Korea has experienced a rapid warming of 1.5℃during the last 100 years and even faster rise of air temperature is being projected in the future. This experiment was done to figure out the impact of the predidted temperature rise on the growth and yield of rice. Two rice varieties, "Hwaseongbyeo" and "Dasanbyeo" were grown in 1/5000a Wagner pot under the four plastic houses that were controlled to ambient, ambient+1.5℃, ambient+3℃ and ambient+5℃ throughout the rice growing season. Heading dates in the elevated temperature treatments were three to five days earlier than in the ambient temperature treatment. Rice growth was affected by temperature treatments differentially according to the tested cultivars. Hwaseongbyeo(japonica) showed significant reduction of shoot dry weight under ambient+5.0℃ treatment compared to the other treatments, while Dasanbyeo(tongil-type) showed significant increase of shoot and root dry weight under the elevated temperature treatments. The number of panicles per pot and spikelets per panicle and per pot was not significantly different among temperature treatments in both cultivars tested, but significantly lower grain yield was observed under the treatments raising the air temperature to the level of 3.0℃ and 5.0℃ above the ambient air temperature. This lower grain yield in the elevated temperature treatment of ambient+3℃ was attributed mainly to the decrease of grain weight due to the shortening of grain filling period, while the drastic yield reduction in the treatment of ambient+5℃ was caused not only by the lower grain weight but also by the marked increase in spikelet sterility due to the high temperature at meiotic and flowering stage. In conclusion, the ongoing global warming is expected to decrease the grain yield not only by decreasing the grain filling period in the near future but also increasing the spikelet sterility under the long-term projected climate of Korea.

This experiment was conducted to evaluate the effect of temperature rise on the phenological development and yield of oilseed rape in temperature-controlled plastic houses located at Suwon in 2008 and 2009. Two varieties "Halla" and "Naehan" were grown using 1/5000a Wagner pots in the three plastic houses greenhouses in which temperature was controlled to ambient temperature (AT), AT+1.5℃, and AT+3.0 through the growing season. Compared to the ambient temperature, leaf appearance was speeded up by temperature elevation, resulting in earlier flowering by 7 and 19 days at the treatments of AT+1.5℃and AT+3.0℃, respectively. YGrain yield was decreased by approximately 15% for each temperature elevation of 1.5 ℃. The yield decrease was attributed to the increased sterility and the decreased grain weight under the higher temperature conditio

Temperature rise of 4.0℃ is projected under SRES A1B greenhouse gases emission scenario in 2100 and this climate change is anticipated to affect the growth, phenological development, and yield of soybean. The objective of this experiment is to calibrate and validate CROPGRO_soybean model and evaluate the projected climatic change impact on soybean phenological development in Korea. For simulation experiment, four cultivars with different maturity groups, Hwaeomputkong(MG1), Sinpaldalkong(MG4), Taegwangkong(MG5), and Daewonkong(MG6) were calibrated and validated using data that were collected from the experiments of planting dates and daylength treatment. The calibrated model predicted the phenological stages with considerable accuracy for the data acquired independently of the calibration data. As global warming proceeds, days to flowering and days to physiological maturity on average across varietal groups and planting dates are anticipated to decrease by about 7 and 5 days respectively under the projected normal climate during the period of 2071~2100 compared to those under the current normal climate condition.

objective of the current study was to evaluate the change of rice yield under the projected climate change condition. The rice model included in "Decision Support System for Precise Management of Rice Culture” developed in Crop Environment and Production Technology Lab. of Seoul National University was validated prior to simulation experiment. For model input, the daily weather data were generated by SIMMETEO method from the monthly normal maximum and minimum temperatures and precipitation of the current period, 1971-2000 and the three periods in the future, 2011-2040, 2041-2070, and 2071-2100. The climate change projected using A1B emission scenario by Korea National Meteorological Institute was used for the periods in the future. Simulation experiments were carried out using three cultivars, Odaebyeo, Hwasungbyeo and Dongjinbyeo under six transplanting dates from May 10 to June 30. The vegetative and ripening period is expected to decrease respectively by 10 and 30 days in 2071-2100. High temperature-induced sterility is projected to increase by about 8% until 2071-2100. Rice yield on national average was simulated to decrease by 3, 7, and 13 % in 2011-2040. 2041-2070, and 2071-2100 periods, respectively. Though adaptation strategies that select the cultivar among the current cones and change the transplanting date would alleviate the yield decrease, the yield decrease of about 7% is still anticipated in 2071-2100.

