• Korean Journal of Soil Science and Fertilizer
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• v.48 no.6
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• pp.658-665
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• 2015

Temporal and spatial variation of soil moisture is important for understanding patterns of climate change, for developing and evaluating land surface models, for designing surface soil moisture observation networks, and for determining the appropriate resolution for satellite-based remote sensing instruments for soil moisture. In this study, we measured several soil moistures in upland soil using Advanced Microwave Scanning Radiometer 2 (AMSR2) Soil Moisture Content (SMC) during eight-month period in Chungbuk province. The upland soil moisture properties were expressed by simple statistical methods (average, standard deviation and coefficient of variation) from the monthly context. Supplementary studies were also performed about the effect of top soil texture on the soil moisture responses. If the results from this study were utilized well in specific cities and counties in Korea, it would be helpful to establish the countermeasures and action plans for preventing disasters because it was possible to compare with the relationship between soil moisture and top soil texture of each region. And it would be the fundamental data for estimating the effect of future agricultural plan.

• The Korean Journal of Ecology
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• v.5 no.2_3
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• pp.123-131
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• 1982

The growth and the resistance of Amorpha fructicosa L. under water control was experimented in frames out of doors. The plant grew in a wagner's pot under water control. The soil moisture content was controlled at 5%, 10%, 15% and 20%. The growth of leaf, stem and root in the groups of 5% and 10% soil moisture content were different from values in the groups of 15% and 20%. The T/R ratio in the groups of 5% and 10% soil moisture content were different from the ratio in the groups of 15% and 20% soil moisture content. The T/R ratio of former was lower than the latter, but the C/F ratio of the former was higher than the latter. RGR and NAR of Amorpha fructicosa decreased in 5% and 10% soil moisture content but increased in 15% and 20% soil moisture content during growing period. The maximum values of RGR and NAR were respectively 0.089 and 0.080 at 20% soil moisture content. The highest value of LAR was 1.560 at 5% soil moisture content. RGR and NAR were comparatively affected by soil moisture content.

• Water Engineering Research
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• v.4 no.1
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• pp.31-43
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• 2003

The impacts of climate change on soil moisture in sub - Arctic watershed simulated by using the hydrologic model. A range of arbitrary changes in temperature and precipitation are applied to the runoff model to study the sensitivity of soil moisture due to potential changes in precipitation and temperature. The sensitivity analysis indicates that changes in precipitation are always amplified in soil moisture with the amplification factor for flow. The change in precipitation has effect on the soil moisture in the catchment. The percentage change in soil moisture levels can be greater than the percentage change in precipitation. Compared to precipitation, temperature increases or decreases alone have impacts on the soil moisture. These results show the potential for climate change to bring about soil moisture that may require a significant planning response. They are also indicative of the fact that hydrological impacts affecting water supply may be important in consider-ing the cost and benefits of potential climate change.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.152-152
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• 2018

Soil moisture is a important factor in hydrologic analysis. So, if we have spatially distributed soil moisture data, it can help to study much research in a various field. Recently, there are a lot of satellite derived soil moisture data, and it can be served through web freely. Especially, NASA (National Aeronautics and Space Administration) launched the Soil Moisture Aperture Passive (SMAP) satellite for mapping global soil moisture on 31 January 2015. SMAP data have many advantages for study, for example, SMAP data has higher spatial resolution than other satellited derived data. However, becuase many satellited derived soil moisture data have a limitation to data accuracy, if we have ancillary materials for improving data accuracy, it can be used. So, in this study, after applying the alogorithm, which is data assimilation methods, applicability of satellite derived soil moisture data was analyzed. Among the various data assimilation methods, in this study, Model Output Statistics (MOS) technique was used for improving satellite derived soil moisture data. Model Output Statistics (MOS) is a type of statistical post-processing, a class of techniques used to improve numerical weather models' ability to forecast by relating model outputs to observational or additional model data.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.1
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• pp.57-70
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• 2017

In this study, we evaluated daily root zone soil moisture dynamics and agricultural drought using a near-surface soil moisture data assimilation scheme with Soil Moisture Active & Passive (SMAP, $3km{\times}3km$) soil moisture footprints under different hydro-climate conditions. Satellite-based LANDSAT and MODIS image footprints were converted to spatially-distributed soil moisture estimates based on the regression model, and the converted soil moisture distributions were used for assessing uncertainties and applicability of SMAP data at fields. In order to overcome drawbacks of the discontinuity of SMAP data at the spatio-temporal scales, the data assimilation was applied to SMAP for estimating daily soil moisture dynamics at the spatial domain. Then, daily soil moisture values were used to estimate weekly agricultural drought based on the Soil Moisture Deficit Index (SMDI). The Yongdam-dam and Soyan river-dam watersheds were selected for validating our proposed approach. As a results, the MODIS/SMAP soil moisture values were relatively overestimated compared to those of the TDR-based measurements and LANDSAT data. When we applied the data assimilation scheme to SMAP, uncertainties were highly reduced compared to the TDR measurements. The estimated daily root zone soil moisture dynamics and agricultural drought from SMAP showed the variability at the sptio-temporal scales indicating that soil moisture values are influenced by not only the precipitation, but also the land surface characteristics. These findings can be useful for establishing efficient water management plans in hydrology and agricultural drought.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.4
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• pp.235-241
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• 2014

