Pil-Kyun Jung

Water Saving Irrigation Manual of Autumn Chinese Cabbage

The water management of crop is different according to the area as well as climate condition and growth stage, however it is the most important and difficult problems for the farmers. The optimum irrigation manual those irrigation interval and amount of irrigation as water saving, are developed based on the lysimeter experiments carried out by the RDA for 11 years about PET (Potential Evapo-Transpiration), crop coefficient (Kc). The average PET (Potential Evapo-Transpiration) during 30 years of 45 regions for the autumn chinese cabbage cultivation was a 2.17 mm day

Development of the Model to Estimate Potential Evapotranspiration in Korea

우리나라는 연중 강수량의 70% 정도가 여름철에 내리는 특성을 갖고 있어 여름철의 풍부한 강수를 잘 보존하여 가을, 겨울 봄철의 물 부족에 대응하여 왔다 (Eom, 2010). 물 공급량인 강수량과 물 소모량인 잠재증발산량을 비교해보면 1월에서 4월까지는 강수량보다 잠재증발산량이 더 많고, 5월에서 9월까지는 강수량이 더 많다가 10월에서 12월까지는 다시 잠재증발산량이 많은 양상을 보이고 있다. 계절별로 보면 여름철의 경우 강수량은 1920년 대비 2000년대 163.9 mm가 증가하여 이로인한 홍수피해가 빈발하였고, 봄철과 가을철 특히, 겨울철 37.4 mm의 강수부족으로 인해 가뭄피해가 심화되고 있다. 한편 기후변화로 강수량이 증가하게되면 유효물량이 증가하여 인공적으로 공급해 주는 관개용수량을 저감시키는 효과가 있다 (Eom, 1982, 1999, 2009). 농업용 수자원의 공급과 소모에 대한 대책마련으로 용수의 절약방법과 효율을 높일 수 있는 용수량 조절이 필수적이다. 이와 같은 필수적 관개용수량을 조절하기 위하여 증발산량의 산출자료를 기초로 하여 식물에서 대기로의 증발산 특성연구 (Hong et al., 1997), 작물별 적정 관수량의 실태조사 (정 등, 1981)가 시행된 바 있으며, Landast TM 자료를 이용한 광역 증발산량 추정 (Chae et al., 2000), 농업용수 수요량 분석을 위한 잠재증발산량 공간분포 추정 (Yoo and Choi, 2006)등의 연구가 보고되었다. 하지만 기상조건이 다르기 때문에 대기의 증발요구량 (잠재증발산량)이 지역별, 시기별 차이에 의해 달라지기 때문에 관개용수량의 공급 정도도 달라지게 된다 (Klute, 1986).실제 잠재증발산량은 여러 요인에 의해 정량화하기 어렵기 때문에 일반적으로 Lysimeter에서 실측한 값과 기상자료를 이용한 추정모델을 설정하여 산정하고 있다. 따라서, 본 연구에서는 우리나라의 지역별 잠재증발산량 변동 양상을 예측하기 위하여 30년간 기상 관측소의 기상자료를 이용하여 관측된 자료의 소형, 대형 증발량 값을 이용하여 산정된 식을 바탕으로 우리나라 7개 지역에 대한 잠재증발산량의 변동양상을 분석하여 잠재증발산량의 변동양상을 추정할 수 있는 모형을 개발하고자 하였다.

Evaluation of the Effect of Urban-agriculture on Urban Heat Island Mitigation

Vegetation can make not only to lower the urban ambient air temperature (UAAT) by crop evapotranspiration (ET) and increasing solar radiation albedo, but also to reduce the urban air pollution by uptake and emission in addition to the reducing ozone concentrations by aid of lower the UAAT. To evaluate the effect of vegetation on urban heat island mitigation (UHIM), the climate change of 6 cities during 30 years are analysed, and the amount of ET, uptake, emission and ozone concentrations are estimated in Korea. The most hot season is the last part of July and the first part of August, and the highest average UAAT of a period of ten days was during 30 years (1979 - 2008). The mean values of maximum ET of rice and soybean in urban area during urban heat island phenomena were 6.86 and , respectively. The effect of rice and soybean cultivation on lowering the UAAT was assessed to be 10.5 and in Suwon, respectively, whereas the differences between the UAAT and canopy temperature at urban paddy and upland in Ansung were 2.6 and . On the other hand, the urban-garden in Suwon city had resulted in lowering the UAAT and the surface temperature of buildings to 2.0 and , respectively. Furthermore, the amounts of uptake by rice and soybean were estimated to be 20.27 and , respectively. The amounts of emission by rice and soybean were also assessed to be 14.74 and , respectively. As other cleaning effect of air pollution, the ozone concentrations could be also estimated to reduce 21.0, 8.8, and 4.0 ppb through rice-, soybean cultivation, and urban gardening during most highest temperature period in summer, respectively.

Yield Response of Soybean to Drought Stress under Different Fertilizer Level

This study was conducted to investigate the yield response of soybean to drought stress in 1984 and 1986 at the experiment field of the National Academy of Agricultural Science using experiment plots with different soil water tension and fertilizer levels. The average yield response factor (YRF) of soybean to evapotranspiration (ET) calculated as [(Ya/Ym)/(ETa/ETm)], where Ya, average yield; Ym, maximum yield; ETa, average ET; and ETm, maximum ET, was 0.91 with the range from 0.74 to 1.16. Relationship between yield index (YI = [Ya/Ym]) and evapotranspiration index (ETI = [ETa/PET]) was YI = 0.87·(ETI) + 0.09. Relationship between YI and the maximum soil water tension (Hmax) was YI = 1.23 - 0.23·log (Hmax). Relationship between YI and the days of drought stressed (Dr) was YI = 0.877·exp (-0.01·Dr). The relation between YI and fertilizer level (F) was YI = -0.21·F2 + 0.36·F + 0.33, under very serious drought condition as the maximum soil water tension was 0.3 MPa.