Plant leaf color is an important indicator for diagnosing the plant nutrient status. A software was developed by Crop Environment and Production Technology Lab. of Seoul National University to analyze the color image of rice canopy taken at panicle initiation stage (PIS) with digital camera and to recommend nitrogen fertilizer rate for target yield or protein content of rice. The software was coded in Visual Basic Ver. 6.0 and includes subroutine to calculate color indices from the digital image and several model equations relating the color indices to biomass and nitrogen accumulation of rice canopy at PIS, the grain yield to nitrogen density at PIS (PNup) and nitrogen accumulation from PIS to maturity (PHNup), and the PHNup to PNup and nitrogen fertilization rate at PIS. The objective of this study were to test the performance of the Software. Using the Software, nitrogen fertilization rate at PIS was recommended targeting the rice protein content of 6.3% for the 12 plots subjected to different amount of basal and tillering N fertilizer. N recommendation using the software reduced the coefficient of variation (CV, %) of rice yield and protein content among plots compared to the conventional N treatment plots. However, the actual protein content of rice was lower than the predicted value. This discrepancy would be attributable to the much better weather condition during grain filling period in 2009 compared to the normal year that assume in the Software for N recommendation. Additional calibration process is needed to improve the accuracy of this Software.

In order to investigate the genotypic variations of Zn accumulation in rice plant, thirty-five rice cultivars of different cultivar groups (temperate japonica, tropical japonica, tongil, and indica) were irrigated with irrigation water containing 2 ppm Zn throughout all growth season in a field experiments in 2007. At harvest, thirty-five rice cultivars showed large difference in Zn concentrations in root, shoot, straw, grain, chaff, brown rice, rice bran, and polished rice. Zn concentrations in polished rice ranged from 5.15 to 21.24 mg/kg. The total Zn accumulation in shoot varied from 12.18 to 54.84 mg/m2. Two japonica rice cultivar groups (temperate japonica, and tropical japonica) presented the higher Zn concentration in shoot compared to indica and Tongil cultivar groups. The large genotypic variation suggested the possibility of breeding low Zn accumulating rice varieties.

In the present experiment, thirty-five rice cultivars were irrigated by irrigation water containing 2 ppm Ni throughout all growth season in order to investigate the genotypic differences in Ni accumulation of rice. At harvest, thirty-five rice cultivars showed large difference in Ni concentrations in shoot, straw, grain, chaff, brown rice, rice bran, and polished rice, but not in root. Ni concentraions in polished rice ranged from 0.43 to 2.28 mg/kg. The total Ni accumulation of shoot varied from 0.63 to 2.93 mg/m2. Indica cultivar groups presented the highest Ni concentration of polished rice, but no significant difference from the other cultivar group. At the same time, indica cultivar group significantly accumulated more Ni by shoot compared to the other cultivar groups. The large genotypic variation suggested the possibility to breed low Ni accumulating rice cultivar.

In order to investigate the genotypic differences in Pb accumulation of rice, thirty-five rice cultivars were irrigated by irrigation water containing 10 ppm Pb throughout all growth season under field condition. At harvest, thirty-five rice cultivars showed significant difference in Pb concentrations in straw, grain, chaff, brown rice, rice bran, and polished rice, but not in root. Pb concentration in polished rice ranged from 0.02 to 0.22 mg/kg. The total Pb accumulation in shoot varied from 0.77 to 2.74 mg/m2. There were no significant difference of Pb concentration in all of rice parts among four rice cultivar groups. Indica and tongil cultivar groups presented the higher Pb accumulation in shoot. The large genotypic variation suggested the possibility of breeding low Pb accumulating rice cultivar.

