유수분화기 식생지수와 SPAD값에 의한 벼 질소 수비 시용량 결정 = Determining Nitrogen Topdressing Rate at Panicle Initiation Stage of Rice based on Vegetation Index and SPAD Reading

다국어 초록 (Multilingual Abstract)

The core questions for determining nitrogen topdress rate (Npi) at panicle initiation stage (PIS) are "how much nitrogen accumulation during the reproductive stage (PNup) is required for the target rice yield or protein content depending on the growth and nitrogen nutrition status at PIS?" and "how can we diagnose the growth and nitrogen nutrition status easily at real time basis?". To address these questions, two years experiments from 2001 to 2002 were done under various rates of basal, tillering, and panicle nitrogen fertilizer by employing a rice cultivar, Hwaseongbyeo. The response of grain yield and milled-rice protein content was quantified in relation to RVIgreen (green ratio vegetation index) and SPAD reading measured around PIS as indirect estimators for growth and nitrogen nutrition status, the regression models were formulated to predict PNup based on the growth and nitrogen nutrition status and Npi at PIS. Grain yield showed quadratic response to PNup, RVIgreen around PIS, and SPAD reading around PIS. The regression models to predict grain yield had a high determination coefficient of above 0.95. PNup for the maximum grain yield was estimated to be 9 to 13.5 ㎏N/10a within the range of RVIgreen around PIS of this experiment. decreasing with increasing RVIgreen and also to be 10 to 11 ㎏N/10a regardless of SPAD readings around PIS. At these PNup"s the protein content of milled rice was estimated to rise above 9% that might degrade eating quality seriously. Milled-rice protein content showed curve-linear increase with the increase of PNup, RVIgreen around PIS, and SPAD reading around PIS. The regression models to predict protein content had a high determination coefficient of above 0.91. PNup to control the milled-rice protein content below 7% was estimated as 6 to 8 ㎏N/10a within the range of RVIgreen and SPAD reading of this experiment, showing much lower values than those for the maximum grain yield. The recovery of the Npi applied at PIS ranged from 53 to 83%, increasing with the increased growth amount while decreasing with the increasing Npi. The natural nitrogen supply from PIS to harvest ranged from 2.5 to 4 ㎏/10a, showing quadratic relationship with the shoot dry weight or shoot nitrogen content at PIS. The regression models to estimate PNup was formulated using Npi and anyone of RVIgreen, shoot dry weight, and shoot nitrogen content at PIS as predictor variables. These models showed good fitness with determination coefficients of 0.86 to 0.95. The prescription method based on the above models predicting grain yield, protein content and PNup and its constraints were discussed.

목차 (Table of Contents)

• ABSTRACT
• 재료 및 방법
• 결과 및 고찰
• 적요
• 사사
• 인용문헌