A ground-based microwave scatterometer has an advantage for monitoring soil moisture content using multi-polarization, multi-frequencies and various incidence angles. In this paper, ground-based multi-frequency (L-, C-, and X-band) polarimetric scatterometer system capable of making observations every 10 min was used to monitor the soil moisture conditions in a corn field over an entire growth cycle. Measurements of volumetric soil moisture were obtained and their relationships to the backscatter observations were examined. Time series of soil moisture content was not corresponding with backscattering coefficient pattern over the whole growth stage, although it increased until early July (Day Of Year, DOY 160). We examined the relationship between the backscattering coefficients from each band and soil moisture content of the field. Backscattering coefficients for all bands were not correlated with soil moisture content when considered over the entire stage ($r{\leq}0.48$). However, L-band Horizontal transmit and Horizontal receive polarization (HH) had a good correlation with soil moisture ($r=0.85^{**}$) when LAI was lower than 2. Prediction equations for soil moisture were developed using the L-HH data. Relation between L-HH and soil moisture shows linear pattern and related with soil moisture content ($R^2=0.77$). Results from this study show that backscattering coefficients of microwave scatterometer appear to be effective to estimate soil moisture content in the field level.

• Journal of Ginseng Research
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• v.22 no.2
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• pp.122-125
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• 1998

Adequate available soil moisture level is considered to be one the most important components in growing high yields of good quality ginseng. Excessive soil moisture may promote stillborn fungal pathogens and cause serious diseases in ginseng fields. This study showed that soil moisture levels for optimum growth and health of ginseng varied with soil texture. Fifty- percent available moisture for sandy loam and 75% for silty loam are the best moisture levels for good growth and higher yield.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.1
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• pp.46-51
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• 2004

The film coated snap bean (Phaseolus vulgaris) seeds with five different coating materials treated with 3% increase in seed weight were planted at sandy loam soil controlled moisture content of 18, 19, 20 and 21 %. The oxygen diffusion rate (ODR) was calculated from the different moisture content soil. The number of normal seedlings, seedling vigor, and seedling capability in field (seed vigor x dry matter weight) were observed at 9 days after planting and compared to the changes of ODR. The germination rate and ODR were sharply decreased simultaneously in the seeds planted at 21 % soil moisture content. Seedling emergence did not occur at all as the soil moisture content increased above 22 %. Hence this value should be considered as the threshold of soil moisture content for seedling emergence. An ODR value under 20% did not influence the percent emergence significantly. The certain difference observing in the emergence at the same ODR was not related clearly to the condition of soil. So it can be assumed that the limit of soil moisture content for the emergence of snap bean was approximately 20%. The value of 18% soil moisture content may be considered as the optimum for snap bean emergence. There was close relationship between the mean value of ODR in different soil moisture contents and the emergence. The germination rates of the seeds coated with the different materials were quite different when the seeds were planted at 21 % soil moisture. Dry weight of the seedlings from film coated seeds was decreased slightly, but the germination rates were not much different from the non-treated control under relatively higher soil moisture content (21 %). Major factor lowering emergence rate was oxygen stress while film coating act as a minor constraint for snap bean sown in excess soil moisture condition.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.1
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• pp.67-75
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• 1993

This study is to analyze both root growth and soil moisture extraction pattern during the growing period of upland crops with respect to soybean, redpepper, sesame. Field and lysimeter tests were conducted under 12 treatments of soil moisture level by the San Cristobal experimental design(1981) and 3 soil type(sand, sandy loam, silty loam) for 4 years('87-'90) at the experimental plot of Rural Development Administration located in Suwon. The results of this study are summarized as follows : 1.For soybean, redpepper and sesame, root growth in dry soil was better than that in wet soil and it could be expressed as a sin function in terms of time. Maximum root depth was about 55cm, 44cm, 40cm respectively. 2.The average soil moisture extraction pattern for soybean, redpepper and sesame were 61.4%, 62.8%, 79.5% for zone l(0-l5cm). 25.5%, 27.1%, 18.3%, for zone 2(15-30cm).11.4%, 9.8%, 2.3% for zone 3(30-45cm), 1.7%, 0.3%, 0.04% for zone 4(45-60cm) respectively. This means that Zone 1 would be the dominant zone in irrigation scheduling. 3.With respect to soybean, the soil moisture extraction pattern(SMEP) was varied somewhat according to the erent maintenance of soil moisture level. The average SMEP for high maintenance of soil moisture was 46%, 29%, 17%, 8%, for middle maintenance of soil moisture was 43%, 29%, 17%, 11 % and for low maintenance of soil moisture was 40%, 28%, 20%, 12%, respectively. 4.With respect to soybean, the soil moisture in the upper layer was distinctly consumed more than that in the lower layer for clay loam soil and the soil moisture of all layers was consumed evenly for sand soil. The SMEP for sandy loam soil showed a middle result compared with the above 2 soil types.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.3
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• pp.19-28
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• 2012

Greenhouse cultivation has been increasing for high quality and four season crop production in South Korea. For the cultivation in a greenhouse, maintaining adequate soil moisture at each crop growth stage is quite important for yield stability and quality while the behavior of moisture movement in the soil has complexity and adequate moisture conditions for crops are vary. Drip irrigation systems have been disseminated in the greenhouse cultivation due to advantages including irrigation convenience and efficiency without savvy consideration of the soil moisture redistribution. This study aims to evaluate soil moisture movement of drip irrigation according to the soil moisture uniformity assessment. Richards equation and finite difference scheme were adapted to simulate soil moisture behavior in soil. Soil container experiment was conducted and the model was validated using the data from the experiment. Two discharge rate (1 ${\ell}/hr$ and 2 ${\ell}/hr$) and three spaces between the emitters (10 cm, 20 cm, and 30 cm) were used for irrigation system evaluation. Christiansen uniformity coefficient was also calculated to assess soil moisture redistribution uniformity. The results would propose design guidelines for drip irrigation system installation in the greenhouse cultivation.