In order to investigate the genotypic differences in Cu accumulation of rice, 35 rice cultivars of different cultivar groups (temperate japonica, tropical japonica, tongil, and indica) were cultivated in a field condition that rice was irrigated by irrigation water containing 2 ppm Cu throughout all growing season in 2007. Thirty-five rice cultivars showed large differences in Cu concentrations in all rice parts, including root, shoot, straw, grain, chaff, brown rice, rice bran, and polished rice. Cu concentrations in polished rice ranged from 0.78 to 2.84 mg/kg. The total Cu accumulation of shoot varied from 1.31 to 4.54 mg/m2. Indica and tongil cultivar groups presented the higher Cu concentration and accumulation comparing the two japonica rice cultivar groups (temperate japonica and tropical japonica). The large genotypic variation suggested the possibility of breeding low Cu accumulating rice cultivar.

Cd contamination in irrigation water can imperil human health through food chain. In order to investigate the genotypic differences in Cd accumulation of rice, thirty-five rice cultivars of different cultivar groups (temperate japonica, tropical japonica, tongil, and indica) were grown with irrigation water containing 2 ppm Cd throughout all growing season under the field condition in 2007. At harvest, highly significant differences in Cd concentration in different rice parts (root, shoot, straw, grain, chaff, brown rice, rice bran, and polished rice) was found among rice varieties and rice cultivar groups. Cd concentration of polished rice ranged from 0.26 to 1.85 mg/kg. The total Cd accumulation of shoot varied from 0.69 to 7.87 mg/m2. Indica cultivar group showed significantly higher Cd concentration and accumulation compared to the other rice cultivar groups. On the other hand, the distribution ratio in polished rice was the highest in Tongil cultivar group. The large genotypic variation suggested the possibility of breeding low Cd accumulating rice variety.

Korea has experienced a rapid warming of 1.5℃ during the last 100 years and it is projected more faster rise of air temperature in the future. Temperature is an important factor that impacts directly on the growth and development of plants. To figure out the impact of temperature rising on rice growth, grain yield, and quality, an experiment was conducted at the 3 plastic houses that were controlled to ambient, ambient+1.5℃, and ambient+3℃throughout the growing season at the Seoul National University Experimental Farm. A rice variety "Hwaseongbyeo“ was grown using 1/5000a Wagner pot under two nitrogen levels of 12 and 18kg/10a. Heading date in elevated temperature treatments was earlier by two days than in ambient temperature. Compared to the ambient temperature, number of tiller, leaf area index, and dry weight of root, stem, leaf, and panicle was greater in elevated temperature conditions throughout the rice growing season, the difference being smaller in later grain filling period. There was no interaction effect on growth between nitrogen levels and temperature treatments. Grain yield and grain quality are under measurements.

Leaf color can be used as an indicator of the plant healthiness, and thus digital image analysis may provide farmers and researchers with time- and resource-saving methods for diagnosing plant nutrient status. The digital images are dependent on the ambient light, therefore the color indices of digital images should be compensated for the difference of ambient light. The objectives of this study were to develope the calibration methods for color indices under variable irradiance condition. Four color panels were used for RGB (Red, Green, Blue) values and color indices calibration purpose. Reflectance for each panel was measured by spectro-radiometer with a waveband range of 300 - 1100 nm. The reflectance values of four color panels was used as a reference for calibration of RGB values and color indices. Using digital camera color images were taken for rice canopies together with reference panel that was set up at the level of canopy surface. Digital images were obtained form rice fields with variable nitrogen fertilization managements at active tillering to panicle initiation stage. The calibration coefficients for color image indices were calculated by using the linear regression equation between the pixel values of color image for reference panel and their known reflectance values. The determination coefficients (r2) of linear regression between non-calibrated mean B values of plant pixels in color image and shoot nitrogen contents in four rice varieties, Odae, Hwasung, Chucheong, and Ilpum, was 0.30, 0.27, 0.37, and 0.27, respectively, while the respective r2 values were increased to 0.79, 0.85, 0.77, and 0.53.by applying the calibration coefficient. These results imply that color digital image analysis could be a promising method for diagnosing nitrogen nutrition status of rice canopy.

