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정강호,손연규,장용선,한경화 한국토양비료학회 2015 한국토양비료학회지 Vol.48 No.1
This research was performed to test the hypothesis that the optimal fertilization rate for lettuce is various with soil moisture conditions. The experiment was conducted under a rainfall-intercepted facility in Suwon, South Korea from 2002 to 2003. Soil was irrigated at 30, 50, or 80 kPa of soil moisture tension at 15 cm soil depth in 2002 spring and fall and 20, 30, 50, or 80 kPa in 2003 spring. Fertilization was performed with four levels in spring for both years: none, 0.5, 1.0, and 1.5 times of the recommended N, P, and K fertilization rate. The irrigation amount increased with decreased irrigation starting point as soil moisture tension. The maximum yield was found at the lowest soil moisture tension in spring while irrigation at 50 kPa resulted in the greatest yield in fall. The yield responses of lettuce to fertilization rates were various with soil moisture condition. In spring, maximum yield was found at 1.0 or 1.5 times of the recommended fertilization rate at 20, 30, and 50 kPa irrigation while 0.5 or 1.0 times of fertilization rate resulted in the maximum yield in fall. Especially for 80 kPa irrigation in 2003 spring, yield was decreased by fertilization. It suggested that the optimum fertilization rate for lettuce is affected by soil moisture condition and that lower fertilization rate should be suggested when soil is managed in drier condition.
Responses of Capsicum annum (red pepper) to Fertilization Rates at Various Soil Moisture Conditions
정강호,손연규,한경화,장용선 한국토양비료학회 2014 한국토양비료학회지 Vol.47 No.5
This research was performed to test the hypothesis that the optimal fertilization rate for red pepper is changedby soil moisture condition. The experiment was conducted in rainfall-intercepted fields in Suwon, SouthKorea from 2002 to 2003. Soil was irrigated at 30, 50, or 80 kPa of soil moisture tension at 20 cm soil depthin 2002 and 30, 50, 100, or 150 kPa in 2003. For both years, fertilization was performed with four levels: none,0.5, 1, and 1.5 times of the recommended N, P, and K fertilization rate. The irrigation amount was the greatestat 30 kPa irrigation while the water use efficiency increased with decrease of irrigation amount. The Irrigationamount was 508 mm at 30 kPa irrigation and ranged from 355 mm to 435 mm at 50 kPa irrigation. Themaximum yield was found at 30 kPa irrigation and 1.5 times of the recommend fertilization rate in 2002 and2003. The yield index of red pepper increased linearly with the fertilization rate at 30 kPa which implied thatexcess irrigation induced nutrient leaching and reduced nutrient availability. The maximum yield in 50 kPaand 80 kPa was found at the recommend fertilization rate while the yield decreased by fertilization at 100 kPaand 150 kPa irrigation. It implies that reduction of fertilization is the feasible practice to mitigate drought stressin fields without stable irrigation resources.
정강호,손연규,허승오,하상건,정문호 한국토양비료학회 2015 한국토양비료학회지 Vol.48 No.5
Pedotransfer functions (PTFs) were developed for each soil horizon to estimate hydraulic characteristics of mountainous forest soils in South Korea. Twenty one dominant soil series from 8 soil catenae such as granite-originated catena and volcanic ash-originated catena were selected for the study; gravel contents of selected soils were 10% or lower. Saturated conductivity (Ks) was measured for each horizon in situ. Particle size distribution and organic matter content of each horizon were also determined. Based on correlation analysis with total data set, sand separate showed positive relationship with Ks (r=0.24*) while clay separate had negative relationship with Ks (r=-0.29**). The correlation coefficients of sand, clay, and organic matter content with Ks increased to 0.41**, -0.67***, and 0.58***, respectively, using data from granite- or gneiss-originated catena with exception of volcanic ash-originated catena and sedimentary rock-originated catena. Determination coefficients of PTFs were 0.31 for A horizon, 0.25 for B, and 0.35 for C with all data set while those were 0.74 for A, 0.48 for B, and 0.54 for C. Organic matter was a dominant factor affecting Ks in A horizon but clay content was selected as the only factor influencing Ks in C horizon. It implies that PTFs should be developed with understanding characteristics of parent materials and horizons. Developed PTFs for granite- or gneiss-originated catena were following:A horizon: Log (Ks x 107) = -0.031C + 0.398OM + 3.49B horizon: Log (Ks x 107) = -0.028C + 0.141OM + 4.05C horizon: Log (Ks x 107) = -0.072C + 4.66where C is clay separate (%) and OM is organic matter content (g kg-1). The unit of Ks is cm sec-1.
정강호,이광승,오양열,이충근 한국토양비료학회 2022 한국토양비료학회지 Vol.55 No.4
The Korean government has performed the international cooperation project to develop rice cultivationmethods under desert climate and alkaline sandy soils with the UAE government. Rice can be cultivated inalkaline sandy soil with paddy condition while it demands too much water. Four treatments were tested underprotected plastic house: paddy cultivation with an impermeable layer (PP), furrow cultivation (F), furrowcultivation with an impermeable layer (FP), and furrow cultivation with clay dressing (FB). The impermeablelayer prohibited percolation. Furrow cultivation reduced evaporation by irrigation only in the furrow. Claydressing extend flooding periods to decline infiltration rates. Daily water consumption rates were 5.4 to 5.5mm in furrow cultivation accounting for 57% of that in PP. The number of tiller was 16.0 in PP flooding allthe time while they ranged from 4.4 to 6.8 in furrow cultivation treatments. The productivity in FP and FBwere 84.1% and 78.9% out of that in PP. The water use efficiency in FP and FB, therefore, leached 1.4 to 1.5times of that in PP. Based on the water use efficiency, FP and FB were proposed the applicable practices forreasonable productivity and water consumption. Furthermore, FP and FB have potential to raise productivityby increasing seeding rates considering low tillering rates.
Hydraulic Characteristics of Arable Fields in Korea and Applicability of Pedotransfer Functions
정강호,손연규,허승오,한경화,조희래,서미진,정문호,최세영 한국토양비료학회 2016 한국토양비료학회지 Vol.49 No.6
Relationships between saturated conductivity (Ks) and separate contents were evaluated from 44 soil series of arable lands: 18 for paddy fields and 26 for upland crop fields. Saturated hydraulic conductivities of A, B, and C horizons were determined with tension infiltrometer and Guelph permeameter in situ. Sand, silt, clay, and organic matter content of each horizon were analyzed. Based on correlation analysis, sand separate had a positive relationship with Ks for both paddy (r=0.27, p=0.017) and upland fields (r=0.24. p=0.030). Clay content had a negative relationship with Ks for paddy soils (r=-0.32, p=0.005) while significant correlation between them was not found for upland crop fields (r=-0.20, p=0.07). Organic matter content showed a positive relationship with Ks only for upland crop fields (r=0.33, p=0.002). Due to low correlation coefficients between separate contents and Ks, performance of pedotransfer functions was not enough to estimate Ks. It implies that hydraulic properties of arable lands were affected by other factors rather than particle characteristics. Platy structure and plow pan were suggested to limit Ks of paddy fields. Soil compaction and diversity of parent materials were proposed to influence Ks of upland crop fields. It suggests that genetic processes and artificial managements should be included in pedotransfer functions to estimate hydraulic properties appropriately.