Myung-Chul Seo

Estimating nitrogen and phosphorus contents using model integrated in small agricultural watersheds.

Abstract The Agricultural Nonpoint Source Pollution Model (AGNPS) was applied to estimate the loads of nitrogen and phosphorus according to antecedent soil moisture conditions (AMC) using probable rainfall in a stream draining small agricultural watersheds. Calibration and verification of the model were performed using observed data collected from rainfall events in the Imgo watersheds during 1997–1998. Evaluation of model outputs was based on graphical displays contrasting observed and simulated values for each rainfall-runoff event, and standard statistics such as coefficient of efficiency. The coefficient of efficiency of peak flow, total N, and total P in the estimation were 0.97, 0.93, and 0.74, respectively. Probable rainfall of Imgo watersheds was computed for several return periods using the frequency analysis of Gumbels extreme value distribution. As the probable flood increase, concentrations of total N and total P generally decrease. Loss of N and P was proportional to the preceding soil water content in the same probable rainfall. The excessive fertilization under AMC-III condition can cause relatively higher outflow of N and P from the soil. It can be concluded that surface runoff and sediment transport influence soil quality and the quality of water absorption and AGNPS can provide realistic estimates of nonpoint source nutrient yields.

Assessment of Nitrogen Impaction on Watershed by Rice Cultivation

It is important to understand and evaluate the environmental impacts of rice cultivation for developing environmentally-friendly agriculture because rice is main crop in Korea and rice cultivation have both functions of water pollution and purification with environmental and cultivation conditions. This paper presents the evaluation of nitrogen impact by rice cultivation on water system. A simple protocol was proposed to assess the potential amount of nitrogen outflow from paddy field and most of parameters affect on the nitrogen outflow from paddy field such as the amount of fertilizer application, water balance, the quality and quantity of irrigation water, soil properties, nitrogen turnover in the soil and cultivation method were considered. To develop the protocol, coefficients for parameters affected nitrogen turnover and outflow were gotten and summarized by comparison and analysis of all possible references related, and by additional experiments at field and laboratory. And potential amount of nitrogen input and output by water in paddy field were estimated with the protocol at the conditions of the nitrogen contents of irrigation water, amount of fertilizer application, and irrigation methods. Where irrigation water was clean, below 1.0 mg of nitrogen concentration, rice cultivation polluted nearby watershed. At the conditions of 2.0 mg of nitrogen concentration, 110 kg of nitrogen fertilizer application and flooding irrigation, rice cultivation had water pollution function, but it had water purification function with intermittent irrigation. At the conditions of 3.0 mg of nitrogen concentration and 110 kg of nitrogen fertilizer application, rice cultivation had water purification function, but that had water pollution function with 120 kg of nitrogen application. Where irrigation water was polluted over 6.0 mg of nitrogen, it was evaluated that rice cultivation had water purifying effect, even though the amount of nitrogen application was 120 kg .

Implementation of Polyacrylamide in the Agricultural Environment and its Recent Review

Nonpoint sources of pollution (NPS) is defined as diffuse discharges of pollutants (e.g., nutrient, pesticide, sediment, and enteric microorganism) throughout the natural environment and they are associated with a variety of farming practices. Previous studies found that water soluble anionic polyacrylamide (PAM) is one of the highly effective measures for enhancing infiltration, reducing runoff, preventing erosion, controlling nonpoint source of pollutants, and eventually protecting soil and water environment. Potential benefits of PAM treatment in agricultural soil and water environments have been revealed by many research and they include low cost, easy and quick application, and suitability for use with other Best Management Practices (BMPs) for NPS control. This study reviews the various applications of PAM and discusses its further potentials in agricultural environment.

Infrared Estimation of Canopy Temperature as Crop Water Stress Indicator

Decision making by farmers regarding irrigation is critical for crop production. Therefore, the precision irrigation technique is very important to improve crop quality and yield. Recently, much attention has been given to remote sensing of crop canopy temperature as a crop water-stress indicator, because it is a scientifically based and easily applicable method even at field scales. This study monitored a series of time-variant canopy temperature of cucumber under three different irrigation treatments: under-irrigation (control), optimal-irrigation, and over-irrigation. The difference between canopy temperature (T c ) and air temperature (T a ), T c – T a , was calculated as an indicator of cucumber water stress. Vapor pressure deficit (VPD) was evaluated to define water stress on the basis of the temperature difference between leaf and air. The values of T c – T a was negatively related to VPD; further, cucumber growth in the under- and over-irrigated fields showed water stress, in contrast to that grown in the optimally irrigated field. Thus, thermal infrared measurements could be useful for evaluating crop water status and play an important role in irrigation scheduling of agricultural crops.

Assessment of Environmental Conservation Function using Changes of Land Use Area and Surface Temperature in Agricultural Field

This study was aimed at assess environmental conservation functions by analyzing the change of land use areas in agricultural fields between 1999 and 2006, and comparing land surface temperature distribution between 1994 and 2006 in Yongin city. Land use maps of Yongin city were obtained from soil maps for 1999, Quickbird satellite images(less than 1 m) and parcel map for 2006. The land use area for Yongin city was in the order of forest > paddy field > upland > residence & building in 1999, and forest > residence & building > paddy field > upland in 2006. Decrease of paddy and upland fields reduced 34% and 41% of the capability of agricultural multifunctionality as to environment including flood control, groundwater recharge, and air cooling. Land surface temperature(LST) was derived from Landsat TM thermal infrared band acquired in September of 1994 and 2006 and classified into three grades. The results impplied that green vegetation in agricultural field and forest play an important role to reduce land surface temperature in warm season.