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이변우,Lee, Byeon-U 한국작물보호협회 2009 자연과 농업 Vol.30 No.1
곡물가격 급등은 일시적 현상 아닌 소비증가 추세에 기인한 구조적 현상이다. 세계 잠재 생산량의 33.7%가 병해충 및 잡초에 의해 없어직고 있다. 방제효율을 높이는 것만으로도 식량안보에 크게 키여할 수 있을 것이다.
건답직파재배에서 요소 비료 시용시 벼의 질소 이용과 손실
이변우 서울대학교 농업개발연구소 1999 농업생명과학연구 Vol.3 No.-
The objectives of this study were to evaluate the loss and recovery of urea nitrogen applied at sowing as basal nitrogen and topdressed shortly after flooding at four- to six-leaf stage of rice, and the effectiveness of nitrogen split application method, a nitrification inhibitor, DCD (dicyandiamide), and a slow release fertilizer, latex-coated urea(LCU) on the nitrogen economy and yield performance of rice sown directly on dry paddy field. Urea applied at seeding was lost almost completely during dry paddy period of 20 to 30 days before permanent flooding. Plant recovery of nitrogen applied at sowing was only 2.5 to 3.2% with 91 to 96% loss during dry paddy period until 4-leaf stage, showing little year to year variation. Nitrogen loss due to ammonia volatilization covered only 1 to 11%, and the rest substantial part of loss appeared to be due to leaching and denitrification. Both leaching and denitification were important mechanisms of nitrogen loss during dry paddy period before permanent flooding. Urea topdressed shortly after flooding at four-leaf stage was utilized 8 to 40% by plant with 15 to 50% loss within 10 days after fertilization, being much less in N loss compared to urea applied at sowing. Nitrogen topdressed at this stage was lost primarily due to leaching at very early stage of fertilization because of very high rate of water percolation. Ammonia volatilization loss was very low, accounting only for below 2% of applied nitrogen. The data suggested that urea fertilization at sowing as basal fertilizer should be avoided or reduced to a minimum amount and the nitrogen alloted to basal fertilizer in conventional dry-seeding rice culture rather be supplemented to the topdressing shortly after permanent flooding at four to six-leaf stage of rice for improving nitrogen fertilization efficiency and rice yield. DCD increased slightly the plant recovery of fertilizer nitrogend and rice yield. However, such a degree of improvement might be achieved by other means of fertilization practice without chemical.
벼의 한계질소농도 결정 및 군락반사율을 이용한 질소영양상태 추정 연구
이변우 서울대학교 농업개발연구소 2000 농업생명과학연구 Vol.4 No.-
Critical nitrogen concentration(Nc) which is defined as the minimum nitrogen concentration to maintain the maximum growth rate at any time was investigated for rice plant. Based on Nc, nitrogen nutrition index(NNI) was calculated as its ratio to actual nitrogen concentration to examine the relationship with yield and yield components. In addition, investigated were the feasibilities to apply canopy reflectance measurements to diagnosing the nitrogen nutrition status nondestructively. Shoot critical nitrogen concentrations had no differences between rice varieties, Hwasungbyeo and Dasanbyeo, having the relationship with shoot dry weight(DW) as Nc=5.26DW-4.138(R2=0.966). This Nc dilution curve can be applied only in case that DW is greater than 1 to 1.5t/ha. For the early growth stage with DW less than 1 to 1.5t/ha, Nc should be determined with further detailed experiments. Nitrogen nutrition index(NNI), which is calculated as the ratio of Nc to actual N concentration, represented nitrogen nutrition status of rice very well. Showing the close relationship with rice yield and its components. Visible light reflectance had no great variations as LAI increases above 2. While near infra red(NIR) reflectance increased with LAI increase. Visible light reflectance decreased but NIR reflectance changed little with the increased nitrogen application levels. In cas of LAI less than 2, it was difficult to estimate canopy characteristics such as plant nitrogen concentration and NNI by canopy reflectance as the background reflectance of paddy soil and water contributed too much to canopy reflectance(ρ). Whereas, plant nitrogen concentration and NNI of rice canopy with LAI above 2 had very significant correlations with visible band reflectances, RVI, NDVI and so forth. Especially, RVIgreen(□) and NDVIgreen(□) showed the close linear regression relationship with NNI which had coefficients of determination of R2=0.802 and R2=0.845, respectively, indicating that these vegetation indexes could be used effectively to estimate NNI nondestructively. However, further studies to get rid of background effects on canopy reflectance are needed for the effective diagnosis of nitrogen nutrition status with canopy reflection measurements even in early growth stage with LAI below 2.
이변우 서울대학교 농업개발연구소 2001 농업생명과학연구 Vol.5 No.-
Under the constant daylength the final number of rrice leaves on the main culm(FNL) was constant regardless of temperature in rice variety 'Kwanganbyeo'. Leaf appearance rate(LAR) increased with rising temperature and decreased with phenological development. LAR was well fitted to the following model; dL/dt=(T_i-T_0)·(-a^-1·b^(1/c)·c·(a-L)^((c-1)/c)·L^((c+1)/c)) where dL/dt is LAR, t_i and T_0 are daily mean and threshold temperature, L is the number of leaves appeared, and a, b, and c are constants that were estimated as 41.8, 1098.38, and -0.9273 in Kwanganbyeo, respectively. FNL shoed very close relationship with the average daylength during photosensitive period(PSP) of six-leaf stage to panicle initiation, being well fitted to the following rational function(R^2=0.98); FNK=(a+bD)/(1+cD), where D is daylength and a, b, and c are the constants that wee estimated as 14.694, -0.992, and -0.068 in Kwanganbyeo, respectively. The rice phenology model, which was composed of the two component models for LAR and FNL, predicted developmental stage very accurately. The differences between the observed and predicted days to heading was less than two days in the sowing date field experiments in 1999 and 2000 of which data were not used for the model construction.