Although there can be some differences among varieties, the developmental rate of soybean (Glycine max) is mainly influenced by temperature and photoperiod. The objective of this experiment, that is the first step for creating phenology model of soybean, is to investigate the developmental characteristics under different temperature and day length conditions. Considering maturity, employed were five cultivars, Hwaeomputkong, Sinpaldalkong, Taegwangkong, Daewonkong, and Seoritae. They were sown at three different dates and grown under natural day length throughout growing season in 2008, while in another field they were subjected to longday of 16 hours by the supplemental lighting from July 6 to maturity. Developmental processes were investigated every five days after seeding. Days to flowering and final number of node increased in late maturiity cultivars. These traits decreased in delayed seeding, while increased under longday treatment. Even though there were some varietal differences in the slope of the line, V-stage(the number of nodes) of soybean consistently showed the linear relation(r2>0.95) with the sum of effective temperature from emergence to flowering. Daylength would be a cardinal factor that determines development including final number of node and duration of reproductive stage. However, it has not been figured out completely. Further studies will focus on the effect of temperature on reproductive stage and developmental response to daylength.

A pot experiment was conducted to investigate the effects of soil burial depth on seedling emergences of rice (Oryza sativa) and Echinochloa spp. and to model such effects for mathematical prediction of seedling emergences. When the Gompertz curve was fitted at each soil depth, the parameter C decreased in a logistic form with increasing soil depth, while the parameter M increased in an exponential form and the parameter B appeared to be constant. The Gompertz curve was combined by incorporating the logistic model for the parameter C, the exponential model for the parameter M, and the constant for the parameter B. This combined model well described seedling emergence of rice and Echinochloa species as influenced by soil burial depth and predicted seedling emergence at a given time after sowing and a soil burial depth. Thus, the combined model can be used to simulate seedling emergence of crop sown in different soil depths and weeds present in various soil depths.

Response of grain yield and milled-rice protein content to nitrogen (N) rates at various growth stages is critical for quantifying real-time and real-amount of applied N requirement for target grain yield and protein content. An experiment including 10 N rate treatments at transplanting, tillering and panicle initiation stages with four rice cultivars in 2003, 6 N treatments with two rice cultivars in 2004 and 2005 was conducted. Increase of N rates at PIS significantly increased both grain yield and milled-rice protein content but increase of N rates at tillering stage significantly increased grain yield but not milledrice protein content. Therefore, high grain yield and low milled-rice protein content would be difficult to obtain only by adjusting N rates at PIS. Internal N use efficiency (INUE) was 60.5 kg grain/kg N accumulation on an average over N treatments, cultivars, and experimental years, showing considerable reduction especially at high shoot N accumulation in the experimental year of low sunshine duration. Milled-rice protein content tended to increase almost linearly with increasing shoot N accumulation, but it revealed big variation even at the same shoot N accumulation at harvest. Milled-rice protein content decreased with increasing INUE. N accumulation in the milled rice increased at an almost constant proportion of 45.5 percent of the shoot N accumulated at harvest, showing slight decresing proportion with the increasing shoot N accumulation.

