their size was larger resulting in heavier dry weight than that at high temperature. The apothecia were formed from the sclerotia that were buried in March, April and September upto 3cm soil depth, but formed from those buried only 1 em soil depth in October. Sclerotia buried in June and December did not form apothecia regardless of soil depth by 90 days. The sclerotia buried in the 5cm of soil depth did not form apothecia. Sclerotia that were embedded in wet or flooded soil at $25^{\circ}C$ and $30^{\circ}C$ for 5 weeks lost their viability. Infection of lettuce was possible with mycelia originated from sclerotia on autoclaved lettuce plant fragments. The fungus was pathogenic on 25 plant species in 8 families in artificial inoculation tests. Lettuce seedlings appeared to be infected by airborne ascospore originated from sclerotia on crops and weeds around paddy fields, because sclerotia existing in soil might perish under long flood conditions during rice cultivation.