Response of grain yield and milled-rice protein content to nitrogen topdress (N) timing at panicle initiation stage (PIS) is critical for quantifying real-time N requirement for target grain yield and milled-rice protein content. Two split-split-plot experiments with three replications, one in 2004 and the other in 2005, were conducted in Experimental Farm, Seoul National University, Suwon, Korea. The experiments included three N rates at tillering stage (TS), three N timing treatments at panicle initiation stage (PIS) and two rice cultivars. The N rates at TS, N timing at PIS, and rice cultivars were randomly assigned to main plot, sub plot, and sub-sub plot, respectively. Results showed that the delayed N application at PIS reduced grain yield in 2004 and increased milled-rice protein content in both years significantly at 0.05 probability level. The calculated optimum N timing at PIS from pooled data by N rates and rice cultivars in two years was at 28 days before heading (DBH). However, real-time of N timing at PIS was dependent on plant growth and N status around PIS that in turn was dependent on applied N rates at TS. The optimum N timing at PIS was at 30 DBH for no N treatments at TS while at 27 DBH for 3.6 and 7.2 kg N/10a treatments and at 27 and 29 DBH for Hwaseongbyeo and Daeanbyeo, respectively. In general, earlier applied N at PIS resulted in lower milled-rice protein content but the highest grain yield was expected to be obtained when N topdress at PIS was applied at the time when shoot N concentration started to drop below about 23 mg/g due to dilution effect after transplanting. In conclusion, the results of our experiments imply that the currently recommended N topdress time (24DBH) at PIS in Korea should be reconsidered for the higher grain yield and the better quality of rice.

ice yield and plant growth response to nitrogen (N) fertilizer may vary within a field, probably due to spatially variable soil conditions. An experiment designed for studying the response of rice yield to different rates of N in combination with variable soil conditions was carried out at a field where spatial variation in soil properties, plant growth, and yield across the field was documented from our previous studies for two years. The field with area of 6,600 m2 was divided into six strips running east-west so that variable soil conditions could be included in each strip. Each strip was subjected to different N application level (six levels from 0 to 165kg/ha), and schematically divided into 12 grids (10m ~times10m~;for~;each~;grid) for sampling and measurement of plant growth and rice grain yield. Most of plant growth parameters and rice yield showed high variations even at the same N fertilizer level due to the spatially variable soil condition. However, the maximum plant growth and yield response to N fertilizer rate that was analyzed using boundary line analysis followed the Mitcherlich equation (negative exponential function), approaching a maximum value with increasing N fertilizer rate. Assuming the obtainable maximum rice yield is constrained by a limiting soil property, the following model to predict rice grain yield was obtained: Y=107651-0.4704*EXP(-0.0117*FN)*MIN(I-clay,~;Iom,~;Icec,~;ITN,~; ISi) where FN is N fertilizer rate (kg/ha), I is index for subscripted soil properties, and MIN is an operator for selecting the minimum value. The observed and predicted yield was well fitted to 1:1 line (Y=X) with determination coefficient of 0.564. As this result was obtained in a very limited condition and did not explain the yield variability so high, this result may not be applied to practical N management. However, this approach has potential for quantifying the grain yield response to N fertilizer rate under variable soil conditions and formulating the site-specific N prescription for the management of spatial yield variability in a field if sufficient data set is acquired for boundary line analysis.

Rice yield and protein content have been shown to be highly variable across paddy fields. In order to characterize this spatial variability of rice within a field, two-year experiments were conducted in 2002 and 2003 in a large-scale rice field of 6,600m2 In year 2004, an experiment was conducted to know if variable rate treatment (VRT) of N fertilizer, that was prescribed for site-specific management at panicle initiation stage, could reduce spatial variation in yield and protein content of rice while increasing yield compared to conventional uniform N topdressing (UN, 33kg N/ha at PIS) method. VRT nitrogen prescription for each grid was calculated based on the nitrogen (N) uptake (from panicle initiation to harvest) required for target rice protein content of 6.8~% , natural soil N supply, and recovery of top-dressed N fertilizer. The required N uptake for target rice protein content was calculated from the equations to predict rice yield and protein content from plant growth parameters at panicle initiation stage (PIS) and N uptake from PIS to harvest. This model· equations were developed from the data obtained from the previous two-year experiments. The plant growth parameters for the calculation of the required N were predicted non-destructively by canopy reflectance measurement. Soil N supply for each grid was obtained from the experiment of year 2003, and N recovery was assumed to be 60~% according to the previous reports. The prescribed VRT N ranged from 0 to 110kg N/ha with an average of 57kg/ha that was higher than 33 kg/ha of UN. The results showed that VRT application successfully worked not only to reduce spatial variability of rice yield and protein content but also to increase rough rice yield by 960kg/ha. The coefficient of variation (CV) for rice yield and protein content was reduced significantly to 8.1~% and 7.1~% in VRT from 14.6~% and 13.0~% in UN, respectively. And also the average protein content of milled rice in VRT showed very similar value of target protein content of 6.8~% . In conclusion the procedure used in this paper was believed to be reliable and promising method for reducing within-field spatial variability of rice yield and protein content. However, inexpensive, reliable, and fast estimation methods of natural N supply and plant growth and nutrition status should be prepared before this method could be practically used for site-specific crop management in large-scale rice field.

For developing the site-specific fertilizer management strategies of crop, it is essential to know the spatial variability of soil factors and to assess their influence on the variability of crop growth and yield. In 2002 and 2003 cropping seasons within-field spatial variability of rice growth and yield was examined in relation to spatial variation of soil properties in the· two paddy fields having each area of ca. 6,600m2 in Suwon, Korea. The fields were managed without fertilizer or with uniform application of N, P, and K fertilizer under direct-seeded and transplanted rice. Stable soil properties such as content of clay (Clay), total nitrogen (TN), organic mater (OM), silica (Si), cation exchange capacity (CEC), and rice growth and yield were measured in each grid of 10~times10m . The two fields showed quite similar spatial variation in soil properties, showing the smallest coefficient of variation (CV) in Clay (7.6~%) and the largest in Si (21.4~%) . The CV of plant growth parameters measured at panicle initiation (PIS) and heading stage (HD) ranged from 6 to 38~% , and that of rice yield ranged from 11 to 21~% . CEC, OM, TN, and available Si showed significant correlations with rice growth and yield. Multiple linear regression model with stepwise procedure selected independent variables of N fertilizer level, climate condition and soil properties, explaining as much as 76~% of yield variability, of which 21.6~% is ascribed to soil properties. Among the soil properties, the most important soil factors causing yield spatial variability was OM, followed by Si, TN, and CEC. Boundary line response of rice yield to soil properties was represented well by Mitcherich equation (negative exponential equation) that was used to quantify the influence of soil properties on rice yield, and then the Law of the Minimum was used to identify the soil limiting factor for each grid. This boundary line approach using five stable soil properties as limiting factor explained an average of about 50~% of the spatial yield variability. Although the determination coefficient was not very high, an advantage of the method was that it identified clearly which soil parameter was yield limiting factor and where it was distributed in the field.

The deep irrigation of rice plants brings about some beneficial effects such as reduced tiller production which results in the formation of bigger panicles, prevention of chilling injury, reduced weed growth, etc. The present study was carried out to examine the involvement of ethylene in the suppression of tiller production due to deep water irrigation in rice (cv. Dongjinbyeo). The ethylene production was induced in leaf sheath within 24 hours after the deep water irrigation and has increased even until 30 days after the treatment, recording 4.5-fold increase as compared to the shallow-irrigated rice plants. In the deep water irrigated rice plants, ethylene was accumulated to a high concentration in the air space of submerged leaf sheath as the irrigated water deterred the diffusion of ethylene out of the leaf sheath and ethylene biosynthesis was accelerated by the deep irrigation as well. The ethylene concentration recorded 35-fold increase in the deep-irrigated rice plants for 35 days. The tiller production was reduced significantly by the deep irrigation with water, the tiller bud, especially tertiary tiller bud differentiation being suppressed by the deepwater irrigation treatment, whereas the rice plants deep-irrigated with solutions containing 10-5 M or 10-6 M silver thiosulfate (STS), an action inhibitor of ethylene, showed the same or even higher production of tillers than those irrigated shallowly with water. This implies that the ethylene is closely linked with the suppression of tiller production due to deep water irrigation. In conclusion, ethylene, which was induced by hypoxic stress and accumulated in the leaf sheath due to submergence, played a key role in suppressing the tiller production of the deepwater irrigated rice